Have you tried swapping in different ICs from the SUT to the RCM? Probably not the solution but worth checking. I have several sets of perfectly nice, unshielded ICs that cause an awful hum when placed between SUT and phonostage, although they're silent anywhere else.
Why my SUT hums only with certain phonostages ?
Hi,
I use a vintage Ortofon STM-72 SUT with my Lyra cartridge. Curiously, when I connect it via my solid state RCM Sensor prelude phonostage, there is a strong hum. The hum lowers when I connect the earth lead of the phono cable to the phonostage earthing point, but still there is a hum which is distracting. However when I connect the SUT to my Shindo Aurieges MM phono stage there is absolutely no hum. I dont even have to connect the earth lead. What is the reason ? Is it my SUT or my phonostage ?
I use a vintage Ortofon STM-72 SUT with my Lyra cartridge. Curiously, when I connect it via my solid state RCM Sensor prelude phonostage, there is a strong hum. The hum lowers when I connect the earth lead of the phono cable to the phonostage earthing point, but still there is a hum which is distracting. However when I connect the SUT to my Shindo Aurieges MM phono stage there is absolutely no hum. I dont even have to connect the earth lead. What is the reason ? Is it my SUT or my phonostage ?