I mentioned in another thread that I'm working on a Nelson Pass Sony VFET project so having let the cat of the bag i thought I should follow up with some information about the build.
I bought the PCBs and part kits, sans VFET devices, from the DIY Audio store - fortunately I have three pairs of 2SK60s. I'm recycling a large heatsink from a solar panel inverter, I had it accurately sliced in half by a model engineer chum and have been fabricating metal work to complete the chassis. Power supply is Mean Well SMPS brick with a filter board incorporated into the chassis. I've made one change, replacing the single 10000uF electrolytic output cap with boards holding 10x 1000uF Nichicon Muse caps (and a film bypass)
Almost there! I've been doing the internal hook-up wiring today and have done some initial checks/adjustments/tests - voltages are what they should be! I just have to hook up the input phono sockets now before I can finish checking and, hopefully, listen to some music - sadly that will have to wait for a few days as I'm out of time today.
I've been listening to my VFET project this afternoon and it is already making exquisite music - I say already simply because there is definitely more to come as I'm only using a Samsung phone as the source and my Noir HPA to drive it. The VFET is a follower with no voltage gain.
I listened initially with my Ariston workbench speakers but the gain of the Noir (9dB IIRC) wasn't enough for anything but a test listen, but once it was clear all was OK I moved to my listening room and hooked up my Lowther BLH speakers - these were efficient enough to have a good listen at a reasonable volume. Firstly thing to note, bearing in mind the efficiency of the Lowthers, was that with nothing playing there was silence, absolutely no hums, buzzes or whatever...
I have to say that the VFET and Lowthers seem to have a really promising synergy; with my SE-OTL amps I always had a nag that the balance was a little forward and the bass a bit light but not with the VFET, which delivered a robust but sweet and subtle sound quality - I had one of those listening sessions where you start to go through your recording library! Tomorrow I will try one of my DSD DACs as the source.
I've not quite finished the build as I still need to contrive some sort of front panel for the chassis - maybe get something 3D printed.
