Turning off tone controls on amp while maxing volume ?

[Tomm Williams]

I've seen this technique discussed here and there but not a great deal. I tried it last night with one of my amps and it sounded quite good. Now this amp sounds really good anyway so I'm not certain I accomplished anything different. I guess the advantage is driving the tubes harder ? Anyone care to comment about this ?

[1001gear]

Some Boogies have a "boost" function that just bypasses the tone stack. Or do you mean turning down all the knobs and diming the gain?

[Tomm Williams]

I'm referring to turning down the tone controls (treble and bass) and then achieving the desired volume with the volume control. Of course with the tones off, it becomes necessary to drive the volume higher to achieve the desired results. Any adjustments in tone would then be made though sparsely to avoid having to turn the volume control back down ( much)

[onelife]

The older Fender amplifiers with a midrange control will not pass signal through the tone stack with the tone controlls turned all the way down.

[Tomm Williams]

And I've only tried this with one amp as mentioned. While it did seem to drive the tubes harder, I'm not sold that it was some great discovery. I spend an awful lot of time messing with my amps and pedals looking for subtle changes. I think sometimes I might get a bit carried away.

[onelife]

Some amplifiers have the tone controls before the overdive (my preference) while others have them after.

 

In the first case, the tone controls would affect the overdrive in a manner similar to that of the gain control while placing the tone controls after the overdrive affects the overdrive more like the master volume would.

 

What particular amplifier were you experimenting with?

[Tomm Williams]

I tried it on a '66 Ampeg Gemini II. It worked just fine but not sure it was a big difference from a more normal approach. I also had the Accordian channels jumped.

[WRGKMC]

Most amps tone stacks cut frequencies. If you want to hear how the preamp and power amp actually sounds you simply max them all out.

 

All you do by turning the EQ's down is to remove frequency responses using simple band pass/block filtering using caps.

 

A well designed EQ will use an LRC circuit using a cap resistor and a coil. Amps don't normally use coils, just caps and resistors so their band cutting is essentially broad and overlaps quite a bit. A Graphic EQ often uses coils with the caps and resistors to get higher Q to the frequencies being cut or boosted. Some of your most revered EQ's had no preamps. They were 100% passive and would cut gain quite a bit because they had no additional preamplification. (one reason +4db is used with professional gear because its a hotter line level signal)

 

Having the preamp before or after can make tonal changes. Most amps have at least one gain stage before the tone stack. Feeding weak guitar signal through a passive EQ before amplification just wouldn't work very well because the signal is too weak to get caps to pass a signal very well.

 

Marshalls use 2~3 gain stages before the tone stack.

 

Vox places its tone stack after the 3rd/4th stages on many amps. Vox had some amps that used a three way mid control called MRB (mid range boost) (listen to the end of the Beatles - Back in the USSR and you'll hear this effect being used like a 3 tone wah wah.

 

It was essentially a Varitone circuit used by Gibson that included three different caps and a coil to get the frequencies to peak. Unlike Gibson who used this circuit in guitars, Vox placed it later in the amp circuit. The guitar signal would already be driving before it hits this mid circuits and to me it has a much better tone that way.

 

This kind of leads into how various wah pedals work too. Some have the coil and caps early in the circuit or have wider/milder bands, Some boost the signal more before the filter circuit.

 

Most Fenders have the tone stack after the first gain stage. I suspect, because the signal gain is lower when placed there, the caps consume more of the signal and produce a darker tone because of this, giving you a brown sound.

 

Ampeg has some strange ones, as do companies like Sunn. The V2 I used to own had Treble and Bass after the second stage - Midrange was placed between the 5th and 6th tube stages using a Toroidal Transformer for the three way Midrange switch and the pot would boost or cut these frequencies leaving the tone flat in the center.

 

The coil would produce narrow bands of midrange boost/cut this way, much like a wah or Graphic EQ do. This is one amp that is an exception to most amps cutting frequencies. It used a multi staged, multi staged tube specifically for boosting the midrange tones so the amp actually boosted or cut midrange tones.

 

The Gemini is more like a Marshall having the tone stack after the second gain stage.

 

Having two gain stages before the tone stack has its benefits. It ensures the signal stays stronger and often makes for a more potent EQ sweep. String touch tends to remain constant too. Fenders tend to become less dynamic to string attack as you cut treble and bass.

 

I'd suspect turning the EQ down on an Gemini would cut gain to the power amp and make the signal hit the power amp more lightly. If you like that tone, you might want to try 5751 preamp tubes instead of 12AX7's. I do this in my Marshall to reduce the gain channel a bit.

[Mikeo]

I have a Dr Z Maz 18 with reverb and the eq mod bypass. The sound is a bit dark to me in the bypass mode, but in a good way.