Electronics > Projects, Designs, and Technical Stuff
OK audio gurus: What are the highly regarded FET-input op amps these days?
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helius:
Analog IC technology may not be advancing. Smaller feature processes are developed for highly-integrated digital ICs, but have worse analog performance. It is entirely believable that the greatest op-amps were designed in the 1970s.
spec:

--- Quote from: Mechatrommer on December 06, 2018, 06:22:02 pm ---1) you may not like the answer (since you provided open question)
2) i'm not audio guru, just a repair stuffs, like you mentioned... but...

TL072 (from AQ-2000R 2KW Class-D amp)
(picture 1)

4558D (from PA37-M350 2.5KW monoblock)
(picture 2)

4558D (from AQ-854 1.5KW Class-AB amp)
(picture 3)

another i checked 4558D from AQ-2580R 350 x 4W ab-amp
(no picture)

its looks like 4558D wins but it aint fet opamp, if you want fet, then we have TL072 there appearing once in my statistics. they are not new chip, but they are far from obsolete, even in hung low grey beard market, and they cost like dirt... ymmv.

--- End quote ---

Apart from not being MOS input, the 4558 is two 741s, which are not good for audio work... sorry :)
spec:

--- Quote from: floobydust on December 06, 2018, 06:00:58 pm ---It's not that simple, you have to consider what the op-amp is seeing and doing.
Line driver? Tone controls? DAC reconstruction filter?

The better FET-input op-amps are expensive because they are laser-trimmed and prices can be crazy.

I would recommend OPA2134 or OPA134 and if you have money the OPA627 or OPA637. But $40-57 each :o

Careful swapping in a higher bandwidth part, they can oscillate in "old" circuit designs and not all parts are unity-gain stable.

--- End quote ---

Second the OPA2134 and OPA134. Nicely behaved, nice price, and sound nice too. :-+
Marco:

--- Quote from: floobydust on December 06, 2018, 06:00:58 pm ---OPA627 or OPA637. But $40-57 each :o

--- End quote ---

OPA637 might make some sense if it just fits your application perfectly and component cost is largely irrelevant. Getting an OPA627 instead of an OPA140 is just throwing money away though. OPA627 is a joke at HiFi nutter's expense.
Marco:

--- Quote from: helius on December 07, 2018, 09:13:52 am ---Analog IC technology may not be advancing. Smaller feature processes are developed for highly-integrated digital ICs, but have worse analog performance. It is entirely believable that the greatest op-amps were designed in the 1970s.

--- End quote ---

FETs seem exceedingly dependent on the consistency of the process and nothing that old seems to have a decent 1/f, we might have peaked with BF862 though since the market for good quality high area devices is drying up.
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