2. amps-preamps
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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
jea48
4,595 posts
 
...I've checked and made sure the dish is grounded properly;
05-31-11: Mribob
Mribob,

Properly.... Please explain.
jim
mribob
229 posts
 
Jea; I had electrician come out to house and attach dedicated ground wire to a grounded piece of metal on house; ie; electrical conduit. I did try to put a piece of steel rod in the ground to a depth of 5', and attach copper grounding wire; but that proved a bit problematic. What ideas do you have about properly grounding a sat dish? how come my bedroom sat system has no ground hum; only my more sensitive main listening area when I switched out my Meridian 861 processor for a Marantz 7005 processor;(no hum before with same sat box and connections) and added a VAC tubed preamp. System stone quite in 2 channel listening mode; only hums when Marantz is powered up; and attached to Directv dish; take away the hdmi cable from sat dish to marantz; no hum...hummmm; any help would be appreciated. Added a ARTcessary DTI (dual transformed isolator) running as rca plugs instead of balanced to connect Marantz to VAC for front channel for home theater rig; and made a big reduction in the hum; so at least is only mildly anoying, but not eliminated.bought from MCM electronics catelogue...
I would appreciate any and all helpful tips on this problem...sure others have similiar issues with Directv dishes; since the Jensen product works by eliminating the hum; but if fails to allow the video/audio signals to be sent thru as well....
jea48
4,595 posts
 
Mribob,

how come my bedroom sat system has no ground hum;
More than likely the associated equipment is two wire cord and plug. Is that correct?

I switched out my Meridian 861 processor for a Marantz 7005 processor;(no hum before with same sat box and connections)
Marantz uses a two wire cord and plug. Does the Meridian 861 processor use a three wire cord and plug?

I had electrician come out to house and attach dedicated ground wire to a grounded piece of metal on house; ie; electrical conduit.

Does not meet NEC code......

Good chance what you have with the metal conduit is a poor lightning grounding conductor at best. Every fitting, connectors and couplings, could be adding resistance to the length of the conduit run.

NEC code says the cable grounding block shall be bonded, connected, to the main grounding electrode system of the main electrical service by means of a ground wire. NEC code is bare minimum safety standards.....

How far is the SAT cable grounding block from the main electrical service panel?

For a test, test only, disconnect the existing pipe ground wire from the SAT cable ground block. Check for hum and post back.

Note:
The ground block must be earth grounded for lightning protection. For the test you will not cause any harm....
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