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Turntable Hum Issue.

Yesterday my system developed a hum when playing vinyl records. Not the standard 60 HZ hum or buzz but a sort of resonating hum or howl around 120 HZ. Nothing with the system has changed in years which makes this more difficult to troubleshoot. Yesterday I played a recent garage sale find record and around 45 or greater on the volume level the hum appeared. I can replicate the sound by resting the stylus on the record and tapping the turntable base and/or tapping the console that it sits on. Otherwise, dead quiet. Other records I have had for years are now doing the same thing.

Set up is: VPI Classic table with an Audio Technica OC9XSL Moving Coil Cartridge with 2 Grams Tracking Force. Preamp is a McIntosh C49 using built in Phono Preamp. A picture of the console it sits on should be in my System Profile. House is hardwood floor and built in the 1940’s. I have no idea where to start. I was thinking on moving to a Moving Magnet Cartridge. Perhaps less gain might help the problem. With that said, what is a good middle of the road MM Cart around $500 give or take a bit?

I still would like to solve the root cause as I do kind of like that Cartridge. I thought the VPI table was heavy enough to isolate that type of issue that is why I purchased it. Feet, isolators, etc… did not work in the past with other tables.

chippieboy
chippieboy OP
30 posts
 

Okay people, first of all thanks for all the responses. I would not know where to begin without all of you.

I have been very busy in the last 10 days or so trying to figure this issue out.

I have been doing all the test with headphones to remove the speakers and floor vibrations out of the equation.

I rebooted the Mac Preamp in many different ways. Hard, Soft Etc.... Did not help. Plugged Table into a different power sources, across the room as well.

Cleaned all connections. Tried different RCA Cables, nothing. Changed to a new Moving Magnet Cart (thinking less amplitude than a MC would lessen the howl, plus rule out a defective cart), no difference at all.

Placed Sorbothane pads under the Tables feet. Nothing.

Thinking it might be the Mac Phono Section I used 2 different Preamps, same issue. I rang out cart wires to the Preamp ends of the RCA's. All less that 1 ohm and no shorts to ground or to any metal on the table. Inspected the Tables RCA Junction Box, looks great.

At this point, any slight tapping on the plinth is just like ringing a howl type bell. If the speakers are connected the howl turns into a runaway.

I'm not to sure what to do at this point short of a new Turntable. No idea on what might be a good replacement table. I have a feeling if I send the table or any part of it to be serviced they will not be able to replicate the issue. 

I did order the HW 40 feet from VPI.

limomangus's avatar
limomangus
2,073 posts
 

Did a wire get loose ?

chippieboy OP
30 posts
 

Doesn't seem so. Wires at the cartridge connection point to the RCA ends that plug into the preamp all ring out good. Less than 1 ohm, no continuity to the others wires and any grounds or metal. Each wire from beginning at the Cartridge to the RCA ends check out perfect.

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