Second pedal build, based on fuzz face, are there any bad practices I'm doing?

[twoheadedfetus]

I finished designing my second pedal, I just tweaked around with a fuzz face, and looked at the woolly mammoth schematic for some inspiration of what to try, and I'm pretty happy with how it sounds. Here's the schematic:



My main concern tbh is the 220n cap to ground after the input cap, I never saw something like this on a schematic, usually its a much smaller cap and often there is a resistor before it, but this cap filters out almost all of the noise, and I like the sound I have, tried doing it with a resistor before it but I prefer this sound. Are there any drawbacks to this?

[GibsonGM]

It does seem large in value, but - it's YOUR tone, and if YOU like the sound, that's all that matters!

Drawback could be the shunting off of high frequencies that would otherwise be clipped and provide treble harmonics...but since you already said you like the tone, is that really an issue?  I think you've answered your own question already.

You could design a pedal with 500 ohms input impedance, massive tone-sucking...and if YOU like it, then it's great!  (for you and your needs)

[PRR]

> often there is a resistor before it

There is ALWAYS a resistor, or something, "before it".

These things are usually fed straight from guitar, which is a high but complicated impedance. Generally a real big cap across a guitar will cut-down the high frequencies. Because the FF is real good at making-up high frequency fuzz, this may end up a balanced sound.

But a different guitar, even different settings on the same guitar, will be different.

Come from an opamp pedal/buffer and the high-cut may be negligible, a very different sound. (Come from an under-engineered opamp, the big cap makes the opamp crazy, and strange things happen.)

So it is good to go, for you, in the setup you have tried. Just be aware it may be fussy about what drives it.

[thermionix]

Is R3 supposed to be 1M or 100k?  Is R2 really doing anything?

[stallik]

These 'fussy about what drives it' circuits always make me wonder. Do they sometimes sound better with the same guitar and amp than the same effect sanitised for more universal use?

I have an effect that sounds unbelievable but only with one guitar and amp. I refer to it as a perfect customisation but for anyone else it would be rubbish

Oh, and welcome

[iefes]

Is R3 supposed to be 1M or 100k?  Is R2 really doing anything?

1M should give less feedback = more gain, so why not? I guess, R2 is there just to be able to simulate a potentiometer for the common gain-control on a fuzzface. With R2 = 1Ohm its fully cranked.

[thermionix]

1M should give less feedback = more gain, so why not?

Got it.  I'm just not used to seeing "1000k" so I thought it might be a typo.

R2 is there just to be able to simulate a potentiometer for the common gain-control on a fuzzface. With R2 = 1Ohm its fully cranked.

Can you hear any difference with R2 omitted?

[twoheadedfetus]

Is R2 really doing anything?

its just how I simulated the pot in the spice model, theres a gain pot and a volume pot on the real version

and yes its a 1 Mega ohm resistor

[PRR]

> Is R3 supposed to be 1M or 100k?

In general, depends on the transistor. 1Meg may work with a hi-hFE low-leak device. We often see 100K so we can put any old part in it and sell it.

> in the spice

SPICE is antique FORTRAN at its core. Old FORTRAN did not know letter-case. You might think "M" is Mega and "m" is milli, but to SPICE they are *both* "milli". If you want Meg, spell it out "Meg". (Or "1000k", little wrong with that except some of us old-eyes have trouble counting the zeros.)

[Rob Strand]

SPICE is antique FORTRAN at its core. Old FORTRAN did not know letter-case. You might think "M" is Mega and "m" is milli, but to SPICE they are *both* "milli". If you want Meg, spell it out "Meg". (Or "1000k", little wrong with that except some of us old-eyes have trouble counting the zeros.)

The "m" thing is a real pain in Spice.

I'm pretty sure the spice text files, which is how you used to enter circuits, were called "cards" or "decks".   That comes from old computer lingo.

[PRR]

I remember when you fed SPICE actual decks of cards. Textfiles are an approximation of that.

There was also an early re-write from FORTRAN to C. C customs are mostly files not cards, even the early H&R assume textfiles for most stuff. Also upper/lower-case terminals. But by that time SPICE was in such wide use that the parser still sipped textfiles like punch-cards.

[Rob Strand]

I remember when you fed SPICE actual decks of cards. Textfiles are an approximation of that.

I didn't realize it actually went that back.  I remember SPICE text files on the old main-frame running that old IBM OS.

There was also an early re-write from FORTRAN to C. C customs are mostly files not cards, even the early H&R assume textfiles for most stuff. Also upper/lower-case terminals. But by that time SPICE was in such wide use that the parser still sipped textfiles like punch-cards.

I've only seen the C version.   When I was looking the source code I was dreading only finding the Fortran version.  I've had to check C ports of Fortran code in the past - very time consuming.   You can get software that translates Fortran to C but the output is less readable than the original Fortran code and far from what a C programmer would write!

[PRR]

https://www.allaboutcircuits.com/textbook/reference/chpt-7/history-of-spice/

1972, punch-cards were still in very wide use. Starting to fade in 1975, though punchcards were still sold in the bookstore.

The C re-write was not until 1985. There may have been an un-sold pack of cards in the bookstore still (they had slide-rules through 1999!) but no long in wide use. But the FORTRAN legacy was strong.

BTW, that site reminds me that SPICE core has an interactive mode. You type your netlist at the command line. And I dimly remember that if you did not redirect the output, it scrolled off your greenscreen.