Nice... I am getting a T amp soon.. and it will be driven by a diy tube pre-amp (I actually had it long time ago). I also have the vintage CORAL 8A-40 full range driver but no enclosure yet..

Oh.. I have no idea about the "batch 5"... I am getting it from here... Diyparadise

this it the amp



as for the diy tube pre-amp, I am using the famous Marantz M7 tube pre-amp circuit but it is already enhanced where all the tone control is taken out.. (I prefer to run flat), The power supply is also improved by using a solid state regulator and a regulated DC heater supply... I wish I can post the schematic here but I no longer have it.. unless it is somewhere inside the boxes where all my junks is stored..

Huh... sorry to hear that...mine is completely diy.. no PCB... it is hard wired point to point an have no problem..

in tube pre-amp / power amp,
there is a lot of thing that needed to be considered such as the placement of the power transformer (distance / orientation) from the audio circuitry.
ground loop is also the major cause of hum besides the heater supply wiring and type of voltage fed to the heater...