wrote:

Well, I'm just a tech hack so, I worked backwards and replace the
motors/brake assmbly first, and replace the complete transport control
PCB/switch assembly. Voila! so it was a good upgrade to all the newer
parts and the A67 is behaving better than ever. It was a joy to work
on, sort of like a tiny little car. BTW, is there a direct replacement
for the Lm-301 ic's in the A67. I've not heard good things about them,
but the deck sounds real good. If it can sound better, I'm up for it.

That's a funny thing.

The thing is, you can replace the LM301 with just about any standard
singleton pinout opamp. OPA604 is a typical one.

The problem is that lots of circuits using the LM301 have all sorts of
goofy things hanging off the side of them in order to compensate for
the LM301 deficiencies. I have a B&K recorder that has something like
six different poles in the NAB filter... and most of them are were
probably the result of cut-and-try engineering to get the circuit to
behave.

So, look at the circuit. If it's a straight gain stage, consider
trying a modern op-amp. Be aware that the much higher bandwidth of
a modern op-amp may result in stability problems. If you see all sorts
of inexplicable LCR stuff hanging off the feedback loop, or it's part
of an equalization network, you might want to hold off on the op-amp
swaps there.

I will say that Studer managed to get better performance out of the LM301
than anyone else out there. The Studer consoles use them throughout but
still manage to sound good. On the whole, though, the LM301 is the sort of
thing that gave op-amps such a bad name in the seventies and eighties.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."