TL072 Help

The parts list for the IR3109 has this footnote:

“Op-amps with good offset performance are recommended for IC4. Op-amps with good audio characteristics are recommended for IC2 and IC6.”

Can someone elaborate?


you can use better quality audio grade opamps, some OPA i guess should be drop in replacements.
don’t know which it is for the 072 though atm without browsing the datasheets

TL072s cause a bit of noise/distortion, which make people with very sensitive ears prefer the sound of more expensive op-amps (AD817, OPA2134, OPA275…). IC2 and IC6 are the op-amps through which audio goes, so if you want to do the upgrade that’s the place!

However, you shouldn’t play this op-amp swapping game zith IC4, since it processes CVs, not audio (DC performance is more important than AC performance, and you can’t get both).

TL082 have supposedly better DC performances and TL072 have supposedly better AC performance – that’s why I use TL082 on CV paths and TL072 on audio paths ; even if the difference seems to be marginal.

A last note: whatever distortion/noise the TL072 introduces is ridiculous compared to the amount of noise introduced by OTAs (be they in a LM13700 or in a CEM/SSM/IR chip). So far a true audiophile sound, eliminate those terrible chips first :smiley:

Ok. So I can forget the TL072 (distortion = 0.003% 595-TL072BCPE4) for IC2 and IC6, and get two OPA2134s, (distortion = 0.00008% Mouser # 595-OPA2134PAG4)? I can also use a TL082, for IC4 since it’s in the audio path.

What about the TL072 in the CEM3379 filter? Does it process CV or audio?

The TL072 on the CEM3379 board processes audio.

An OTA produces about 0.05% of distortion in optimal conditions. There’s no reason to believe the gain cells in the IR3109 have better performance. On the SMR4, to improve the signal/noise ratio I run the signals at a much higher level, so the distortion is in the 0.2% range. And this accumulates at each filter stage. Just to put things into perspective…

“The TL072 on the CEM3379 board processes audio”

Would the same IC swapping apply to the CEM3379? That is, can a person with sensitive ears replace the TL072 in this filter with a OPA2134?

Yes, a person with sensitive ears can do the swap.

haha funny how you put that.
i happen to be a person with less sensitive ears, but i have some OPA2134 here. i’ll try tonight if i can do the swap too.
but i kinda doubt that i’ll hear much difference.