A cold clipper for an amp's effects loop

Started by Derringer, June 18, 2019, 09:28:37 AM

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Derringer

Long story short, is there a better way to do this? The initial idea came from Michael Weidenauer's Sonic Tonic concept where he purposely misbiased a bjt buffer to the result of it clipping the negative cycle of the signal : https://www.diystompboxes.com/smfforum/index.php?topic=73226.msg593893#msg593893
I want to make my amp clip more asymmetrically, but without adding gain, and without modding the amp. I'm thinking in terms of how a cold biased triode stage (2203/4 - SLO, etc) works. A little gain is ok, but I'm not after a boost.
Here's what I came up with to make it more asymmetric:



Short story long.
I like the lead drive on one of my tube amps, an Egnater Tweaker 88, but it's lacking that certain "grind."
I scoped the preamp's output and, not surprisingly, the signal was very symmetric.

The circuit does the trick pretty well. That "grind" is definitely there. I can't turn down the 1K clipping pot too far because then it just makes ugly static-y noises when notes decay but it really doesn't need to be turned down all that much anyway.

Is there a better, more stable, possibly more variable way to do this?  Would different transistors allow me more play on that clipping-pot on Q1's emitter?

thanks

pinkjimiphoton

is the input cap 0.047 or 0047? i can't quite tell.. if its 4.7n, i'd go bigger.

to clip just one side of the wave, maybe try a shotke and led or germanium and led in series off the output cap? add like, a 50k trimmer or so between the 2 diodes n ground, and you should be able to dial in just a bit of half wave rectification.

i dunno if it would work in your circuit as well, but i find ge's drop too much output and cause a lot of fuzz, and led's tend to neuter distortion but are loud n buzzy, but the combo of the two in series is really musical and a bit louder than some other alternatives i've tried.

the led clips at about 1-1.5v, the ge at .03, and the thing is leds get weird on the note decays... they kinda fizzle out, or change pitch, or just cut out... but the ge keeps conducting and makes the decay a lot more smooth n natural. and tho ya gain some bite and compression, you don't lose too much output.

a single diode somewhere may make it come to life. i like 4739 reverse biased from how hemmo did the bazz fuss for a nice hint of asym clipping too.

hope it helps bro
rock on!
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Derringer

Thanks Jimi

Yeah, diodes are probably the easiest way to accomplish this.
I suppose I just had it in my head from the start that I wanted an active/variable clipper of sort.
Putting a pot in series with a diode and ground would probably do the same.