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HELP - I Weird Hum or FeedBack Problem

I have a Cortese preamp and I get a hum , actually I think it's feedback when I turn the volume to 10 oclock, 7oclock is off. I only get the hum or feedback when the cartridge needle is on the record.I don't get any hum when using the cd or anything else it's only when using the phono stage. I tried using different plugs for the power cords and also unplugging the tv but I still get the hum.
Another thing when I first turn on my preamp my left channel speaker makes a squeaking noise and the driver vibrates and I hear a puff .... for about an hour until it warms up and the noise gets softer and softer but never goes away. If I turn the volume up to 12oclock and the cartridge is in it's locked position with the cartridge in mid air. I will hear this pulsing noise or a light puff ... but no feed back.
Before emailing Supratek I thought I would post here for a a solution. The last time I shipped my preamp to New York it got damaged.

Any suggestions are appreciated.

Abill
abill
abill OP
80 posts
 
Yes I checked the ground connection the feed back is the same each with or without the ground.
I also changed my cartridge , thinking it was bad but it didn't make a difference.It's weird because I only get the feedback if I lower the tonearm onto the platter or the record. Turn up the volume to about 10 oclock and I get very bad feedback.
I think there is something wrong with the preamp.
kjweisner's avatar
kjweisner
293 posts
 
Abill:

Could be the motor of your tt is putting out enough EM for the cartridge to be picking it up. Might be good to know what turntable and cartridge you have. There are certain cartridges that are known to be susceptible to this.

On the other hand, it could also be that the phono stage of your pre-amp is the issue, or the pre-amp itself is the source.

So, how to isolate?
One idea would be to borrow a phono pre-amp and then plug that into a line level input of your pre. If the hum is still there when you lower the arm, then you could rule out the internal phono stage, meaning it's either the table or somehwere else in the pre.

You might also try lowering the arm onto the record with the tt powered off and/or unplugged, but still using the pre-amp's phono stage. If you turn it up and still get the feedback, the indication is the pre-amp. If it's gone when the t/t is unplugged, then I'd suspect a motor/cartridge interaction. Good luck with the testing.
hevac1
812 posts
 
Sounds like bass feed back. Move your turntable to another location, see if it go's away. Stay away from corners in the room and your speakers.
abill OP
80 posts
 
Thank you everyone for the suggestions.
I couldn't get a phono amp to try but I'm confident it's the phonostage in the preamp. I changed my cartridge to a denon 103r I was using a dynavector xx2 mkII with a vpi aries 3 table and I still get the feed back and if I don't touch the cartridge to the platter and turn up the volume I hear a pounding noise from both speakers.Something else when I first power up the preamp I hear a squiking noise from the left speaker and the driver vibrates in and out with the squeaking noise.
I emailed Supratek a few minutes before posting this .
I'll post what the outcome is.

Thank you
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