Quote Originally Posted by DSJR View Post
Barry, it may be worth Googling on FM3 mods. Depending on the tuner's vintage (there was a fairly major revision to the decoding circuit at around #5000 as I recall), there are some caps that can be usefully changed - three supply ones for larger values and at least five around the decoder and audio output coupling. This makes a subtle but beneficial difference to the sound
. I have to get my FM3 out and remind myself what these caps are - I've just found a couple of spare 3300uF 25V caps you could usefully put in the supply feed under the mains transformer (I had to buy five)

http://www.geocities.com/ResearchTri...uadfm3doc.html

The recommendation of C100 and C104 is a thorny one though. I was urged to retain the original value and just replace these with modern ones, but having done the mod exactly as described, I felt it sounded better (I did as I was told in the end), but the important ones not mentioned are the audio output coupling caps (I'll find the numbers).

Suitably serviced, the FM3 still sounds a touch "dry" but I thought the clarity was better and if it's feeding a high impedance pre as recommended (50K at least), you should get a pretty truthful reproduction (I still find the FM2 too soggy and soft, but I'm told it's the stereo decoder at fault).
Hello Dave

Thanks for the link. My FM3 has s/n < 5000, so the revision you mention could be applied. When I get the Troughline up and running, I will have a chance to 'mod the Quad'.

The idea of possibly including an FM2 in the comparison was simply to try another valve tuner. Many years ago I had a Quad valve set (kept as a back up to my s-s gear): 22 preamp, 2 x Quad II monoblocks with the FM1 and AM1 tuners. The FM1 used a little regarded stereo decoder sitting 'piggyback' on the tuner. The FM2 is, I think, simply a re-packaging of the FM1 in a new case with integral power supply and decoder. It is not yet certain if I can borrow the FM2, but if I can, it will be interesting to hear it again.

Regards
Barry