Master Fuzz - low volume

[Spark_Trooper84]

Hey all,
I just got done with the Master Fuzz board.

Just a quick question that I don't think I've seen asked here from searching.

This thing really drives down the overall volume.

While playing it's output is easily half or more of any other pedal I've built. To get a decent volume in my signal chain, I have to run it before my built of the Parentheses board and run the Boost circuit from it.

Thing is, I don't really love the effect with the fuzz and volume pots cranked, but I can't really get a great volume out of it without them pushed up and without using the boost circuit from the parentheses pedal.
But, that has other issues for when I don't have the pedal on and am wanting to switch from it to another on the fly (like blowing out my ears while practicing).

The issues remains whether or not I'm running it as part of the signal chain on my board, or on its own.
It's getting power from an isolated supply on one of the 9v 300mA outputs.

Is this just a normal thing, or what's going on?

I built the Carbon Black fuzz PedalPCB board a while back and had similar issues (among other things).
So, is it just a fuzz thing?

 

[Betty Wont]

You should be at unity volume after noon on the volume pot. And the Carbon Black gets plenty loud. Some vintage fuzzes were not designed to boost, but most should.

 

[Spark_Trooper84]

You should be at unity volume after noon on the volume pot. And the Carbon Black gets plenty loud. Some vintage fuzzes were not designed to boost, but most shoul

Yeah,
It doesn't even reach unity at full volume, kinda far from it.

At half volume, it's barely half of unity, maybe even a quarter.

There's also a bit of a shrill circuit noise when the tone switch is in the down position.

Might take the audio probe to it later today and see where the volume is going.

Just wanted to check if anyone else had the same trouble and had a known fix

 

[Spark_Trooper84]

ok
I've audio probed the circuit and have some more data.

I have relatively normal (unity) volume up until C9. in the locations I have circled green, i have basically unity volume.
In the locations I have circled in red, I have half or less than half unity volume, and it remains that way all the way to the potentiometers.

The volume pot affects no increase in volume past around 9-10 oclock on the dial.

The cap in place for C9 is a 1nf box film, as the PCB calls for.

Could this cap, or the value, be wrong or bad?

As for the circuit noise,
That's apparently coming from my power supply situation on the board.
On the workbench, running off a 9v battery (9v jack pigtail) there is no circuit noise.

 

[pricklyrobot]

Is the volume any different depending where the Tone switch is set?
Because it looks like one position of the toggle would be bypassing the whole section where your circles are.

 

[Spark_Trooper84]

Is the volume any different depending where the Tone switch is set?
Because it looks like one position of the toggle would be bypassing the whole section where your circles are.

no difference in volume depending on the tone switch.

Further probing and playing gives me this.
The green circled areas are basically unity
The orange is maybe half that, the red maybe half that again.
on leg three of Q5, it amplifies back up to around where green is all the way to output.
so, the 2N3904 at Q5 seems to be doing it's job just fine and the lowered volume while probing before it is just how the circuit works.

That said
I may have misspoke earlier about not having volume unity completely.
It seems like the biggest issue is really that after about 1/4 turn on the volume pot, I get no noticable change in volume at all.
I'd say it stops just shy of unity, and just remains there.
it seems that maybe I have a bum pot?
I don't relish the idea of unsoldering it to really test it.
but, while testing it on the multimeter in circuit, the volume pot between legs 1 & 2, at full down i get 0.0 ohms and 78.5 kohms at full volume up, about 45 in the approximate middle

Between legs 2 & 3, at full down i get 80.1 kohms and 0.0 at full up and about 45 at the approximate middle.

Between 1 & 3, 80.2 at full down and 78.5 at full up

I would at least expect going over unity past noon on the volume pot.

as for the B500k fuzz pot

across legs 1 & 3, i get 135 kohms, At full down, across legs 1 & 2, I get 0 ohms, at full i get 34.9 kohms, at mid i get about 35 kohmsAcross 2 & 3m i get 135 kohms at full down, 0 at full up, and 120.9 at about half.

so, maybe that fuzz pot is bad.
I'm gonna desolder it and test it out of circuit

 

[Spark_Trooper84]

I just unsoldered both pots,
Both test good outside of the circuit, within about 5-10% of their rated resistance

now i'm really stumped as to why the volume pot seems to have no affect at all beyond about 1/4 turn

 

[Spark_Trooper84]

ok, so,
For right now i'm going to call this as almost fixed, but definitely a bodged 'fix'

With the help of a couple people over on the Audio Electronics DIY discord server, we tried to diagnose what was going on and ultimately it was suggested to pop a capacitor to ground from Pin 1 of Q1 just to boost volume.

So, I did that with a 4.7uf cap.
It's not incredibly perfect, but it's perfectly acceptable for now.

The consensus over there seems to be that there's something odd/weird about how the circuit handles the fuzz and volume controls that isn't immediately intuitive as to why i was experiencing the issue I am.