"Jim Lesurf" wrote in message
...
..

BTW I just looked at my copy of the 306 diagram. If you are referring to
'IC1' (TLC271) then you might like to note that IIUC its role seems to be
to null the dc offset of the amp. The 2M2 resistor (r33) and 680nF cap
(c3)
mean it only really does much around the 1 Hz region and below.

Indeed, unlike the 405 in which the TL071 op-amp is in the signal path. So
why is anybody stupid enough to waste good money "upgrading" the op-amp in
the 306?

David.