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
 
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. 

teppas OP
7 posts
 
Thanks, I tried both of the above suggestions, but no luck. I today went and bought a hifi grade ground loop isolator (for implementation on the interconnect between pre and power amp). It did the trick! No buzz. But regrettably left me with impaired bass response. Clear sound otherwise, though. Damn ground loops😁🥵
barts's avatar
barts
709 posts
 
@hshifi
Both of these pieces are solid state.

To the OP, please ensure that ground wire between the two is a real good metal to metal contact.  Also you might try shorting out any unused RCA inputs, take that cheap interconnect you have layin' around and cut the end off about an inch back, strip the wires and twist together, plug it in.
It's a long shot, please do this with the units turned off.  In fact make up as many as you need and short all of the RCA inputs (so there are no inputs) and turn them back on.

Regards,
barts
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