Softening the Orpheum/FY-2/Fuzz-Rite

[Mark Hammer]

A bass-playing long-time friend asked me if I could maybe make him a fuzz.  We both agreed that one of the benchmark bass tones we both loved was that of original Grand Funk bass player Mel Schacher.  So, with that in mind, I set out to make him something that aimed for that territory

I had a modded Shin-Ei FY-2 sitting around on perf-boad, and thought that perhaps it could be co-opted to be more suitable for bass.  The first change was to replace the midscoop between the Fuzz and Volume pots with a simple 2-pole lowpass filter to smooth out the sound.  I picked rolloffs starting at around 3.4khz, 1.2khz, and 600hz, using a DPDT on-off-on toggle.  Nice.  Takes the edge off and certainly eliminates any hiss in the process.  Turns into a smoother, more refined, Fuzz-Rite.

The second change was to use a 100k fuzz control, instead of 50k, to be able to fade the fuzz part further into the background.  No impact on the fuzziest sounds, but allows more for less fuzzier sounds.

The 3rd change was to increase the values of the two caps on each audio path feeding the fuzz pot.  The .0022uf cap became .01uf (which I think I'll up to .022uf), and the .0033uf cap became .047uf.

The 4th change was the "body" control that varies how much of the total resistance between V+ and the collector of Q2 the .047uf cap sees.  Actually becomes more useful with bass.

With more bass, and obviously with no midscoop to cut the output off at the knees, there is quite acceptable output.  Sounds great, and gets that nice farty raspberry sound that Mel got, but I wish I could get LESS fuzz; or rather, I wish I could get it to be cleaner sooner.  The problem is that the thing sustains far too much.  That's great if one is playing a psychedelic guitar solo, but less great if you're holding down the bottom in a band.  I want the fuzz effect to be more short lived, and just be there for part of the note, not for the full duration.  I can get that if I turn down the volume of the bass, but obviously that's problematic if he wants to switch back from fuzz to clean.

So the question is: "How do I turn down the gain of Q1?

[CynicalMan]

Would the usual resistor or pot in series with the input work?

[Mark Hammer]

I don't know.  It's not a Fuzz Face. 

[analogguru]

a.) Add an emitter-resistor/pot

or

b.) reduce the value of the C-B-resistor

analogguru

[doug deeper]

Adding a pot to the emitter of Q2 works really well in these circuits.
I like to do two pn2222a transistors with 470k feedback resistors, a 10k on the first collector, and a 22k on the second.
Then add a 10k pot off the emitter of Q2 and it has a very usable range.
I imagine with all the filtering the FY-2 has things will get quite a bit darker as you decrease the FUZZZZZ.
You could also wire in a volume control between the two stages with a .1uf cap on either side.

[Mark Hammer]

Thanks gents.

I'll try tacking on something in parallel with the 2M2 first, because that's easiest, play with an emitter resistor if that doesn't seem to do the trick, and report back when I'm done.

[doug deeper]

I've never had much luck with a feedback resistor gain control in this type of circuit for making things less fuzzy, it does seam to make things  little less sustainy though, so this my be just the ticket!
(I've spent an embarrassing amount of time playing with this type of fuzz.) 

[Mark Hammer]

Well, a quicky late-night pre-pajamas experiment of no great substance (I put a 5M6 in parallel with the 2M2 for a combined value of roughly 1M6) didn't seem to result in any noticeable gain reduction, though to tell you the truth, I didn't listen to what Doug noted.  So, I'll try again.

[Gus]

As analogguru posted an emitter resistor could be used

you could try the first stage of this
http://www.diystompboxes.com/pedals/gusRitefuzz.gif
Or use a 470ohm emitter resistor as a starting point with the 22K of the stock circuit

[Mark Hammer]

I accidentally bought some 500R pots that I thought were 500k.  About time to find a use for them.  Thanks for the idea.  I'll try that out.

[Mark Hammer]

I started playing with the emitter resistance.  Inserting 220R between ground and the emitter of Q1 softens things a bit.  Sticking as little as 100R between the emitter and ground for Q2 completely kills any fuzz.

So, I think I'll cut my losses and stick with the added 220R on Q1.  It doesn't quite reach the goal of being able to sound just a little dirtier than clean, but I guess that job is perhaps best left to a different sort of device.  I figure it's best to let this thing do what it desperately wants to do.  Who knew that pedals could self-actualize?

This is a big-sounding bass fuzz.  Sounds terrific through an autowah (even makes a Dr, Q sound good!).  If it was able to nail Mel Schacher's tone more closely, it would have been legended as "Mel's Rockpile", but I think I'm gonna call it the "Chewie Louie".

I never would have thunk that this fuzz platform could have yielded a decent bass fuzz.  I was wrong.

[Earthscum]

I didn't care much for the sound of these style of circuits much on bass at all, but I came across a simplified one and then I made THIS. It's just a basic circuit, but I found lots of funky stuff to do with it since I posted it. I took a .0047 cap (and a couple others) across the diode in the first stage. Changed the sweep from almost buzz box to a farty sound. I did something else, didn't jot it down, but it made the entire clean sound of the bass come through all the way through the sweep. Maybe used a pot in series with the first stage diode and found a sweet spot? (seems right) or maybe different sized caps on either end of the mixing pot (larger from 1st stage and small from second). Or a combination of both? I just went crazy for an hour or two plugging at it one night.

Someone else tried it HERE, and I gotta agree with him. I boarded one up on a fuzzrite clone board I had, and it's not what I was expecting. Different, but filtering the first stage, using higher gain transistors, and trying different pot values can grab some really interesting results.

[Derringer]

I started playing with the emitter resistance.  Inserting 220R between ground and the emitter of Q1 softens things a bit.  Sticking as little as 100R between the emitter and ground for Q2 completely kills any fuzz.

So, I think I'll cut my losses and stick with the added 220R on Q1.  It doesn't quite reach the goal of being able to sound just a little dirtier than clean, but I guess that job is perhaps best left to a different sort of device.  I figure it's best to let this thing do what it desperately wants to do.  Who knew that pedals could self-actualize?

This is a big-sounding bass fuzz.  Sounds terrific through an autowah (even makes a Dr, Q sound good!).  If it was able to nail Mel Schacher's tone more closely, it would have been legended as "Mel's Rockpile", but I think I'm gonna call it the "Chewie Louie".

I never would have thunk that this fuzz platform could have yielded a decent bass fuzz.  I was wrong.

will the circuit allow you to just attenuate the incoming signal with a pot to get the desired (or lack of) sustain?
then you could just tack on a gain stage at the output, like superfuzz style with the pot before the gain stage, to bring things back up to the level you want

[Mark Hammer]

I didn't care much for the sound of these style of circuits much on bass at all, but I came across a simplified one and then I made THIS. It's just a basic circuit, but I found lots of funky stuff to do with it since I posted it. I took a .0047 cap (and a couple others) across the diode in the first stage. Changed the sweep from almost buzz box to a farty sound. I did something else, didn't jot it down, but it made the entire clean sound of the bass come through all the way through the sweep. Maybe used a pot in series with the first stage diode and found a sweet spot? (seems right) or maybe different sized caps on either end of the mixing pot (larger from 1st stage and small from second). Or a combination of both? I just went crazy for an hour or two plugging at it one night.

Someone else tried it HERE, and I gotta agree with him. I boarded one up on a fuzzrite clone board I had, and it's not what I was expecting. Different, but filtering the first stage, using higher gain transistors, and trying different pot values can grab some really interesting results.

I can't see the drawings here at work.  Is there another link you can point me to?

will the circuit allow you to just attenuate the incoming signal with a pot to get the desired (or lack of) sustain?
then you could just tack on a gain stage at the output, like superfuzz style with the pot before the gain stage, to bring things back up to the level you want

That's sort of the approach the Boss-Tone uses.  I'll see if that works.  As is, the circuit is capable of outputting something about 2x the input level when the fuzz is set to min and the volume is maxed.  I'd prefer not to compromise that, but if there is no output-level penalty, then it's worth a shot.

[Earthscum]

might be too late, but shot you an email (from gmail)

[CynicalMan]

I played around with this a bit in LTSpice, and the best way I found to drop the gain of the first stage is to increase the value of the 1n cap. Increasing it to 2n2 drops the gain by 2-7dB, increasing to 4n7 drops it by 6-11dB, and increasing it to 10n drops gain by 12-18dB. I'm saying it in a range because it reduces the high-pass filtering, but that should be that big an issue, especially with bass. Adding in an emitter resistor would change the bias, so I'd personally prefer this method. Your call, though.

Edit: Heres a graph. The traces are cap at 1n, 4.7n, and 10n.

[Mark Hammer]

might be too late, but shot you an email (from gmail)

Received.  Many thanks, David.  I see how it could go on a Fuzz-Rite or Orpheum board.  Same general topography, it just gets there a different way.  I don't have much time to finish boxing this thing up before my friend rolls into town on Friday, so I will stick with what I have, but I'll definitely try building your right/wrong somewhere in the not too distant future.

[mac]

Mark, have you tried a series pot between Q1 C and Q2 B, something like the BMP sustain pot?

mac

[analogguru]

at 100 Hz the reactance ("resistance") is for a:
1n  :  1M6
2n2:  800 k
4n7:  320 k

This shows that a 5M6 in parallel to the 2M2 will not lead to audible results.
The resistor between C-B of Q1 has to be between 470k and 2M2.

analogguru

[CynicalMan]

But that's going to affect the bias, which could lead to gating, more distortion, or a different sound in general. I think changing the capacitor is better because it reduces high pass filtering, which IMO is too high stock for bass, and it won't change the DC bias.