Jim Lesurf wrote:
In article , Wally
wrote:


The pre-amp is a Cambridge A75. The chips it uses are NE5534N
op-amps, evidently low-noise and suitable for high quality audio. My
intention was to use the same chips for my active filter / output
stage, on the assumption that the pre-amp's PSU will be delivering
the right voltage(s). However, it looks like these chips are no
longer made - what would be a suitable alternative?

Erm... despite the magazines, etc, I'd say almost anything would do.
:-)

I dare say. :-)


My personal favourite has always been the Hitachi HA12017, but these
are now hard to find, and require more components than most. Despite
the hostility of some of those in audio, you could consider the
TL071/81 families as used by Quad in the 34 pre-amp. These are quite
easy to use.

Righto.


Dunno. However I'm not sure what you are thinking of an an
'integrator'. A genuine integrator has a gain that approaches
infinite as you go down to d.c. and hence is nominally unstable. Its
phase lag is 90 deg at all frequencies.

Then the thing I read about must have a different name... :-)


Have a look at some of the pages on filters in the 'Scots Guide'. This
inlcudes some basic stuff on designing simple filters with ICs.

Scots Guide? One of your pages?


--
Wally
www.artbywally.com
www.wally.myby.co.uk