HK Citation 1 RF Noise in Phono Section
OK, this is meant to be informative for me and maybe helpful too. Forgive the long-winded pre-amble.
I have a fully re-capped HK Citation 1. I'm running into McIntosh Mc60s on the HF and MC250 on the LF bi-amping a pair of Altec A7s (Emilar HF drivers and 416a 16ohm).
In Phono 1, using a MM Cartridge (currently a Shure V15 VMR or a Decca Gold) I get a lot of radio noise when discs aren't playing or in the runout. When playing, that all kind of goes away, but I think I hear things during quiet passages. I have a Denon AU320 SUT in Phono 2 where I've got a moving coil AT33 Mono cartridge coming in there. When Phono 2 is set to 3ohms or 40ohms, Phono2 is not radiophonic. Phono 2 is radiophonic when set to bypass on the SUT. None of the other channels (AUX, Tuner, Etc.) are radiophonic.
From what I understand, Phono 1 and Phono 2 share the same 4 12AX7 Telefunken tubes (gain & eq for each channel).
I've put shorting caps in any unused inputs just to see if it helps. It does not.
I've tried an external MM phono section into Aux and there are no radiophonics.
So it's not the cartridge, the cables to the speakers or the cables to the amps.
So here's my question: Even though the SUT would theoretically add noise (extra gain) when in use, it seems like the resistance of the SUT in 3 or 40 ohms quells the radio noise.
Apart from tube rolling or faraday boxes or any other luxury devices, can anyone point me in a helpful direction? I'm tired of hearing NPR coming through my phono stage. Is there additional shielding or other re-wiring mods that can quiet the phono section of the Citation? I like the sound of it playing, just not the dollop of extra noise.