I bought diy amp chassis on AliExpress. There are plenty of choices if you are willing to spend some time looking. They made of extruded aluminum and comes with knobs , power switch , power inlet etc. sone even have predrilled holes for input/outputs. This one had selector switch knob and holes for 4 inputs, so I had use it.

Thanks a lot!

Forgot to ask, my output transformers have 3.2k impedance on primary and you use 5k in your design. I am not sure why I choose 3.2k I guess because 300b i checked had 4000 oms output resistance and 3.2 seemed to me closest I could get. Did I screw it up?

Thanks a lot for great suggestions and your help. I would probably rebuild my amp with asymmetric layout and implement all suggested improvements. I will have to find out what to do with the top plate if the chassis cut the new plate or "island patch" it. Again - thanks you very much! BR/Val

Thanks for the suggestion, I will definitely do that. A voltage before the regulators is 6.3 ( it Is little bit higher). The regulators are adjustable and set to 5v. I am regretting about my amp layout as I went for symmetric that looks nice, but now I see that it makes sense to keep power supply pars on one side. having power transformer in the middle even turned 90 ged vs output transformers I still have some “coupling” I can hear from power transformer.

Could be 5v heater problem . I used XPWR011 power transformer that has only one 6.3v winding , I connected 2 dc 5v regulators to that winding in parallel . Do you see it is a problem ? Drivers heaters are powered from separate transformer. the hum pots adjusted to the position that gives less hum when amp works . Should It be in the middle? It definitely creates significant hum when in the middle.

I used original schematic you started with (without cascode connection of triodes), as at the time I built it I had no idea about this great source existence. I will definitely make a change in future. Without driver tubes the hum is still existing, however it is only fist wave (you can hear it on video there are 2 waves). It is in both channels, and volume position does not affect it (with drivers or without).