Hello Burnedfingers and all music lovers!
It looks, that we have almost the same Aikido amp.
Do you use a regulated power supply for the heaters?
In my amp, when I used AC on the filaments, I hear a clear hum, during soft passages with my headphones.
After I used DC, the hum was gone.
In my other preamp, also with the 6CG7, at AC no hum at all....
Is it possible the RCA cleartops are a little more sensitive, then the Electro Harm. or the GE?
Now I use a power supply with skottkey rectifiers, aerovox 100uF, 5 H choke ,aerovox 470 uF , each channel.
This gives me a B+ of about 210 V.
The sound is very good.Maybe better than with a tube rectifier.
When I use it as a pre amp ,she makes a very good match with class D power amps.
Greetings, have fun.
Hansel.