Bipolar opamps with desirable clip behavior

[phasetrans]

Hey all,

Does anyone have a list of (bipolar preferred) opamps that clip with no nasty side effects? Ideally on both single and dual supplies, and at or near unity gain.

Especially curious if anyone has tried ST TS522...

[PRR]

> near unity gain.

If both stages are on same/similar power supply, then the stage before the unity-gain stage will control clipping distortion.

[antonis]

edit: Paul said it concisely..!!

[phasetrans]

> near unity gain.

If both stages are on same/similar power supply, then the stage before the unity-gain stage will control clipping distortion.

Sure. I was intending to reflect from a stability standpoint what the loop gain should be.

[antonis]

https://www.analog.com/media/en/training-seminars/tutorials/MT-033.pdf

https://www.analog.com/en/technical-articles/loop-gain-and-its-effect-on-analog-control-systems.html

https://www.ti.com/lit/an/sloa020a/sloa020a.pdf?ts=1605423656034

https://www.ti.com/lit/an/slyt367/slyt367.pdf

[MikeA]

Intersil CA3260A.  It's MOSFET input and CMOS output, so twice not BJT, but in the Ibanez MT10 with 100mV input, the clipping stays softly rounded all the way up to max gain.  The wave never squares off.  I haven't tried it with higher (boosted) level inputs, that would be a good experiment.  It's stable at unity gain.  Mike

[Mark Hammer]

Just received my stash of 3260 chips from China this past week.  Plunked one into the MT10 clone I had built.  Still need to  swap different chips into the socket to listen for what difference it might make.

[iainpunk]

UA741 with 1k resistors between the Vcc and Vee pins and the supply. also works with the CA3140 and CA3180. your mileage may vary.

cheers, Iain

edit:
forgot to say that it has some (a lot) of problems with double and quad op amps, so only use single op amps
i just re-read my post and noticed that what i wrote could be interpreted wrong, so here is a schematic:

[MikeA]

Just received my stash of 3260 chips from China this past week.  Plunked one into the MT10 clone I had built.  Still need to  swap different chips into the socket to listen for what difference it might make.

Mark, I got a few from UTSource last winter and tested them head to head with my Intersil stash from Mouser.  They may catch fire tomorrow, but they have all the right markings, tested 100% the same on the scope and sounded the same in the pedal, so I keep a stock now for my MT10s.  I do plan to test each batch in the future, and these came from UTSource directly, not one of their marketplace suppliers.  Mike

[phasetrans]

Intersil CA3260A.  It's MOSFET input and CMOS output, so twice not BJT, but in the Ibanez MT10 with 100mV input, the clipping stays softly rounded all the way up to max gain.  The wave never squares off.  I haven't tried it with higher (boosted) level inputs, that would be a good experiment.  It's stable at unity gain.  Mike

Mike,

Thanks. Just the cheat sheet sort of insight that puts another line on my "parts to try" order.

[Steben]

Is it me or do I see a noninverting feedback clipper in the MT10 schematic?  Not much opamp clipping there. Or is the last stage?

[iainpunk]

the 2nd gainstage clips, probably
4 diodes = 4 x 0.6 = 2.4V
2.4x4.7 (2nd gainstage)=11.28
11.28 > 9v  so yes the 2nd gainstage will clip, even if we ignore the fact that there is also a bunch of clean signal added due to the soft clipping, which i ignored to balance out insertion loss of the tone controls.

cheers, Iain

[dschwartz]

My favorite is a humble inverting 4558 with blue leds on the feedback..it has plenty of headroom, low noise, and 2 of those stacked can go very high gain.
Never bothered to experiment with uncommon opamps clipping..with leds, the behavior is more predictable and its just a tad below the normal opamp clipping powered by 9v

[Steben]

the 2nd gainstage clips, probably
4 diodes = 4 x 0.6 = 2.4V
2.4x4.7 (2nd gainstage)=11.28
11.28 > 9v  so yes the 2nd gainstage will clip, even if we ignore the fact that there is also a bunch of clean signal added due to the soft clipping, which i ignored to balance out insertion loss of the tone controls.

cheers, Iain

Not sure it is 2.4v into that stage... i see passive tone controls.... will have to look further what loss this means

[willienillie]

Just received my stash of 3260 chips from China this past week.  Plunked one into the MT10 clone I had built.  Still need to  swap different chips into the socket to listen for what difference it might make.

I was not familiar with the MT10, so I looked up a demo.  Sounds pretty good!  Since I don't have any 3260s, I'm curious what the results of your comparisons were.

[iainpunk]

the 2nd gainstage clips, probably
4 diodes = 4 x 0.6 = 2.4V
2.4x4.7 (2nd gainstage)=11.28
11.28 > 9v  so yes the 2nd gainstage will clip, even if we ignore the fact that there is also a bunch of clean signal added due to the soft clipping, which i ignored to balance out insertion loss of the tone controls.

cheers, Iain

Not sure it is 2.4v into that stage... i see passive tone controls.... will have to look further what loss this means

yes, but its also soft clipping, so i guesstimated that the same amount of clean would be added as the subtracted signal if the tonecontrolls are all set to max., and the opamp in question already clips at a way lower level than the headroom of the supply.

cheers

[Steben]

yes, but its also soft clipping, so i guesstimated that the same amount of clean would be added as the subtracted signal if the tonecontrolls are all set to max., and the opamp in question already clips at a way lower level than the headroom of the supply.

cheers

That might be true.
Can't find datasheets with the output curves.... Perhaps it functions as CMOS buffers.... more yet softer clipping amount at lower supply voltages...