AT-120LP Hum woes (Portland Area)

Aloha gang,
Anyone in the Portland/Vancouver area that could possibly help me out with my TT hum issues? Need to eliminate (what seems to be) RF/proximity hum. Get close to TT, hum get more intense, move away, hum decreases, but still present. Super modest system, but it's a huge upgrade from what I just had.
Any help would be most appreciated! Really want to enjoy my new setup, and resurgence with Vinyl!!
Thank you!

AT-120LP / Ortofon 2M Blue

 

Not an expert in the area. Hum issues are the worst. I hope you get the help you need.

I had a hum issue with my technics 1200 recently. Turns out the tonearm was not being properly grounded through the RCA cable ground. Diagnosed with a piece of speaker wire, attached one end to the phono ground, and tried touching various parts of the table, and the tonearm was the winner. Added another ground wire from the tonearm mounting plate to the phono, totally noise free now.

Other hum issues I've had in the past have been from other electronics too close to the tonearm cable or phono stage, as well as a wifi internet modem positioned too close. Can you power off/unplug everything else in the area to be sure it's not causing the issue?

 

Welcome to the forum ;^)

Would just like to ask if you have fidgeted around with the grounding post a little. Sometimes you just need to twist the connection on the post a little to get it silent.
This doesnt sound like such a problem but its worth a try.

Try turning off all electronics in your house for a second to see if that helps, even turn off the lights. Also make sure that the table, specifically tonearm is as far away from the table or sectioned of with some wall of furniture or similar to eliminate disturbances there.

Also try touching your equipment all over, like amp, table, tonearm etc.

On a side note, have you yet to remove the pre amp in your LP120?

 

Do you hear the hum when using the built-in USB soundcard?

Do you hear hum when using the built-in preamp and then connecting RCAs to a normal input (not a phono input)?

Either of these options should eliminate a phono grounding issue; if the problem continues, it's internal to the turntable or the connection to the cartridge. Of course, don't hook up the turntable to phono inputs if you are using the built-in preamp.

Did it work correctly before? What change broke it?

 

That much hum at close proximity, without touching the turntable must be a broken ground connection. This can occur anywhere in the signal chain or on the chassis ground. Difficult to isolate the problem without an in person inspection, I hope you find someone who can help. Here is a step by step troubleshooting procedure:

1) Disconnect the RCA cables to the phono preamp (pre-amp off while doing this) Turn your system on, turn up the volume
a) hum (no change) the hum is from the phono preamp
b) no hum, the pre-amp is ok, the hum is coming from the cable or the turntable

2) Check the ground wire connection on the phono pre-amp (some turntables do not have a separate ground wire) Check the RCA cables that they fit snug.

3) Check the connections at the cartridge, that they are not loose. Cartridge pins are not standardized. Some are slightly smaller, which sometimes the jumper wire connector may fit loosely on the pins.
a) hum, or little to no change, your RCA cables could be bad. I have experienced cables going bad for no apparent reason. The cause is usually bad solder, or frayed/ broken shield. Replace/borrow another cable (can be a cheap one) just for troubleshooting purposes.. process of elimination.
b) no hum, problem solved, indicates the problem was in the pin connection.

4) Jump the ground to the tone arm with a length of wire. Simply connect one end to the ground post on the phono preamp, and touch the other end (bare copper) to the tone arm.
a) hum, the problem is not the chassis ground, could be a defective cartridge/ open coils
b) no hum, problem almost solved, but not repaired.. you have a broken chassis ground, possibly a defective turntable that is not carrying ground to the tone arm.

Lastly, if you have sound, the problem is almost certainly a bad chassis ground. Check the ground connection.

good luck!

 

Responses to your very helpful replies:

• Brand new TT. RCA internally connected. no additional/external ground wire
• Turned off Smart TV and removed cabinet LED bulb; no change
• Grounding post? No post, I believe
• I'll try turn off cable box...
• Touching different parts has no affect
• Never tried USB
  
• Forgot to mention that I do have an external Pro-Ject phono box e. I'll try take this out of line

I will try The FRiNgE step-by-step tomorrow.

Thank you all for your time & help!

 

Never heard of the LP120s having grounding internally built into the RCA cables. I thought only Rega did that. Are you sure this is the case?

 

Yeah... Only RCA. No additional ground wire..

 

Ok well did you specifically try to touch all over the tonearm while having the other hand on your amp?

This sounds like a ground loop to me.

 

it sounds to me as if you need a ground wire, whether or not there's a labeled post. Try running an insulated wire from the turntable chassis to the preamp. There's often a little corner cranny where you can wedge a wire without any need to solder. And almost certainly there are assembly screws. Just loosen a screw on the metal of the turntable chassis and one on the preamp or receiver, run the wire between those, and tighten.

 

The headshell connectors may be the culprit. I tightened them once, and seemed to alleviate the hum, but some are loose again. Connectors seem to be too short and too large of diameter. Might need to purchase an Ortofon headshell to match Ortofon cart. Does this sound like a common issue when upgrading cartridge?

 

Yes it is, sort of. Some connectors are too big or too small sometimes and need adjustment. What I did was squeeze the metal end of the cable together a little so that its slightly too small for the pin connector. Then with some good plyers I gently used force to push them on. Gives a pretty snug fit. Be very careful though, and dont pull on the cables too much, especially not on the colored part, only the metal end.

 

Definitely going to give this a shot. I know in the Ham Radio world, when you think you have enough grounding.....ground some more!

Thanks!!

 

Grounding results...

Well, finally got some time to ground the AT-LP120 turntable to the Pro-Ject Phono Box E pre-amp. It took some doing, but great results! No Hum!!! Had to remove the bottom cover of turntable. No metal parts on outside of turntable housing. On the bottom, there is a large flat metal plate. I used one of the mounting screws to attach lug connector, with the other side going to the pre-amp. It was a bit of a b1tch getting the cover to go back on due to 8 tiny brass bushings needing to be aligned to the mounting screw holes. They were all just sitting on to of mounting holes, they kept falling off. Finally put a spot of crazy glue to hold them in place.
Anyway.... HAPPY CAMPER!!! I now can turn up the volume on albums!!!