What Makes An Audio Op Amp An Audio Op Amp?

I thought he was making a turntable preamplifier.

Greg

I think has a 1458 on my mind..

Jamie

The fact that it has a typical input noise voltage of 5nV per root Hz (worst case 6nV) at 1kHz also played a part.

There are plenty of lower noise op amps around, but the NE5532 was cheap and available in volume.

-- Bill Sloman, Nijmegen

"Abby Brown"

Q. What op-amps do audio designers like to use ?

A. Ones that can economically replace discrete transistor, small signal audio circuits with equivalent or better performance.

Back in the late 1960s, when general purpose op-amps like the 741 and 301A became available at low enough cost, audio designers pounced on them for the reason given above.

The next step in reducing board area and circuit cost was by employing dual and quad op-amps like the 4558 and 4136 - which were intended to be used in audio circuits.

The game is all about cost and often the op-amps used have performance characteristics way beyond what is strictly needed for processing audio signals.

.... Phil

The LM833 is still our go-to high-voltage opamp.

Probably the 742 ie with 2 per pack, as opposed to the 744 etc

Hi Phil. Nice to hear from you. I'm in Sydney at the moment - we should get together for coffee.

According to the Sydney Morning Herald, "Bill's" (no relation) serves the best coffee in Sydney, and it's on Liverpool Street in Darlinghurst, five minutes walk from where I'm living. It's a bit noisy for anybody who makes the money in audio, but "The Bunker" - which is a block closer along Liverpool Street - is much quieter, and teh coffee is almost as good.

Send me an e-mail at snipped-for-privacy@ieee.org ...

-- Bill Sloman, Darlinghurst (at the moment)

"Dirk Bruere at NeoPax" Phil Allison wrote: "Jamie the Radio Ham jerk"

Or in 8 pin DIL the LM1458

The quad 741 is the LM148 - also in 14 pin DIL.

.... Phil

On a sunny day (Thu, 7 Jul 2011 11:52:08 -0700 (PDT)) it happened Glenn Gundlach wrote in :

I disagree, I have used them a lot, not for audio mind you. Seems to work great in my thermocouple setup, and in my fluxgate compass.

What do you mean by high-voltage? The supply voltage? +/- 18V doesn't seem that high? (I'd love an opamp that worked with maybe 50 or 60 volts of supply, without having to use an expensive Apex part.)

George H.

OPA552.

John

Thanks,

Anything above 5V. ;-) That generally means 24-30V.

It is when you have to boost to get there. When almost everything else is

Use the trick Larkin has shown here a few times, with the FETs driven from bias networks in the power leads.

If you cascode that, you can go to +-500 volt rails from a low-voltage opamp.

And there's my ought-to-be-famous HV opamp circuit...

ftp://jjlarkin.lmi.net/HVamp.JPG

John

But where does FB go? ;-)

Wherever you like. It's an opamp.

Cool thing is that the rails don't have to be +-200. They could be -50 and +350, or +2000 and +2400.

John

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Hmm, I thought I needed BJT's in the power leads. I thought it was a current gain circuit.

George H.

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That's Great! It's a current 'gain' thing again. I could do with a fairly low time constant, does the FB take care of the cross over distortion?

George H.

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OK now I need an opamp with low idle current. (did you already recommend one?)

George H.