I bought a set of Dynaco MKIII in working, but marginal condition. I decided to rebuild them for client.
The driver boards are being upgraded to 6SN7 based boards. And the units are being completely rewired with new tubes.
I will document the build in this thread
Before starting the project, I needed to consider the objectives.
I decided to remove the transformers, transformer bells, and hand polish, but not restore the chassis.
I also decided to purchase new boards from one of my IG followers. I’ve tried replacing updating on previous Dynaco re-caps, and found them finicky and difficult to work with. I wanted this build to be stone reliable which was more important that pure orginality.
Eager to see your progress on this! I am running the VTA 12AU7 board in my ST-70 rebuild for the last 2 years or so, and it really does sound nice. Plays well with every source I have tried with it too.
Interesting that the MK3 driver board appears to use half of the input stage 6SN7 unused… you could very easily configure that as a cascode stage for the cost of a handful of passive components.
The stock config on the VTA70 board is great, but I did recently switch from the supplied Audyn caps to Mundorf EVO paper-in-oils, jury is still out on those. The main improvement was that I made a very specific point to determine the outer foil leads and point those towards the lower impedance side of the circuit, which seemed to make a difference in noise I was getting in one of the channels.
I find reviewing these pics like the one above pretty valuable. I did find one wiring error while reviewing the pic
