Originally Posted by Mrtn77
Alas, my intermittent high-pitched hum has returned, as random and maddening as before.
Bought new cables in case my old ones were the problem. Turns out they were not, but I did notice the turntable's left-channel RCA plug offered a very loose fit.
Could the cable slightly slipping off cause my intermittent hum? I did notice fiddling with it seemed to help.
Any way to deal with the plug's loose fit that doesn't involve sending the turntable back where it came from?
Ever heard of pliers? You can practice on some cheapo RCA, best to use is some thin rubber/plastic between RCA minus and pliers, so that cosmetics will remain unscaved.
I hate the godamm RCA connetors, they are not spec'd tight enough and specially with phono CAN cause erratic behaviour like you describe.
With RCAs, there is an infinite possibility of either minus (screen connected to ground ) or plus (signal) being either totally "in the air" or have much higher resistance than it should have. Reason is dimensions of males and females are simply too loosely specified. Now if anyone will bring WBT Next Gens up - it will simply show he/she has money to burn. With over 200 $/Euro per MONO connection (male + female) that is simply out of reach for the vast majority. Simply count the RCAs on the back of your (pre)amp, mulltiply by the above price, add labour - not exactly appealing proposition.
No wonder few manufacturers recently started to offer DIN terminated cables for phono - much better executed than vintage DIN monstrosities that gave them bad name. They also by default are well shielded - NOT like RCAs having minus/ground totally exposed. No conductor is without resistance and that minuscule resistance can (and DOES) lead to hum pickup, RFI, and other things you would like to omit at all costs.
Everything above is especially critical with low impedance low output moving coil carts. I use Ortofon MC100/200/TMC200 cart with 0.09 mV (correct, less than 0.1 mV ) and 3 ohm internal resistance for both turntable wiring as well as phono preamp testing. If it is quiet with this one, it will be more than quiet with more normal setups.
Now imagine Audio Note IO Limited cartridge ( with electromagnet instead of permanent magnet of its lesser versions ) - 0.04 mV and IIRC 2 ohm ...