This used to be a light overdrive circuit.

[Buildtestrepeat]

I clearly have little idea of what I'm doing.  However, this thing makes a bigger noise than I was expecting and I think you fine folk can help refine it and make it something useful or possibly tell me to drop it and move on.  This is my first time manipulating a circuit on a breadboard.  It started out as a Kaustic machines Kaiser overdrive to which I tacked on a screaming bird circuit for no other reason than because I could.  I put the complimentary darlington pair in instead of a single transistor because I wanted to see how they went together.  It works a whole lot better with humbuckers than it does with my mid 80's active emg singles.  I don't have any normal singles to try it with.  I'm still not sure posting this is a good idea but here goes..........

P.S.  I called it Scooter boost overdrive in honour of my last boss who is a very skilled guitarist.

[Gus]

I like the first stage pair I posted a "lead boost" using that type of pair at this forum
You might want to think about the first stage.
The 470K feedback bias lowers the input resistance.
Have you tried it after a buffered effect? Does it oscillate?
What are the collector voltages at both transistors?

What are you trying to build? That will help adjust the circuit.

Two gain stages in series is a good circuit to learn from a few have been posted at this forum over the years.
You can change coupling cap values, change the bias of the transistors, change resistor values adjusting loading and gain

[Buildtestrepeat]

Cheers Gus,  I'll take a look around the site and have another play on the breadboard.  Ultimately I'd like a smooth controllable overdrive that cleans up well. 

I thought it was about time I looked at how things interact after building a few pedals 'paint by numbers' style on vero.  I'll post again when I've had time to try a few of your suggestions.

[robthequiet]

My comment would be to consider a smaller value cap for the input, say a 1nF to start and work up/down. Season to taste, of course. I'm thinking that a smaller cap might give you less in the way of lower frequencies, so less flubby on the bass end. Just something to try. Lots of possibilities here.

*Edited for cap value*

[Buildtestrepeat]

This is starting to get usable.  Most of the values are what they are because I have a limited choice of components to work with.  I've borrowed the tone/volume circuit from another boost I found.

[balkanizeyou]

that's a good old Big Muff tone control 
looks good - you might try putting the boost stage after the tone control, not before it, and see how it sounds.

[punkbass]

hey,
cool schematic!
i think its too much gain is because of the sziklai pair/complemaentary pair has such a high Hfe, the equation for the combined Hfe is:
Hfe1 * Hfe2 + Hfe1 + Hfe2,
in my experience both transistors have a Hfe of about 220, so:
220 * 220 +220 + 220= 48840
thats a huge amount of gain, i use such a pair in my RustFuzz, (Ge for the PNP and a Si for the NPN), and thats without a second stage of gain
i'd say enlarge the 1k2 (to about 100k, or use a 100k trim-pot to set the gain) and maybe even ditch the 22uf to lower the gain,
if you want, you could use a volume pot at the front end of the pedal to reduce the signal that goes into the first stage...

one last note though, it could be me whos wrong, but the "boost" pot is kinda odd, i mean, shouldnt the incoming and outgoing wires be the other way around?? or am i missing something???

good luck building this thing!!!
greets,
      Iain

[robthequiet]

one last note though, it could be me who's wrong, but the "boost" pot is kinda odd, i mean, shouldnt the incoming and outgoing wires be the other way around?? or am i missing something???

I see that too but seems to me it's still a voltage divider, just puts the adjustment on the other side, so would it just reverse the knob direction?

[PRR]

> the "boost" pot is kinda odd

Yes, but that works too. It was actually the common way for very early transistor amps, also used in some Pentode amps, and one notorious Triode amp (Fender DeLuxe).

> still a voltage divider

TWO voltage dividers. Source impedance to bottom of pot, and top of pot to load impedance. This can give a quasi-"audio taper" with a linear pot.

It expects some source impedance (so the sound is not distorted with wiper at ground) and some load impedance (else the top of the pot does little good). This seems to be the case here.

> would it just reverse the knob direction?

No.

[Hemmel]

one last note though, it could be me who's wrong, but the "boost" pot is kinda odd, i mean, shouldnt the incoming and outgoing wires be the other way around?? or am i missing something???

I see that too but seems to me it's still a voltage divider, just puts the adjustment on the other side, so would it just reverse the knob direction?

Just add "1" where it heads to the 0.033µ, "2" on the wiper and "3" on the line that heads to the base of the 2N5088.