On Mon, 16 May 2016 15:47:04 +0100, Eiron
wrote:

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.

If I had gone to the trouble of unboxing an old amp, I would certainly
change any 20 year old electrolytics. I mean, you have to unsolder
them from the circuit to measure them so why would you put end-of-life
caps back? Just stick new ones in. If the amp was worth the effort to
strip, it was worth new caps.

d

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