Pass XP-25 reboot - Obsession to the max
I've been obsessed with this unit for years, trying to remove hum it picks up. Although I had shielded the main unit underneath with mumetal - as well as the PS transformer - this time I decided to wrap it all around - top, sides, back - because it was still picking up surrounding hum. This, in addition to lifting its ground. The $200 investment in more mumetal paid off big time, removing all traces of this noise, enabling me to turn up the gain to 76dB from 66 and the "loading" to 47K, and finally, with the preamp turned all the way up (some 90+ dB total gain), there is no hum. The additional dynamic headroom is really arresting, as is the increase in clarity, timbre and articulation. This unit also has those incredible power diodes I've mentioned upthread, and no capacitive "loading".
The noise floor is so low that I can easily hear slight motor whirring on some Reference Recordings LPs, in the lead-in and lead-out grooves and between tracks (e.g. Arnold Overtures); at first, I thought it was my motor, but thankfully not. I don't understand why I did not do this years ago. One caveat, I need to open a hole somewhere for internal heat to escape...
But the obsession could not stop there... ever since inserting Isodamp between the A90 and the headshell, I lost metal contact, which means no grounding all the way to the cartridge body, i.e. slightly more hum.
Laugh all you want, as I do, but here's what I did
, and it works wonders:
Short of treating your equipment with disinfectants for cleaner sound, this surely is one of the most idiotic things I have personally seen, but it restores the ground connection but probably adds a little more mechanical noise back in via the tiny wire.
Nevertheless, the overall improvement with the Isodamp in terms of lowering distortion all around is unmistakable. The Symphonic Dances' crescendos have never sounded as clean and controlled.
Yeah I know, just get better gear... Some day...