Another why is this FuzzFace so quiet quesiton?

[FingerBlisters]

Morning guys,

Here's the schematic drawn in Eagle:



It's a FF based circuit.

Signal comes in, goes through a 'pregain' control, into a input cap blend control, then into Q1, through Q2, into a BM style tone stack before heading out with a 100r/100n low pass to just remove any sizzle still there.

Thing is, it's really quiet. It's above unity on full tilt but turning down slightly and you're buried.

Short of whacking a LBP style boost on the end is there something that could be done with the 15k/2k/820r network around the Qs to massively juice the volume? I understand the stack eats some volume but I've never encountered this much loss before.

[idy]

Is this already built or just a simulation?
Have you tested it without the tone stack to make sure the FF is good?
Why did you add a BMP tone stack without the recovery stage that always accompanies it in a Muff? That is purpose built for the tone stack; and LPB is more gain I think...

[bean]

You could try increasing your 2k resistor a bit more and adjust the 820R collector resistor as needed. The BMP tone stack is a bit lossy so adding a little gain recovery stage would probably solve the problem with only a few extra parts.

[Lino22]

As said above, the BM tone stack drains a lot of your signal to the ground. But if you add a recovery stage, the FF sound character will change. It will lose harshness and become more "hollow". I have been there. But you may like it after all.

[Lino22]

If you want to test a general change in the sound character, place a booster pedal after it and check for yourself.

[Elektrojänis]

You could try increasing your 2k resistor a bit more and adjust the 820R collector resistor as needed. The BMP tone stack is a bit lossy so adding a little gain recovery stage would probably solve the problem with only a few extra parts.

How about taking the output of the fuzz itself straight from the collector of the Q2?

I've never really understood why most FF-derrivatives religiously clone the output voltage divider too. After all the thing has a volume control in the end anyway so the voltage divider on the collector of Q2 just limits the volume range. I quess too big range could be a problem in some cases. In this one the tone control will eat away some of the level anyway. Why lower the level before the tone control and use a gain recovery stage when you could just not lower the level in the first place?

I'd test the output of the fuzz without the tone control first though, to see that the fuzz itself hasn't got anything funny going on.

[antonis]

Have you tested it without the tone stack to make sure the FF is good?

I'd test the output of the fuzz without the tone control first though, to see that the fuzz itself hasn't got anything funny going on.

What they said..

[merlinb]

Volume control says 500 instead of 500k... is that just a drawing error?

[PRR]

Volume control says 500 instead of 500k... is that just a drawing error?

Collector Q2 has a "R820"; isn't that zero point eight two ohms?

[FingerBlisters]

You could try increasing your 2k resistor a bit more and adjust the 820R collector resistor as needed. The BMP tone stack is a bit lossy so adding a little gain recovery stage would probably solve the problem with only a few extra parts.

How about taking the output of the fuzz itself straight from the collector of the Q2?

I've never really understood why most FF-derrivatives religiously clone the output voltage divider too. After all the thing has a volume control in the end anyway so the voltage divider on the collector of Q2 just limits the volume range. I quess too big range could be a problem in some cases. In this one the tone control will eat away some of the level anyway. Why lower the level before the tone control and use a gain recovery stage when you could just not lower the level in the first place?

I'd test the output of the fuzz without the tone control first though, to see that the fuzz itself hasn't got anything funny going on.

That's what I was getting at I think. To not lower the level before hitting the tone control, could those voltage divider resistors be removed altogether? So the collector of q2 goes straight to 9v?

[antonis]

could those voltage divider resistors be removed altogether? So the collector of q2 goes straight to 9v?

No Collector resistor - no Gain..

More seriously..
ANY CE amp DOES need some resistance between PS and Collector for two reasons..
1. In the absence of that resistor ALL Collector signal should leak to PS (AC Ground)..
2. The DC voltage drop across that resistor sets quiescent point where the AC voltage drop sets the output amplitude..

[Lino22]

By the way i would have two questions concerning the pre-gain part



1. Is there a preferred way of making the cap blender? I understand they will differ in max and min capacitance.
2. Why does the OP design have a divider instead of just a pot in series?

[Elektrojänis]

That's what I was getting at I think. To not lower the level before hitting the tone control, could those voltage divider resistors be removed altogether? So the collector of q2 goes straight to 9v?

As others said, you still need a collector resistor. The original FF has it split to two to divide the signal down. The idea was to leave the resistors in and just move the connection to the 220n cap to the collector of the Q2. You really need only oe combined collector resistor after that instead of two in series. 2.7 kohm would probably do or something close to that).

Collector Q2 has a "R820"; isn't that zero point eight two ohms?

That would practically mean there is no divider for the signal. I assumed that this and the output pot where just schematic errors and he's actually experimenting with a real circuit on a breadboard or something. There's some good sayings about assumptions though...

[antonis]

By the way i would have two questions concerning the pre-gain part



1. Is there a preferred way of making the cap blender? I understand they will differ in max and min capacitance.
2. Why does the OP design have a divider instead of just a pot in series?

1. Upper configuration is (Rx + 1μF) // 10nF where lower is (Rx//10nF) + 1μF..
Basic difference is 10nF/1μF parallel/series configuration..

2. 'Cause a pot in series needs "some" further down resistance to work as a voltage divider (signal amplitude attenuator)..
In particular circuit, a series pot should be added on signal source internal impedance and the sum of them should be added on input cap(s) capacitive reactance to form the upper part of a voltage divider on Q1 Base..
(the lower part of the divider should be comprised of a rather complex parallel combination of Base reflected Emitter resistance, 150k feedback resistor in series with 1k/22μF parallel equivalent impedance and 330pF cap capacitive reactance multiplied by Q1 stage gain plus unity..) 

[antonis]

A minor suggestion..

IMHO, Si FFs don't sound "good" (if there is such a term/definition) when powered with 3V, so it might be more fruitful to wire STVB10K pot as variable resistor..
(by reversing the pot and shorting lugs 1 & 2..)

[abc1234]

How about taking the output of the fuzz itself straight from the collector of the Q2?

Do this.

The FF is ridiculously loud when you output from the collector.

Like unity at 9 o'clock-loud.

Like do it and you'll return to this thread to ask how to reduce the volume-loud.

[Lino22]

Fuzz Face's Q2 stage turns the strength of the signal into distortion, it has no clipping diodes, if you give it wider headroom, it will distort less. You cannot have both loud and distorted. For that you would have to go for 18V DC i guess.

[antonis]

You could try increasing your 2k resistor a bit more and adjust the 820R collector resistor as needed.

Sometimes we don't see the obvious..

2k and 820R resistors need swapping..

[merlinb]

Sometimes we don't see the obvious..
2k and 820R resistors need swapping..

What? that will reduce the level even more

[pinkjimiphoton]

yes, you can take your output cap directly off the c of q2 and get more output to drive the tone stack. i've done this on many pedals based on the fuzzface, including the skydog that was ripped off and the schizoid face.  you can even make it footswitchable so you have a boost or normal output level.

you need the c resistances for the transistor to work and develop any gain, but you can take that resistance and divide it up however you want to control the volume from that stage.  normally it would be an 8.2k resistance, but 10k is close enough if ya wanna add a trimmer <you can go bigger than 10k in some cases, 20k trimmer will work, too>... so say, the loudest would be with the output cap coming right off the 8.2k and c node... but you could also use say, a 4.7k resistor and a 5k trimmer, which would be right in the middle of the output, or 1k and 10k trim or whatever... i think ya can see where this is going.

you can also bump the 330r resistor coupling the two stages up to 470r or 1k even, hell, even higher than that with some q's if ya need more volume.

so yeah, lots of ways to do it, easiest i just described, next easiest is add a third stage for gain recovery.