Shielded cables?

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#3
I have found that using good grounding practice (separate the high level and low level grounds and join them at the star point) and shielded cables result in no hum at all in my gainclones (which aren't in a metal case, BTW). I also found that using a non-shielded cable to the input of my GC from the source resulted in a slight hum, which went away when I used shielded cable. All shields are grounded at one point.

- Ashwin
 
#4
I use a metal case for my gainclone and chasis is connected to star gnd. And inside my signal cables are all shielded. But positioning of that cables very important, because when I move closer the shielded cables to the transformer, I heard a 100Hz noise! Shouldnt I use shielded cables inside the metal case? Does it make problem?

And the second question; for preamplifier, if I use the same mains transformer (with the gainclone) the 100Hz noise problem is back again! Now I use another little transformer for it. Does it always happens? Do you use two seperate transformer for gainclone and preamp?

Thanks a lot..
 
#6
Dxvideo said:

And the second question; for preamplifier, if I use the same mains transformer (with the gainclone) the 100Hz noise problem is back again! Now I use another little transformer for it. Does it always happens? Do you use two seperate transformer for gainclone and preamp?

Thanks a lot..
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This sounds like a ground loop. If the preamp and amp are fed from the same supply, then you need to run only one wire (i.e. the signal wire) from the preamp output to the amp input. Don't run the ground wire in the shielded cable from the preamp output to the amp input.

Hope that makes sense.

- Ashwin
 
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