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Anyone Know Where I should Look to Figure Out This Hum?

http://https//www.dropbox.com/s/faxmop972rok7i1/Noise.m4a?dl=0

I recently purchased a Lamm LP2. First couple days, silent. Now this. It's coming from both sides equally, turning up the volume makes it louder. It's not the cartridge. Noise still there when I unplug the turntable inputs from the phono preamp. It sure doesn't sound like a ground hum and since it's both channels I don't think it's going to be a bad tube . I have another set of tubes on the way but they won't be here until next week so I can't double check that. I swapped out the rectifier tube and that changed nothing. 

Help!
dhcod
imhififan's avatar
imhififan
2,208 posts
 
First couple days, silent. Now this. It's coming from both sides equally, turning up the volume makes it louder.
My suggestion is unplug everything from the unit, check inside the unit for any loose connection and make sure all tubes are firmly insert to their sockets then reconnect the unit to your system. From the picture I can see some (2?) cable with screw-in connectors inside the Lamm LP2.

https://www.lammindustries.com/PICS/LP2/modified/LP2%20inside.jpg


dhcod OP
710 posts
 
Yeah, done all that. Swapped all the tubes now. It's definitely not a ground hum or related to a tube. Waiting to hear from Lamm.
atmasphere's avatar
atmasphere
11,859 posts
 
@dhcod  That isn't a ground loop or bad ground. Those both produce a buzz, and what you have here is a hum. Its a defect (like a damaged filter capacitor or bad solderjoint in the power supply). So the preamp is going to need service.
dhcod OP
710 posts
 
Thanks so much for this confirmation. Now I just have to figure out how to get it repaired without shipping cross country. Can't find a schematic online so there may be no other option unless Lamm will provide one. Hopefully they'll respond soon.
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