Hum Only When Needle Touches Vinyl

I've had a hum in my phono stage for a while now, and I just assumed it was the lack of ground in my outlet. Maybe it is, but I just noticed something odd about it.

When the needle is off the record there is no hum. As soon as it touches vinyl, whether the motor is running or not, the hum appears. Actually, if the motor is on and I stop the platter from spinning with my finger, the hum is the same as when it's spinning. If I turn off the motor, the hum is still there but not as loud.

Could this be the hook-up wires for my cart? I did have one connector come off, and I resoldered it myself. I didn't notice the hum until after that though... but it doesn't necessarily mean that it wasn't there before.

Any ideas?

 

Sounds like your problem is directly related to that wire you soldered. I'd replace it first to see if that's causing the hum. You don't have any spares?

I think I may have some if you need them.

 

I had a similar problem at one time. I would pick up hum when the cartridge was about half-way across the record. Turns out that the motor/power supply inside the 'table was leaking stray electromagnetic fields and my cartridge was picking it up when it passed overhead. I had to get an outboard power supply for the motor. That helped. It's possible that you are experiencing something similar, but that you don't notice it when the arm tube is in its rest - only when the cartridge is on the record and closer to the platter. Have you tried setting the cartridge down on the record when the platter is not turning? Do you hear anything then?

 

I'm battling the same problem with my Clearaudio turntable. I've been wanting to do needledrops for months, but can't until I solve it.

 

I have this issue as well, but it's not severe. I chalked it up to it being a low-end model. I can fix my needle drops by taming the very low hum with NR without touching the rest of the spectrum. Yes, I painfully made sure I didn't affect the sound in any way.

 

Hum

Try star earthing all your components if the cartridge clip repair doesn't work. Very cheap tweak and extremely effective, I can't live without it now!

 

"Star-Earthing"... May I attempt an interpretation?

Interpretation:
I believe this means running all grounds to the same point together, from all gear, to one pin-point spot, the "star" center.... Is this correct? R.E.

P.S. This should help control problems with "ground-loops" as a hum source.

 

If it's only present with the needle *touching* the vinyl, then the problem is definitely mechanical. Vibration is of course sensed by the stylus and played through the speakers. Culprits are the motor, any transformers on the 'table, any other equipment on the same stand, even the refrigerator on the other side of the wall. Isolating the table may cure it.

If it's there when the needle is not *touching* then it's induced from a magnetic field and could be earthing or bad connections.

IIRC the MMF is a manual only table and doesn't cut the output when you cue or start (many auto and semi-auto tables do).

What's the phono preamp? There's no way anything at even this level should hum electrically or mechanically significantly.

 

A few thought on the source of "hum" on TT platter?

A few things might be the source here... Try and see if the motor vibrates even with the power switch off, test this by removing the platter and touching the motor shaft or pulley, and rotate it and see if you feel a "vibration" or something buzzing like. I have found a few synchronous motors will do this, even with the switch off.... Possibly it is doing this and not well isolated from the platter, it is transmitting this vibration to the platter/stylus/arm/preamp/transducer then to your ear.... Try unplugging instead of switching off the AC to the whole TT, and see if it go's away...? If it does, the motor is suspect, but....could be magnetic, read on...

Alternatively, perhaps magnetic energy is "leaking" from the motor windings to the magnetic cartridge as it nears the motor, you did not say if it gets louder the closer it gets to the motor area under the platter? This could be an important clue...

Finally, could be a ground problem... Try running a wire from the chassis of the TT and the preamp you connect the phono to. See if anything changes in the "hum? situation?...

 

Yes, it's only when the needle touches the vinyl and I can lessen it by making sure the motor isn't touching the table. Now that I think about it, it obviously must be the hum of the motor transfering through the stylus. I probably just have to set things up better so I won't get any motor nose transfer (a proper platform, isolation tricks, etc...). As you can see in the picture below (not my pic, mine isn't blue) the motor sits within a hole in the left rear.

 

For my table, the hum does not get worse as the cart gets closer to the center of the record. I'll try those steps you suggested.

 

When the needle touches the vinyl, eh? I had this same problem for a while, but experimentation showed it only happened with a specific LP, the self-titled debut of the experimental group Hum, from 1982. That record was two side-length songs, "Hum I" and "Hum II," and on my system they sounded almost exactly the same. I put the LP away and forgot about it, until I acquired a copy of the group's second album, More Hum, which had the same problem. They must have been into some strange mastering technology, because when the members of Hum reunited in the 90s as an industrial-music collective, Grating Digital Whine, the CD was notorious for its harsh treble. I think they were Slovenian or something. Never did figure out what the problem was.

 

Wow, lots of ideas here. Thanks! I'm at work right now, but I'll be trying a few things tonight. By the way, if you are wondering what kind of gear I'm using, check my profile...

After reading all the responses and thinking about it, I'm willing to bet that this is related to the motor and/or the amp. Why? Because I'm using a stereo stand that has glass shelving (I've been meaning to replace them with MDF). Anyway, the Fisher tube amp is on the shelf directly below the turntable. I bet that's it... if so, I'll probably make the TNT stereo stand this weekend.

 

Oh, I *loved* their debut! I was so thrilled when I found an original UK copy because it uses a different mix. The American record company, in typical fashion, decided that the original mix was too slow-paced for audiences here, so they sped it up and added a few extra harmonics. Fans refer to the UK/European issue as the 50Hz mix, while the North American version is usually called the 60Hz mix. Some fans view this mix as heretical, having revised the group's original artistic vision, while others enjoy it as a different, but worthwhile, listening experience.

 

OK, the motor only vibrates when I turn on the power switch. I feel that hum all over the TT base. Now what?

 

OK, we found the culprit, the MOTOR!

So, the villain is (as I suspected...) Vibrating Motor! now we must isolate that motor from the platter somehow.... but how???? Try everything you can think of, foam rubber,??? unscrewing it from whatever it may mount on? I don't know, but that is your project now.... report back any findings, we await your results...

 

You also might try grounding both the tonearm and the table at some point to your preamp...I had the same problem and opened up my table to find that the arm wasn't grounded, and when I connected it (amazingly, there was a connection for it that the maker hadn't used) the problem went away.

 

Was that your Technics SL-1800?

Where are tonearm grounds usually located?

 

Yes, Rolf, that's exactly what I am thinking! And, i've already decided to try placing thin rubber washers between the base and motor. I really don't think it will work, but it's worth a try. I notice that they use a thin rubber band to support and isolate the motor housing from the table, but there are two screws that are not isolated.

My good friend, also a vinyl advocate, recommends that I stick with the foam mat that came with the platter. What I did have trouble with is static electricity. I have found a way to reduce or eliminate the problem: just place or remove the record from the platter while the table is spinning.

I read so many reviews that said this table was very quiet. Considering that this TT was cheap, I guess "you get what you pay for" applies once again!

Now, again, the hum/rumble isn't bad at all. And, it's still a nice little table and a big step up from what I was using before. It allows the sound to open up. I can't wait to hear how a better table/tone arm will sound.

 

Yes, it was...I'm going from memory, but I seem to recall there was just a lug connector at the base of the tonearm that didn't have anything attached to it...from looking at it it was clear that it was connecting to the right things, so I tried it and it worked. Sorry; I realize this isn't very technical but without opening it up I can't remember much more. I do recall it was obvious once I saw it.

 

If you're talking about the MMF 2.1... we were both duped.

That's why I'm gonna pick up a Technics SL-1200mk2. I can't afford to get what I REALLY want (a Scoutmaster). The Technics is probably the best bang for your buck without spending more than $500.

 

No, that does help. I didn't get a chance to investigate my hum problem last night, but hopefully I can look things over tonight.

 

I've been reading this thread and am confused. Is the problem hum or rumble? Hum is electrical and rumble is vibrational. Placing the stylus on a record changes the position of the maget/coil relationshp. If you cartridge is moving magnet placing the stylus on the record changes the position of the magnet in relation to the coils, which are fixed. If your cartridge is moving coil placing the stylus on the record changes the position of the coils in relation to the magnets, which are fixed.

It is possible that the internal parts of the cartridge are out of alignment so placing the stylus on the record causes hum.

If you are picking up vibration from the motor the problem isn't hum, it is rumble. Rumble usually occurs at very low frequencies, but higher frequency vibration still isn't considered to be hum.

 

I can only speak for my problem: it's hum, not rumble. I get the hum as soon as the needle touches the vinyl, whether the platter is spinning or not. I'm listening carefully with headphones... it's HUM.