On 16/05/2016 14:35, Don Pearce wrote:

This is worth a read. It describes an upgrade that reduces gain by
10dB - designed to match the higher output levels of more modern
source.

http://www.desmith.net/NMdS/Electron..._upgrades.html

Basically it is a change to the feedback circuit around the input op
amp, originally 330k/22k for a gain of 23dB, now 100k/22k which gives
a gain of 13dB. Does that sound about right?


Upgrade? That's a bit of an exaggeration.
And it's simply not true that 25 year old electrolytics will need replacing.
They might, but if they measure OK, they are OK.

--
Eiron.