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Turntable Hum/Howl Issue (moved and reposted)

In hindsight I should have posted this in Analog not Misc.

Therefore here we go.

Original Posting:

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. It will runaway unless I reduce the volume immediately. I can replicate the issue by resting the stylus on the record without spinning and tapping the turntable base and/or tapping the console that it sits on. Otherwise, dead quiet.

Set up is: VPI Classic 1 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.

My finds in the last 10 days:

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 as suggested. Boot methods used: Hard, Soft, holding power button on Etc.... Did not help. 

Plugged Turntable into a different power sources, other rooms as well. Nothing.

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 cartridge wires from the cartridge to the Preamp ends of the RCA's. All less than 1 ohm and no shorts to ground or to any metal on the table. Inspected the Turntables 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. 

Out of desperation, I did order the HW 40 feet from VPI.

chippieboy
chippieboy OP
29 posts
 

Yes, that is what alerted me to the issue in the beginning. All of a sudden listing to a record and the loud howl came out of nowhere. Similar to a PA system feedback. PA feedback I think is around 1khz. By using a online tone generator, my issue compares to about 120HZ

audphile1's avatar
audphile1
7,857 posts
 

So if there’s no ringing while record is playing, don’t tap on the plinth.

chippieboy OP
29 posts
 

There is ringing while a record is playing. That is my main issue. I am trying to narrow it down to the specific component causing it.

lewm
14,658 posts
 

This problem could go away spontaneously or you need some outside local help from someone who has an oscilloscope.

seymour-krelborn
102 posts
 

@chippieboy 

I would rather not read this entire thread, so forgive me if my questions are repeats.

From some of what I have read, you get the hum when you turn up the volume.  So to me that eliminates your amp(s).

It is either your pre-amp, phono-amp, or a component of your turntable.

Have you disconnected your phono-amp from your pre-amp, and turned up the volume?

If no hum, then plug it back in.

Have you disconnected your turntable from your phono-amp, and turned up the volume?

If no hum, then plug it back in.

Or, work it from the other direction.  Start by disconnecting the turntable from the phono-amp, and see if the hum goes away.  Etc.

And it might be a cable.  So treat your cables as components, and disconnect them, one at a time, too (or plug them in, one at a time, if you want to work in that direction).

I doubt that your pre-amp is at fault, because then your digital would have hum, too.  That is, unless there is an issue with the ports on the back of your pre-amp where your cables from your phono-amp are connected -- or -- if those specific cables have a defect.

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