Big Muff output capacitor, dose size matter?

[carboncomp]

Looking at a bunch of schematics the Big Muffs seem to have had a 0.1uf, 0.47uF, 0.68uF, 1uF and 10uF output capacitor with 0.1uF the most common.

How much of an audible range is that in real terms, in theory, would I hear the difference in a 0.47uF over a 1uF?

And is 10uF a mistake, only seen one schematics saying that high?

[GGBB]

The output cap forms a high pass filter in conjunction with the volume pot which is typically 100k. So cap value affects bass roll off knee of the filter, but 0.1µ with 100k will be ~16Hz well below guitar bottom frequencies. Anything bigger would be even lower. So nothing to hear really.

[antonis]

The output cap forms a high pass filter in conjunction with the volume pot which is typically 100k.

More presicely, resistive part of HPF is upper side of Volume pot in series with lower side in parallel with next effect input impedance..

0.1µ with 100k will be ~16Hz well below guitar bottom frequencies.

Only true for Vol pot set to max and next effect input impedance much higher than 100k..

P.S.
IMHO, one must not loosely calculate that kind of 1st order filter without taking into account what comes next..
e.g. for Vol pot settting other than extremes (FCW - FCCW) there is a series resistance before the wiper and a shunt capacitance after it (next effect input capacitance) so we actually have a 2 pole band-pass filter..

[GGBB]

Only true for Vol pot set to max and next effect input impedance much higher than 100k..

The RC filter math is true in all cases - any volume setting. You are describing a more complex circuit which is not what I am referring to. The high pass output filter of this pedal does not change because of what it's connected to - the combined circuit of the two pedals is what varies.

IMHO, one must not loosely calculate that kind of 1st order filter without taking into account what comes next..
e.g. for Vol pot settting other than extremes (FCW - FCCW) there is a series resistance before the wiper and a shunt capacitance after it (next effect input capacitance) so we actually have a 2 pole band-pass filter..

Technically that's true. But on a practical level it's kind of moot I think. 0.1µ with 100k is going to work fine with the vast majority of pedals or amps and show no audible adverse effects at any volume setting. And for the few pedals that might be problematic - which pedal is at fault? Okay 220n or 330n IS "safer", 1µ probably overkill, but sure why not.

Back to the question - going to hear a difference between 0.1, 1, and 10? Not likely. Unless you have an oddball pedal or amp after it - and many other pedals probably would do the same thing.

[antonis]

Just wanted to prevent moot from become mooted..

Definatelly agree for 100nF/100k HPF is more than adequte but I suspect of OP's next query might be something like: "Why the vast majority of pedal circuit designers aim for 100 to 470nF/1M input HPF, 1M being op-amp non-inverting input bias resistor.."

[carboncomp]

Out of interest, why do the vast majority of pedal circuit designers aim for 100 to 470nF/1M input HPF?

[antonis]

 

Have you verify it or just took my word for it..??

P.S.
Sorry Gord.. I walk out on thread..

[GGBB]

Out of interest, why do the vast majority of pedal circuit designers aim for 100 to 470nF/1M input HPF?

If they do (I wouldn't know), it's probably more of a convention than a design goal (splitting hairs). Makes it work well with all things guitar related - especially guitars (pickups) themselves which have a very well known range of output characteristics. How we got to where we are is the entire history of guitar pickups, electronics, effects, and amplifiers. It's a "known" system for the most part - you generally want your stuff work within the system.

[PRR]

.... is 10uF a mistake, only seen one schematics saying that high?

10uFd will be an electrolytic. Which has often been much cheaper than a large film cap. We used 10u e-caps like candy.

[ElectricDruid]

Out of interest, why do the vast majority of pedal circuit designers aim for 100 to 470nF/1M input HPF?

Because that's what everyone else does!

There's good and bad aspects to that. Bad if you have no idea what you're doing, but started your own boutique pedal brand anyway and blatantly copied some other design! Good if you understand what the components do and why those values are the way they are and (since you're solving the same problem as everyone else who came before you) you come up with very much the same answer as everyone else.

Personally, I tend to use 100n on the input, since 1M impedance means something larger really isn't necessary. For the output cap, I'd often go with 220n or 470n which is still comfortable with 100K volume pot even if loaded by something else, but I avoid electrolytics in the audio path if possible (and it generally is).