Built by forum member ‘Disarmament’ of Art of Sound.
This hand built pre-amplifier proved highly capable during a local bake-off against the likes of Modwright, Music First and Ayre, enough for the host to commission one. Below is a brief description from the engineering wizard responsible regarding the valves used etc.;
The first gain stage valves are RCA 37 single triodes from the 1930’s, the cathode follower stage is a 6SN7GT. The design is based on a design by Bruce Berman first published in the Sound Practices magazine. Although Bruce Bermans design used RCA 76’s in the first gain stage. The 37 and the 76 are very similar, but the 37 is a lower Mu valve than the 76 so the gain is lower.
The preamp has a voltage gain of around 4.
Both the 76 and the 37 triodes are very linear, but in my opinion the 37 sounds the nicest out of the two.
The preamp can use either the 37 or the 76 without changing anything. However both these valves are becoming scarce, especially the 37. Replacing the valves would need some care as these can be microphonic so it may need a selection of valves to find the best pair.
Photographs show how well made this thing is, the case has one or two minor blemishes, but nothing significant. Collection/AA taxi/Lopwell or meet up preferred, not a fan of couriers. I am not in any rush to sell, so may just bring it along to Lopwell for anyone to try out.
For sale at a price well below the price of the parts used - £450.