Fuzz Output Pot Value?

[seedlings]

Is there a 'best' load for Q2?

I just noticed the Tone Bender fuzz straps a 47K across the 500K volume pot, and wondered if a 50K pot is any 'better' than a 500K.  Was the 500K chosen because the factory had a bunch of them lying around, or is there a specific reason related to the load on Q2?  What about 10K?  1M?

I ask because I've been listening to tons of different Ges lately and ended up with two 10K pots for volume and bias, then have a 470K in place of a 500K pot for the 'load'.  Some transistors need less than 10K to bias, some more, which is the reason for the second pot.  They're very interactive but functional since I didn't have a 500K pot for volume.



CHAD

[seedlings]

Sorry to bump, but can anyone comment to the acceptable range of resistance for output volume pot on a traditional fuzz circuit? 
Is 100K too low?
10K?

Or, is it calculated the same as tubes:

(Voltage drop across transistor divided by current through transistor) || (collector resistor)? <-- assuming the emitter resistor is bypassed

CHAD

[PRR]

> They're very interactive

Looks obscenely "interactive" to me.

Get a 100K pot. They aren't very expensive.

[seedlings]

> They're very interactive

Looks obscenely "interactive" to me.

Get a 100K pot. They aren't very expensive.

I get it- I didn't phrase it very well (I didn't need to say anything about my test setup) but I want to know why there is a 500K pot for a fuzz face and a 47K on the Tone Bender.  More than that I would like to know what the output impedance of Q2 is with a 10K ish Rc.  In reading I'm getting the impression that the output impedance is basically equal to Rc... which makes me wonder why not a 10K volume pot, wouldn't that match?

CHAD

[PRR]

> output impedance is basically equal to Rc...

Yes for most practical purposes.

> why not a 10K volume pot, wouldn't that match?

But we often do not want to "match". We want "lightly loaded", or load 2X to 20X the source impedance.

> Was the 500K chosen because the factory had a bunch of them lying around

That's my bet. And when a few customers with long cables noted a "dull" sound, they used-up the 500K and re-stocked with 50K.

[LucifersTrip]

The vol pot size totally depends on the circuit. In general, a smaller value will give you less volume and more treble and a larger value vice-versa.

If you put a 100K (instead of 500k) in a Fuzz Face it'd be much thinner and sharper and lower volume....many builders do that and it's very useable, but not the original sound. It's all up to taste.

But try putting a 500K (instead of 50K) in a Shin-Ei FY-2 GE and you'll have an unusable, boomy, muddy mess:
http://www.luciferstrip.com/fuzz/fy-2-ge.jpg

I would've thought the designers "matched" that volume pot to the output to get the "best" or at least the fuzz tone they thought sounded cool.

Recently, I was working on a Univox Square Wave:
http://fuzzcentral.ssguitar.com/schematics/squarewaveschem.gif

The volume was way too low, so I increased the volume pot to 1M, but by doing that, I increased the bass & boomy-ness, so I had to alter other values in the circuit to compensate.

[seedlings]

Thanks that answers my question.  Especially the

But we often do not want to "match". We want "lightly loaded", or load 2X to 20X the source impedance.

Thank you both for solid answers <thumbs up>.

CHAD

[DavenPaget]

The vol pot size totally depends on the circuit. In general, a smaller value will give you less volume and more treble and a larger value vice-versa.

If you put a 100K (instead of 500k) in a Fuzz Face it'd be much thinner and sharper and lower volume....many builders do that and it's very useable, but not the original sound. It's all up to taste.

But try putting a 500K (instead of 50K) in a Shin-Ei FY-2 GE and you'll have an unusable, boomy, muddy mess:
http://www.luciferstrip.com/fuzz/fy-2-ge.jpg

I would've thought the designers "matched" that volume pot to the output to get the "best" or at least the fuzz tone they thought sounded cool.

Recently, I was working on a Univox Square Wave:
http://fuzzcentral.ssguitar.com/schematics/squarewaveschem.gif

The volume was way too low, so I increased the volume pot to 1M, but by doing that, I increased the bass & boomy-ness, so I had to alter other values in the circuit to compensate.

To me , shouldn't 100k give more volume and 500k give less volume at the top end ?

[seedlings]

I 'see' now.  This is what the output looks like so far as AC is concerned.  It's just a voltage divider.



CHAD

[LucifersTrip]

The vol pot size totally depends on the circuit. In general, a smaller value will give you less volume and more treble and a larger value vice-versa.

If you put a 100K (instead of 500k) in a Fuzz Face it'd be much thinner and sharper and lower volume....many builders do that and it's very useable, but not the original sound. It's all up to taste.

But try putting a 500K (instead of 50K) in a Shin-Ei FY-2 GE and you'll have an unusable, boomy, muddy mess:
http://www.luciferstrip.com/fuzz/fy-2-ge.jpg

I would've thought the designers "matched" that volume pot to the output to get the "best" or at least the fuzz tone they thought sounded cool.

Recently, I was working on a Univox Square Wave:
http://fuzzcentral.ssguitar.com/schematics/squarewaveschem.gif

The volume was way too low, so I increased the volume pot to 1M, but by doing that, I increased the bass & boomy-ness, so I had to alter other values in the circuit to compensate.

To me , shouldn't 100k give more volume and 500k give less volume at the top end ?

try it and see...

[DavenPaget]

try it and see...

OH SHIT , i forgot the voltage divider theory ... I forgot we weren't talking opamps .
the closer you get to the R1 the closer you get to half voltage . And the further you go from R1 you get more and more ...

[ricothetroll]

I 'see' now.  This is what the output looks like so far as AC is concerned.  It's just a voltage divider.



CHAD

I might be wrong but I think that for AC signals (considering the output coupling cap as a short circuit) Q2's collector sees 8k2 in series and 500k || 330R (or 470R) for the fuzz face, as Vcc acts like Gnd for AC. For the tonebender that would be 2k2 || 47k || 500k.

The treble loss of the fuzz face at intermediate volumes is actually quite a pain.

[zombiwoof]

The vol pot size totally depends on the circuit. In general, a smaller value will give you less volume and more treble and a larger value vice-versa.

If you put a 100K (instead of 500k) in a Fuzz Face it'd be much thinner and sharper and lower volume....many builders do that and it's very useable, but not the original sound. It's all up to taste.

But try putting a 500K (instead of 50K) in a Shin-Ei FY-2 GE and you'll have an unusable, boomy, muddy mess:
http://www.luciferstrip.com/fuzz/fy-2-ge.jpg

I would've thought the designers "matched" that volume pot to the output to get the "best" or at least the fuzz tone they thought sounded cool.

Recently, I was working on a Univox Square Wave:
http://fuzzcentral.ssguitar.com/schematics/squarewaveschem.gif

The volume was way too low, so I increased the volume pot to 1M, but by doing that, I increased the bass & boomy-ness, so I had to alter other values in the circuit to compensate.

One article (I think it's the GEO one about Fuzz Faces) mentions that Eric Johnson prefers a 100k vol. pot in his FF's.  Your answer explains why this might be.  Maybe it cleans up more at lower volume?.  What would the 100k volume pot do at full volume compared to the stock 500k?.

Al

[Gus]

I started a new thread about 100k vs 500k
http://www.diystompboxes.com/smfforum/index.php?topic=96381.0