Amp tweaking, talk to me

[Christian Miller]

If you view adjusting simple levels as hocus pocus, you're not very smart. We're playing jazz with a bassy sound and some detail on top lol. Set the mids to medium and adjust the bass and treble to taste, will work every time. If there are other parameters like presence or master volume, I don't view those as insurmountable obstacles.

a jazz tone shouldn’t be bassy. Unless there’s no bass, in which case knock yourself out. If you do have a bass, they might knock you out :-)

[JCat]

The tone stack explained in English for humans:

The guitar amp. Why does one control seem to alter what another one does? Why does the mids knob affect volume? And why is the treble pot more like a blend control? Because they’re connected in ways we could not intuit.

After searching repeatedly for a layperson’s explanation of the tone stack – the EQ section found in guitar amps – I realized one would not be forthcoming. There seemed to be two camps: guitarists, who, despite an adorable belief that the three knobs do what the labels suggest, have no understanding of it; and amp builders, who understand it too well and talk to each other in Martian.

This is it.

Thanks Litterick!
I have now read the article on the FMV tonestack ("used by Fender, Marshall, Vox and the hundreds that followed in their footsteps"). Here's a short summary:

• The Treble control is a balance control. It balances the mix of the highest frequencies relative to the lower. Meaning that when Treble is reduced, it makes room for Bass and Mids. It doesn't boost anything, It can only reduce treble frequencies so that more of the lower frequency content can be heard. The Bass and Mid pot settings affect the Treble cutoff frequency , basically meaning that Treble is controlled not only by the Treble pot, but also by tweaking Bass and Mids. Note: This is not a simple matter of balancing sound energy (reducing one makes room for the others), but a direct consequence of the technical implementation; Bass and Mids settings control the balance point of the Treble control and what content is supposed to fall under "Treble".
• The Bass control is straight forward, in that it directly determines how much of the bass content will be shunted to ground, where signals are sent to die. However, the Mid control setting determines what content is supposed to fall under "Bass".
• The Mid knob controls the volume of the signal leaving the tone stack and thereby the output volume. In addition it has the ability to shunt some of the mid range frequencies to ground. But when rolling back the Mid knob, it will simultaneously kill some of the bass and treble that will leak to ground together with the unwanted mids. And then, the amp gets noticeably quieter because almost every range of sound it makes is being diverted to ground. "This is scientific proof that a person that aggressively scoops out his Mids is confused by tone and tries to avoid as much of it as possible."

It's obvious to me, that no human being is capable of operating such tonestacks with consistent results. The interactivity could be compared to a primitive form of life, like predicting the whereabouts of an amoeba. ("While several hypotheses have been proposed to explain the mechanism of amoeboid movement, its exact mechanisms are not yet well understood.")*

I will go out on a limb here and make the following claim:

There are amps that, for no other reason than being equipped with a 3-knob tonestack, cannot be dialed in for a decent tone. Then those knobs are but bells and whistles that forfeits its purpose.

*(Amoeboid movement is the most common mode of locomotion in eukaryotic cells. It is a crawling-like type of movement accomplished by protrusion of cytoplasm of the cell involving the formation of pseudopodia ("false-feet") and posterior uropods.)

[Tal_175]

^ Yes, the Fender tone stack is basically a mix between graphic and parametric EQ. Actually it's even more complicated than that since the volume control also interacts with the tone stack. You set the EQ to what you like, if increase the volume, then your EQ is changed again. Also all these controls interact with the later stages of the amp.

[JCat]

^ Yes, the Fender tone stack is basically a mix between graphic and parametric EQ. Actually it's even more complicated than that since the volume control also interacts with the tone stack. You set the EQ to what you like, if increase the volume, then your EQ is changed again. Also all these controls interact with the later stages of the amp.

Thanks Tal, very good summary.

The tonestack is a simple network of high- and low pass RC-filters (Resistors and Capacitors). Behavior is determined by component values, carefully tried out by the designer. If these values are changed, the range of each knob and the way they interact will change.

Guitar players understand the importance of guitar electronics and that there's a significant difference between 300k and 500k guitar Volume pots for humbuckers. What many don't know is that a "500k pot" is sometimes closer to 400k, because there's a +/- 20% tolerance.

A traditional amp potentiometer is not much different from a guitar pot. And the actual value of a resistor or a cap is also a matter of tolerances and component drift.

Some designs and specs are clearly more robust than others, still not two amps of the same model are identical.

[mhch]

This thread reminds me of the chasing of "That Sound"..
This expression means "The sound of the lead guitar in that British guitar band named The Shadows", as used by Hank Marvin, a very specific sound with quite a bit of reverb.

During the early sixties many folks got involved in playing the guitar from listening to the records of that band, lots of amateur similar group tried to play that music, myself included. Most of them ended up sounding muddy, the lead guitar sound being a bit drown in the overall sound, even if playing the proper Fender Stratocaster instrument

A number of people invested a lot into finding how "That Sound" had been created, many failed to find out the how.
A few very experienced folks having a lot of electronics and sound recording experience recently identified a few tech tracks and came up with several ideas and relatively good imitation, thanks to the modern electronics and computer based analysis tools. They still continue these explorations. By the way, none of the Shadows Band players ever disclosed anything

- a specific low pass filter had been added to the Vox amp to eliminate low frequencies (36db/octave !)
- to compensate for the loss of the corresponding low frequency energy, the medium frequencies were boosted quite a bit
- higher frequencies were also filtered out
- some folks even conjectured that the lead guitar was plugged int the two inputs of the Vox amp, each having different circuitry behind it, low frequencies (< 1200 Hz) on one side, the higher frequencies on the other side.
Subtle sound variations can be obtained by using the volume knobs of each circuit.

On top of that of course came the tricks performed by the reording engineers with their studio equipment, reverb units and the likes.

Sorry for being a bit off thread, but the similarity between the quests of "That Sound" and the "Jazz Guitar"sound strikes me ! So I wrote this for the fun

[Franz 1997]

a jazz tone shouldn’t be bassy. Unless there’s no bass, in which case knock yourself out. If you do have a bass, they might knock you out :-)

It's not that simple; if a "jazz tone' has NO bass, it will sound clanky and thin ( unless you're playing gypsy..). The top string fundamental is right in the middle of the 'low mid' are at around 300 hz. This is partly covered by the bass control, and not at all by the treble - so you can turn down the treble all you like, but the top will still sound thin with NO bass. It's more a question of how much bass you have to add to stop that top-string thinness. Fender amps have their many charms, they are cool, and I have owned most that Fender have made, including the Princeton. But they are far from ideal for jazz, because Leo wanted them to have that big mid- scoop.

Anyway, upright basses aren't bassy

Best plan with a Princeton to get a fat sound without too much bass is to add a speaker that emphasises lower mids. Or find an old Polytone, or get a Hendriksen with graphic eq.

[Litterick]

I will go out on a limb here and make the following claim:

There are amps that, for no other reason than being equipped with a 3-knob tonestack, cannot be dialed in for a decent tone. Then those knobs are but bells and whistles that forfeits its purpose.

The knobs can be turned to adjust the tone, but it would be folly to approach the amp with a particular tone in mind. The sweet spot does not exist.

[citizenk74]

The knobs can be turned to adjust the tone, but it would be folly to approach the amp with a particular tone in mind. The sweet spot does not exist.

From That Pedal Show: "What is a good lead sound? One that can be heard."

The sweet spot exists, but it is ephemeral - always changing in context. But on a good night you can chase it into your corner for a while and ride it like the wind, which is also moving air.

[pauln]

For those that would like to experiment, here is a nice tone stack model. It has the particular versions for different amps, lets you set the controls and view the frequency graph, and if you know some electronics you can change the values of components in the modeled circuit to see the effect as well.

TSC

It looks like this:



Hours of fun!

[Gary J]

After years of tone-tweaking and knob-twisting, push-pulling my old Boogie Mk IV controls, I sold it. Full disclosure: The amp sounded fantastic, and over the years I learned its sweet spot. The reason for the sale was mostly due to its weight, fewer gigs...and my age.

I recently discovered the purity of Leo Fender's original amps, and bought one of Fender's updated 5e3 amps, a 57 Custom Deluxe. For me the head version was all I needed since I have a variety of speaker cabs to plug it into.

Three knobs (2 Volume & 1 Tone) plus four inputs are all I need. I wish I had tried this earlier.

100%. I have this 22-watt version for more headroom and volume, and of course it's also perfect for rock and blues



I turn this on with mids rolled all the way down the tilt at 12:00 when I want a more blackface tone:



Super simple, two great tones.

[Gitfiddler]

100%. I have this 22-watt version for more headroom and volume, and of course it's also perfect for rock and blues



I turn this on with mids rolled all the way down the tilt at 12:00 when I want a more blackface tone:



Super simple, two great tones.

I've read great reviews on Little Walter amps. Glad you dig yours.

[sicourtjon]

Hi,

I think for jazz guitar all you really need is the three basic parametric eq. Controls: bass, middle and treble and maybe a splash of reverb, after all, the old traditional players had this combination to produce some classic 'trad' tones.

A while ago I decided to change my amps to simpler smaller clean only sounding combo amps with minimal controls. I ended up with a lovely DV Mark 12.....sorted!

To get the amp sweet spot (for any amp with the sound eminating from a speaker) I have used the following method for any venue, valve or solid state amp with success:
Turn all tone controls B, M, T to zero or off.
Select neck pick up.
Play an open E major chord and turn the Bass control sweeping it around its travel until you hear a noticeable difference i.e, where it seems to 'kick in' and leave it set there.
Now select the neck and bridge pick up position. Now play an open A major chord and repeat the procedure for the Mid control.
Thirdly, select the bridge pick up position. Now play an open D major chord and repeat the procedure for the Treble control.
Finally, adjust your volume control.
Usually, I have my guitar volume and tone controls on 10 but playing jazz, I now find I play around with them a bit more.

I would suggest with the multi knob amp you have, turn all the other ones/functions off. Keep it simple. The less knob tweaking you do the more playing you will do. If I am playing through my DV Mark 12 amp I never touch it. Mainly though at home I use an Electro Harmonix headphone amp and JVC in ear headphones....very clean and just has one volume knob.

[Litterick]

• The resistance of the treble pot only affects the ‘treble filter’.
• The resistance of the bass pot affects the ‘bass filter’ and the ‘treble filter’.
• The resistance of the mid pot, last in the chain, affects all three.

Here. If you adjust the mid, it will affect the bass.

[JCat]

(Dude tweaks a Blues Jr)..."and that's how I find the best tone possible from any amp". (+730 000 views, +12 000 likes)

• The method below suggests that any amp has one tone that is universally "the best".
• This method ignores tonestack and volume interactivity (It's like telling the user to surrender before he's begun; don't even try).
• This method puts the tone deep down in a mid-scoop, where the guitar fundamentals drown in tubby bass and sibilant highs, which possibly qualifies as the worst tone possible (unless you belong to the 98% of the community that plays Country & Western and Rock n' Roll).

[sgosnell]

I haven't watched the video, and don't plan to, but I think that's a reasonable starting point, depending on the amp. I don't know what amp is in use there. For a Fender/copy, I agree with you. For an amp with a Baxandall tone stack, that's close to flat, and flat is where I start. Jimmy Bruno has said that he starts by turning the amp up very loud, far louder than he will play, guitar tone full open, volume full closed, amp flat, and increases the guitar volume until it's loud enough. He may roll the tone off just a little if it's much too bright, but not much. Doesn't adjust the amp. His tone sounds fine to me, and it's usually very close to the same. He likes Henrikson solid-state though, seldom plays a Fender, so I don't know how he would approach those.