Another why is this FuzzFace so quiet quesiton?

[pinkjimiphoton]

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.

yep, right off the collector is valid.

[Elektrojänis]

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.

Do you mean it affects the clipping threshond if you take the signal from the collector or between those resistors comming of the collector? I don't think so. For the signal those two resistors are just a basic voltage divider. The waveform at at the junction of tose resistors is just a quiter version of the signal on the collector.

[Elektrojänis]

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

Like unity at 9 o'clock-loud.

Hmmm... I think the one I use for bass has the volume set mostly at about 9 o'clock. (Can't check it now though as it's permanently at the rehearsal space.) The volume control is still workable though and if I want to push the amp a bit or a lot, I have that option.

[antonis]

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

What? that will reduce the level even more

Thanx Merlin..
(mind trouble, as usually..)

[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.

Do you mean it affects the clipping threshond if you take the signal from the collector or between those resistors comming of the collector? I don't think so. For the signal those two resistors are just a basic voltage divider. The waveform at at the junction of tose resistors is just a quiter version of the signal on the collector.

You are right. Thank you.

[anotherjim]

Given that the added tonestack is expected to lose some volume, why not just take the output from Q2 collector or replace the collector load with a trim pot? Reverse the 820 and 2k but the 2k is now a pot and its wiper feeds the output cap to the tonestack.

[pinkjimiphoton]

exactly the point i was trying to not state outright, but exactly correct, jimmy

[FingerBlisters]

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.

Sorry for the lateness, I've been in hospital.

So getting back to speed: the output should come out of the junction of Q2's collector and the little cap? If that goes straight to the output I'm wondering where the tone stacks fits in, or are you suggesting omitting the tone stack entirely?

Apologies that might be a silly question but I'd prefer to look stupid and have the right answer than forge ahead ignorantly.

I'm also seeing suggestions of amalgamating the 2k/820R series resistors into a single ~2.7k resistor. That's great. Less parts is always a good shout but makes me wonder why they didn't do that on the original FF circuit... too much volume perhaps.



Oh, R820 is 820 ohm, not 8.2 ohm as may have been inferred. Sorry about that.

[Elektrojänis]

Sorry for the lateness, I've been in hospital.

No need to be sorry about that. The really important stuff like that comes first and now that you are back you can concentrate on the stuff thats only important like building pedals.

So getting back to speed: the output should come out of the junction of Q2's collector and the little cap? If that goes straight to the output I'm wondering where the tone stacks fits in, or are you suggesting omitting the tone stack entirely?

We were talking about the output of the fuzz circuit itself without the tone control. You connect your tone control to that point.

Simply move the 220nF capacitors left side from the two resistors to the Q2's collector and you should have at least a bit more output. If not, try without the tone control to see if the fuzz itself is ok. That way it should be very loud.

I'm also seeing suggestions of amalgamating the 2k/820R series resistors into a single ~2.7k resistor. That's great. Less parts is always a good shout but makes me wonder why they didn't do that on the original FF circuit... too much volume perhaps.

That's kind of meant to be the next step after the change above. After all, at that point the two resistors are just in series and nothing else is connected to the junction between them. Two resistors in series act as one resistor with the values combined. The way they did it originally in FF is probably just to lower the volume to what probably was considered more sensible. You can always go back and see what R. G. Keen said about it in 1998: http://www.geofex.com/article_folders/fuzzface/fffram.htm



Oh, R820 is 820 ohm, not 8.2 ohm as may have been inferred. Sorry about that.
[/quote]

[FingerBlisters]

Oh I see. Thank you. So move the 220n to the 820r/100p junction at q2, and then use 1 resistor to bias q2. That's a good call and removes a part which is always a bonus.

I also will amend the current voltage starve control to the stability control zvex uses - a 5k pot in series with the 9v+ working as a clr. That's a much simpler idea that achieves the same thing (hopefully).

[antonis]

2K resistor (or 2k7 mod in case of a single one), STVB10k pot, 220nF cap and Tone stack form a complex band pass filter so, IMHO, Collector resistor (the one from 220nF node to STVB10k pot wiper) + pot 2-1 in parallel with (pot 2-3 + 5k1) resistance must be kept as low as possible while 220nF cap value must be raised (470nF, at least..)

Another way to keep Collector resistor in acceptable limits without raising Q2 output impedance is to decouple pot wiper with a cap..

[FingerBlisters]

2K resistor (or 2k7 mod in case of a single one), STVB10k pot, 220nF cap and Tone stack form a complex band pass filter so, IMHO, Collector resistor (the one from 220nF node to STVB10k pot wiper) + pot 2-1 in parallel with (pot 2-3 + 5k1) resistance must be kept as low as possible while 220nF cap value must be raised (470nF, at least..)

Another way to keep Collector resistor in acceptable limits without raising Q2 output impedance is to decouple pot wiper with a cap..

That's amazingly helpful, thank you.

Would you suggest either method of voltage starve over another? The zvex fuzz factory version is the pot in series, whereas this one was pulled from (I think) a ggg kit from way back. The zvex one seems to work as the fuzz factory has been around for years.

I'll make the 220n a 1uf because I have a load of them and will try a 2k7 in the r spot. Maybe a 5k trimmer there might be better with something like a 470r in series so the q2 always sees some resistance. Worthwhile?

With regards to the q2 collector: in the most basic terms for a simpleton, does it go something like the lower the resistance the more voltage the Q receives and therefore it produces a higher output? I realise there's a network around the base and emitter but to begin getting my head around it, if one wanted to squeeze more juice from a given bjt you could just give it more volts/less resistance from the power source?

Also, how the hell do you just quote parts of a message? I'm trying to avoid replying with the whole block of text to save space.

Thanks so much for the help this far guys.

[FingerBlisters]

Something like that for the starve/voltage control.

Also lowered the values of the C-B caps to not kill the high end.

[antonis]

I think GGG method provides more stable voltage 'cause it's partially dependent on current drawn (the one drawn by Q1 & Q2)  where ZVEX one is solely dependent on transistors current..
(Kirchhoff's Current Law..)

I'd say the trimmer idea is OK but after Collector resistance "ideal" setting, measure trimmer resistance (plus stopper resistor) and replace them with a single resistor of the nearest common value..

More volts, yes.. More resistance, depends on transistor working current..
Better study the basics for CE amp: https://www.electronics-tutorials.ws/amplifier/amp_2.html
(C2 above shunts R_E for AC so you may consider Emitter grounded, like in your circuit..)

I quote the whole post and delete/edit whatever I want to..

[antonis]

Also lowered the values of the C-B caps to not kill the high end.

Very well, so far as there are no oscillations..

[FingerBlisters]

Also lowered the values of the C-B caps to not kill the high end.

Very well, so far as there are no oscillations..

That's a good point.

And hey, could you explain the use of the electrolytic to ground you included there please? The one marked 22uf-47uf. Is that to filter the power supply? If so, there's a 100uf/100n upstream I thought would do the same thing... but I'm prepared to be wrong.

After looking into voltage controllers I reverted back to the original method (9v to lug 3, lug 2 output to circuit, lug 1 to GND through a R) as the prospect of introducing oscillations didn't sound like a great idea.

[Steben]

I would replace the 2k7 with a 5k trimpot.

[antonis]

And hey, could you explain the use of the electrolytic to ground you included there please? The one marked 22uf-47uf. Is that to filter the power supply? If so, there's a 100uf/100n upstream I thought would do the same thing... but I'm prepared to be wrong.

You're not wrong..
(you're partially right..)

That cap indeed filters power supply but to a further degree..
You see, 100μF/100nF serve as reservoir cap/HF shunt cap right on 9V point where the above mentioned cap forms a Low Pass filter with the resistance between 9V and pot wiper..
(right on the top of Collector resistor..)

A more significant role is to decouple anything upper Q1 & Q2 Collector resistors (it's considered AC ground) resulting into "constant" values, regardless STV pot setting, hence constant stages gain..
Without that cap, Collector resistances should be considered their actuall resistances in series with the parallel combination of pot wiper - lug 3 and (pot wiper - lug 1 + 5k1)
(we're talking about reversed pot.. - lug 3 to +9V..)
Last but not least, Q2 output impedance is kept relatively low, making Tonestack drive more effective..

@Steben: Trimpots aren't famous about their stability (time/vibrations)..

[Lino22]

Here is an interesting AMZ article on aging batteries.
http://www.muzique.com/lab/batteryz.htm

[FingerBlisters]

Alrighty guys, progress was made with suggestions incorporated.

Current schematic:



You will see the 1k2 resistor at the collector of Q2. That value provides a range of around 0.8v-7v when manipulating the 10k STARVE control, meaning you get the 4.5v 'sweet spot' as well as the gnarly and the sputtery. It works really well.

The sound generally is very good on all settings and it handles well.

However, there's one big problem I seem to be having which is a lack of high end. The filtering isn't very aggressive with only a pair of 47p caps and a 100r/47n LPF providing the filtering but there's still a suck somewhere.

Could it be the value of the fuzz pot? I used a 1M there, but could easily clip a R over it to make it whatever value if that's the culprit. According to the TSC it shouldn't be this dark but, in the room, it is.

Any ideas on where my treble is going?

And thank you so much for your help this far guys. You're all amazing people.