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previous: GFR Yes, you sure has something new (or... -- 4/8/1998 12:26 PM

Re: Soft clipping, CMOS and the Muff

4/9/1998 2:05 AM
MHelin	Re: Soft clipping, CMOS and the Muff This approach of varying the input resistor can lead to some interesting sounds. Doesn't increasing the input resistor add noise, too? Are there other factors that could be modified, how about biasing the diodes in FB loop. If you put the diode(s) between two caps you could change the DC voltages at both ends. Maybe you could take the bias voltage from envelope follower so that increasing level would keep the diode just below conducting, or you could use there a differential amplifier to keep the voltage across the diode below Vf (don't know). Though it would be simpler to get a DSP kit with A/D and D/A and start thinking numbers. I would sugggest (c) setting a DC bias in the input voltage so that you can chose the operating point on the feedback diode V-I curve. I have simulated some DC bias & diode clip circuits, and they seem to produce nice distortion when used together. The DC bias can be generated by the envelope of the signal, it can be inverted, and it's attack/decay times changed by changing cap/resistor values. I'm going to build a prototype which combines DC bias shift with soft, symmetric JFET clipping. I think even Tube Screamer circuit could be given a new life with the addition of dynamic DC bias shift. I just tend to go a little basic (excuse me, obvious) in my replies in such things as feedback amps, gyrators, boards layout, wave shaping, etc. cause I note that a lot of AMPAGErs don't have formal education in electronics. That's good, as I'm one who doesn't have any formal education in electronic... -Mikko

4/9/1998 2:05 AM

MHelin

Re: Soft clipping, CMOS and the Muff

This approach of varying the input resistor can lead to some interesting sounds.

Doesn't increasing the input resistor add noise, too? Are there other factors that could be modified, how about biasing the diodes in FB loop. If you put the diode(s) between two caps you could change the DC voltages at both ends. Maybe you could take the bias voltage from envelope follower so that increasing level would keep the diode just below conducting, or you could use there a differential amplifier to keep the voltage across the diode below Vf (don't know).
Though it would be simpler to get a DSP kit with A/D and D/A and start thinking numbers.

I would sugggest
(c) setting a DC bias in the input voltage so that you can chose the operating point on the feedback diode V-I curve.

I have simulated some DC bias & diode clip circuits, and they seem to produce nice distortion when used together. The DC bias can be generated by the envelope of the signal, it can be inverted, and it's attack/decay times changed by changing cap/resistor values. I'm going to build a prototype which combines DC bias shift with soft, symmetric JFET clipping. I think even Tube Screamer circuit could be given a new life with the addition of dynamic DC bias shift.

I just tend to go a little basic (excuse me, obvious) in my replies in such things as feedback amps, gyrators, boards layout, wave shaping, etc. cause I note that a lot of AMPAGErs don't have formal education in electronics.

That's good, as I'm one who doesn't have any formal education in electronic...

-Mikko

Replies:

Jack Orman I'm going ... -- 4/9/1998 7:42 AM
GFR Doesn't in... -- 4/13/1998 6:38 AM