2. amps-preamps
  3. 1306375007

Hum issue - driving me more crazy

Page 1

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.
imdoc
magnumpi205
504 posts
 
The dimmers must go, off is not good enough.
Have replaced components, cables, used cheaters,aligned cables, changed conditioners and surge, replaced tubes, replaced power cables.
As soon as I took out the dimmer switches, problem solved.
shay123
72 posts
 
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.
forrestc
89 posts
 
You don't have a TV or tuner connected to cable or satellite whic is connected to your system do you?

Cable and dish installations are often grounded in a different location than your mains ground which almost always creates a ground loop though your audio system.
rwwear
2,692 posts
 
Make sure the cables are plugged in all the way.
imdoc OP
17 posts
 
Dan_ed

If you are going to lift the ground (cheater plugs) try to do that on the preamp and let everything ground through the amps. >>>>>>>>Will try but I think this worsens other hums

If you haven't already, try to plug both amps into the same outlet and see if the hum is diminished.>>>>>>NO help

Matter of fact, you may need to plug everything in your system into one outlet to see if this helps even more.>>>>>>>>Will try

Try swapping the ICs between amps and see if the hum follows the change. >>>>>>No help

When you can, try turning off all of the breakers in the house except the one feeding your system and see what happens. >>>>Have tried without obvious source as I recollect but will try again

Jea48

*How long is this IC cable? >>>~ 15'
*What type of cable supports are used under the floor? Plastic? Metal? >>>>>>>>Blue flex hose supported with plastic hangers
*How often is the cable supported, distance between supports?
>>>>>>>>About 5' apart as I recollect
*What is the area, space, under the floor? Basement? Crawlspace?
Space is under entire first floor of house ~ 1800' I guess
Room is 15X20 -sort of isolated from other parts of house Crawl space is ~ 18" dirt to bottom of rafter

Magnumpi205 - > I don't disagree and will try this
Shayl123 - I have -> no help
Rwwear -> I have -> no help

BUT I replaced right channel with balanced IC's tonite AND SO FAR NO NOISE. Can even use the dimmers in room that were clearly problematic. Able to remove the cheater plugs without hum (which was an issue before)

Not ready to declare victory (as there was variation in level of hum) but things are looking up so far.

MAGIC SO FAR
More to discover