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amey01

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Hi Guys,

Over the weekend I upgraded from a Primare Integrated amp to a Copland all tube preamp and a Rotel 1080 power amp. Since connecting it up I am getting some really funky stuff happening.

Frist I had quite a loud hum coming from the speakers when the power amp was turned on. I then cut the ground pin off the connector and tried again. The hum was now reduced to a more acceptable level (not gone, but certianly liveable).

But now when I turn the preamp on I get the same loud hum. Then, turning the preamp off does not reduce it.

I just can't figure this one......any suggestions?

Thank you in advance!
Adam.
 

Sky Saw

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It's possible that your interconnects between the pre and power amps are picking up some RF. Have you tried moving them away from other cables, and away from any walls?

Failing that, have you tried plugging the amp into a different outlet?

Any chance your Copland is the CTA-301 MkII? That is my preamp, and I absolutely love it. It has tons of air, and has been a rock-solid performer for me for I think about 9 years (except for 2 new sets of 6922s as regular maintenance).

Good luck with the hum issue - it can be a real nuisance, but everybody solves it eventually.
 

amey01

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Thanks guys for the help so far! I really really appreciate it!

1: I am running Aerius MLs

2: I have tried the Power amp in another outlet on the other side of the room - no difference!

3: - No, my Copland is the CTA-305 - absolutely love it too!

4: I have ensured all cables are neatly routed and have improved the hum problem somewhat (still not gone though) - thanks Sky Saw!
 

attyonline

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You likely have a ground loop. You need to methodically disconnect each component one at a time from the pre and see if that cures the hum. If your pre is three pronged grounded, get a cheater plug on it and see if that helps. Also do the same with your speakers since they have three prong cords. BTW, it is dangerous to cut off your ground plug on your amp, depending on the wiring in your home, you may create a severe shock hazard for you and your family. Suggest that you replace this cord with a new one wiht a ground prong.
 

lexor

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hum

if you have cable hooked up to your system or an antenna unplug it. this is well known for causing hum.
 

kach22i

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Tubes..............yummy.

This is just a two channel setup, no A/V hook up?

A/V hook up may cause ground loop hum.
 

SugarMedia

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attyonline said:
BTW, it is dangerous to cut off your ground plug on your amp, depending on the wiring in your home, you may create a severe shock hazard for you and your family. Suggest that you replace this cord with a new one wiht a ground prong.

Agreed. Get that ground back on asap... it's very unsafe to cut it off. Secondly, it helps to protect expensive electronics from power surges.
 

amey01

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THANK YOU so much for your help guys. Hum problem is now almost solved. There is a small amount of hum, but I can live with it - it cannot be heard from the listening position.

I tried removing the antenna conection and that improved the problem somewhat. That led me to find the culprit - The VCR - connected via RCA to the preamp. With this disconnected the system is fine - even with the antenna connected.

No idea why I didn't have this problem with my old Primare amplifier though?

Thank you all again for the help.

PS. Ground pin is now back on the amplifier!
 
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