Mr Liang 845 SET

Before I got back into using Solid State or 'Sand Amps' I had already gone through using a few tube amp kits, push-pull builds and a 300B Mono-Block SET. I eventually got talked into buying a 845 SET. This was my last Tube amp before switching to a Nelson Pass F5. Standard build for a china made amp was high and this thing weighed a ton. It really is a two man lift. As good as the sound was on first use it soon became obvious that it could be easily improved and it had a few flaws.

Most notable improvements beside the obvious coupling cap upgrades on the pre-amp stage were tube changes. Changing the small input tube to NOS 6AC7 brought a more refined much cleaner sound. Finally changing the driver stage tube to an EL34, 6L6, 5881, KT66 or KT88 made quite an improvement in terms of scale and bass. However in order to fully take advantage of this tube change the cathode resistor for this tube on the pre-amp pcb needed to be altered to drive it properly.

The first image shows the resistor change needed and the replacement green wire-wound resistor. The original resistor R106 used 2 x 75K in parallel and I used a single 24K 12W. This drives the tube >5mA since with the original resistor it was barely switched on.