Simple Drive

[Bill Mountain]

The bass version offered some nice boost but I didn't get any dirt.  It would we be a great input stage to a dirt pedal though.  I may use something like this in my next muff build.

[Gus]

The bass version offered some nice boost but I didn't get any dirt.  It would we be a great input stage to a dirt pedal though.  I may use something like this in my next muff build.

Thanks for trying it

That reads like it worked as I simmed it.  It should help by driving a stage(s) after it with more signal level with EQ and some distortion from the grounded emitter gain stage.

Yes it should make a nice first stage for a BMP
it is the same type circuit as in the BMP first stage
it is adjusted different, grounded emitter and added AC feedback R11, C5

What type bass did you try it with?   

[Bill Mountain]

The bass version offered some nice boost but I didn't get any dirt.  It would we be a great input stage to a dirt pedal though.  I may use something like this in my next muff build.

Thanks for trying it

That reads like it worked as I simmed it.  It should help by driving a stage(s) after it with more signal level with EQ and some distortion from the grounded emitter gain stage.

Yes it should make a nice first stage for a BMP
it is the same type circuit as in the BMP first stage
it is adjusted different, grounded emitter and added AC feedback R11, C5

What type bass did you try it with?  

I used a G&L SB-1 tuned to C Standard with a off the shelf fender p pickup.  I actually populated a PCB with this basic setup in Q1-3.  Due to PCB limitations I wasn't able to include R11 & C5 with each stage.  I may be able to swap out the feedback caps with R11 & C5 but I worry there will be too much hiss and shrill highs.  I guess I could at least try it with input stage.  When I breadboarded it I couldn't really here a difference with R11 & C5 removed but the only amp I have on my bench is a small crate guitar combo amp.

I was worried about a low-ish input impedance but with all the frequency manipulation and the feedback caps, I don't hear any loss of highs when I don't buffer the input.  Further experimentation is required though.

It's funny.  I've tried 1000's of different tweaks to big muffs over the years and I've even played around with grounded emitters but last night was the first time I was able to achieve that gritty overdrive texture that I've heard about but never experienced.  I always get harsh synthy distortion with stock Muffs.  I also used 47nf series diode caps so it clips less bass but it's also boomy so I need to tweak that as well.  I wired it with no "sustain" control and replace R5, R4, & C1 with a 4.7uf and 500k reverse log pot as a "sensitivity" control.  I didn't want to lose any bass at the input because I am cutting some bass already in the later stages (to help limit the synthy textures).

The trannies measure about 4v on the collectors.

I wanted to avoid working on a Muff because that horse has been beaten to death but there is so much that one can do that you could spend your entire stompbox modding career tweaking this simple design.  I'm not sure if it sucks or its awesome that so many vintage circuits got it right 40 years ago.

[Gus]

I built the bass version and installed it in an enclosure. 
The low end boost is hard to hear in headphones I need to try it with an amp and speaker setup.

I used a 50K gain control for R5 and 100K volume for R6. 
I might put a set of clipping diodes across R6.

[The French connection]

Schemas and layout not verified yet!

[Gus]

The Foxx select a fuzz got me thinking about post 16.  I wonder if the cap resistor from Q2 collector to base are for kind of the same EQ