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OK audio gurus: What are the highly regarded FET-input op amps these days?
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basinstreetdesign:
I have been using LM4562 for a while now with no complaints.  They are VERY linear, quoting an amazing 0.00003 % typ distortion, 55 MHz GBW, unity gain stable and with Ibias of only 72 nA.  They are in standard pinout in soic-8 and stk at DK at USF$2.79 for 1.

https://www.digikey.ca/products/en/integrated-circuits-ics/linear-amplifiers-instrumentation-op-amps-buffer-amps/687?FV=1f140000&k=lm4562&pkeyword=lm4562&stock=1&ColumnSort=1000011&cur=USD&lang=en

They are characterised for distortion, CMRR, PSRR, etc up the yin yang.
Marco:

--- Quote from: floobydust on December 07, 2018, 06:55:56 pm ---There have been audio op-amp distortion measurements and comparisons with double-blind listening tests.

--- End quote ---

Increasing the distortion by 80 dB to do a "listening" test ... is that to emulate the audio chains you will find everywhere with 200 opamp circuits? :)
GregDunn:
I have several audio boxes which use either the TL07x or NE553x op amps; some of them are just low or unity gain amplifiers, others are single or double pole filters.  I've driven them with millivolt levels (phono preamp) up to 5-10V levels and they behave just fine.  All are suitably low noise for audio and transparent.  We actually did a double-blind test against a very high end tube preamp about 30 years ago and couldn't tell them apart.  Pretty much any op amp in the same category will be more than good enough if you pay attention to the spec sheet when picking them.  I think the NE5532 is unity gain stable whereas the NE5534 requires compensation?
Mechatrommer:
I guess in audiophewlery, first there's blind test or post. And then there's double blind post, and then there's showing real circuit. I see a lot of work was done on filtering, those tantalum and ceramics caps?  and then there's discreete power stage AB topology with careful biasings. And then there's speaker box resonant calculator or whatnot. Is it worth  arguing something that contributes less than 1% from the whole system? And then there's tube transistor that sounds white, man.. i cant hear 1MHz anyway..
Zero999:

--- Quote from: GregDunn on December 08, 2018, 04:19:07 am ---I have several audio boxes which use either the TL07x or NE553x op amps; some of them are just low or unity gain amplifiers, others are single or double pole filters.  I've driven them with millivolt levels (phono preamp) up to 5-10V levels and they behave just fine.  All are suitably low noise for audio and transparent.  We actually did a double-blind test against a very high end tube preamp about 30 years ago and couldn't tell them apart.  Pretty much any op amp in the same category will be more than good enough if you pay attention to the spec sheet when picking them.  I think the NE5532 is unity gain stable whereas the NE5534 requires compensation?


--- End quote ---
The NE5534 is stable in gains of 5 or less, but is faster than the NE5532.

Yes, it's all a load of bollocks, the distortion produced by modern op-amps is negligible, compared to speakers and the room acoustics.


--- Quote from: basinstreetdesign on December 08, 2018, 01:34:49 am ---I have been using LM4562 for a while now with no complaints.  They are VERY linear, quoting an amazing 0.00003 % typ distortion, 55 MHz GBW, unity gain stable and with Ibias of only 72 nA.  They are in standard pinout in soic-8 and stk at DK at USF$2.79 for 1.

https://www.digikey.ca/products/en/integrated-circuits-ics/linear-amplifiers-instrumentation-op-amps-buffer-amps/687?FV=1f140000&k=lm4562&pkeyword=lm4562&stock=1&ColumnSort=1000011&cur=USD&lang=en

They are characterised for distortion, CMRR, PSRR, etc up the yin yang.

--- End quote ---
The LM4562 is a completely unsuitable replacement for a J-FET op-amp. It's a BJT input op-amp with a high bias current of 72nA, compared to, 65pA typical, 20nA worst case, for a J-FET op-amp such the old TL072 and a 55MHz of GBWP could be far too fast for a circuit and layout designed for one with a GBWP of 3MHz. The input current noise for the LM4562 is 1.2pA/√Hz which will make it vary noisy when the inputs are connected to a high impedance. The old TL072, with an input current noise of just 0.01pA/√2 will be less noisy in applications when the input is connected to a higher impedance than 15k.

Note that it's only specified for that very low level of distortion when in unity gain configuration and with an output voltage of 3VRMS, not that you'll notice the increased distortion at lower and higher output levels. It's just a case of the figures being manipulated to make it look good.
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