Installed my 370BX transformer replacement yesterday and it was working fine for many hours until 3am this morning. The 370BX is more robust than the 270BX and was barely warm to touch after hours of playing.
Since it has only been a couple hours old, I obviously cannot form a definitive opinion yet. However, it is already sounding great. The texture is refined and grainless. Lots of dynamics and warmth (compared with my SS preamp). Hights are extended and mids are open. The bass is not as tight as I like and I hope it would improve with burning in. My speakers are "analytical" i.e., bright to my liking. The Cornet seems to have tamed the brightness. Now, my whole chain is tube driven. This is my current setup: Linn SP12, Linn Itok arm, older Grade Signature cartridge (1.3 mv), Cornet Octal, AES/Cary AE3 Signature preamp, Cary SE572 Signature monoblocks, and GR Research Paradox 3 speakers. I am using NOS Sylvania 6SN7W and 6SL7s (1940 vinatage) in both the Cornet and the line preamp. In the Cornet, I use all Riken resistors, Multicaps, and Jensen copper foils at the critical locations. Kimber RCA jacks and single strand silver wire for the input and output.
The remaining area I have to tackle is a slight hum even without input. There is a dimmer in the vicinity but not in the same power circuit. I have implemented the hum fix (star grounding of the couple caps and diodes) and isolated all the RCA jacks. I also use nylon standoffs for the PCB so the only grounding point is at the ground binding post at the chassis. I stick to the exact original layout except that I have replaced all the five 47uF electrolys with paper in oil caps and I have to mount them off the PCB, on the chassis around the transformer. They are big -- 2.5" in diameter. The connections to these caps were made by triple shielded wires so they should not be picking up interference from the transformer. I will try using a cheat plug to disconnect the ground from the 3-pronge plug and run a ground wire from the cheat plug to the preamp or amp and I would appreciate any suggestion to get rid of this hum.
I will update the circle with more listening impressions after burn-in.
Tom
