How to increase circuit output - possible without a boost?

[tracer03]

Okay, so I have been reading and trying to learn to dissect/modify circuits while I wait for my breadboards to arrive. I recently boxed my first build - a Lovepedal Silicon Fuzzmaster, and while I'm extremely happy it worked and is fuzzy and all - I noticed a couple of things:

1. The output is slightly above unity (or equal to),
2. Monkeying with the blend and fuzz, I seem to have a small range where the fuzz and blend cooperate: if I increase the fuzz beyond that sweet spot, it gets 'thin'. That's with single coils and humbuckers (PAFs).

So, if I was going to try to modify the circuit for more bass, I know I would need to increase the input or output cap - likely the output cap. And according to the layout, that would be the 100n in the upper right, connecting to Level 3.

However, I'm not sure what I would modify in this circuit to increase the output (or if it's possible).

SO:
1. Is the 100n in the upper right the cap I would increase?
2. Is it possible to get more output from the circuit without adding a boost? If so - what would I be looking for?

[Frank_NH]

You could potentially modify the original circuit to get more output, but then the sound would change, as you've mentioned.  I would put a simple JFET gain stage at the output to provide a clean boost of the fuzz signal with the current circuit.  Just need about a 3 - 5 times boost, which is achievable with a 2N5457 or MPF102 JFET.

If I have some time, I may play around with this on my breadboard.

[Ciaran Haslett]

A popular Fuzz Face mod to increase volume is to raise the 470r to 1K or higher.  This may have an effect on the amount of fuzz you get.

Worth an experiment.

[Frank_NH]

Did a quick LTSpice sim tonight.  Tacking on a simple 2n5457 JFET gain stage does the trick, increasing the signal by a factor of 4 or so.  Below shows the output for 800 Hz sine wave, 0.1V peak-to-peak.  Red curve is the normal output with the volume up full, and as you can see it's barely above the input amplitude.  The blue is the JFET-boosted signal.  Note that the JFET stage inverts the signal, which shouldn't cause any trouble.

The JFET stage has: Rs = 1K, Rd ~ 5.1K, 1M resistor before the gate, 1 uF after the drain, and a 100K at the very end to ground.  Hope this helps.

[rocket88]

Interesting concept frank. I wonder how it will affect the tone of the fuzz if at all.

[Frank_NH]

The wave form is inverted and boosted in amplitude but isn't much different in shape from the original, so I don't think it would affect the tone much at all - just louder!  

[rocket88]

hmmm...... you know frank, i've got a really big project i'm working on, but i may have to get another breadboard just to mess around with them and see. looking at the graph it should be damn near identical, which does open up a lot, and i mean a lot of possibilities.

[Frank_NH]

Yeah - one thing to point out.  What looks good in LTSpice may NOT always work in practice, so prototyping on a breadboard is always the next step.  If you end up liking the circuit, you can then bang out a vero layout and use the breadboard components in your build.  Of course, you could go one more step and make a PCB layout, but I'm not at that stage yet...

[rocket88]

I comepletely agree. What should work in theory doesn't always work as expected in the real world. This won't help with my project at hand, but does get my mind running for other things.

[tracer03]

Wow, thanks for all the help. I'm going to try and breadboard this, but reading schematics is not exactly my forte...any chance you could make it easy for a rookie like me?

My only concern would be with increasing the output AND the bass might make it boomy - but we won't know until we try, right?

If anyone gets a chance to set this up, post back with findings!

[Frank_NH]

I put this on the breadboard tonight and...it works!    The JFET booster gets the fuzz plenty loud.  Here's my quickie demo on Vimeo link below (please mind my hack playing).  Guitar is an American Standard Tele and amp is my Roland BC-30 set clean.  In the middle I play with the volume control pot.  I didn't play with the bass control (it's set on minimum bass) , but it works fine and increasing the bass increases the "fuzziness" and warmth of the signal.  Enjoy...

Fuzz Demo

[tracer03]

OUTSTANDING! It even sounds like there was a bit more 'crunch' to the fuzz!

FYI, your link didn't work at first - looks like the forum software adds some garbage at the end of the url.

Copy and paste (DON'T CLICK) to check out the demo:

https://vimeo.com/206517153

[Frank_NH]

Thanks.  I created a quick (unverified) vero layout for the modded fuzz master here:

Silicon Fuzz Master with FET Boost

I will build this over the weekend to verify it, using my old 2N5138 PNPs which I've had lying around.  I knew they'd be useful for something.  

Let me know if there are any other mods that people would like to see with this.  It sounds pretty good as is, and to me is more of cross between a fuzz and a distortion.  The frequency analysis from LTspice confirms this, as it seems to overall emphasize the upper mids.

[Addy Bart]

Sounds great! Thanks for sharing the info on the JFET boost... I've got a build or two in need of some extra oomph.