question about increasing volume of Pedalpcb Mantle Fuzz

[snow123]

hey, I recently built a PedalPcb Mantle Fuzz and found it to be too quiet (even when the volume is maxed, its still a little bit below unity), and I found it to not have as much gain as I would like, and after doing some probing I realized that before R16 and R17 (like while probing lugs 1 and 3 on the blend pot), the fuzz/octave effect has some more gain, and is much louder. so I'm thinking that lowering the value of R16 and R17 should fix the issue, would that be correct?

[PRR]

https://www.pedalpcb.com/product/mantlefuzz/
https://www.pedalpcb.com/docs/Mantle.pdf

[snow123]

https://www.pedalpcb.com/product/mantlefuzz/
https://www.pedalpcb.com/docs/Mantle.pdf

?

[snow123]

these are the 2 resistors im talking about:

[bluebunny]

?

Paul was posting the schematic, which you neglected to include.  Not much we can do without it.  "R16 and R17" is meaningless, as is a layout.

[snow123]

?

Paul was posting the schematic, which you neglected to include.  Not much we can do without it.  "R16 and R17" is meaningless, as is a layout.

Ooooh, ok. I'm talking about R16 and R17 on the schematic.

[antonis]

so I'm thinking that lowering the value of R16 and R17 should fix the issue, would that be correct?

Better try with 100k OUT pot

[Gargantula]

R16 and R17 look like a voltage divider, so I don't think changing them would make any difference. I think Antonis is probably on the right track though, changing the value of the volume pot would probably help but I'm not sure how much. Replacing resistors on the board comes with the chance of burning off a pad though, so I wouldn't try anything like that until you get a definitive answer from someone who knows better than I do, but replacing a pot is easy enough.

[PRR]

There's heaps of gain and not much loss. I'm thinking assembly error.

What is the voltage across C7? Idle, and when playing?

[idy]

It is an MXR Blue Box, and there are threads complaining of low output on those. One mod is to remove/switch the final 10n cap, C9. Will also be brighter and rougher.

try searching blue box low output. Sometimes (maybe?)google search leads you to more threads here than the built in search.

[snow123]

There's heaps of gain and not much loss. I'm thinking assembly error.

What is the voltage across C7? Idle, and when playing?

when idle, im only getting 0v to .2v, but occasionally ill get 2.5v to 3.2v.

edit: now (when idle) im getting anything in between 0.1v to 4.0v.

[snow123]

There's heaps of gain and not much loss. I'm thinking assembly error.

well the fuzz part of it just sounds dark and pretty low gain with not much definition.

[snow123]

There's heaps of gain and not much loss. I'm thinking assembly error.

What is the voltage across C7? Idle, and when playing?

when idle, im only getting 0v to .2v, but occasionally ill get 2.5v to 3.2v.

edit: now (when idle) im getting anything in between 0.1v to 4.0v.

and when playing, the positive side fluctuates in between 3.5v-5.2v.
and i dont get anything on the negative side since its grounded.

[Vivek]

Has the schematic mixed up the inverting and noninverting pins on IC 1.2 ?



Hope I read the schematic properly

[snow123]

Has the schematic mixed up the inverting and noninverting pins on IC 1.2 ?



Hope I read the schematic properly

nope, i just checked the tonepad schematic and its the same way.

[Vivek]

Oh, IC1.2 a comparator, not a linear gain stage !!

Which means it will swing from rail to rail even with a very small input signal.

That could lead to a lot of spurious signals !!

Are D1, D2 and near by components some kind of a noise gate ?

[ElectricDruid]

Are D1, D2 and near by components some kind of a noise gate ?

In a manner of speaking, yes.

I think that part is an envelope follower, generating a basic half-wave rectified envelope signal across C7. This envelope signal is then used as the collector voltage for the two transistors Q2 and Q3. Q2 is switched on and off at the input frequency. Q3 is switched on and off at a frequency two octaves lower, by the looks of it. So instead of getting a fixed voltage level switched on or off, we get an envelope signal switched on or off - e.g. we get some DYNAMICS!!! oooohhh!!

A side effect of this is that the envelope will hopefully die down to close to zero by the time that the fuzz and flip-flop tracking goes wayward, so we might lose that "splattery" decay that this type of pedal is prone to. And we also gate out any noise since the envelope will go down close to zero with no signal coming in, so even massive gain within the circuit shouldn't be noisy.

*I think*. I haven't analysed it closely, but that's my reading of it. Corrections welcomed.

[iainpunk]

well, IC1.2 is actually a Schmidt trigger, so its gating to begin with, although the threshold is quite low considering the gain stage in front of it. the threshold is about 0.044v above and below Vb

cheers

[ElectricDruid]

well, IC1.2 is actually a Schmidt trigger, so its gating to begin with, although the threshold is quite low considering the gain stage in front of it. the threshold is about 0.044v above and below Vb

Yes, that's true - there shouldn't be a bad noise problem.

There are two basic problems with this type of comparator-style fuzz though: You lose all the dynamics completely, even more than you would with high-gain fuzz, and you tend to get that spattery decay as the sound dies away and goes intermittantly above and below whatever threshold is involved. This modulating-the-square-waves-with-an-envelope method is a way of dealing with those two problems.

[snow123]

can anyone help me with the issue tho?