Favorite quad op-amps for synth design?

Batz Goodfortune batzman at all-electric.com
Wed Mar 22 08:14:40 CET 2000


Y-ellow Y'all.
	for the record. I don't have a wife. It's a waste of space in bed where I
can fit more data books. Think I need a bigger bed.

At 11:06 PM 03/21/00 -0500, Harry Bissell wrote:

>LM324:  I hate this op-amp. If I was on Apollo 13 and likely to die I'd use
>it... if the pinout matched...
>But seriously folks... Its single supply only. Dual supply has a crossover
>notch
>that makes it suck for audio. Some say a resistor to the negative rail fixes
>it...
>but to me thats like "Taking something that tastes bad and making it hard to
>eat too..."

Heh Heh. Actually I like the 324. On the grounds that I would never use
them for audio. Ever! These things are the bee's knees for any voltage
buffering (Or voltage Buggering as the case may be.) you might want to do.
they're cheap and reliable for this kind of stuff.

I've seen people trying to use 3900s for audio too. Great if you like
noise. Otherwise...

>4136: wierd pinout... avoid

Now these things I really hate with a vengeance. These things remind me of
the cone of silence in "get Smart". Where protocol may dictate that you use
one but god help you if you do. These things never work right and always
with a different finicky problem. And the pin-out sucks.


>LM3900 Norton:  Very little experience. Used to think it sucked, but I
>didn't
>understand it. NOW I think its very clever. Its a Current Controlled Voltage
>Source basically. Like that ARP filter that used it. Two stars **

Noise will be noise. Never tried it in a current app. Never needed to but
for audio.... Yuck.

I tend to consolidate my op-amps for audio because it saves me trying to
buy 12 different parts to do basically the same job. Traditionally I use an
LM833 (Dual) or it's quad equivalent, the LM837. IMHO, these things are
wonderful. though they are roughly identical to the NE5532/5534 types. Only
I don't think you can get those in a quad. The LM833s are generally cheap
by the bucket load and if you can do everything audio with just those chips
then you don't need to go buy bucket loads of anything else.

For the record though, It's bloody hard to get anything decent here at a
decent price in anything less than a bucket load. And then usually by
getting it direct (Or indirectly) from the States anyway.

Now your mileage may vary. You might find that it's actually cheaper and/or
easier to get a tube of those new fangled op-amps from AD. But since
obtaining AD stuff from here is something akin to pulling teeth, I couldn't
vouch for them.

I do use the FET input types as well. LF347 etc. I bought a bucket load of
them years ago and still have about half a bucket load left. What I do is
only use them where I really need their qualities. For the rest of the
time, in audio circuits, I use 833s 837s.

Generally speaking, an op-amp in an audio circuit is interchangeable. Just
that some perform better than others in audio. You can have a great op-amp
with low drift and as close to bugger-all offset as you like, but it's
going to be no good to you if it's a bit noisey. Or if it's  gain bandwidth
product and slew rate are going to amount to a lowpass filter or something.
Offset isn't important in audio. Well if it were a couple of volts it would
be but it's not as important as noise VS gain. And output impedance is
another factor. Regardless of the other specs it may have, if it can't
drive a 600ohm load then it's not worth the beach sand it was made from.

Most op-amps these days have the standard pin-out and are interchangeable.
If they're audio types then pick the one that gives you the most bang for
buck and buy a bucket load.

Use a 324 for buffering voltage etc. Use a fet/hi-z input op-amp for doing
sample holds etc. But use any audio type op-amp for audio. And grind up
your old 741s and put them back on the beach where they belong.

>H^)    Harry (who does not exhibit phase reversal, has fairly high input
>impedance, but cannot tolerate crossover distortion.....)

That's just what Reverend Nile said about the Sydney Gay and Lesbian Mardi
gras.

(I love these guys. Every year they get out there and prey for rain. It
never does. Buy even if it did, it would only turn it into a "wet 'n' wild"
night.)

Be absolutely icebox.

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