Use 6LY8 electronic tube.


I never had any trouble with noise on IEMs with ECP Audio tube amps. All of the tube amps are transformer-coupled (Torpedo, T2, T3, T4, etc.) and do well with IEMs. I still have a pair of Ety ER4 MicroPros that sound great on my T4.
BTW, the power stage is most important in controlling noise. Like a lot of cheaper tube amplifier kits and PCBs on Ebay and elsewhere, your schematic shows absolutely nothing about the power supply. Where and how does the 200V come from and where is any power supply for the tube heaters? With few exceptions, this omission is for the very thing that controls whether noise is acceptable or not.
JMHO, but I don't think a switching power supply is the way to go for 200V in a tube amp. Anyway, good luck!Power supply I plan to use a switching power supply. The schematic will be completed in the next few days. I think switching power supplies have lower noise and lower internal resistance.