New Distortion Design

[Joe Hart]

I found this site.

http://www.bcae1.com/opamp.htm

It could be helpful to others (although there may already be stuff like this in circulation here at Aron's site).

I haven't had a chance to explore the page yet, but I will.

-Joe Hart

[petemoore]

Two Words...
 Bread
 Board
 [long story] I use perfed sockets Alot!!
 THere are reads on all this stuff, but combining the reads with experiments tells much more.
 The Oa [depending on how it's set'] brings the voltage swing of the signal up to where when it 'see's diodes to ground, they clip...harder the higher the voltage swings at the OA output...[output diodes to ground like you have]...
  Raise the clipping threshold by going from Ge's to Si's to LED's, and/or set the opamp for less to more ouput for harder clipping.
 Two sets of clipping diodes...work but seem harder to tune...for tones that I like anyway..they seem to like a 'certain' setting...well I do.
 Being able to tune the circuit is the big key to finding the hard or soft clipping distortion one is looking for...consider switch to choose diode clip stages, warp or saturation controls for the clipping...etc.
 As shown the circuit will 'work' and may sound good, may sound rough..

[Joe Hart]

Bread Board. I hear you. I just wanted to get some of the obvious problems out of the way. Like that second opamp going to ground through the diodes. It seems obvious now, but I NEVER would have thought of that two days ago! And I would have had a non-working circuit with NO IDEA why.

Anyway, I was thinking of using more pots.

Maybe volume and gain for each of the two stages (4 knobs), 2 rotary switches for diode sets (2 knobs), and then maybe a 3-knob active tone stage at the end? I know this is 9 knobs, but what the heck. If they all provide useable tones, why not?

Any ideas on this?
-Joe Hart

[Ansil]

joe i had a friend of mine look at this as he was wanting to build it so i told him to get a bread board and this is what we came up with.

k 2.2uf instead of the 10k 1uf

brings the corner freq up to 72.4hz instead of 15.9hz

100k feedback resistor.
.001uf cap in the feedback loop instead of the 100pf

1k after the 4.7uf cap. into 2 5mm red leds. instead of 4 3mm ones

10k resistor after the leds and into a .002uf cap to ground.
into the second opamp. i doubled the second opamps measurements with the first except for i kept the same measurements you had. freq wise. i went for a 500ohm and a .47uf cap and a 100k and a 200pf aprox cap in the feedback loop.

i didnt' have any germaniums so i just used a silicon one and a red led.

my student quite likes this. and is going to make a board for it. in the next few days.

[Joe Hart]

Interesting. What's the number before the "k" in your second sentence?
Now I'm getting very interested in trying this out. How did it sound?
-Joe Hart

[Ansil]

Interesting. What's the number before the "k" in your second sentence?
Now I'm getting very interested in trying this out. How did it sound?
-Joe Hart

sorry 1k and a 2.2uf.  it sounded very nice kind of reminded me of your other pedal, but with a little more flexabliltiy to it. a little less highend on there. still plenty of highs but not hissy or shrill.  i liked it. i would build my own but i am way to busy with tubes right now. plus i enjoy the size of tubes as it doesnt cause my hands to cramp soldering them. like it does with ic's