On Tue, 17 Aug 2004 23:13:16 -0400, "Arny Krueger"
wrote:

"Chris Morriss" wrote in message


An LM3875 makes a useful little amp. It's basically a power op-amp
with just the five active pins, so it's easy to wire up a neat design.

I've got a three channel LM3875 amp I built to try out active
crossover networks to drive the bass, middle and tweeter of speakers.
I've used stabilised +/- 35V rails and it sounds and measures pretty
well.
(Actually, the wiring structure is important, I've heard of marginally
stable 3875 amps where people don't know how to return signals to the
0v line in the right place.)

The latest version of this part appears to be the LM4780 - reference
http://www.national.com/ds/LM/LM4780.pdf

Note that *with careful PSU design*, this amplifier is capable of
being made into a low-cost 'monobloc' using parallel operation, which
will equal or exceed the performance of any 'high end' 50 watt
amplifier. As the excellent article by Hennessy notes (as do the
application notes in the data sheet above), it is absolutely critical
to get the PSU design and layout correct. It's just good basic 'star
earth' engineering practice, but it *is* important.
--

Stewart Pinkerton | Music is Art - Audio is Engineering