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AT-LP120 Ground Loop Buzzing Noise

VinylRescue

VinylRescue

Member
I recently had a motor pulsating noise from my AT-LP120 and replaced it with a new motor this week. It was a simple swap with two connectors and two ground wires to re-solder - no biggy right? Now it has a constant ground loop buzzing noise that won't go away. I did the internal grounding method and it reduced it a bit, but still annoying. I had a separate ground wire for it before internally grounding it and it didn't help afterwards either (gotta try something). I rechecked the ground wire from the tonearm as nothing was touched except for the motor swap. I've attached a link below to my YT channel with sound to show exactly what I'm dealing with. Thankfully this is not my main TT as I bought a Rega Planar 2 back in December and I'm just trying to get this back up to par strictly for occasional listening in my living room. Thanks for any help!
 
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I don't have an internal built in ear drum frequency analyzer but that does sound like a buzz to me. Most people don't actually distinguish between hum and buzz but those are two different interference types. I think you're right about the buzz but it seldom, if ever (unlike hum), has to do with grounding. This actually sound like a DC interference and I'd bet it has to do with the motor feed. DC servo motors usually have 4 wires, out of which 2 are power supply and two are feedback. They may have one grounding lead too. Perhaps recheck your motor wiring? Try to disable the onboard pre-amp and check if this buzz persists. It may hint at the origin of the problem. If this is a full volume only type of buzz, barely audible with regular music listening, well... you're just gonna have to live with it as it comes with the territory in these types of budget TT's. ...Or, maybe not. This guy had enough of it and decided to do something about it:

 
woodj said:
What exactly is a "ground loop buzzing noise"?
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It's just a wrong description with a bad diagnosis. It's not "buzzing" noise it's "hum". It's when a mains low frequency (50Hz/60Hz) becomes audible in amplification systems. It's mainly due to a potential (voltage) discharge path being established in a system more than once, hence "loop". "buzz" is higher frequency disturbance and there are many reasons for that to happen starting with anything like bad transistors, cheap, high ESR capacitors, noisy switching power supply's and bad chips, bad DC motors and even going to external electromagnetic interferences.
 
Sorry I didn't mention this, BUT I removed the built-in preamp over 4 years ago. I replaced the original tonearm wiring directly to new RCA plugs in back of the plinth with a separate grounding terminal. I did not have this noise before replacing the motor as I had previously mentioned. It only came about after replacing the motor. I had made this turntable very quiet with pretty much no background noise when turned on, but now the new motor has changed all that and that's all that has changed. It doesn't' matter if the motor is grounded or not it's still noisy.
 
tnsilver said:
I don't have an internal built in ear drum frequency analyzer but that does sound like a buzz to me. Most people don't actually distinguish between hum and buzz but those are two different interference types. I think you're right about the buzz but it seldom, if ever (unlike hum), has to do with grounding. This actually sound like a DC interference and I'd bet it has to do with the motor feed. DC servo motors usually have 4 wires, out of which 2 are power supply and two are feedback. They may have one grounding lead too. Perhaps recheck your motor wiring? Try to disable the onboard pre-amp and check if this buzz persists. It may hint at the origin of the problem. If this is a full volume only type of buzz, barely audible with regular music listening, well... you're just gonna have to live with it as it comes with the territory in these types of budget TT's. ...Or, maybe not. This guy had enough of it and decided to do something about it:

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I've seen this video and this helps with a different noise issue. I had done this mod, but I have some kind of electrical issue. It seems to be grounding since when I touch the grounding terminal with my finger it lessens. I did not have this noise before replacing the motor. It was pretty much dead quiet. When playing an album you can't hear it, but it's there before I even turn on the turntable's power.
 
tnsilver said:
It's just a wrong description with a bad diagnosis. It's not "buzzing" noise it's "hum". It's when a mains low frequency (50Hz/60Hz) becomes audible in amplification systems. It's mainly due to a potential (voltage) discharge path being established in a system more than once, hence "loop". "buzz" is higher frequency disturbance and there are many reasons for that to happen starting with anything like bad transistors, cheap, high ESR capacitors, noisy switching power supply's and bad chips, bad DC motors and even going to external electromagnetic interferences.[/QU

Ok, but all I did was place the motor. This turntable was dead quiet before that. It had two ground wires that I had re-solder and it makes no difference if they're connected or not. It was a lot worse before I did the internal grounding. I had listened to various YT videos and to me it sounds like a buzz more than hum. All I'm trying to do here is to get rid of the noise back to where it used to be. I'd throw this POC in the trash, but I've put so much time and work into this with money spent on mods.
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VinylRescue said:
I did not have this noise before replacing the motor.
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Well... that certainly reduces the scope of the problem - doesn't it? If you're sure about the wiring and it's no different than the previous motor and it's the same version and specs - isn't it safe to assume you got a dud? You know, bad Asian DC motors aren't unheard of... I think the grounding issue just throws you off course. If it was a grounding loop and you'd solve it, it wouldn't lessen, it would be gone. Plus, you got a buzz - not a hum which would indicate a grounding issue. It's possible the motor's internal grounding is faulty but there's very little you can do about that without risky tinkering with the motor innards.
 
tnsilver said:
Well... that certainly reduces the scope of the problem - doesn't it? If you're sure about the wiring and it's no different than the previous motor and it's the same version and specs - isn't it safe to assume you got a dud? You know, bad Asian DC motors aren't unheard of... I think the grounding issue just throws you off course. If it was a grounding loop and you'd solve it, it wouldn't lessen, it would be gone. It's possible the motor's internal grounding is faulty but there's very little you can do about that without risky tinkering with the motor innards.
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Sort of sounds like I'm screwed. I had even tried switching over to my Schiit Mani, but no difference. That's when I did the internal grounding. I use a Schiit SYS to switch back and forth between my TTs and my Rega is dead quiet, and the AT-LP120 is noisy. It's not overbearing at all when I play and album, but rather an annoyance when I turn it on. It shouldn't be there and I did hear that crappy pulsation noise I had before replacing it. Can't seem to win with this POC. Thankfully it only cost $70, but I could have spent that on something better!
 
Check your new motors wiring make sure when you replaced it somehow the motor wire is not closer to your tonearm wires.

You might try putting a shield up between your motor wires and pickup wires, as that is most likely what your getting. Or maybe your little turntable uses a lower voltage motor you might need to replace the caps on the power supply, those low budget tables might have used cheap caps. But I would tend to think of shielding the motor wires so your pickup wires don't pickup the noise from your voltage lines.
 
While not exactly the problem the OP is describing, MY 120 has developed a nasty cogging noise that eventually stops after the platter "settles" on a 33RPM speed -- the problem occurs when I kick the platter up to 78RPM in order to dust off the surface of a record and then immediately return the speed to 33 (or 45)...once I do this, the platter starts cogging pretty heavily and eventually quiets down before I spin a record. I wonder if this is just the 78RPM "instability" that some owners have reported (I don't use the speed for any vinyl playback) or something is going wrong with my deck's motor (I already lost the pop-up stylus light on this thing, which failed just months into owning it, and my cue lever is beginning to squeak pretty badly and won't drop smoothly anymore onto a record, though I understand this can be fixed by adding some damping fluid of some kind).

I think I need to dampen this damn platter with a thick rubber mat, too...
 
AnzacSonata said:
the problem occurs when I kick the platter up to 78RPM in order to dust off the surface of a record and then immediately return the speed to 33 (or 45)
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Here's a thought... Why not just don't do it? Doesn't this thing have a break, a stop button. somethin'? I don't think there's anything wrong with the motor. This isn't a masterpiece of audio engineering you know. You didn't exactly pay for a Mercedes Benz here - right? Stop pushing it to the limit, it obviously can't impede the high speed and stabilize it fast enough. It wasn't designed for this consecutive abuse and it wasn't designed to last either. Cue mechanisms typically use friction provided by silicon oil and many use 300,000cSt viscosity. It's standard RC cars differential fluid, it's cheap and common online and with hobby shops. Pilot lamps' bulbs aren't hard to find either, so it's all fixable.
 
tnsilver said:
Here's a thought... Why not just don't do it? Doesn't this thing have a break, a stop button. somethin'? I don't think there's anything wrong with the motor. This isn't a masterpiece of audio engineering you know. You didn't exactly pay for a Mercedes Benz here - right? Stop pushing it to the limit, it obviously can't impede the high speed and stabilize it fast enough. It wasn't designed for this consecutive abuse and it wasn't designed to last either. Cue mechanisms typically use friction provided by silicon oil and many use 300,000cSt viscosity. It's standard RC cars differential fluid, it's cheap and common online and with hobby shops. Pilot lamps' bulbs aren't hard to find either, so it's all fixable.
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First of all, this was supposed to be a PROFESSIONAL table designed for DJ use, so it's kind of pointless to say "it wasn't designed for consecutive abuse"...I used to DJ with two 1200s, and the speed variations would CONSTANTLY swing, depending on what you were doing with the decks (scratching, back-cueing, etc.). I don't understand what the brake and stop button have to do with my problem; I speed the platter up to 78RPM because it creates the fastest turn speed to dust the records off (just makes it easier), but what would the stop button have to do with it?

Further, with regard to the stylus light, AUDIO-TECHNICA THEMSELVES told me that my light shouldn't have burned out that early, and that they NEVER heard of a case of it burning out so early into the product's life...I don't want to replace the light myself when it had little to no use before it burned out; it shouldn't have happened. I was reporting it as something that pretty much broke on this thing when new. Almost everyone I have discussed this with said it was a reflection of the quality, regardless of whether it could be fixed or not
 
Pal, I'm trying to help here, wanna get this fixed or wanna talk bad luck? As a rule of thumb, any product that says "professional" just isn't. It's marketing. Professionals don't need "professional" labels on their gear or anyone telling them what's professional. You DJ'd an SL-1200 so you must be aware of the difference - right? Does it even feel the same? If you wanna keep your AT live and well for long, I just suggest you use the break or the stop button between spinning at 78 RPM's and going back to 45 or 33. Yes, it's very unprofessional but what do you prefer? A spinning turntable or a professional door stopper? Really, what do you expect AT to tell you when a pilot lamp burns a few months from new? It's probably a LED rather than incandescent and should even last longer. I'm with you! I totally agree it's quality issues, or rather the lack thereof and lack of due quality control. It's a shame really, but that's economy and you should know you get what you pay for. Sorry.
 
Okay, some of may believe this or not, but I found the problem! My Cambridge Audio 551p preamp was causing the stupid hum or buzzing noise. I hooked back up my Artcessories DJ Pre II preamp and it went back to being as quiet as it used to be before replacing the motor. My Cambridge Audio has the grounding problem. Whew! This was driving me nuts as all I did was replace the stupid motor. I want to thank everyone for their input as again I've learned more from this POC TT. My main listening and recording TT is my Rega Planar 2 with my Ortofon MC-3 Turbo cart going through my Schiit Mani preamp to my Novation 2x4 USB interface to my computer. My AT-LP120 is strictly just for other listening as I've learned so much from it as to what NOT to buy in the future. If anyone is interested in my current setup and how it sounds then drop by my YT channel at Vinyl 2CD Rescue: https://www.youtube.com/user/1980smetalrules/videos
 
I later replaced the grounding screw on the back and it works fine now. It wasn't tightening very well as the plastic head was stripped and not tightening the wire to the case as needed.
 
I recently picked up an ATLP120 and have yet to actually listen to it. Is there a 'master list of mods' somewhere for this unit?
 
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