I need some opinions

[whomeno]

Which IC would be the better one in a mxr custom badass 78?
The TLC2262
The 4558 or
The TLO72
Or is there no deference in them?

[bluebunny]

It's a distortion.  Which is cheapest?   

[anotherjim]

If it has enough gain that it can clip, then NOT a TL0xx.
The TLC2262 might be best on full drive - but could be noisy.

[iainpunk]

both the 2262 and the 072 are Jfet opamps, while the 4558 is a bjt opamp, im my experience, a circuit like the mxr custom badass 78 really benefits from "slower" opamps, like the lm358, ua747 and of course the 4558.

but i suggest you put a dip8 socket on the board and you try them all out

[Fancy Lime]

The TLC2262 is a MOSFET, not a JFET opamp. Big difference. MOSFET opamps sound quite nice when overdriven, JFET opamps tend to sound awful when overdriven. If it matters at all depends on the circuit. I would need to see a schematic before I can really give any substantiated advice.

Andy

[iainpunk]

here is the schematic



really, do jfet and mosfet op amps sound different when overdriven? i never tried mosfet op amps to be honest, because i just assumed they sound like jfet op amps... how foolish

but to be honest, i have used the switch up effect of Jfet op amps to make a shitty octave fuzz on one of my oldest pedals. in a lesson on bad op amp behaviour, the teacher told us about that switch up problem in jfet op amps and i instantly thought : octave fuzz, yeah!!!

cheers,
Iain

[Fancy Lime]

here is the schematic



really, do jfet and mosfet op amps sound different when overdriven? i never tried mosfet op amps to be honest, because i just assumed they sound like jfet op amps... how foolish

but to be honest, i have used the switch up effect of Jfet op amps to make a shitty octave fuzz on one of my oldest pedals. in a lesson on bad op amp behaviour, the teacher told us about that switch up problem in jfet op amps and i instantly thought : octave fuzz, yeah!!!

cheers,
Iain

Yes, MOSFET opamps and "JFET" opams are completely different beasts. I put JFET in quotes because these are actually mostly BJT opamps but with a JFET input stage. Many of these have the latch up problem which sound horrible when fed with too large an input signal. Or interesting depending on the application. MOSFET opamps do not do that. In fact they are usually rail-to-rail opamps and clip quite gently, very much like CMOS inverters. Many people call that "tube like" but really it is just clipping without the harshness of BJT transistors being smashed into rails. Many of the Sansamp circuits use a MOSFET TLC2262 or similar hitting the rails to produce their "tube simulation", which many people seem to find convincing. Beware, there are schematics floating about the interwebs that claim that the clipping opamps in those are TL072's. Those are wrong (at least all the ones I've seen).

In the circuit you posted, it probably does not matter much. D2 should prevent latch up of a JFET input opamp (I think) but there is no advantage in using JFET opamp here. Hearing any difference between a BJT or a MOSFET opamp through the diode clipping afterward is probably going to be difficult. The gain of Q1 is so large that this stage will dominate all noise anyway. I would use a NE5532 or NJM2068 simply because I have those lying around. If you have a 4558 or 4580 or LM358 or really any ol' opamp, those should be just as fine here and sound extremely similar. This is not a circuit that relies on the characteristics of the opamp.

Andy

[Rob Strand]

here is the schematic

There were some updates to the schematic on the "other" forum.

[Phoenix]

It seems that latchup and output phase reversal are being conflated here, they are definitely not the same thing.

Latch-up occurs in some mosfet ICs when an input is taken outside of the common mode range, whereby the complementary pair totempole output form a parasitic SCR, the two transistors keep each other saturated and "latch" the output to one of the rails, and will continue to do so until they are no longer forward-biased, which almost always requires power-cycling. CMOS is particularly susceptible to latch-up.

Output phase reversal also occurs when an input is taken outside the common mode range, but instead this causes an input device to lose bias and turn off, causing the output voltage to swing to the opposite rail until the input returns to the common mode range and the input device turns on again. This causes a crude frequency doubling. This effect is mostly associated with BiFET op amps, but can occur in any op amp type including bipolar and FET unless specified not to, and may not always occur in op amps not so specified. The TL07x was formerly well known for this effect, with app notes going into specifics of how to avoid it, but most examples these days do not exhibit this behaviour.

[anotherjim]

With the clipping diodes, the op-amp clipping will be hidden - but any misbehaviour of the opamp may not be.
I do know that a TL (BiFet) instead of a TLC (MOS) opamp in a Sansamp clone makes a horrible fizz when overdriven that the originals don't exhibit.
A cheat is to fit feedback limiting diodes/LEDs with enough Vf to get maximum swing before it limits at the supply rails. For a 9v circuit, a Vf around 3v is about right.

[iainpunk]

It seems that latchup and output phase reversal are being conflated here, they are definitely not the same thing.

Latch-up occurs in some mosfet ICs when an input is taken outside of the common mode range, whereby the complementary pair totempole output form a parasitic SCR, the two transistors keep each other saturated and "latch" the output to one of the rails, and will continue to do so until they are no longer forward-biased, which almost always requires power-cycling. CMOS is particularly susceptible to latch-up.

Output phase reversal also occurs when an input is taken outside the common mode range, but instead this causes an input device to lose bias and turn off, causing the output voltage to swing to the opposite rail until the input returns to the common mode range and the input device turns on again. This causes a crude frequency doubling. This effect is mostly associated with BiFET op amps, but can occur in any op amp type including bipolar and FET unless specified not to, and may not always occur in op amps not so specified. The TL07x was formerly well known for this effect, with app notes going into specifics of how to avoid it, but most examples these days do not exhibit this behaviour.

yeah owkay, i meant output phase reversal octave fuzz, but still, it was a fun little box

[Fancy Lime]

@Greg,

you're right. I should get my terminology straight before posting, sorry 'bout that. Thanks for the corrections.

Cheers,
Andy

[Phoenix]

@Greg,

you're right. I should get my terminology straight before posting, sorry 'bout that. Thanks for the corrections.

Cheers,
Andy

Sorry, don't mean to be a pedant, just hope clarification is helpful 

[Elijah-Baley]

I try on the breadboard the ROG Mockman 2.0: http://www.runoffgroove.com/mm2.html Two  inverted input stages, high gain setting and none diodes clipping.
I bought a TLC2262 for it, one of the recommended by ROG, but the sound was like I was using a wah pedal in completely heel position. I swapped the opamp with a JRC4558 and with the circuit sounded more balanced, more normal.

I found the TLC2262 sound a bit weird. Did somebody got it, too?

[Fancy Lime]

@Greg,

you're right. I should get my terminology straight before posting, sorry 'bout that. Thanks for the corrections.

Cheers,
Andy

Sorry, don't mean to be a pedant, just hope clarification is helpful 

Yes it is helpful. I was being sincere when I said: thank you for the corrections! Somehow people often assume I am being sarcastic when I am not. Happens to me in person as well, not just in the sarcasm-innuendo prone world of online forums.

Cheers,
Andy

p.s.: Nothing wrong with being pedantic when you're right.

[anotherjim]

To quote ROG

...with strong equalization in each stage: a high-frequency emphasis combined with an aggressive low-frequency cut.

That TLC parts speed may be too different and messing with the intended EQ. That said I'd have to study datasheets. CMOS amps are normally/generally slower than bipolar. I thought the TLC2272 was the better-rated part for audio in the range; that is,
TL062, TLC262, TLC2262 versus TL072, TLC272, TLC2272. I assumed there was some logic in the Texas numbering system. "6x" low power, "7x" low noise and "8x" precision. I could be wrong about that.

[rankot]

If it has enough gain that it can clip, then NOT a TL0xx.
The TLC2262 might be best on full drive - but could be noisy.

TLC2272 seems to be the same as TLC2262, except it's less noisy?