What is the standard gain to obtain with a volume potentiometer?

[savethewhales]

Hey!

I have this frequency response from a circuit I'm doing, with the volume potentiometer on maximum, plus a feedback resistor. Is that peak gain of 6dB enough for most pedals? Or I'm going the wrong way and it's needed more gain?


Thanks in advance.

[merlinb]

A buffer has unity gain. A distortion pedal could have a gain in the hundreds of thousands... depends what you're doing.

[antonis]

Secret circuit, Volume pot setting Gain with frequency responce by its own, a graph with "imaginary" 6db peak gain - only these..?? 

You have to admit you could make it much more obscure, couldn't you..??

[Mark Hammer]

I agree with Antonis.  We need a little more information from you in order to provide a useful reply to your question.

[savethewhales]

You guys are right about the obscurity.

Here is the circuit:



So I'm designing a phaser pedal (the phasing stages are just like the phase 90) and I wouldn't actually know what would be a normal gain for a phaser pedal (but I wanted the gain to have a "boost" with the volume potentiometer on maximum, or tturned all the way around, as well as have a "boost" on gain with the feedback resistor, which is switched).

As I'm thinking, phaser pedals should (or it's common) have 0 dB gain?

[merlinb]

6dB sounds fine for some clean boost

[antonis]

Things are made clearer now.. 
(You name "Volume" an actually Gain pot..)

>As I'm thinking, phaser pedals should (or it's common) have 0 dB gain? <

It depends on every particular circuit..
MXR Phase 90, for example, has a feedback resistor in some versions (replaced by a pot in later vesions), giving some boost (up to distortion level) where former versions haven't..

IMHO, a phaser shouldn't need any "boost" other that for recovering in-out impedance attenuation..
(in the mean of it should be a badly designed circuit..)

[savethewhales]

Ok. Nice! I guess you guys are right, maybe I'll take advantage of the 25k pot I have and use it to make a "feedback/ressonace" pot, which if turned all the way up, gives a boost of approximately 6dB,if turned all the way down, the Vout has 0dB gain.

Thanks!

[Mark Hammer]

One of the reasons why phasers generally have unity-gain output is because FETs can distort when pushed too hard.    You may have seen schematics in which there is a network of components linking the drain and gate of FETs (as in the MXR Phase 45).  This network provides some immunity from FET distortion, although I was given to understand that in the absence of that network, distortion rises gradually, and has a more sudden onset (albeit at a higher threshold) when the network is used.

Susceptibility to FET distortion is a matter of input level, and any gain-stages feeding the phase-shift stages.  One can always keep the signal level feeding the phase-shift stages modest, and simply add gain on the mixer/output stage.  The problem is that such added gain would simply amplify any accumulated noise in the phase-shift stages.  Indeed, if one has ever tinkered with higher feedback/resonance settings, you likely found a noticeable increase in noise levels...UNLESS a feedback cap was inserted into one of the phase-shift stages to filter out higher-frequency content.

Optical phase-shifters won't experience any of the distortion inherent to using FETs as the control element, but neither will those phase-shift stages be resolutely hiss-free.

So, there is a logic to why one tends not to see much increment to signal level in phasers.  I'm sure that some phasers somewhere do it, but it entails some audible risk that needs managing.  And that can complicate design. not to mention increasing production costs.