2. amps-preamps
  3. 163657-117913

Strange buzz issue!

Hello audio friends! I’ve got a weird problem. I have an old ARC D-100B power amp (love the sound of it) and bought an ARC LS9 pre amp to match it with. Nice enough. Connected the LS9. Buzz/hum from both speakers. Consistent (clearly audible from listening position) at all volume levels/sources on the LS9. Crap, the LS9 must be faulty, I thought. For fun I connected the LS9 to two other power amps (Yamaha and Vincent). Dead silent. I then connected an old Yamaha pre amp to my D-100B. Silence. Same place, same cables. So, neither the LS9 nor the D-100B are faulty, but together they, or one of them, cause a pretty loud buzz. I’m going mad here! Any ideas? Thanks! 
teppas
teppas OP
7 posts
 
Ok, Thanks:) Yeah, it very much sounds  like a ground loop kind of buzz. I think the plug on the power amp cord has been exchanged (due to change to grounded outlets here in Sweden). I tried connecting the power amp to a DC trap, but still the same problem. But a ”cheater plug” is something else? 
jond's avatar
jond
5,778 posts
 
A cheater plug in the US lifts the ground it changes a three prong plug into two prongs basically. In Sweden you would use Schuko plugs which are two prong so a cheater wouldn't work.
teppas OP
7 posts
 
Ah ok, I’ll try some filter options, I think.
 These two sound so good together I really want to get this sorted Out! Thanks! 
oldhvymec
5,101 posts
 
Run a good ground wire between the two. Cost 1.00 usd. crimp an eyelet or spade on either end of a good copper # 16. Mount it direct, chassis to chassis.

Regards
hshifi
572 posts
 
Hello,
First,
 Are the amp and preamp on the same power strip. Try a cheep power strip so the outlets are not fully separated.Second, 
 Sometimes changing the tubes helps. On a preamp that does not cost a lot. Next would be the ones on the amp. That will hurt a little. Third, 
Is there something on the circuit causing the hum. A dimmer switch will do it. 

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