Thanks for all your responses-I appreciate your taking the time to have a peek and share your thoughts. Sure does mean a lot to me.
As for the outputs, it's 7591s in PP AB1. Dual 5AR4s, dual 0A3s for separate screen regulation and 6AN8s in cathodyne setup for gain/phase splitting.
The larger pots near the power xfrmr are for individual channel adjustment of cathode bias. The two smaller knobs near the 6AN8s are for AC and DC balance.
The small black test points in front of the 7591s are for measuring DC balance and if you look closely at the third image from the top in the first post you can just make out one of the red test points for AC balance.
With this setup, you balance the DC (each pair of cathode resistors per channel are individually grounded, and each has it's own test point) then adjust bias for .9v for each tube. That way you set bias by proper current levels rather than fixed bias.
As for how long it took to finish, I'd hazard a guess of @ 9 or 10 months.
The star grounding setup is a "true" star ground in that every single grounded componant in the amp has it's own dedicated ground run back to the chassis/earth ground. The amp is dead silent even at full volume with my ear on the speaker.
Not a single shielded wire in the entire amp and still no hum or noise.
Paint is powdercoated "official International Harvester Tractor Red" and was the final solution after 3 botched attempts by myself to pain it red.
As for the sound, I might be a bit "biased" but I think it's the best amp I've heard so far.
By the numbers:
perfectly sharp square wave response with no overshoot-the vertical plot lines disappeared entirely, leaving just two offset lines of dashes-from 20hz-20khz. +/-1db. When overlapped each wave matched exactly.
Able to pass a perfect sine wave at 4hz. The VR tubes started blinking in time with the wave at that point-cool.
Power supply showed very minimal grunge-not too shabby since the VR tubes make using a choke a little complicated.
As for the sound, It has all the clarity, detail and transparency of the best SS amps, but with that great big, full 3 dimensional sound I so enjoyed in my 299C. Base response is fantastic. It doesn't just blow away my 299C, my 296 also pales in comparison.
Separation and imaging are are another level as well. I'd contribute this to the outputs-a faithfull, fully interleaved copy of Dyaco A-420s, 6-60k response, but oversized for a 70 watt rating, and the Dual 500k Shalco stepped attenuator used for volume control-30 steps, make before break in 1.2 db steps.
The article stated that the screen regulation, AC and DC balance allow extremely low distortion ratings-.1% at 35 watts.
Measure full output was 34.6 watts.
I think I've got a keeper!
Best,
mr mojo
