Blue (New) Clipper with diode-Compression Op Amp

[3/4 North]

I thought the Clipper would be a good canidate for this op amp since it clips the ic.  But it didn't work.  I breadboard the project twice and could not get any volume let alone distortion. Anyone else try it with the clipper?

[Joe]

Point me to the schem & I'll try it out.

[3/4 North]

Thanks Joe!

But the third time really is a charm. It's working great!  First I breadboard the Blue Clipper with a 4558 chip and got it working, then pulled the chip and breadboard your op amp in its place.  That op amp sounds amazing, less noisy & smoother sound.

Here's the Blue clipper schem...


...although I used the original 200k and 240k resistors instead of the 22k's.
Since the input is grounded I was wondering about the 1uf cap you recommend adding across the 10k resistor in the op amp. I tried it but it seemed to have no effect. Is it necessary?

I'm going to tweek and perf board it, be back with pictures.

[Joe]

Glad it works now. You don't need the 1uF cap in that circuit, it's non-inverting. It might be a good idea to stick a 5-10pF ceramic between base & collector for stability.

[d95err]

Glad it works now. You don't need the 1uF cap in that circuit, it's non-inverting. It might be a good idea to stick a 5-10pF ceramic between base & collector for stability.

Which base & collector? On all transistors in the discrete opamp, or?

[Joe]

I meant to say on the output transistor.

[3/4 North]

Here's a schematic of the Blue Clipper with the op amp.  This is how I built it on the breadboard with an added toggle and gain pot. The toggle is interesting, I can really hear the compression kick in and I get some added sustain when I lower the tone.

Joe, I put the cap you suggested in red, is this where you say it should be?



Because of the way our server is set up I can't see the image, let me know if it doesn't show.

[WGTP]

Now you'll have to try Joe's alternative diode compression circuit out with it.   

[WGTP]

http://www.diystompboxes.com/smfforum/index.php?topic=48507.0

[3/4 North]

http://www.diystompboxes.com/smfforum/index.php?topic=48507.0

Cool, I'll give it a try!

hey Joe, how 'bout drawing up a JFET version of the op amp for us "electrically ungifted"?

[Joe]

You can use some P-channels with slight tweaking of the 6.8k or 4.7k resistors. I tried inverting the circuit and used J201 inputs/2N5087 output and flipped voltage/diode/electrolytic polarites, and didn't have to change a thing. The problem is that the gain is way too low, and I'm not sure it sounds better. I think a MOSFET discrete opamp is in order, maybe that's coming next?

P.S. R6 should be 6.8k.

[3/4 North]

Thanks, I fixed the schem

And I thought I'd post the original unmodified Dan Armstrong schematic


I attempted to add a tone control but the toggle on the input cap just wasn't doing it for me.  It went wimpy to muddy.  But the gain pot works well.

This is where I'm at now.


The soft clipping diodes sound good and helps the tone, probably because of the caps.
Not much left of the original clipper.

[WGTP]

If you want to try tone switching, try doubling or halfing C4, the 4.7uF cap.  That should have lots of effect on the "character".   

[3/4 North]

Thanks! I'll give it a try tonight

[WGTP]

Forgot, might jack up R12 150K resistor to 470K, 825K or 1M for more gain, if you need it.   

[3/4 North]

This thing has tons of gain and good sustain, that's why I was thinking the JFET op amp would be no problem.

[WGTP]

Mosfets, BS250's and BS170 should work with resistors tweaked.   

[3/4 North]

The 4.7uf cap had no effect on tone, guess I'll perf board it the way it is, unless Joe posts a mosfet version soon...

[WGTP]

Hmmm.  You should hear a difference, but if the gain isn't maxed, you may not be able too.  I'm such a gain pig, I usually set things up on my bread board without a gain pot.

[3/4 North]

I did a perf board layout


since these are usually disastrous for me I took an Arts & Crafts approach this time and wove the traces in with copper wire.



Here's a shot of the finished board (with an added 1k resistor to ground off the gain, so it's not so crazy sounding)



And here's the back



It's a good sounding distortion with lots of volume and sustain