Xref: utzoo rec.audio:8234 sci.electronics:3807
Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!ucsd!brian
From: brian@ucsd.EDU (Brian Kantor)
Newsgroups: rec.audio,sci.electronics
Subject: Choosing Op-Amps
Message-ID: <1152@ucsd.EDU>
Date: 14 Sep 88 06:16:10 GMT
Organization: The Avant-Garde of the Now, Ltd.
Lines: 27

As part of my design for a really wonderous hi-fi preamp, I've been
trying to choose the right op-amps to use - or indeed, to discover
whether simple discrete transistor or FET amplifiers might be better.

For the RIAA phono preamp section, a simple LM540 with about 20dB of gain
winds up with a frequency response well past 20kHz, and a slew rate of
better than 3V/uS, which is pretty respectable (I think).

For the tone-control section, a pair of MC1556s make a nice high- and
low-frequency shelving equalizer with maximum of 20dB of boost and cut,
and knee frequencies of 2kHz and 200Hz respectively.  This part of the
circuit will be bypassable by a "FLAT" switch.

Finally, I think a LM540 will do nicely for providing the required 10dB
or so of preamp gain to drive the power amp to full output from
line-level input signals, and also the tape deck dubbing outputs.  I could 
use an LM715, but it lacks the output capability to drive more than about 
30pF of load, and I'm afraid that the several tape deck inputs in
parallel would probably be more than that.

These are based on a 10-year-old IC op-amp design book.  Are there
better chips for this purpose made these days?  Any recommendations?

	Brian Kantor	UC San Diego

   "There is more harmony in films than in life."
	- Francois Truffaut