ZT Amplifiers Club - Comprehensive Evaluation

Introduction


ZT Engineering provided an evaluation "Club" amplifier with the same understanding previously agreed upon for review of the ZT "Lunchbox": I was free to treat the device as my own - to disassemble, measure, abuse and allow friends to use the amplifier so long as the non-disclosure agreement was observed. (I can disclose no information that ZT regards as proprietary without permission.)


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This evaluation won't resemble a "magazine review". We've all read reviews based on a brief experience with a product and that sometimes seem like manufacturer's advertising literature reworded as personal opinion. The "sample of 1" review is not very useful, in my opinion. In fact, if a sole evaluator is biased in any way (e.g. the manufacturer advertises in the writer's magazine … or happens not to advertise in the magazine but a competitor does) then the review might be questionable.

The five of us who worked on this project are of diverse professional (and musical) backgrounds but we share many years of musical experience with a variety of musical instruments and equipment. We did this work from the motivations of providing useful and objective information to fellow guitarists and because it was interesting. We spent weeks on this evaluation not to mention the shipping costs and other direct costs associated with measurements, materials, computer simulations and experiments that might reveal additional insight into the product design and performance.

As with any five randomly selected individuals, opinions vary and that is the greatest benefit of a review configured like this one. The larger the sample size, the more accurately the product is portrayed. A sample size of five evaluators starts to become unwieldy if a project is expected to be conducted quickly and where geographical locations are so widely dispersed: west coast to east coast, southern national boundary to northern national boundary and Chicago, musical, industrial and financial midpoint of the U.S.

The team that was assembled to review the Lunchbox offered so much diversity of background, knowledge and experience that the evaluation would have been impaired by reducing the team by even a single person. This is a good time to express my appreciation to these team members - they put a lot into this effort. We hope that you appreciate their work and take seriously their comments originating from over 130 years of combined musical experience.

During our evaluation, frequent communication with the amplifier manufacturer was exchanged. There was no lack of cooperation; design and reliability questions were promptly answered in detail - even to the point that proprietary drawings of critical parts were shared. As I noted in the introduction to the "Lunchbox" review, this level of cooperation is completely unprecedented. Therefore it is also appropriate to express the gratitude of the evaluation team to "ZT Amplifiers Inc." for their forthright responsiveness. Comments that weren't always complimentary received thoughtful and courteous attention from this manufacturer.

In the review of the "Lunchbox" the first sections were directed to the technical performance of the amplifier. I've revised the format for this evaluation so that the engineering aspects of the evaluation now comprise the final part of this review. I believe that this will be more satisfactory to the average reader.

First Reviewer's Evaluation
by LPDeluxe

The ZT Club is a step up from the Lunchbox produced by the same company. It is larger, with a 12” speaker in place of the 6.5” unit in the Lunchbox, and additional controls, detailed below. Randy will provide pertinent measurements and statistics.

I have already published my opinions of the Lunchbox, and it may be helpful for anyone reading this review to review the evaluation of that amplifier. In any case, most of my comments will be concerning the Club, with comparisons made to the other when necessary for clarity.

As with our team evaluation of the previous model, my tests consisted of playing various musical material through the amplifier in an ensemble setting, using Gibson ES-335 and SG electric guitars and a harmonica through a Shure 520DX harmonica microphone. I compared the Club with several Fender amplifiers, in my living room, to “calibrate” my impressions. I used no effects pedals which is my usual practice.

Note that these opinions are entirely my own, based on individual taste and abilities. Your mileage may vary widely – but these impressions might assist you with a road map.

My playing partner capably provided rhythm guitar accompaniment with a Taylor acoustic-electric (through a Vox modeling amp) and percussion was supplied by an Alesis SR-18 drum machine. We performed the evaluation in a large rehearsal studio, about 40’ by 40’ (similar to a medium-size club venue). My partner sang through the studio PA system.

He and I have been playing together seriously since 2003: he was vocalist/rhythm guitarist and I was the bassist in a reasonably long-lived dance band that gigged steadily. (We performed C&W and rock material of all eras - prior to metal !) As a result, we share a lot of songs, which made it easy to try the Club on music of a variety of genres. These included loud and fast rock songs, mellow, jazzier ones, and a fair number of ballads.

The ZT Club is a small, lightweight and easily portable device, silver in color. I did an informal poll of studio visitors: most thought it looked like an electric space heater, with others preferring (take your pick) a humidifier or de-humidifier. Unconventional, in short, but it’s the typical small flattened cube (about the size of the speaker cabinet of the Fender "Jazzmaster Ultralight" amplifier) often seen in such animals.

The controls are mounted on a recessed panel near the rear of the top surface. In my experience, this location will minimize accidental damage. Included is a “reverb” adjustment. Its digital algorithm is that of a “plate” reverb, rather than the “spring” reverb common to most guitar amplifiers. There are the bass and treble, volume and gain controls, along with a pilot light and input jack.


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An on/off switch resides on the back, along with controls to turn the internal speaker on and off (not being familiar with this feature, it took me a minute to figure out why I couldn’t initially hear my guitar through it) in conjunction with an external speaker jack. Nearby are a headphone jack and its volume knob. I didn’t use either an external speaker or headphones in my playing tests. The Club will fit on my narrowest guitar stand (the same one I use for the Fender "Jazzmaster") but it’s happy – and remains stable – on a chair or desk top. Elevation greatly improves your ability both to hear it and to adjust the controls.

The 12” speaker is a welcome change, with a rounder overall tone than the smaller one. The Lunchbox worked better on up-tempo, complex playing; the Club will allow you to play slower and more exposed lines. It feels, and sounds, a lot more like a conventional guitar amplifier, although it gives up the very small footprint and light weight of the other. Both amps are easily loud enough to play in a band with drums, bass, and other instruments.

Both the Lunchbox and the Club impose color in their reproduction of your guitar tone. In the case of the Lunchbox, it takes the form of a high-mid emphasis that makes harmonica sound harsh, and does not well match the tonal characteristics of my 335; on the other hand, it likes my SG and turns it into an aggressive, although smooth-sounding, rocker. The larger amp has more of a midrange emphasis. The Club proved that siblings don’t always share preferences: with this amplifier, the SG never quite worked, but the 335 sang.

Color is not a bad thing in a guitar amplifier or in musical gear in general. When recording, the knowledgeable engineer selects a microphone, not based upon the flatness of its frequency response curve, but upon the degree to which its particular color, or flavor, enhances the voice or instrument being recorded.

There is a school of thought that such color is unwanted distortion (literally, distortion is any deviation from exact reproduction – the use of the term “distortion” to specifically refer to the sound of an overdriven [especially vacuum tube] circuit is a recent development in the history of electronics). Those of us who have tried recording an electric guitar directly into a recorder understand that coloration is necessary to achieve musicality, and that the guitar amplifier is a natural source of that color.

Long before EQ became shorthand for a way to fit a given recorded track into a mix, telephone engineers depended on “equalization” to restore losses incurred in the generation, transmission and reproduction of audio signals, EQ was used to make the signal heard through the receiver “equal to” the original, at the other end of a long chain of cleverly kludged circuitry (trust me on this: carbon-grain microphones are non-linear devices), perhaps thousands of miles in length. The purpose of all this jiggery-pokery was simply to make telephone conversations intelligible to both parties.

First Reviewer's Evaluation (continued)
by LPDeluxe

But our modern ears perceive EQ, and the resultant coloring, as spice on the audio enchilada. Certainly, many of us (this includes me) own several guitar amplifiers, microphones, and whatnot, for the distinctive frequency-dependent emphasis or de-emphasis each places in the signal path; ideally, this improves the sound of one’s playing or singing. As it happens, the range of the electric guitar is similar to the range of the human voice, so that tricks learned with one generally apply to the other.

With the ZT amplifiers, this coloring is a large part of their charm, and also their limiting feature. To use a figure of speech, if other guitar amplifiers could be said to sound the way coffee varieties taste, most of them run the gamut from instant "Folger’s" to the custom roasted and blended: they’re all different, but they’re all still coffee. The Lunchbox is, shall we say, more like Creole coffee with chicory added while the Club is closer to coffee with hazelnut flavoring. They are still recognizably coffee, but now another element has climbed into your cup. To expand this idea: you can add cream and sugar to any of the conventional coffees to mask the original flavor, but the chicory remains chicory and hazelnut is ever hazelnut and neither is exactly coffee.

The tone of the Club is similar in a way that is important to me: it lacks the harmonic richness of my Fender Deluxe Reverb Reissue or Silvertone 1484. This want is much more noticeable in solo playing; as part of a band, it becomes an advantage, allowing your guitar to be heard without its having the insistent quality of the Lunchbox. Were I to always play ensemble, I wouldn’t hesitate to use the Club.

The emphasis in this amplifier’s response is right in the midrange. The 335 sounded smooth and compelling, with no harshness, and the tone reacted nicely to changes in the pickup/tone configuration. Rolling the treble off while playing through the neck pickup, I achieved as “jazzbo” a sound as I’m ever likely to enjoy in this lifetime. It was sweet and musical, with plenty of dynamics available through manipulation of pick attack. It can be addictive, respite coming only when the band counts off something more rock’n’roll. Then, like its smaller sibling, it has a snap that works well for a lot of the faster songs – never, however, losing its mid-rangy character. There is a vocal quality to this amp that allows you to go places you wouldn’t with others. Clarity is never lost.

After a couple of hours with the 335, I plugged the Green Bullet harmonica microphone into it and we did a blues and slow and mid-tempo ballads.

This is where the Club excels, for me personally: the lack of complexity and its midrange peak complements the harmonica and microphone, giving an upper baritone flavor to the instrument. To repeat an earlier observation, it had an appealing vocality to it that gave harmonica lines heft and emotion. If it had spring reverb, I would seriously consider acquiring one just for harmonica.

As much as I liked its sound for the jazz and harmonica roles, the Club isn’t for every one. A couple of days later, I plugged the SG into it in my living room. I can almost repeat what I wrote about the Lunchbox with the 335: I never found the sweet spot. To my ear, these two beasts should be kept in separate cages.

The Club is a mature musical instrument: it reflects conscious decisions made to achieve a “sound” without having to work around the physical limitations of the Lunchbox. The smaller amp, to me, had more novelty than utility. I could easily envision situations where I would be happy to have it at hand, but, despite its low price, it didn’t tempt me. The Club adds enough value that I could almost buy one. The tone has improved by rotating the emphasis from upper to middle midrange, making it practical for harmonica and seductive for the right electric guitar. If I played only jazz, this would be the killer amp for me. Its street price is less than I’ve ever paid for a new amplifier, making it particularly tempting. Its tradeoffs are not deal-breakers – I could be reasonably happy with this and an outboard reverb and my 335 and harmonica mic (but I may as well give away the SG).

Naturally, to be “reasonably happy” is not what electric guitarists aspire to, and this is where I part company with the Club and return to my Fender amplifiers. While a useful addition to my herd, it could never be the alpha male.

I’ll end this with a caveat similar to that concerning the Lunchbox: try before you buy. This is an amplifier with a decided character, and you, it and your guitar may or may not find mutual happiness. With the right guitar, and the right material, it sings. Final thoughts:

I expect my colleagues in this evaluation, who play regular jazz gigs, to love it unconditionally.

Taking into account the versatility afforded by the external speaker and headphone jacks this amplifier would be excellent for someone needing both a giggable powerhouse and a bedroom practice amp.

Portability would be sacrificed by hauling along another speaker cabinet, but the Club takes up about the same amount of space as a head-only amplifier, making it practical. I can imagine using the internal speaker as a stage monitor with an external cabinet to blast the dance floor.

Finally, its low price means that it’s within reach of a great many guitarists, making this product a potential hit.

Second Reviewer's Evaluation
by Jmrosett

I should start my review by mentioning that I've been using a ZT Lunchbox as my primary guitar amplifier since July 2009. I play an old (1948) Epiphone archtop with a floating pickup, which is prone to feedback. The 6.5" speaker in the Lunchbox really helps keep the low frequency feedback to a minimum. The Club, with its 12" speaker was a lot harder to control, so my stage use of the Club was limited to lap steel guitar, an instrument that I play as a member of a local Western Swing band.

For steel guitar, I found the Club to be pretty ideal. I have been playing through a 1965 Fender Bandmaster head and a 2 X 10" cabinet. It sounded okay, but the Club was much smoother sounding. I was very happy with the bass and treble controls, as opposed to the Lunchbox's single tone control, and even though I don't use a lot of reverb, I like having some, and the Club's reverb sounded fine. It was very easy to get a great tone from the amplifier.

I don't know if it's just the extra speaker size, the added tone control, or what, but the Club is easily twice as loud as the Lunchbox. I was playing with a 7 piece band, standing next to a pretty loud guitarist, and the Club was turned up about one third (I had the "volume" turned up all the way, and the "gain" at 1/3.) I like a fat, clean tone on steel, and the Club sounded just the way I wanted it to. My bandmates all commented on how good it sounded and a couple of people even commented on how much I've improved on the steel!

I played the Club in my home studio with the old Epiphone, a Stratocaster, a solid-body 5-string electric mandolin, and an acoustic mandolin with a passive piezo pickup. Like the Lunchbox, the Club was pretty worthless at amplifying the piezo pickup. It has a real midrange bite with those pickups that sounds just plain bad. Most amps designed for electric guitars are like that.

The 5-string mandolin sounded good, and the warm tone of the amp helped give it some depth. I think that people who play Stratocasters and Telecasters will like the Club more than the Lunchbox. I have never gotten a great sound out of the Lunchbox with a solid body guitar, but the Club sounded fine with my Strat. The Epiphone sounded wonderful at low volume, but the feedback kept me from turning it up very loud. It would probably work fine at low volume solo or duo gigs, but I wouldn't want to try it with a loud band.

When I received the Club, it had taken a pretty forceful hit to the back side, puncturing the box. I was worried but the amp was rock solid. This seems like a good indication of its road-worthiness. Still somehow, the case seems fragile, and I would want a bag of some kind to transport it. Even though it's approaching regular combo amp size (at least compared to the Lunchbox), it's still quite light weight and easy to carry.

I also thought about how it compares to the competition. The only amp that I've owned that I can compare it to (size, price) is a Peavey Classic 30. I prefer the Club to the Peavey hands down. It has a smoother, sweeter sound, more clean headroom, and it weighs less. I would recommend the Club to guitarists and steel guitarists who favor a cleaner, warmer sound and are tired of the hassles of tube amps.

The Lunchbox is a great tiny amp, and is a great tool for a lot of settings, but the Club is a real step up in terms of tone and clean headroom. Like the Lunchbox, the Club packs a whole lot into a pretty small box. I would buy one over most small tube combos that I can think of.

Third Reviewer's Evaluation
by Mr. Beaumont

FIRST IMPRESSIONS

As an original Lunchbox owner, the look of the Club was not surprising, nor was the build quality—from the outside, it’s as solid as it gets, and even knowing what to expect I was still surprised at the weight/size ratio. While it’s definitely light compared to most amplifiers, it’s still a bit of a surprise to pick up something so compact but with some mass.

ZT has kept many of the design elements the same, the metal grille, the slightly metallic gray MDF cabinet, the small, top mounted knobs. They’ve replaced the LB’s hard plastic handle with a softer, flexible handle that seems more than strong enough to carry the weight of the amplifier, and it’s also relatively comfortable on your hand when carrying the amplifier. The control panel features a two band EQ and actual reverb along with Gain and Volume knobs. Like on the original LB, it seems like it would have made more sense to have the Volume knob as the “accentuated” knob (via a cutaway and more “fingerspace” around it), but that’s a small concern since the controls are simple and there’s not an abundance of knobs that would make on stage tweaking confusing. Despite the larger space available for mounting the controls, the control panel is still small, as are the knobs, and they are packed closely together.

The power switch is located on the back, and rather low to the ground—a bit difficult to find just feeling around, I found I either needed to tip the amp towards me or physically look behind it to turn it on and off. A small complaint, but a design flaw nonetheless.

THE INITIAL PLUG IN: The Living Room

When an amp is as small and compact as the Club, despite it’s 200 watts of output boasting, it’s also tempting to check out the amp as a practice amplifier. I plugged in several guitars in my living room, and found a few interesting things about the Club at “home friendly” volumes.

First of all, it’s nice to have real reverb on this model, and while the reverb model on the Club won’t have anyone trading in their old fender tanks, it’s a very usable “Room” type reverb that really helps open the sound up a bit. It sounded best set low, to where it was barely noticeable as an effect.

The second thing you notice is, wow—it is loud. And it gets loud fast—but, unlike many SS amplifiers of this ilk, the volume knob is very smooth in the lower register—there’s no quick “jump” from barely audible to “too loud” that I’ve encountered on a lot of other amps. It’s a smooth transition, but “loud” does happen soon, and with the gain set about halfway up, things got too loud for home use at about 9 o’clock on the volume knob! The amp sounded better with the gain at least half way up, there was less audible noise, and the sound seemed “fuller” and “warmer.” I set the EQ knobs flat, dialed in a neighbor friendly volume, and proceeded to try out 2 Fender telecasters (one with single coil pickups, one with a neck humbucker) a Godin fifth avenue (neck position P90) a Kay K-1 archtop (with a DeArmond floating pickup) and a Yamaha Silent Guitar (nylon string model)

The consensus was reached quickly—the amp was pretty dull sounding with all the guitars. There was plenty of bass thump, which was a nice addition compared to the lunchbox, but the midrange hump I had come to expect and enjoy from the Lunchbox was not as pronounced, so the amp had little “cut” at low volume. With the Kay, which sported the floating DeArmond, the higher strings were barely audible without some drastic EQ tweaking, which then made chords sound brittle. The Godin fared only marginally better, with the teles sounding the best, but still not great. The Yamaha is an interesting beast, which likes few amplifiers, and I found the Club was no exception (conversely, the Yamaha loves the original lunchbox—it’s all about the midrange) Overall, the tone was comparable to a lot of lower end solid state amps, and was quite disappointing.

I was ready to write the Club off as a misfire from ZT, until…

Third Reviewer's Evaluation (continued)
by Mr. Beaumont

THE REAL TEST: On The Stage

Luckily, I was able to test out the Club in another environment, and the difference was night and day. Rehearsing with a four piece band in an empty 600 seat theater was a decidedly different environment than my living room, and the Club showed up to play.

I had been using the original Lunchbox in this same theater recently, so I had no worries about volume, and the Club delivered on that aspect easily—keeping up with a drummer, keyboards, and bass easily (the bassist and keyboardist both using amps that easily outweighed the Club by 3 times) But volume was not the only thing the Club did well.

First, the speaker moved some air! Stepping back from the band with a long cable, I was amazed at how well the sound spread out, easily audible at all points of the stage (whereas the drummer had previously requested I point the lunchbox towards him for un-mic’d rehearsals)

Furthermore, the tone difference from my living room was an incredibly nice surprise. Unlike many solid state amps that sound pretty much the same until very high volumes (where they usually sound like garbage) the Club sounds better the louder it gets. Another interesting feature—through a single coil pickup, at least, it stays quite clean, even as you crank the Gain knob. This meant that with the gain maxed, the sound was not a saturated distortion but rather like the grit of a tube amp being pushed right to the edge—a tone good enough that it inspired a little impromptu “Highway to Hell” jam. This would mean anybody needing a more distorted tone than that would have to use a pedal of some sort, but the ZT’s in general are very pedal friendly, and the Club seems to be no exception.

I am primarily a jazz player, and at stage volume, the Club makes a fine jazz amp—lots of presence, a nice flat tone that allows the character of the guitar to shine through, a subtle reverb that adds a nice bit of “ambiance” and plenty, and I mean plenty, of clean headroom. With the combination of that and the small package, I would definitely put this into the category of “good jazz gigging amps.”

IN THE END…

What you have here is a small, affordable, gig-ready package that weighs as little as many “practice” amps and takes up about as much space as well. I seem to want to focus on the phrase “gig ready,” as I really feel this amp shines when turned up—in fact, it doesn’t sound like anything special at all at “bedroom” volumes. It’s a genuine contender to the Henriksens and Polytones of the world, making up for what it lacks in tweakability in sheer power and convenience.

Possibly the Club’s biggest contender might be its little brother, the original Lunchbox. It’s the only thing smaller that has just as much usable volume (both get loud enough to where if you were actually playing that loud, the band had better be mic’d and put thru the house) and takes up as little space.

The Club makes three big improvements over the little Lunchbox, the inclusion of actual reverb, a more tweakable two band EQ, and the added bass from the bigger speaker—but with a lot of added weight, and compared to the LB, size as well. You won’t be popping the Club in a shoulder bag and running for a subway…

Which almost makes me wonder if ZT didn’t miss an opportunity—could the bass response have been increased with a 10” speaker to save some size and weight? What about an 8”? Could a two band EQ and a real reverb fit inside the original lunchbox? Or does this simply open the floor for more options and ZT products in the future?

Either way, this very happy original Lunchbox owner will strongly be considering a Club.

Fourth Reviewer's Evaluation
by Tom Karol

Background/Test Plan

I have been a part-time professional musician for more than 40 years. I have a smattering of recording studio experience, and I spent a brief amount of time working in consumer audio as well. I believe my hearing is still quite acute, but I suspect that its high end now tops out at no more than 14 kHz.

While I’ve owned about 20 different tube and solid state guitar amplifiers over the years, my only amp rig for all genres now consists of a stock Henriksen JazzAmp 112, with or without Henriksen’s outboard tweeter, and sometimes supplemented with a VOX ToneLab ST multi-effects unit.

My alternate/backup amp was a Roland Cube 60, an eminently gig-able amp and a great value, but I recently availed myself of an opportunity to trade it away advantageously. So, I actually need a new #2 amp. My requirements remain simple: As small and light as possible, ability to hold its own effortlessly in a variety of performing situations, satisfying standalone sound including good reverb with no external effects required, and a 12” speaker.

I had previously tested the ZT Lunchbox against the Cube 60. I will now be testing the ZT Club mostly in standalone mode. However, the Henriksen is my personal reference amplifier for superlative jazz tone – it doesn’t do much of anything else without help from the ToneLab – so I will evaluate the ZT Club’s ability to produce jazz tone in comparison to the Henriksen. It is only fair to note that the Henriksen JazzAmp 112 is 10 lbs. heavier than the ZT Club and sells for about twice the price.

I have 4 electric guitars:

1) A Crafter SEG480TMVS. This is a maple-bodied 335 clone. It’s a great budget jazz guitar. Since I only got it 10 days ago and have been playing it exclusively since then, I’ll start with this one.

2) A Crafter SA. This looks quite similar to a Taylor T5, but it’s actually a thin-line semi-hollow archtop with an acoustic bridge. It has a Kent Armstrong lipstick-style single-coil neck pickup and a Baggs piezo. It has onboard active EQ (bass, middle, and treble @ ±12db) and a slider to blend the magnetic and piezo pickups. Mixing just a bit of acoustic tonality into the mellow twang of the magnetic pickup yields a very good sound for solo and duo situations.

3) A Hamer T-51 (Tele clone) with Harmonic Design Vintage Plus pickups. These single-coil pickups are a bit hotter than normal Tele pickups with a touch of P90 character. It’s my rock/blues/country guitar, but it can do jazz quite well too.

4) A little Vagabond acoustic travel guitar which has a passive piezo pickup under the bridge saddle.

Testing will again be performed in my living room, a sonic environment very familiar to me (see Photos).

Results

Initial Impressions, Day 1:

This thing is as light and compact as seems physically possible for a 1-12” combo amp. It doesn’t look, sound, or work like any other amp with which I’m familiar. Initially the way it seemed to be voiced was very disconcerting – very heavy in the mid-bass and not much high end. Then I put it up on an upside-down plastic milk crate – its compact dimensions allow it to fit neatly. The tonal spectrum opened up dramatically. Lesson #1: Get the thing up off the floor (with one exception). The bass and treble controls now became effective.

Speaking of the floor, the noise floor seemed to be pretty high. But the instructions say that in order to keep the S/N ratio low, set the gain as high as possible (without distorting the signal – unless you want to; I generally didn’t want to) and then adjust the overall level with the volume knob. OK, better! By the way, there seems to be some kind of low-threshold noise gate always active.

Then there’s the (digital) reverb; it’s a bit weird. First of all its effect is pretty mild compared to the ubiquitous Hammond spring unit with which many are familiar. I generally set it on 5 (there’s 0-10 dot-scale on all the knobs, so that’s 12:00 O’clock), and it was still subtle. On a Fender-type amp, I usually set it on 3. And there’s also the character of it; I was under the impression that it would be a plate simulation (and maybe it is) but it sounds to me like a small room program. It’s not bad, mind you, but it just adds a bit of air to the sound without getting in the way. Even if you turn it way up, there’s surely no surf tone to be had here.

The last thing I’ll mention is that it makes a somewhat disturbing pop when you turn it off, but it’s not the only amp I’ve encountered that does that and I’ve been told that it’s nothing to be concerned about.

OK, so let’s get to it!

Fourth Reviewer's Evaluation (continued)
by Tom Karol

1a) Jazz with the Crafter SEG480TMVS:

I’ve been playing this through the Henriksen alone for the last 10 days. I’ve got it dialed in quite well. The neck pickup is a touch woofy in the deep bass, but I’ve been able to compensate nicely by turning the 100 Hz knob on the JazzAmp down just a bit. So, we’ll see how the ZT Club handles that issue.

I was able to get very satisfying balanced jazz tone, not as rich in the bass or as detailed in the mid-range or as fat in the high end as the Henriksen, but quite pleasing and gig-worthy just the same.
Amp settings (from left to right as the controls appear on the panel):
Reverb 5, Treble 5, Bass 2, Volume 3, Gain 5

Tomorrow, I’ll see if this guitar can do soul, blues, fusion, and stuff like that with the Club, which incidentally it doesn’t really do effectively with the Henriksen.

2) Solo with the Crafter SA (with the Henriksen Tweetey, optional):

This guitar is very amp friendly. It has onboard active EQ, so a wide spectrum of tonal variety can be dialed in from the guitar’s built-in pre-amp. It sounded quite alive through the Club – better, frankly, than I expected it to.

I decided to plug the Henriksen’s outboard tweeter (8 ohms, 75w, built-in crossover with level control) into the extension speaker jack; while not vital for a good sound, it did add some nice sparkle to the more acoustic flavored tonalities. This combination is eminently suitable for solo/duo background music gigs.
Settings:
Reverb 5, Treble 5, Bass 5, Volume 2, Gain 5

3a) Rock/Blues/Country with the T-51 without the ToneLab:

I’m not much of a distortion aficionado, but with the gain up to 8 I got some natural sounding breakup which I could clean up easily by rolling back the guitar’s volume knob a bit. Rolling the knob back a bit more yielded a solid clean rhythm sound. This is not my normal mode of operation, but I believe it is common among rock players using single channel amps without effects. The amp reacted responsively to changes in both the volume and tone controls on the guitar. Oh and by the way, this thing is loud! Settings:
Reverb 6, Treble 6, Bass 5, Volume 2, Gain 8

3b) Rock/Blues/Country with the T-51 with the ToneLab:

Again with the ‘Tele’, I hooked up the ToneLab. It has an output ‘character’ switch with settings of Vox, F, M, and Line (should be self-explanatory); I chose ‘F’ as being the one that sounded best. I have 10 user presets programmed for the Tele that have proven to be highly effective through a number of larger amps as well as direct to a PA.
The amp settings were as follows (all reverb provided by the ToneLab):
Reverb 0, Treble 5, Bass 5, Volume 3, Gain 5

It worked OK. But there seemed to be some occasional digital anomalies or something, almost as if the amp’s digital pre-amp sections were having trouble tracking the signals coming from the ToneLab. Or maybe my ears were getting fatigued, and it was auditory hallucination. Or maybe I just needed to back off on the ToneLab’s output volume a hair. Further experimentation is clearly warranted (tomorrow).

4) Vagabond Travel Guitar (with Henriksen Tweetey):
Being a little acoustic travel guitar with a passive under-the-saddle piezo, it doesn’t have much bottom end. So, I put the amp back on the floor for this test only. I got a balanced, but not full of character, generic A/E sound suitable for impromptu jams and sing-along’s. That’s all that could be reasonably expected.
Settings:
Reverb 6, Treble 3, Bass 7, Volume 1, Gain 7

Additional Impressions, Day 2:

1b) Soul, Blues, and Fusion with the Crafter SEG480TMVS (amp back up on the milk crate):

Not bad! With the guitar’s tone and volume controls wide open (not my normal setting for traditional Jazz tone, where I roll them all back to varying degrees) and the gain set so I’d get just a hint of breakup if I dug in, I got a useful zingy clean tone that wasn’t previously available to me. Frankly, I’d probably just use the T51 in these contexts; but this gives me another option, particularly if the electrical environment necessitated the use of humbuckers.
Settings:
Reverb 5, Treble 5, Bass 2, Volume 3, Gain 6

3c) Rock/Blues/Country with the T-51 with the ToneLab – further experimentation:

A simple fix: I backed off on the output level of the ToneLab a bit. That’s all I had to do. The sound became much more transparent and remained quite loud (note that the amp’s volume is still only on 3)!
Settings (same as before):
Reverb 0, Treble 5, Bass 5, Volume 3, Gain 5

Final Comments/Observations

If I were to get my own ZT Club (and I very well might like to) it would serve as my:

1) Primary Rock amp (usually with the ToneLab) – it’s certainly loud enough (did I mention that yet?)!

2) Grab-and-go rehearsal and multi-purpose jam amp (usually without the ToneLab) – a no brainer!

3) Backup/alternate Jazz & Solo/Duo amp – no excuses necessary!

I think I like the ZT Club better than the Cube 60 I used to own. Why? It’s smaller, lighter, louder, and it has a distinctive voice all its own. For its size, weight, and price – sorry, but I do have to throw those caveats in – I think it’s a really good (and really loud) amp.

Oh, and did I mention that this thing is LOUD!?

Technical Summary

Getting right to the point of the Club, older musicians will smile when they lift the amplifier for the first time. It's been decades since I was able to open the trunk of my automobile, lift out lightweight guitar (ES-330) and lightweight amplifier (GA-79RVT) then walk into a club to set up and play in one trip. That was my first thought when I unpacked the amplifier from its shipping container.

After removing the rear panel and disconnecting wiring harnesses I examined the interior of the amplifier. Some of the internal details were familiar from previous visual inspections conducted on the LB (Lunchbox). At first, I wasn't as impressed by the packaging details of this amplifier as I was by those of the LB. I thought about that as I re-assembled the amplifier, photographed it and set up the equipment required to test it. The following are my conclusions regarding the initial impression.

Because the size of the LB is considerably smaller than the Club I was predisposed toward the LB regarding layout and packaging. While inspecting the LB, I had in mind the proximity of various components to the loudspeaker and possible feedback problems. There are no components known to be microphonic in the amplifier but, in design engineering, the improbable frequently occurs. (I've often encountered microphonic capacitors, for example.)

I'm satisfied with that conclusion and I observed nothing in the Club packaging design that suggested that the amplifier hadn't received an appropriate amount of attention. I definitely liked the accessibility to various subassemblies within the amplifier (compared to the close quarters of the LB) as I unscrewed, removed, examined and replaced them.

The Club differs from little brother Lunchbox in obvious ways: cabinet size, increased weight, output power and speaker cone diameter. The Club also includes additional features such as expanded EQ (described later) and reverberation. Additionally there is a provision for effects send and receive - always desirable for noise considerations provided that the effects loop follows the preamplifier circuit. A low-noise preamplifier (and the Club has a good one, based on measurement) will minimize the noise of any circuits that follow it, at the cost of slightly increased distortion.

Volume and gain adjustments are the same as on the LB and so is the headphone output feature. The headphone output (as on the Lunchbox) is a fully functional line output. Line outputs are useful for connecting an amplifier to any device that requires faithful reproduction of the original signal over fairly long cable runs.

This configuration has been a personal favorite for many years: a small, lightweight amplifier - usually vacuum tube - with a line impedance output for sound reinforcement. I modified two of my more portable vacuum tube amplifiers to include this feature several decades ago. Perhaps we (the evaluators) paid insufficient attention to this point when reviewing the Lunchbox - just a thought.

The Club headphone output, because of its very low impedance (less than 50 ohms) is capable of driving both low impedance and high impedance loads. Note also that the headphone output has the same approximate EQ characteristics as the main output. This means no special EQ is required at the other end of the cable run - any PA input with a flat EQ is perfectly acceptable. The overall response can then be controlled by the amplifier EQ controls.

When we initially reviewed the Lunchbox, knowing that the Club was in the pipeline, it occurred to me that the smaller LB could be an obvious choice for a backup amplifier to the Club. But then, as I noted in the first review, I started considering some interesting implications of performing with both amplifiers, in the interest of either sound reinforcement or delay/chorus effects.

Should it be desirable to operate the Club with a satellite amplifier, ZT has provided an option. Both amplifiers include an auxiliary input that can be driven by an external source. The auxiliary input bypasses the preamplifier so the "gain" control doesn't affect its level; the "volume" control is used to adjust the level.

Surprisingly (to me), I couldn't find an EQ combination that produced a "flat" frequency response from the auxiliary input. This input seems to have the same "scooped" response as the main input and is probably intentional (e.g. to accommodate the internal loudspeaker response).

I don't care for this because, if the line out from another guitar amplifier was routed directly to this input, then the result would be a "double scooped" response and there are many instruments that wouldn't sound very good with this tonal adjustment, including some guitars.

My personal inclination would be a flat frequency response for the auxiliary if the input is to be used as a line in from another amplifier. Perhaps the original intention may have been provision for a CD player or the like (maybe for "break" music). Personally I see more value from the auxiliary port as the input for a "slaved" amplifier but that is a matter of opinion and how a user intends to operate the amplifier.

Discussing this with the Club designer, he suggested that the effects loop be used to drive an additional amplifier. That is certainly feasible but I really liked the headphone output for that purpose, because of its very low impedance (almost impervious to external noise and hum pickup) and the ability to adjust output level. Also, the effects loop would be unavailable for effects if used as a line output.

I tested the feasibility of the headphone output as line driver by connecting a 35 foot length ofcoaxial cable (Radio Shack or similar quality - characteristics unknown) to a high impedance load - which is the worst case for frequency response.

The insertion loss of the Radio Shack cable was about - 4 dB. A simple adjustment of the line out level (headphone volume) compensated for the loss and the adjustment is capable of much greater loss compensation. Bandwidth was about 8 kHz which is greater than the bandwidth required to reproduce guitar frequencies and their significant harmonics. (If the load was a line input, no frequency degradation would have been observed.)

"Single 12" amplifiers like the Fender "Deluxe Reverb" have been a mainstay for two generations of jazz guitarists in clubs and in studios. Characteristics of these amplifiers are simple enough: around 25 watts RMS output, reverb, light enough to be lifted in/out of an automobile trunk and carried to the venue - with guitar - in a single trip. (Sorry to repeat this observation but it's the total package of small size/light weight/high output power/modest cost that makes this product so appealing.)

I have no knowledge of the design goals of this amplifier. Most probably the origin was a synergy of the Lunchbox design and a vision of the next logical progression. Perhaps the previous paragraph entered into the calculation. That doesn't really matter; what does matter is how well the Club performs. My perspectives are those of experienced engineer and experienced user of vacuum tube and solid state amplifiers for many decades.

Technical Summary (continued)

I'd like to make a comment or two about how some important measurements are made. Guitarists aren't usually critical about parameters such as "noise figure" and "distortion" (especially distortion, since many guitarists intentionally adjust their amplification to produce it). But perhaps they should be - let's put a few things into perspective by expanding our understanding of the topics.

Every amplifier (even a hypothetically perfect one) produces noise. It's a fact that the universe is filled with the stuff and only by reducing absolute temperature and resistance to zero can we eliminate noise. The way that we describe amplifier noise is usually with a term called "noise figure", which will be described in a moment. For now, accept that noise power is similar to output power - i.e. +/- 3 dB difference in noise figure will equal either twice or one-half the amount of noise power audible at the amplifier output.

Concerning distortion: if you like it, fine. The most versatile and useful amplifier is one that is perfectly clean - zero distortion - but can be adjusted (internally or externally) to produce desirable tonal modifications, which might include distortion. Unless you KNOW that you'll never require "clean" amplification it's always best to start with the lowest possible distortion.

Like many of you, I play other instruments besides guitar. I prefer that my amplifiers have the flexibility to accommodate a reasonable variety of input characteristics. (There's little interest in distorted reproductions of woodwind, brass or acoustic stringed instruments, for example.) Although this may seem to be peripheral to the Club amplifier discussion, I include the following comments to support assertions that will be shortly proposed regarding low distortion amplification as a desirable baseline feature.

Prior to solid-state amplification, musicians often purchased (and reluctantly transported) large, overpowered vacuum tube amplifiers in order to obtain reasonable amounts of "headroom". The Fender "Twin" has been widely used, even in small venues, because the 85 watts RMS output power guaranteed clean amplification when playing at an effective output power level of perhaps 15 watts (maybe 30 to 40 watts, with a substantial horn section).

The way that noise figure and distortion - the two parameters that completely define dynamic range - are measured by amplifier manufacturers sometimes poses a dilemma in understanding. The following might illustrate why it's hard to compare the two most important specifications of an amplifier:

Best noise performance occurs with preamplifier gain at maximum and post amplification gain adjusted for the desired output volume level while distortion is ignored.

Best distortion performance occurs in exactly the opposite manner: post amplification gain is adjusted to maximum and preamplifier gain is adjusted for desired output volume level and noise is ignored.

These adjustments provide manufacturers with bragging rights for best noise figure and best distortion but neither condition represents a practical amplifier adjustment. And these measurements (because the amplifier controls have been changed) cannot be used to define dynamic range or headroom. If a potential buyer wants to compare the merits of two amplifiers it's usually not possible by comparing specifications even if the specifications were provided. (This is similar to the last ZT review where we discussed the impracticality of output power comparison from manufacturers who specify that parameter differently.)

Having made that point (I hope), please note that ALL of the measurements that follow were made with "flat" tone control settings and with preamplifier and post amplification gain levels set near mid-point. (When I write "flat", what I really mean is the "scooped" response that guitar amplifiers incorporate into internal EQ circuits for best magnetic pickup frequency response.) I believe that these conditions are a practical way to measure noise and distortion, not at arbitrary levels that assure best performance for each parameter but are not representative of actual performance situations.

After re-assembling the Club and taking photos, I lifted the amplifier up to my lab bench (with ridiculous ease), connected it to a signal generator and an external 8 ohm high power load then powered up the amplifier. The amplifier produced about 85 watts RMS (which would be characteristic of the Fender Twin discussed a moment ago) with some clipping visible on the oscilloscope. I backed down the drive level until the output waveform was below clipping level and made a measurement of distortion.

The measurement included harmonic distortion and A.C. line frequency harmonics out to 10 kHz. After correcting the measurement for the generator distortion, the total integrated amplifier distortion was approximately 0.25% at an RMS output power level of nearly 80 watts. And that is impressive. One-quarter of one percent TOTAL distortion !

As an amplifier heats from internal power dissipation, changes occur in the power supply that cause the output power to diminish over time. Most amplifiers have this characteristic; it's mainly related to transformer performance. I'm going to call the Club a 75 watt RMS amplifier because it will produce that amount of power over reasonable conditions of time and temperature. The power consumption of the amplifier at full output power was about 185 watts (18 watts consumption with no input signal applied).

During preliminary measurements, I noted a tendency toward instability. I've observed this in other amplifiers when tested in this measurement set-up although reasonable adjustments of gain/volume usually restored stability. The Club was more sensitive than other amplifiers tested and the test setup was modified because initial results were inconsistent. An explanation of the cause is provided in a footnote at the end of this section.

Looking over my personal amplifiers for a reasonable comparison with the Club, I excluded the Fender Twin/Fender Showman amplifiers for technological dissimilarity, although they are very close in output power levels. I chose to compare, instead, my favorite jazz guitar amplifier, the "Sunn Beta Lead". Please recall that this part of the amplifier evaluation doesn't include sonic qualities, only the technical performance parameters of the amplifier. Loudspeaker configuration and sound pressure level (SPL) performance are excluded.

Referring to the original sales receipt, I purchased this amplifier in 1981 for $561 U.S. which, adjusted for inflation, would now be $1,404. (The Sunn was purchased so that I could retire my Fender "Bassman", the hardest working amplifier that I've owned.) Although I'm very fond of vacuum tube amplifiers, this solid-state amplifier has always been my favorite for jazz - especially when high-volume chording is required and distortion is unacceptable.


Attachment 73936


This is a large, heavy amplifier; in fact my original manual and data package do not state the weight of the amplifier - perhaps from embarrassment? The "Beta" is the loudest amplifier that I've ever owned, including the Twin. The point being that the Beta is NOT a fair comparison with the Club - size, weight or cost so the measured results completely surprised me.

Technical Summary (continued)

Performing the identical measurement made to the Club and the same corrections for generator distortion, the Beta exhibited four times the distortion of the Club, both operating at nominal maximum output power levels with nominal control adjustment. The Beta was operating at an RMS power level of 100 watts. I noted earlier that the results surprised me but actually a better term might be "astounded me". I repeated both of the measurements to confirm accuracy.

(This doesn't imply that the Beta is a "distorted" amplifier, by any reasonable standard. The total integrated distortion over the audible frequency range is about 1% at 100 watts RMS output. I believe that the amplifier was originally specified at 0.25% total distortion, 100 watts RMS output. We must also recall that the loudspeaker characteristics are not included in the distortion characteristics.)

The next measurement was also surprising: "gain linearity". Gain linearity is related to distortion and specifically describes the ability of an amplifier to accurately reproduce input signal amplitude nuances (distortion and noise aren't included in the measurement). Gain linearity is also a pretty good indicator of dynamic range. A perfect amplifier would show zero gain variation (infinite dynamic range), regardless of the input drive level; obviously no such device exists. The point at which linearity comparisons are normally made is called the "1 dB compression point". This is defined as the level where the gain linearity deviates from a "flat" (linear) response by 1 decibel.

Dynamic range is a term used loosely - usually by audiophiles - to describe the performance of an amplifier with low distortion and low noise figure. Engineers define dynamic range as the difference (expressed in decibels) between the noise power produced by an amplifier and the output power at the 1 dB compression point (sometimes other distortion limits are used such as in "spurious-free dynamic range").

Common sense suggests that a guitarist could arrive at a similar definition after some thought. For example a guitarist might observe that the amplifier is useful within the amplitude range where neither noise nor distortion is a problem, fair enough? The difference, of course, is quantification of performance levels, which permits comparisons between amplifiers that don't depend upon the shortcomings of individual human hearing.

But why is dynamic range important? Because it is frequently desirable to emphasize certain passages of music by successively lowering (or increasing) volume levels while introducing or concluding a passage. An example might be a series of ascending triplets played in the concluding phrases of a solo, gradually building in amplitude (and hopefully, enhancing audience interest).

The following graphical information isn't specific to voltage or power levels - those formats aren't convenient for comparing amplifiers that aren't precisely equal in power. The data has been "normalized" to make comparison easier - all parameters are relative. The measurements were made by varying the input signal level by 30 dB while monitoring and storing the input signal and the amplified output signal. Amplifier controls were adjusted for nominal conditions.

This data is logarithmic in both axis.

Attachment 73937

For the Club at average control settings, the 1 dB compression point occurs at a relative input level of about -25 dBV (i.e. 25 decibels below 1 volt).

The same measurement performed on the Sunn amplifier:

Attachment 73938

The 1 dB compression point for this amplifier is -24.5 dBV, only 0.5 dB better than the Club.

This is the same test performed on a Fender Bassman vacuum tube amplifier:

Attachment 73939

The Bassman has a 1 dB compression point of -33 dBV.

In comparison with the two solid-state amplifiers, that's nearly 10 dB less dynamic range and consequently almost 10 dB of excessive and unintentional compression (and distortion). This limits accurate reproduction of transient responses and wide dynamic range passages. To be fair, the vacuum tube amplifier can still produce "listenable" single-note reproduction well past the 1 dB compression point. Chords at volume, however, would be out of the question because of intermodulation distortion - that's why I retired this amplifier and bought the Beta.

(It may be helpful to interpret these data by considering personal experiences of the two types of amplifiers, solid-state and vacuum tube. The two solid-state amplifiers reach saturation very quickly, once past the 1 dB compression point. However the vacuum tube amplifier compresses gracefully well past the 1 dB compression point. That's the reason that many guitarists - especially blues and rock musicians - prefer these amplifiers.)

I think that gain linearity is important and that's why I included these measurement results. I believe that linearity is especially appropriate for jazz musicians and those who are interested more in the sound of their instrument (which may not necessarily be a guitar) than the sound of their amplifier. This opinion is probably representative of a diminishing number of performers and that's neither good nor bad - it's just opinion.

Technical Summary (continued)

If the amplified (and modified) sound is most important to performers then full-body jazz guitars made in the traditional manner will eventually disappear from performances. Incidentally, a personal observation is that the opinion of listeners isn't significant in that regard. Most listeners - and frequently other guitarists - don't distinguish differences between low quality and higher quality instruments.

Obviously this isn't true of the performer - better results generally come from better instruments. I'm not suggesting that listeners lack the ability to distinguish differences. My opinion is that listeners expect musicians to interpret the musical experience. I hope that I'm making my thoughts clear and objective.

Compression and distortion masks uncertain technique: plectrum attack, "clams", hesitancy and timing errors, inadvertent unintentional "chords" (you didn't really mean to strike two strings instead of one). Strings of notes tend to blend together at a constant amplitude - errors aren't noticeable in a saturated, compressed and distorted environment. The ability to crescendo, for example, is mostly lost in that environment.

Skillful rock guitarists - even playing in distorted mode - find other ways to accomplish effects similar to the crescendo; if not in amplitude then in tempo or pitch manipulation. Pop/rock/metal music guitarists rip off long streams of triplets, at incredible speeds, through distorted and highly compressed amplifiers.

But we know that clean, linear amplification always reveals flaws in technique and always rewards those who master the basics and have clear, concise articulation. I'm not advocating a particular characteristic of amplification or of technique - jazz provides infinite avenues of expression, from Mahavishnu to Montgomery.

Many artists are capable of amazingly precise technique but live performances sometimes inhibit their technical expertise for reasons that we should understand. A small amount of amplifier compression or distortion can be useful to compensate for the exhaustion (and boredom from playing the same tunes for years) of a traveling musician.

I apologize for the seeming topic diversion - this may seem unimportant to some. My point was to make a recommendation for the flexibility of an amplifier that can be dialed in from "clean to mean". The "mean" part is fairly easy to obtain and the Club clearly does a great job of "clean". (Recall that these measurements exclude speaker contributions.)

Club tone controls are similar to many Fender vacuum tube amplifiers (e.g. Champ, Harvard, Princeton, Deluxe and Bassman). There is a variable treble control and a variable bass control. The mid-range response (the "scoop" - visible in most of the curves below) is fixed, as in the Fender amplifiers, and at the same mid-band frequency.

The following curves apply only to the Club amplifier and indicate the effect of the EQ controls at various settings. (The "normal" tone control position is with both adjustments set to midpoint.) Please note that both axis are logarithmic NOT linear. The "X" axis is frequency and the "Y" axis is amplitude in decibels. The measurement was made by passing white noise through the amplifier and digitally recording the output spectrum.

Attachment 73940

Attachment 73941

Attachment 73942

Attachment 73943


The bass frequency range has an adjustment range of about +/- 10 dB, which is quite a lot. The treble adjustment range is 5 dB total and some may find that limiting. The manufacturer probably has incorporated internal speaker frequency response compensation into the DSP programming which defines EQ performance. We obtain a more realistic idea of the effectiveness of the tone controls from the musical evaluators' responses.

In any event, the EQ allows 10 to 15 dB of bass-to-treble and treble-to-bass pre-emphasis and that suggests from personal experience that I'd be happy with the tonal flexibility and that my various instruments could be accomodated.

Let's move on to another major performance parameter. We've discussed noise figure, we'll discuss it again in a moment to confirm understanding of this important aspect of amplifier performance. I made noise measurements under full drive conditions, which isn't usual (most noise figure measurements are made under no-drive conditions). This was convenient for the test setup configuration but also for the consideration of signal-to-noise ratio. The maximum noise figure of the Club was about 4 dB and that is very good.

Results of the identical test performed on the Beta indicated that the maximum noise figure was the same as the Club. Because of the difference in RMS output power levels and compression, the Beta had an advantage in signal-to-noise ratio of 1.5 dB.

Considering this parameter, let's review and expand slightly the noise topic discussed earlier. Many musicians regard noise produced by an amplifier as an indication of a flawed design if the hiss "seems" excessive. It's not - noise is universal as previously noted. A perfect amplifier would still exhibit "hiss" in direct relationship to the amount of amplification or gain.

Noise figure is defined as the amount of excess noise produced by a "real" amplifier compared to the noise that a perfect amplifier would produce. This is usually expressed as a ratio, in decibels. Reviewing previous information, an amplifier with a 3 dB noise figure would have exactly twice as much audible noise power than a "perfect" amplifier.

My personal opinion is that, for guitar amplifiers with power levels around 25 watts, a noise figure of up to 10 dB is usually acceptable. Both of the above amplifiers meet that requirement after factoring increased gain and output power.

Technical Summary (continued)

Summarizing the performance of the two amplifiers:

Noise figure: equal for both amplifiers
1 dB compression point: favored the Beta by 0.5 dB
Output power: favored the Beta by 1 dB
Distortion: favored the Club by 0.75% (both amplifiers at their maximum output power level)

Ignoring sound qualities defined by the loudspeaker(s), it is clear that the little Club amplifier competes on near-equal footing with the very heavy, very expensive Beta amplifier, by Sunn. (The Sunn corporation hasn't existed for many years although their products are still widely respected.)

(Two other solid state amplifiers were also measured and compared during this exercise. They weren't included in the summary because they were not as similar to the Club as the Beta - in other words, performance was not comparable. Additionally, in the interest of abbreviating the summary, many data curves have been omitted. If there is specific interest in this information, it is archived and can be provided upon request.)

Test methods:

Many of the simple tests performed on audio amplifiers can be implemented with the use of a computer that includes a high quality sound card. Appropriate hardware/software combinations can provide useful input signals of arbitrary waveforms, noise spectra of various types and combinations of both. The computer can also be used to store the manner by which an amplifier reproduces these input signals. This is useful because post-processing input and output signals reveals subtle amounts of distortion and noise that would otherwise be difficult to detect.

Instability in the test amplifier occurred because the input and output ports of the test computer were adjacent and the small amount of coupling between the I/O ports was sufficient to cause amplifier feedback. The Club couldn't be operated at nominal volume and gain conditions without oscillation so some of the test procedures were modified. Separate external signal generators and noise generators were employed (while "recording" the amplifier output data with the computer) rather than using computer-generated input noise and signal waveforms.

Thank you very much for your generosity in producing these detailed extensive reviews. From earlier posts, I thought comparisons with Polytone (Mini Brute II ?) and Roland Cube 80X were planned. Is this still in the works or did you change your mind ? I have a Polytone MB II and I was looking carefully at a Cube 80X.

When we were evaluating the Lunchbox, I watched a couple of videos on my computer. I have the sound card patched into a "real" stereo rig in my office: the line-out is plugged into an input on a stereo receiver, which in turns feeds four two-way speakers and a sub-woofer. Even so, the sound was inferior: no doubt recorded via a camera's built-in mic, and ruthlessly compressed to get the audio and video to stream. I like to expand the video to fill the 19" screen on the computer, and, when I do so, the low quality is obvious through pixelation and jerky movement. The audio suffers the same problem as the video: what remains of the original sound after negotiating the limited frequency range of the recording mic, becomes squawky and coarse from the data compression algorithm. Speaking as a long-time recording musician, I have never been happy with the sound of mp3s at their best; as heard on computer-based sound clips, they may be at their worst, especially when they are sharing bandwidth with jumpy video.

In other words, the audio/video of the Lunchbox made me think it still had a lot to prove, for me to accept it as an amplifier I would use. And I believe that "sound clips" would suffer the same problem: without disrespecting the capabilities of my peers in this review, we would have at least four microphones choices, four signal chains, and four variations on the best way to EQ; all of these coming from four rooms with widely differing acoustic qualities.

The end result would be essentially useless, and my remark at the end of my evaluation section would still hold true: "This is an amplifier with a decided character, and you, it and your guitar may or may not find mutual happiness." Sound clips would not illuminate that statement any better.

medblues, I have a polytone MB III and a roland Cube 60, so I may be able to speak to that.

Both the Club and Polytone completely put the Cube under in both actual volume, "percieved" volume (how well it fills a stage or big room) and in sounding good as it gets turned up louder.

I would consider the Club as a viable contender to the Polytone. It does not color the midrange quite as much, IMHO (a thing I like about the Polytone, actually) and it is not quite as tweakable tone wise, but the built in reverb is a nice addition, something your MB II already has (assuming it still works;))

I'm truly debating buying a Club to have at least as a backup to my Polytone, which still gets top gig work for me...That said, my recent Kat acquisition sounds much better thru the original lunchbox and a henriksen head/ redstone cab combo I have, so if I gig that guitar, the Club would be third choice, at best.

Wow. Thanks for this. You're work here is pretty impressive. I'm assuming you guys sent the results to the manufacturer.

So .... What's the next thing up fro review? (don't stop now) :)

What has been posted here is just the tip of the iceberg - hundreds of pages of charts, data, temperature measurements, photographs and reports of what we noted about the amplifier are archived. Many of these have been provided to ZT during the course of the evaluation, both for their information and to make sure that I maintained the terms of the non-disclosure agreement with ZT - to THEIR satisfaction.

The original "Lunchbox" is in my posession and the "Club" is en route from Massachusetts to California. When it arrives here, both amplifiers and all peripheral gear provided by ZT will be packed up and shipped back to them. In the package will be a copy of a "final report" detailing pertinent measurements and observations made on the amplifiers.

As noted in the review introduction, ZT has been completely supportive of our efforts and appreciative of the time and expense involved. We believe that some of our suggestions are being considered for future product enhancement.

Thanks John, for your comments.

Returning briefly to the topic of sound clips. For the purpose of critical evaluation, unless standardized audio reproduction equipment was available to every reader of our review, sound clips are likely more harmful than beneficial (a point made by several team members in the above responses).

There was never a single suggestion/proposal of making a sound clip from any of the five team members over the past three months. The impracticality of the sound clip as a useful tool seemed obvious to all, I presume.

Good work, guys! If I were in the market for an amp (I'm not) I'd sure consider a ZT Club now, after reading all of the reports. It's very rare to read such objective and scientific reviews.

Where I live, it's not easy to try out very many different kinds of equipment. I was in the market for a small amp, and I'd read glowing but subjective reviews (and scathing dismissals) of two that got me interested: a Marshall Class 5 and a Princeton Reverb reissue. The local shop didn't have either, so I had to wait to try them out until I visited Toronto in December and January. Two completely opposite amps; I hated the sound of the Marshall, but loved the Princeton. When I got back home I ordered one through the local shop.

I was just thinking (always a risky proposition): If the little one was called, "The Lunchbox," shouldn't they have called the big one, "The Picnic Basket?"

Quote:

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Originally Posted by Tom Karol

I was just thinking (always a risky proposition): If the little one was called, "The Lunchbox," shouldn't they have called the big one, "The Picnic Basket?"

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Well, I heard there's a small extension cab for the lunchbox called "The Thermos" :D Kidding, bad humor :o

Well, I just tried the Club and the Lunchbox.

Made the mistake of trying the Club first, and after that, it was barely worth trying the Lunchbox. However, I didn't have my own guitar with me and I've learned that lesson once already, so I will go back after my upcoming holiday, and give it a proper try. My initial thoughts were...

If I can find a second-hand Henriksen, then I will have that and sell the Cube.

If not, then I will happily have a Club and sell the Cube. It may not have the modelling, channel switching, etc, but it has a great, truly clean sound for Jazz. Anything else I can add/change with pedals that I already possess.

I will keep my Vox for Rock or Blues and put up with the weight.

There, that was easy, wasn't it?

Thanks to all for doing the testing/reviewing and giving me the impetus to try out this amp.:)

I think you're on the right track!
After I got my Henriksen JazzAmp112, I sold my Cube60. The JazzAmp is great for everything, but it needs the VOX ToneLab ST to do Rock. However, I didn't want to trash the Henriksen on Rock gigs, and how can you have only one amp anyway?! So, when I tested the Club I knew I had the solution! (If cost was not an issue, I would have gotten a Henriksen BluesAmp 110 plus a matching extension cabinet to use with the ToneLab for Rock instead of the Club, but that configuration would cost 3 times what the Club sells for.)

Yep, absolutely. I don't do that many blues or rock gigs nowadays, but if it happens, I know the set-up that works for me. Which is another reason why I haven't sold the Strat.

But for jazz - I'm in negotiation for a Jazzamp at around $900 at current ROE. A new one will set me back £899 ($1,400). I have a certain amount of guilt already at owning a guitar that's much too good & valuable for my meagre abilities and even more meagre gig schedule, let alone adding the best part of a grand's worth of amp on top. And if I can't convince myself, how much more difficult to get that one by the long-suffering Mrs. Mango? :o :rolleyes: Not to mention the 2 kids I have to get through college sometime soon...;) :p

However, £399 ($630) for a Club..now that I can handle.

Can't answer your question directly, but I'll tell you this: The Club is noticeably louder than my Cube 60 was, and the Cube 60 was (just barely) able to hang with 3 other guitarists using a Hot Rod Deluxe, Hot Rod Deville, and a Marshall Half-Stack in a backyard barbeque jam a while back.

I've played live outdoors with the Club with a loud drummer, bass, keys, sax, and another guitarist plus vocals, and the Club wasn't even breathing hard.

The Club is probably capable of higher SPL than my Henriksen as well, though in the context in which I use it, I don't push the Henriksen very hard.

Anyway, unless you play at silly (to me) volumes, the Club has more than enough loudness (with headroom) for any situation. And it weighs 22 pounds!

P.S.: I think Randy measured frequency response at the speaker output with a dummy load.