Favorite quad op-amps for synth design?

Haible Juergen Juergen.Haible at nbgm.siemens.de
Wed Mar 22 12:55:03 CET 2000


Reply to various posts of this thread:

	>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. 
	>[...] piece-of-shit LM324..

Now I can't see how a crossover notch would disappear only from calling
+15V "30V" and -15V "GND". 

I agree, avoid low slew rate stuff like 324 or 741, *unless* you want to 
perfectly emulate the behaviour of an existing piece of vintage gear.
In that case, look twice before you throw out an allegedly bad opamp.
The circuit may have been tailored around this "bad" opamp's behaviour.
(even though the original designer would not consider using this chip
for new projects 20 years later, of course.)

If I had blindly replaced all 0.5V/us opamps with TL072's when I cloned
the HiFli, I would have got a bank of RF oscillators, for instance.
(I know, because I *have* blindly replaced them, but thank God I'd used
sockets (;->) )

	>This will be one of the first on the list when those books get
cracked. 
	>I'll assume it does not exibit the dreaded phase reversal (since I
get
	>the sneaky suspician you really don't like that).

The TL084 *does* show phase reversal.

	>You could go so far as to try and use an audio op-amp for other
duties
	>around the home if the economies of scale and application warrants
it.

The most daring circuit in that category might be a stompbox I've seen
(forgot which one), where one half of a dual comparator was cajoled to work
as linear opamp with some weird feedback circuitry. Disclaimer for the
newbies: This is to be *avoided* ! (... but even more brilliant if some
designer
makes it possible, and it works in a commercial product.)

JH.




More information about the Synth-diy mailing list