anyone interested in my new overdrive?..

[wakeuptone]

Great Sound.... If you can put Tone pot,it will more great.

[Johan]

I sort of ran out of steam with this one when there was too many other things that needed attention in my life, but here is how far I got, and where it stands.( I havnt given up on it, it's just pushed to the side for the moment)

tonecontroll. just hang a regular guitar tone controll-style pot and cap to ground across the volume controll. I used a A100k and 0.047uF. the input cap was reduced to 0.047 and the cap to ground in the first firts amp was increased to 1uF. I also reduced the resistor from gain pot to second amp down to 2k2..

..I do think there is a lot of potential in this simple circuit and felt that it gave me a very amp like responce that didnt feel like playing a stompbox. I do think that in some respect that came from low gain, but more experimentation will show the truth about that...I do encuroage anyone to experiment with it
J

[deadastronaut]

@johan. sounds great...a little more gain on that and it would really rip...

as you say well worth tinkering with...thanks for sharing . rob.

[BadIdeas]

Hey, Johan, I did most of what you said, minus the tone control. I think those cap values were a good call, the frequency content is not quite so harsh. Here are some observations and what I have done so far. Much of it is simple "tweak to taste" stuff, but here it is:

There was quite a bit of volume drop and loss of low end with the controls at 12 O'clock, so I added a 47k minimum gain resistor and a 10k minimum volume resistor. That seemed to help the volume some.
The series 10k resistor at the end is now 3k3. I had tried 1k and it seemed to add quite a bit of headroom as well as helped the volume, but i preferred a bit more clipping.

The pedal is sounding much more dynamic and responsive now, but as always, I think there is still room for improvement. The funny thing is, the frequencies that were harsh and offensive before don't seem to distort enough now. Double stops around the 12th fret don't
Ha, I guess I could actually use the gain control.
That's it for now. Keep us posted if you have any other suggestions.

[BadIdeas]

Did some more work today.
I didn't really try your tone control because I was already having problems with the volume level before, plus the frequency content was such that I no longer really wanted to reduce the treble. Instead I went here:
http://www.muzique.com/lab/swtc.htm
and learned about the various versions of the Stupidly Wonderful Tone Control. Not wanting to load the output with another resistor (pot) to ground, I though it would be better if the tone control could be made using the existing circuitry. The third example on the page looked an awful lot like your last clipping stage, minus the diodes. Here's the rundown:

*The 3.3k resistor became R1: 560R and R2: 4.7k.
*Your parallel diodes swap places with the 10k Resistor, which now becomes a pot. CW to the diodes, CCW to ground.
*I put a .22uF cap from the junction of R1 and R2 to the wiper (would have tried .27uF, but didn't have any).
Voila! That's it. Give it a try and compare the two and tell me what you think. Remember to observe the same ratio between R1 and R2 and that the cap must be larger that what is suggested at AMZ because of the lower resistance.

[BadIdeas]

Played around some more, and my conclusion is that my tone control idea may not have been so clever after all, so now I am focusing on other parts of the circuit. Previously, I had increased the gain of the first stage just a bit to make it more usable at lower gain settings. I also found that at these settings, the second stage was nearly unity gain, and added nothing to the sound.

100k*(3.3k+90k from the remainder of the resistor)=1.08

I overhauled the first stage by halving the resistor/pot values and compensating the cap, and the thing was VERY responsive to dynamics, but now it gets unstable and harsh at high gain settings as the two stages multiply.

29.5*45.5>1000

At this point, I think that using the gain pot to control both settings, while clever, is actually a bit of a detriment. I am thinking of reducing of the first stage's gain back down as well as further reducing the resistor/pot values to make the second stage more independent of the first stage. I also believe that replacing the first LED with a 2n914/similar to compensate for the reduced gain will help.

Little gain clips pick w/ silicon --> more gain clips amplified signal w/ LED --> small signals clip diode pair.
Here's what I've done so far. I hope this works; it's my first time hosting my own image.
http://img62.imageshack.us/i/drive3411.jpg/

[BadIdeas]

Newest Verson:
http://img850.imageshack.us/i/drive3511.jpg/
Buffered the second gain stage from the first, so now the gain won't increase exponentially. Forgot to specify in the image (forgive my Paint skills) but the tranny is a 2n5089. Still quite dynamic. The gains pot is perhaps not as useful as it once was, especially for low gain settings, but the higher range is more useful I think. Max gain total: Approx. 150.
To answer your original question, yes I am very interested in your new overdrive. 

[Paul Marossy]

That sounds really good in the right hands. 

[Johan]

cool...I cant build anything since my apartment is being renovated ( all water and sewage pipes are being replaced, pulled out of the walls and floors...) so I have to stay with friends for a month. but Im glad you made it work for you. I will try your mods when I get back inside my own home, but it'll be a while..
J

EDIT: if the purpose of the emitterfollower is to isolate the second stage from the gain pot, wouldn't it be easier to just move the wire on the pot from the outer leg to the viper?..

[BadIdeas]

  I guess you're right. Oh, well. It was good practice. I'm just studying transistor amplifiers in a book and learned how to bias one, but now that you mention it, that should have the same effect. Well, taking that off will free up some space on my board.
After I find time to experiment with feedback caps to make it sound less "fluttery" on big notes, I plan to give tone control another shot. I was going to go with another passive one like you suggested, but since I also plan to add an output buffer, I might sort of combine the two...
Since the effect is inverting like I pointed out earlier, I was thinking about using a dual opamp, a non-inverting unity gain amplifier followed by an inverting. I might use the non-inverting amp as an Ibanez-style tone control. What do you think?