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Hello children of the night,
So i'm planning on doing something with massive amounts of gain, but i'm not sure how I should go about it. I've been toying with the idea of basically using an amp chip, like the LM386, but at the same time, there's always scope for something like a MOSFET or some transistor action. Key point is to keep this pretty damn simple, so if it's transistor based, it'd have to be just 1. Any ideas/suggestions?
N.

Do you want massive amounts of gain, or massive fuzz/distortion/filth? they are not the same. you can have a high gain single transistor gain stage, but unless it's followed by some kind of clipping arrangement (e.g. diode pair to gropund), it's going to act as a large clean boost. there a few single transistor fuzz circuits out there, but they won't have the same filth level as something like a Big Muff. a simple but brutal fuzz can be achieved by taking the big muff schematic, removing the first transistor stage, wire a 10uF input cap folowed by the two clipping stages, then straight to 100k volume knob (i.e. miss off tonestack+Q4), use 2u2 caps to link the clipping stages. LM386 fuzzes are also apparently pretty brutal, but I've not tried one yet.

Gain. Planning on running it into a fuzz based on a fuzz face. I don't think a single transistor boost would do it, now that i think of it.

how much gain are we talking here?

There's a circuit called the Glass blower by Merlin (not sure if he posts here). As the name suggests, it is designed to roughly violate tube amp inputs, so might be just the ticket. It's not that simple, though - Two opamps and two transistors: You can download it free from elektor - http://www.elektor.com/magazines/2010/j ... 2402.lynkx

trad3mark wrote:Gain. Planning on running it into a fuzz based on a fuzz face. I don't think a single transistor boost would do it, now that i think of it.

I think any of the more popular MosFET boost circuits would do it: AMZ MosFET Boost, Super Hard On, etc.

The AMZ provides a TON of clean gain. That's what I would recommend for a boost stage to push a dirt circuit.

I would not use a LM386 for anything intended for monster gain. It's good at monster dirt/clipping, but it doesn't do clean worth a damn.

trad3mark wrote:Gain. Planning on running it into a fuzz based on a fuzz face. I don't think a single transistor boost would do it, now that i think of it.

At some point you're just going to end up with a Schmitt Trigger.

I've made a few AMZ's before. They're great for clean gain. I've 2 modified ones on my own board, and they get a fuck lot of use. However, for this I'm gonna have a go with the LM386. Had a look at the examples on the datasheet, and it looks like if i limit the gain to somewhere between 1 and 100, I might be alright. The plan/block diagram is to go:
Input>LM386 (using the LM386's gain control for the gain knob)>LPF (Using the LM386 for this too) > Some sort of Fuzz Face schematic > Output.

I've an Blowing Up, and I ran it into a few different fuzz's today, and it's close enough to what I want that if I start off with the above, I should be able to tweak it to get it right. Just want some serious sillyness out of this one, and I think LM386 will probably give good results.

trad3mark wrote:However, for this I'm gonna have a go with the LM386. Had a look at the examples on the datasheet, and it looks like if i limit the gain to somewhere between 1 and 100, I might be alright.

If you limit the gain to between 1 and 100, you'll end up with....gain of between 1 and 100. Gain of 1 is practically unity, especially when stating off with a signal as small as that from a passive guitar pickup.

If you want a ton of clean gain (i.e. - a lot more than gain of 1), I don't think LM386 is going to do it.

But if you breadboard it and find out how to make a 386 do loud AND clean, please post your setup, and there are going to be a lot of people interested.


I think your best bet on getting clean gain is to crank up the supply voltage. The further apart the voltage rails, the more gain you can get without clipping.

I'm not really looking for clean though. If it clips to fuck, that's ok. So culture jam do you reckon I should go from say 20-200?

trad3mark wrote:I'm not really looking for clean though. If it clips to fuck, that's ok. So culture jam do you reckon I should go from say 20-200?

Oh, I see. I thought you were looking for a ton of clean gain. Alright then, a 386 is definitely good for clipping like a sum-bitch and still being pretty loud. Have a look at this super-simple little project I did:
http://www.forrestwhitesides.com/node/93

cheers culturejam, although I'm avoiding clipping diodes. I prefer the natural breakup of things like boosts. I was looking at the 386 datasheet, and the schematics they suggest are very straightforward, and pretty minimal part wise. It's also an added attraction that you can incorporate a gain control and a LPF into the one "block" of the 386. In anycase, looking at the likes of the grace/big daddy projects on runoffgrove, or even the Tufnel distortion on beavisaudio, makes me wonder if i need something to pair with the 386. I know you used clipping diodes, and the others use things like a mosfet or jfet gain stage. Alternatively, I could put the fuzz face block before the 386, but i prefer it the other way around.

might look into some other amp chips. see what RS has. hmmm!!

Sounds like you've already got everything figured out. Good luck.

It's been a while since I looked, but isn't the mos/jfet in front of the 386 in those circuits?

why not stick this little transformer between the opamp and the fuzz face. fuzz face needs the impedance to be right
429-7202-RC on mouser
in the same datasheet look at the 429-7201-RC, that might be better than the 429-7202-RC