Since this is out in public, I probably should respond.
Firstly, let it be said that I am very aware that I have not delivered what I promised.
When I went into this I had built a number of controllers using the "T" amp architecture and felt confident that I could do so again. I failed to predict the impact of Tripath going out of business: all my attempts to find a suitable solid state subsitute have failed.
I am also keenly aware that I have stretched people's patience with the time these attempts took and with my poor communication. Some of this was unavoidable due to health issues, some I brought on myself. When I finally called it quits on Friday it brought on a mixture of bitter disappointment that I had failed yet again and huge relief that I'd finally walked away.
The KT88 design has none of these issues: it is simply a marriage of the front end of the new controller with the power output stage of the first controller I designed almost 15 years ago. Both halves work well and I know I can make them play nice together. I now approach benchwork with alacrity rather than the dread and anxiety that characterised recent times.
Regarding the frequency and voltage issues: as Morgan Jones has said, the Garrard motor's winding inductance is barely adequate for 50Hz operation, yet it can become noisy at 60 Hz. Similarly, it can become noisy at higher voltages but can lose dynamics at lower voltages. Some people prefer high levels of drag loading (grease bearing, eddy brake on), some people prefer low (oil bearing, eddy brake off). All three settings interact.
My personal preference is to run at about 53 Hz with the eddy brake fully on, adjust voltage to get close to correct speed then trim the speed using the frequency adjustment. YMMV, my aim is to provide a device which allows you to find your preferred operational points and which then retains them.
I will not discuss delivery and price issues here, the mods don't like it. If you are on the list you'll get an email when my transformer guy gets back to me.
