Hi,
What characteristics of an audio op-amp distinguish it from other op amps? Which of those are most desirable for a high quality circuit? Obviously, it needs appropriate bandwidth. What isn't important? If AC coupled is DC behavior relevant?
Just curious. I have made a few simple audio circuits as a hobby. In the past I've selected whatever was locally available listed as an audio op-amp.
Thanks, Gary
Audio opamp = a very cheap yet not extremely bad opamp.
Inexpensiveness.
Slew rate ~ 1 V/V, reasonably low noise.
Nothing is very important.
Depends.
Now try some other opamps. There won't be any difference except for pathological cases.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
Mainly, the capacity to drive relatively low impedance loads. The standard loudspeaker looks quite like an 8-ohm resistor, and regular integrated circuit op amps aren't designed to drive resistance that low.
Bob Widlar's LM12 integrated circuit amplifier is an exception, but it doesn't seem to have been cheap enough - or sufficiently easy to heat- sink - to take the audio world by storm.
Class-D switching power amplifiers are more efficient, so they don't require as much heat-sink area to survive when delivering useful amounts of power to audio speakers (which aren't all that efficient at converting electrical power into acoustic power) but they can have a tendency to mix the switching frequency with the music signals that they are amplifying, which has given them a bad name in the audio community.
-- Bill Sloman, Nijmegen
4558s are acceptable for many audio applications. Two op-amps in an 8-pin package for under a dime in reasonable quantity.
Superstition, mostly. Some really bad opamps are popular because people think they sound good.
Which of those are most desirable for a high
Just don't use LM324 types. They have visible distortion at 60 Hz.
John
It's not clear if it's just interstage opamps or driver.. Stability, noise, on off stability, circuitry involved can dictate bipolar or not.
Greg
The NE5532 was always a popular audio op amp as, unlike a lot of other op amps, it does not under go phase reversal of the output signal when overloaded.
From memory it was also specifed to drive 600 ohms.
"Abby Brown" wrote in news:w_- dnRA_JaBkWYjTnZ2dnUVZ snipped-for-privacy@supernews.com:
I want to help, but you left out some important information. I don't know your level of "formal" education so I'll hit a few high points. Please don't feel insulted.
An amplifier is basically just a device with gain (can amplify a signal) to which is added a feedback path to "feed back" some of the output to the input. That signal adds to or subtracts from the signal to be amplified, roughly setting the gain factor.
Different kinds of gain elements and feedback topologies give "good results" (adequate values of gain, linearity, noise, etc.) at various frequencies. Audio means signals in the frequency range humans can hear; optimistically, 20 Hz to 20 kHz.
Operational amplifiers were intended to be one-size-fits-all devices that you can hang components onto to make pretty much any kind of active circuit element. They were invented to stand in for linear and nonlinear amplifiers, integrators, differentiators, and other bits of analog computers. With them you can damn near anything from fake inductors to a sort of tunnel diode.
Hence an "audio op amp" is simply one that provides "good results" at audio frequencies. You have to define what "good" means in your specific situation, though, which is why there's more than one kind of opamp out there.
(OK, I left out some details.) ;>)
Now, about the "important information" you left out. What fidelity do you require? What's your load? How much power and heat are you willing to handle?
Answer those questions, find opamp data sheets, decide where you're willing to compromise, select.
Depending on your answers, a 741 could be adequate (not likely, but still) or you might be forced to give up on opamps entirely and think vacuum tubes instead.
Mark L. Fergerson
They're not even good as 14 pin thumbtacks.
G=B2
Most audio you hear has gone through an army of 5532s.
G=B2
But, somehow, passing them through one more tube produces "stunning" improvements in "musicality" or "macrodynamics" or something.
John
I love 324s, theyre cheaper than taking a dump. Distortion depends a lot on how theyre loaded, not that theyre ever quality performers.
NT
Once upon a time they were the least expensive thing around. For low distortion you simply bled enough output DC current to make it class-A. Larkin wouldn't know that in spite of me mentioning it dozens of times here. ...Jim Thompson
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I love to cook with wine. Sometimes I even put it in the food.
Back when I made audio/video kit, pre DVD, for studios we did indeed use the NE5532s by the bucket full.
Another advantage of the NE5532 for audio is that it has an abs max
+/-22V supplies compared to the more normal +/-18V or for the LM358/LM324 +/-16V. This allows one to design with more head room on the signal.
Yup. I guess lack of shoot through on the cross over would do that!
Jamie
if memory serves, aren't those equivalent to the 741 ?
Jamie
I was using some lm833's in the 80's. Like an up graded 1458. Opa132's were pretty good, bidet. National now has some rather spectacular chips at least specs look good.
Greg
Faster, very similar to 4136's quads.
Greg
"Vladimir Vassilevsky"
** What absolute BOLLOCKS !!!Piss off to hell - you stupid jerk.
.... Phil
"Bill Slowman"
Mainly, the capacity to drive relatively low impedance loads.
** Huh ???Read the friggin question !!!
.... Phil
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