making pedals louder

[ninjadave7]

hello friends,
On a pedal like a tubescreamer or rat, how would one go about raising the potential volume?  My question comes from this:  I find that if the gain control is low, then the volume has to be up to at least 2 o'clock before it's even unity, and then there isn't much left.  I could change the pot taper, but I don't think this would change how much volume the pedal has.  Is there a solution?

[jasperoosthoek]

That's different for every pedal. Quite possible for a fuzz face as the output is already attinuated. Just change the attinuation factor.

The tubescreamer cannot be made louder by replacing some resistor values. But what you can do is double the diode stack in the first opamp stage. So instead of two paralles back to back diodes take two or even three parallel diodes in series. Or replace them with LEDs which have a higher forward voltage but that will change how it sounds.

[Philippe]

Use a more powerful amplifier with a greater range of clean headroom.

[Mark Hammer]

Two approaches.  One is to add a single transistor or single op-amp "clean" gain stage on the output.  For instance, on the classic Big Muff Pi, the tone circuit eats up enough signal that the resulting output would be puny unless both Sustain and Volume controls were over 1 or 2 o'clock.  So EHX added a simple booster stage after the tone circuit.  Problem solved.

The other approach is to find a spot within the existing circuit where the gain can be usefully increased, and simply hike the gain.  Myself, I would not go tinkering with the gain of the clipping stage since diode-clipping operates in big steps, even though gain doesn't have to.  You could go with using a 2+2 diode arrangement and bumping the gain up, but there is no guarantee that yu will get the tone you had before with the output level you want.  I'm not saying it wil be a bad tone, but what you've asked fo is whatyuo have now, only louder, and that might not nail it.

Instead, my advice is to bump the gain up in the tone control stage.  Replace the 1k feedback resistor in the second op-amp with 2k2, 2k7, or maybe even 3k3, and see where that takes you.  That way you leave the clipping sound alone.

[ninjadave7]

thanks, I'll try changing the feedback resistor.  Out of curiosity, why does that work?

[oldschoolanalog]

Use knobs that go to "11".
Naturally, this just increases apparent/perceived loudness.

Seriously, putting an LPB (or similar) after anything will make it louder. One tranny & a couple of parts.
No problem.

[Mark Hammer]

thanks, I'll try changing the feedback resistor.  Out of curiosity, why does that work?

The gain of that stage is partly set by the value of the feedback resistance.  At present, it is set to provide just a wee bit of gain, such that the full treble and full bass settings will seem to have the same volume.  Bumping the value of the feedback resistor up may require you to use your volume control more when making tone adjustments.

Take a gander at Jack Orman's AMZ labnote on TS tone control options.  It'll explain how the circuit normally works, and you can try options from there.

[jasperoosthoek]

Instead, my advice is to bump the gain up in the tone control stage.  Replace the 1k feedback resistor in the second op-amp with 2k2, 2k7, or maybe even 3k3, and see where that takes you.  That way you leave the clipping sound alone.

That's what I thought too at first but I don't think changing the feedback resistor will just increase the gain without altering the sound as it is not a simple inverting opamp stage. The fact that the non-inverting input gets part of the signal tells me that the output is a contribution of both parts not equally changed by the feedback resistor. The signal on the non-inverting input will appear on the output regardless of the feedback resistor while it will affect the signal on the inverting side.

Please correct me if I'm wrong .

[Gurner]

Use a more powerful amplifier with a greater range of clean headroom.

Re using a more powerful amplifier - It's a guitar pedal not a guitar amp.

a greater range of clean headroom.

That won't make his pedal louder ...more 'clean headroom' (vs dirty headroom?  )  will simply allow the signal a clearer passage through the pedal without distortion (but the OP is talking about distortion pedals anywayl!)

[Mark Hammer]

Instead, my advice is to bump the gain up in the tone control stage.  Replace the 1k feedback resistor in the second op-amp with 2k2, 2k7, or maybe even 3k3, and see where that takes you.  That way you leave the clipping sound alone.

That's what I thought too at first but I don't think changing the feedback resistor will just increase the gain without altering the sound as it is not a simple inverting opamp stage. The fact that the non-inverting input gets part of the signal tells me that the output is a contribution of both parts not equally changed by the feedback resistor. The signal on the non-inverting input will appear on the output regardless of the feedback resistor while it will affect the signal on the inverting side.

Please correct me if I'm wrong .

Well, you're right AND you're wrong.
Changing that feedback resistor will alter the gain because that stage is configured as a non-inverting gain stage.  The gain of that stage is set by the feedback resistance,and the sum of the 220R resistor to ground and whatever portion of the tone pot lies between the cap and the inverting pin of the op amp.  When the tone control is set to full treble, the gain of that stage is [1k+220R]/220R or 5.45, starting around 3.3khz.  That sounds awfully high, but remember that its preceded by the lowpass filter formed by the 1k/.22uf network, which rolls off above 720hz, so things work out in the end.   Look at the AMZ page on TS-9 tone controls for a more indepth story: http://www.muzique.com/lab/tstone.htm

Changing the 1k feedback resistor to 2k2, will mean that, at full treble, the stage will have a gain of 11x, instead of 5.45, though still at the same boost-point as before.  With the  tone control set a bit lower than that, the gain increase will not be quite as noticeable.  If, say, there is 5k of pot resistance between the .22uf cap and the inverting pin, the the gain of that tone stage becomes [2k2+5k+220R]/[5k+220R] or  1.42, compared to 1.19 in the stock unit.  The ASMZ article will provide some good guidelines and ideas for what to tweak in the way of component values in order to attain decent tone control, but also squeeze some usable gain out of that second op-amp.

[jasperoosthoek]

Changing that feedback resistor will alter the gain because that stage is configured as a non-inverting gain stage. 

That's about what I said : It will increase the gain but more stuff will happen that will change the tone.

Part of the gain equation is increased and another part in a different frequency rang is unchanged meaning that it will change how it sounds. And you said that changing the amount of clipping diodes would change the tone. In theory doubling diode stages will only increase the overall gain by 6dB and nothing else. But then the clipping part of the TS seems to defy theory altogether...