Hi Mike,
Definitely an accident on the plinth. I’m surprised we let that slip through, each preamp that requires a volume control has to be cut and drilled and have the volume pot manually fitted to it and it’s one of the last steps before we ship. So my apologies that this wasn’t done on your unit. I’m glad that it wasn’t necessary in your case, but if you ever decide it is then let us know and we will get you a replacement front panel or plinth with a properly fitted pot.
Having the volume pot out of circuit shouldn’t cause any problems for the amp or the tubes, as long as you have control of the volume at a preceding stage then you should be fine.
For the DC supplies, it all depends on what you intend to run. We like to go oversized with our DC supplies and use 5A for both the 6v and 12v versions. But you don’t need to go that high. We recommend somewhere around double the required current so the supply can safely handle the startup surge. If you’re using 6SN7 tubes, that would be 2 x 600mA for 1.2A total and 2.4A doubled to be safe. For 12SN7 tubes, it would be half that at 1.2A to be safe.
Cheers and happy listening!
Charles