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  1. #1

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    There's so little inside a Polytone Minbrute. Mini indeed..

    There's so little inside a Polytone Minbrute-poly_tone_mini_brute_preamp-jpg
    Preamp


    There's so little inside a Polytone Minbrute-mini_brute_preamp-jpg
    Power Amp
    Last edited by GuyBoden; 06-04-2015 at 05:46 PM. Reason: Sorry, no link. No preamp.
    “I will not let anyone walk through my mind with their dirty feet.”
    ― Mahatma Gandhi

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    The Jazz Guitar Chord Dictionary
     
  3. #2

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    so little, i can't even see it..

  4. #3

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    Are you just looking at the preamp? In the bottom of the cabinet there is a power amp. The power amp is a pretty standard, well-designed amplifier. The preamplifier (in the top) is also a fairly standard and well-designed circuit. The entire circuit was modeled after a circuit that first appeared in Popular Electronics back in the 1960s. I think it may have been a monophonic version of the "Tiger" amplifier circuit that appeared in 1967.

    Polytone amplifiers have always been quite well made amps. They were designed for the professional market. If they had an Achilles heel, it would be the Molex connectors used to couple the preamp and power amp circuits. Molex connectors are notorious for corroding when they get even slightly damp--humidity is enough to make them become intermittent. Secondly, the reverb tanks on the Polytones can get damaged--their isn't much isolation between the tank and the cabinet. The tumbling that a Polytone can take in the trunk of a car is enough to make _some_ reverbs go south. (Mine have always worked, though.) Finally, some of the early, first-generation ICs that Polytone used in the preamp circuit have been known to let moisture into the circuits through the legs. Some of those ICs have begun to fail. Not all of them, by any means, but some of the amps that were stored in basements or other damp environments have become unreliable. Too bad, because the IC--popular in the 70s--is now long out of production. It is a simple op-amp circuit. It can be substituted, but not with a direct, pin-to-pin replacement. What has to happen is that you make what is called a "dead bug" repair. You epoxy a smaller op amp, upside down, on top of an IC plug in adapter that has the right number of pins as the original IC. Then you make small wire connections from the new op amp legs to the correct legs of the IC adapter. Plug it into the preamp and you are back into business. The whole mess looks like a dead bug, hence the name. It is ugly, but it is a viable fix. (Some people complain that the new ICs aren't as gritty and noisy as the old ones.)

    You will note when you look inside of a Polytone cabinet that the entire thing is well baffled with fiberglas. Try not to get that on your skin or breath any loose fibers. It's not asbestos, to be sure, but we don't really know what loose glass fibers do to your innards.

    Meanwhile, enjoy your Polytone amplifiers. They are great amplifiers.
    There's so little inside a Polytone Minbrute-polytone-mini-brute-jpg
    Last edited by Greentone; 06-04-2015 at 03:58 PM.

  5. #4

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    I can see a power amp now...

  6. #5

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    Quote Originally Posted by GuyBoden View Post
    There's so little inside a Polytone Minbrute Preamp. Mini indeed..

    There's so little inside a Polytone Minbrute-mini_brute_preamp-jpg
    That's the underside of the Polytone Mini Brute _power amp_. You are correct...there are not that many discrete components in it. There are about as many as there are in a Fender Twin Reverb power amp, minus an output transformer. Everything is miniaturized, of course, because of the use of transistors instead of tubes.

  7. #6

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    I wish somebody would recreate the classic polytone like they do with all the boutique Fender & Marshall knockoffs. It would simplify the tone search for lots of jazz players . . .

  8. #7

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    I have given this a lot of thought. I used to make boutique Fender and Marshall knockoffs. I have been thinking about resurrecting a "Polytone-ish" amp. Almost certainly I will make myself one or two, just to see how they will sound. Everything looks very straight ahead, to me.

    I believe I will begin with the Baby Brute--my favorite--then build a "II." That was always a popular amp. OTOH, I think an amp with a cabinet the size of the III/IV, but a 12" driver might sound really great.

  9. #8

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    I've been looking at this part of the Polytone's Tone Stack/Preamp (See below), and thinking that maybe I could put it into a pedal. Then plug the pedal into my power amp.



    There's so little inside a Polytone Minbrute-poly_tone_mini_brute_tone_stack-jpg
    Last edited by GuyBoden; 06-04-2015 at 04:29 PM.
    “I will not let anyone walk through my mind with their dirty feet.”
    ― Mahatma Gandhi

  10. #9

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    I've got a diamond tolex 1x12 minibrute -- very nice tone on many setttings.
    Only thing lacking for my tonal bliss is reverb!

    I would love a baby brute.
    A newly designed baby brute with "the tone" plus line out & digital reverb would be ideal IMO.
    I'd buy one

  11. #10

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    Quote Originally Posted by GuyBoden View Post
    I've been looking at this part of the Polytone's Tone Stack/Preamp (See below), and thinking that maybe I could put it into a pedal. Then plug the pedal into my power amp.



    There's so little inside a Polytone Minbrute-poly_tone_mini_brute_tone_stack-jpg


    I have actually been trying to do this for a while. I am having trouble finding a builder to go through with the project.

  12. #11

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    Quote Originally Posted by vintagelove View Post
    I have actually been trying to do this for a while. I am having trouble finding a builder to go through with the project.

    In my opinion, I don't think it would be a difficult task for a good Pedal builder to build the Polytone's ToneStack/preamp into a pedal, if you gave them the schematic:

    Polytone schematics.
    POLYTONE SERVICE INFO


    “I will not let anyone walk through my mind with their dirty feet.”
    ― Mahatma Gandhi

  13. #12

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    I'll be building this in a few weeks, I'm interested in the sound of Baxandall tone stack and using the RC4558 opamp for a preamp, I will keep you posted.





    Last edited by GuyBoden; 06-04-2015 at 05:47 PM.
    “I will not let anyone walk through my mind with their dirty feet.”
    ― Mahatma Gandhi

  14. #13

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    An old forum member, real eletronics wizard, gave me his Polytone pedal project files and a friend of mine is building me it. It's based on the old pre-sonic circuit Polytones and I went with OPA2134 op amps - I will post when I have it. I would love to share the files but I don't have his permission and he's not replying private messages any more!

  15. #14

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    Quote Originally Posted by vintagelove View Post
    I have actually been trying to do this for a while. I am having trouble finding a builder to go through with the project.
    If I get permission from the forum member I can give you the files and / or the contact of a Portuguese guy who will do it and ship anywhere in the world.
    Last edited by jorgemg1984; 06-04-2015 at 07:34 PM.

  16. #15

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    +1 on the bandaxall EQ!

  17. #16

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    For people interested in Baxandal Eqs - comemrcially available there's the RC Booster, Fromel Shape EQ, most acoustic guitar preamps, Barber Linden EQ, VFE Rocket EQ, etc.. The Fromel is brilliant but lacks a volume control (I moded mine to have it).

  18. #17

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    Could it be possible to make a tube amp version of that circuit? I have always thought that Polytones are the most tube amp sounding solid state amps I have heard. With real tubes the sound could rise to the next level!
    The Polytone pedal is wild idea too, I am most interested in it!
    I have a 70's Mini Brute IV and I think that an essential part of the sound is the "impossible" 15" speaker in that small cabinet.
    Interesting amps anyway.

  19. #18

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    Ampegs are Baxandal preamps with tubes... and I bet you could do that with Polytones too.

    I think I have his e-mail, if he's fine with it I will share the files!

  20. #19

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    Quote Originally Posted by Longways to Go View Post
    I wish somebody would recreate the classic polytone like they do with all the boutique Fender & Marshall knockoffs. It would simplify the tone search for lots of jazz players . . .
    Funny cause I have never played a pre 80's polytone that I cared about in the slightest.

    I prefer the 90's ones.

  21. #20

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    Mambos kind of resemble Polytones, a though they have their differences.

  22. #21

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    Quote Originally Posted by jorgemg1984 View Post
    If I get permission from the forum member I can give you the files and / or the contact of a Portuguese guy who will do it and ship anywhere in the world.

    I would appreciate that. I would really like to work with an engineer as I have a couple changes that will be necessary for it to work best.

  23. #22

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    For anyone who missed it a few years back....

    Polytone Fun!

  24. #23

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    Anyone know if the Mambo amp has a Baxandall EQ?
    “I will not let anyone walk through my mind with their dirty feet.”
    ― Mahatma Gandhi

  25. #24

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    It does.

  26. #25

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  27. #26
    Quote Originally Posted by Longways to Go View Post
    I wish somebody would recreate the classic polytone like they do with all the boutique Fender & Marshall knockoffs. It would simplify the tone search for lots of jazz players . . .
    NOOOOOOOOOO. They should couple the preamp to a 300w class D power amp . Then you'd have a great jazz amp with tone controls in the right place and decent headroom. Even the minibrain is underpowered with a loud drummer.

    Nowadays, the 300w class D poweramp will weigh less than 10oz

  28. #27

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    It would sound different.

  29. #28

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    That's a YESSSSSSSS !! JZ. I totally agree with you (for once!) I couldn't care less about historical accuracy -- only good sound & reliability.

    big class D power with a polytone pre-amp -- 8", 10", 12", 15" speaker options -- maybe some lightweight neo speakers too? Yum.

    of course, I'd want my reverb, too

    probably too cool to work in the real world though.
    It would most likely get mucked up on the way to production by the bean-counters . . .

  30. #29

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    Quote Originally Posted by Greentone View Post
    It would sound different.
    I disagree. I have a poly baby brute that Jon Shaw modded with a 180w class D power amp. Sounds the same for all practical purposes; the only difference is that it's now giggable in louder settings, even with the 8" speaker. I can't see why you say it would sound different, if just replacing the power amp.

  31. #30

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    Aside from the electronics, part of the character of a polytone amp came from the speakers.
    I would love to hear if you know of any speakers which sound same/similar to the original polytone speakers.
    I bought a broken polytone just for its speaker. I am using it as a cabinate. It has an Eminence made speaker in it.
    I also had a made in China speaker that is used in the more recent polytone. The two do sound very similar.

    Thanks

  32. #31
    it's funny that folks are waxing poetic about the polytones. In the late '70s my dad was friend's with herb ellis' and barney kessel's agent. I got to drive them around whenever they played at the annapolis inn. I remember them both saying how they hated the tone of the polytones but loved the weight.

    Now folks wax poetic about the glorious sound of polytone. I remember them being tubby and with no headroom. Very grainy sounding, broke up easily and not good with a loud drummer.

  33. #32

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    Quote Originally Posted by jzucker View Post
    it's funny that folks are waxing poetic about the polytones. In the late '70s my dad was friend's with herb ellis' and barney kessel's agent. I got to drive them around whenever they played at the annapolis inn. I remember them both saying how they hated the tone of the polytones but loved the weight.

    Now folks wax poetic about the glorious sound of polytone. I remember them being tubby and with no headroom. Very grainy sounding, broke up easily and not good with a loud drummer.

    Dont forget, those folks grew up with the holy grails of amps, super reverbs, twins, tweeds, etc etc... Hard to go from the holy grail, to a little ss amp. It is still worth noting, even though many didn't love the sound of their polytone..... They still used them.


    Most people sadly don't have the experience with those amps now. I know I am not dragging my sr anywhere, even if it does sound better than the polytone. That being said, polytones are still in my opinion, the classic dark jazz tone, warts and all.

  34. #33
    i can't agree with that. None of the classic jazz tones in history were done with polytones! The tone joe pass got after he switched to polytone compared to his tone on the catch me and joy spring? fuggedaboutit!

  35. #34

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    Quote Originally Posted by jzucker View Post
    i can't agree with that. None of the classic jazz tones in history were done with polytones! The tone joe pass got after he switched to polytone compared to his tone on the catch me and joy spring? fuggedaboutit!

    You either have the classic fender tube sound (really tmb tonestack sound), or the dark ss sound, which there is no better example of then a polytone.

    My ears tend to like fender, my back tends to like polytone.

  36. #35
    none of the jazz guys from the '60s/'70s era that I talked to liked polytone's sound. Pass, Ellis, Kessel, Roberts, Martino though they all liked the portability. Benson got some good sounds out of one for a couple of his albums but he was running in stereo with a tube amp. The combination of the tubes and solid state makes for a really fat tone.

  37. #36

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    People in the 70's -80's used Polytones because they were convenient.

    People in the 90's-00's used Polytones because their heroes used them and they actually grew to dig the sound.

    People in the '10's use Mambos and Henriksens because the Polytone idea has been shrunk and beefed up in power.

    Says this Polytone owner/lover. They're still damn good...at what they do.
    Jeff Matz, Jazz Guitar:
    http://www.youtube.com/user/jeffreymatz

    "Jazz is like life...it goes on longer than you think, and as soon as you're like 'oh, I get it,' it ends."

    --The Ghost of Duke Ellington

  38. #37

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    I've always liked the dark and grainy sound of older Polytones and would pick one up if the price and timing were right -- they just don't show up in Australia that often. Importing one and rewiring the transformer is an option though. I remember Emily Remler said in an interview in the mid-80s that although she had used her Mini Brute for several years and loved the portability it only sounded 'okay' and her favourite sound was from a Fender Twin. However, she couldn't lift a Twin.

  39. #38

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    Jim Hall seemed to like the Polytone sound, although I vastly preferred his tone with the P90 in his ES-175 and his GA-50.

  40. #39

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    Guys...I gigged with an 80s MB II last night and will be using a 90s MB III tonight for a jazz bass gig. The 75 to 100 watt constraints are not a big deal in comparison to the tone. Are drummers that insensitive? (Not the ones that I play with.)

  41. #40
    Quote Originally Posted by Greentone View Post
    Guys...I gigged with an 80s MB II last night and will be using a 90s MB III tonight for a jazz bass gig. The 75 to 100 watt constraints are not a big deal in comparison to the tone. Are drummers that insensitive? (Not the ones that I play with.)
    if you freelance and/or play with a drummer who likes elvin or tony or tain they will be loud. Like 100db loud. Guys who never have problems with feedback or who use 60w amps need not apply.

    It also depends on whether you are playing jazz gigs as a featured jazz group or just playing background music. When the cleveland bop stop was around, the gigs got really loud but it was a listening club. At nighttown, it's more of a dinner club so the drummers are restrained.

    Ask Paul Bollenback or Randy Johnston how a polytone works with Tain!

  42. #41

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    Quote Originally Posted by jzucker View Post
    if you freelance and/or play with a drummer who likes elvin or tony or tain they will be loud. Like 100db loud. Guys who never have problems with feedback or who use 60w amps need not apply.

    It also depends on whether you are playing jazz gigs as a featured jazz group or just playing background music. When the cleveland bop stop was around, the gigs got really loud but it was a listening club. At nighttown, it's more of a dinner club so the drummers are restrained.

    Ask Paul Bollenback or Randy Johnston how a polytone works with Tain!

    I would ASSume most of these gigs where you are not background music, have a sound system and capability to mic an amp, no?

    Second, my minibrute iv is pretty damn loud. Certainly louder than I would be able to use with a hollow body without massive feedback. Certainly louder than a piano or other acoustic instrument. Which brings me back to point 1.

    Lastly, if you are playing a setting where massive volume is required, bring a twin reverb and make everyone within a thousand feet pay for your back pain!!!

  43. #42

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    I owned 6 mini brutes, 2 from the 70's, 1 from the 80's and three from the 2000's (with the sonic circuit). Until Rich Raezer brought his cabinets to the market, I thought Polytone was it. Great jazz guitar sound with save your back portability. that said, I found Polytones to lack headroom and to be unreliable. Cabinet rattle, reverb tank failure, speaker failure and even electronic component failure all took place on the six Polytone combos that I owned. I think that we have better choices today. You can no longer buy a Polytone speaker today ( an integral part of the sound IMO) and I am not so sure that cloning the circuit or making a Polytone pedal will get that classic sound.

    Many of the existing vintage Polytones have replacement speakers and other components and no longer sound like the originals.

    Along with Fender, the Polytone amp sound is a classic jazz tone. I have a 2008 Polytone Mini Brain that I use as a backup for my Acoustic Image Clarus. I do like the spring reverb in the Polytone better than the digital reverb in the Clarus, but the Clarus is lighter, more reliable, has more clean headroom etc.

    For sheer portability, the AER Compact 60 beats the Polytone hands down.

    For Tone and relability, the AI/RE combo beats the Polytone hands down.

    A Fender Tube amp is the standard that Polytone was after. Vintage examples of Fender Tube amps are available and rebuildable ( if you want to carry them)

    For all their faults, I have fond memories of my Polytone combo amps, but I have moved on. If somone ressurects Polytones with a more reliable build, I would welcome that as an additional choice.
    _____________________________________________
    "When the chord changes, you should change" Joe Pass

  44. #43

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    Agreed. There was a period when I wouldn't consider showing up without a Twin Reverb. Nobody try to tell me that a Twin and a Polytone are comparable because the wattages match. In practice, I have to say that a Polytone is half as loud.

    Still, I used to gig with a drummer who learned by sitting in front of Elvin and Tony every night in NYC. He was later in a band with Jaco. Still, the guy is sensitive and can be heard over with a Deluxe Reverb. Been there.

    Oh, I tired of the loud gigs and stopped taking them. I don't mind a big band at full, acoustic cry, but I prefer not to play jazz at rock volumes.

    I guess in Wonka land I'm Grandpa Joe, not Charlie.

  45. #44

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    This reminds me, you can get a massive volume boost out of a polytone by hitting the front with a boost or eq pedal. Btw if you haven't played with an eq pedal and a polytone, you may be surprised.

  46. #45

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    Quote Originally Posted by Stringswinger View Post
    I owned 6 mini brutes, 2 from the 70's, 1 from the 80's and three from the 2000's (with the sonic circuit). Until Rich Raezer brought his cabinets to the market, I thought Polytone was it. Great jazz guitar sound with save your back portability. that said, I found Polytones to lack headroom and to be unreliable. Cabinet rattle, reverb tank failure, speaker failure and even electronic component failure all took place on the six Polytone combos that I owned. I think that we have better choices today. You can no longer buy a Polytone speaker today ( an integral part of the sound IMO) and I am not so sure that cloning the circuit or making a Polytone pedal will get that classic sound.

    Many of the existing vintage Polytones have replacement speakers and other components and no longer sound like the originals.

    Along with Fender, the Polytone amp sound is a classic jazz tone. I have a 2008 Polytone Mini Brain that I use as a backup for my Acoustic Image Clarus. I do like the spring reverb in the Polytone better than the digital reverb in the Clarus, but the Clarus is lighter, more reliable, has more clean headroom etc.

    For sheer portability, the AER Compact 60 beats the Polytone hands down.

    For Tone and relability, the AI/RE combo beats the Polytone hands down.

    A Fender Tube amp is the standard that Polytone was after. Vintage examples of Fender Tube amps are available and rebuildable ( if you want to carry them)

    For all their faults, I have fond memories of my Polytone combo amps, but I have moved on. If somone ressurects Polytones with a more reliable build, I would welcome that as an additional choice.

    to your point about reliability, your comparing amps that are 35 years old with amps that are new. Have a good tech recap and tighten up the insides, replace the reverb tank while your in there. You will be good for another 35 years.

  47. #46

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    Quote Originally Posted by GuyBoden View Post
    I've been looking at this part of the Polytone's Tone Stack/Preamp (See below), and thinking that maybe I could put it into a pedal. Then plug the pedal into my power amp.
    Quote Originally Posted by jzucker View Post
    NOOOOOOOOOO. They should couple the preamp to a 300w class D power amp . Then you'd have a great jazz amp with tone controls in the right place and decent headroom. Even the minibrain is underpowered with a loud drummer.

    Nowadays, the 300w class D poweramp will weigh less than 10oz

    Yes, Jack, I think we're in agreement, that's exactly why I'm building the preamp.

    I'm sorting out the cap values for the three pots in the Baxandall tone stack.

    Treble about 5000Hz
    Mid about 500Hz
    Bass about 100Hz
    “I will not let anyone walk through my mind with their dirty feet.”
    ― Mahatma Gandhi

  48. #47
    Quote Originally Posted by vintagelove View Post
    I would ASSume most of these gigs where you are not background music, have a sound system and capability to mic an amp, no?

    Second, my minibrute iv is pretty damn loud. Certainly louder than I would be able to use with a hollow body without massive feedback. Certainly louder than a piano or other acoustic instrument. Which brings me back to point 1.

    Lastly, if you are playing a setting where massive volume is required, bring a twin reverb and make everyone within a thousand feet pay for your back pain!!!
    There are a few but in most of the clubs around here and in DC, the band provides their own mix. I'm not sure about the IV but the mini brain wasn't clean enough even with 2x12" 4 ohm cab.

    Also, remember that some of us play fusion and other styles, not just standards. I've been to plenty of gigs where a twin didn't have enough headroom. Twins have great headroom with a strat but bring a hollowbody with .014 strings and it's a different story. Again, dinner club 50w is fine. But not always.

  49. #48
    also, i'm not necessarily talking volume. I'm talking pure clean tone. The ability to play above a loud band hitting block chords and/or octaves and not having any distortion. There's a reason benson uses a hot rod deluxe *AND* a polytone even when he's mic'd at a concert setting. It's important to have that loud presence on stage. Get the mix right on the bandstand. It's impossible to play when you're not loud enough onstage even if it can be fixed in the mix. At least that's my experience.

    I'm not a beginner. I've been gigging for 40 years.

  50. #49

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    re: hitting the Polytone with an equalizer--here is the one I used to use:
    There's so little inside a Polytone Minbrute-mxr-10-band-jpg
    No wall wart! Built-in AC power supply.

    jzucker: you are correct about the MiniBrain not being that clean. None of the Polytones are particularly clean. There is something about the old, first-generation preamp ICs that is a little gritty (and noisy). The grit is, in part, what folks were going for with _that_ sound. Generally, when you modernize the preamp ICs to lower the noise floor, you lose the grit.

    People complain about the newer Polytone amps not having the soul of the older ones. What they are actually complaining about is Gumina and company switching over to modern ICs in the preamp--the old ones were no longer available. They sound too clean.

    However, if you want the 21st century "hi-fi" guitar sound, you should probably go with the AI--pristine preamp/high-power, class-D power amp. It's a completely different philosophy. Gumina was intending the MiniBrute to be worked HARD--3-ohm load, and all that. Those 300-watt, class-D amps are loafing, most of the time.

  51. #50
    the grit is *NOT* what folks were going for. Definitely not true. I was using polytone amps in the early '70s . My dad was one of the first polytone users in DC. I can tell you that *NONE* of the guys using them in our area wanted grit. They all wanted a lightweight, clean amplifier for club-dates. That's what the amp was invented for. Maybe years later, folks waxed poetic about the sins and wanted the newer amps to have the sins of the old but I can tell you that none of the guys I played with wanted a grainy tone. Just about every polytone player I knew hated that and tried replacing the speakers to get it to be cleaner.

    I guess you can talk about vintage transistor tone in the same way we talk about vintage tube tone but none of the guys I knew wanted that.