Thoughts on Fuzz Faces for bass...

[Bill Mountain]

I have been tinkering with Si Fuzz Face ideas and I thought I had a winner until another pedal stomped all over it at practice last night.

I have been surprised how smooth and amp-like fuzz faces can sound but I have to remove so much bass to keep it from getting splatty.  I tried adding bass to the end but it's not as natural sounding as a distortion that can process the low end without the need of a clean blend or other tricks.  MY Fuzz face had a cap selector on the input and a bass boost on the output.  It sounded great with headphones but not so much at 500 watts.

The overdrive that laid my FF to rest was a Mesa Bottle Rocket.  It's not the best overdrive (hell my green rhino sounds exactly the same in a band setting) but what it can do is handle my huge low tuned bass single without getting splatty or buzzy(the green rhino gives up the ghost when I'm digging in).

So...this leads me to one of two conclusions.  I either need to run the FF at 250 volts or put a 30dB voltage divider at the input and leave the FF full range.

Any other thoughts?

[Mark Hammer]

Yeah, stick a trimpot - say, 500R - between ground and the emitter of Q1 (which is normally tied directly to ground), so you can reduce Q1's gain a bit and make it respond less to feedback from Q2's emitter.

[Bill Mountain]

Yeah, stick a trimpot - say, 500R - between ground and the emitter of Q1 (which is normally tied directly to ground), so you can reduce Q1's gain a bit and make it respond less to feedback from Q2's emitter.

I understand that less gain is good but what is the effect of less response to the feedback?

My hypothesis is simple.  At the voltage level of my bass there is simply too much low end for a stock FF to process.  If I increase the circuits headroom or decrease the size of the input signal then I can reach a point where the FF will clip the lows just fine.  Are there any flaws in my thinking?

[Mark Hammer]

I don't think yur thinking is "flawed".  My own personal preference for bass fuzz is for the note to sort of fart out at the outset, but simmer down soon after.  I find it sort of counterproductive for whatever fuzz is produced to sustain for longer than is necessary.  The bass gets to function as a bass more when the pedal can go "Okay, I did what you wanted.  What next?", instead of getting carried away.  I like the sustain effect of a fuzz on guitar; not so much on bass.

I could be wrong, but my sense is that the reduction of gain on Q1 will achieve that, all without having to sacrifice S/N ratio, output level, etc..  But we'll let empirical evidence be the decider.

[Bill Mountain]

You see...it helps to let people know where I'm coming from.  I should have been more clear in my post that I wanted to achieve the smooth sustain overdrive-ish sounds that guitarists can get with a Fuzz Face.

This circuit may not be the vehicle for that tone but I was pretty impressed playing through a couple boutique FF's that I wanted to try and build my own.

Anyways...If I were to attempt to increase voltage what biasing considerations should I consider?

Thanks for your help so far!

[Mark Hammer]

Check out the ZVex Mammoth, which is essentially a Fuzz Face tailored for bass.  The madbean Sabretooth is intended to be a clone of the Mammoth.  I made one.  Sounds pretty decent.  Didn't need no stinking germanium trannies either.

[Bill Mountain]

Another thought I had which I haven't explored is reducing the size of the bypass cap to boost less bass.  It would still let the bass through but would boost and clip mostly highs.  I think.

[Bill Mountain]

Check out the ZVex Mammoth, which is essentially a Fuzz Face tailored for bass.  The madbean Sabretooth is intended to be a clone of the Mammoth.  I made one.  Sounds pretty decent.  Didn't need no stinking germanium trannies either.

Thanks.  I'll have another look at the Mammoth.  It was always too splatty for my taste but that could just be the way people set theirs up.

[moosapotamus]

The mammoth also sounds like arse if your bass has active electronics. It's really only usable with passive pups.

~ Charlie

[Gus]

reduce the input cap value

[Bill Mountain]

On the way home from work I started thinking of some Q2 gain control options.  After sitting down at the computer for a few minutes I came up with these (note: All values are picked at random.  These values are for demonstration purposes only.  None of these have been tried by me):



Obviously there are many possibilities (not shown here) and most of these will not work as expected but there could be a diamond in the rough here.  I'm quite partial to the mid-boost options.  You could expand on these ideas and come up with endlessly complicated switching and panning schemes so it's important to define what the desired effect is and go from there.

[Bill Mountain]

For larger value inductors you should be able to get by with gyrators.  Of course I would need to sim it all to get an idea of what effect it would actually have.

Regardless, its fun to think about it.