I had the same issue with my Dynaco pas 3 preamp. All I had to do to eliminate the hum was to twist the rca connectors from the phono in the socket until it made good contact. Try this first with all of your rca plugs and see if that solves the problem. It did it for me, no more hum.
Hum issue - driving me more crazy
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Not sure if this should be here, Tech talk or Cables...
Audio Research Ref 2 Preamp, Pass labs electronic Xover, Bryston 4B ST amps (2), MAGGIE 20.1 speakers. All eqpt working OK.
Pre source eqpt left rear of room
spkr amp & XOVER left front of room
spkr amp right front of room
Separate 20 amp circuit for hifi eqpt. Other plugs in rooms for lamps, etc. Many of lamps on dimmers
Singlended IC's (now double shielded)are "under" flooring (pier and beam construction) & has been moved away from other wiring & cross at right angles
Initially some hum from dimmers (on separate circuit), etc. Have learned to leave them off.
But there is constant low level hum - right side only EVEN with preamp and XOVER turned off.
Not sure if this should be here, Tech talk or Cables...
Audio Research Ref 2 Preamp, Pass labs electronic Xover, Bryston 4B ST amps (2), MAGGIE 20.1 speakers. All eqpt working OK.
Pre source eqpt left rear of room
spkr amp & XOVER left front of room
spkr amp right front of room
Separate 20 amp circuit for hifi eqpt. Other plugs in rooms for lamps, etc. Many of lamps on dimmers
Singlended IC's (now double shielded)are "under" flooring (pier and beam construction) & has been moved away from other wiring & cross at right angles
Initially some hum from dimmers (on separate circuit), etc. Have learned to leave them off.
But there is constant low level hum - right side only EVEN with preamp and XOVER turned off.