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Audio Technica lp120 USB

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Audio Technica lp120 USB

Postby Joja » 14 Dec 2013 19:42

Hello
Some months ago I bought Audio Technica lp120 USB. I found out that Grado Prestige cartrige as well AT F7 MC cartrige gives low-frequency hum ones mounted. Is that due to the non-shielded lp120 motor or my turntable's defect? It seems that my device works only with AT MM cartriges? Such a pity!
Can any body help with advice?
Sergey
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Re: Audio Technica lp120 USB

Postby Tedrick » 15 Dec 2013 04:12

The Grado is unshielded and may hum with some direct drive 'tables, so it is entirely possible that is why the Grado hums. However, the AT is shielded and should not hum in proximity to the TT motor. A couple of things immediately come to mind:

  • Do you have the ground wire connected? If not, that could be the source of your hum.
  • If the ground wire is connected, disconnect it. Sometimes, they actually cause hum.
  • Does the turntable site on or near a large power amp or other device with large power transformer?
  • Are you using the USB output or the RCA cables for output? Be sure they are not routed near any power amps or other large transformers.
  • What are you using for a phono pre-amp? The LP-120's built-in phono pre-amp is for MM carts only, and does not have enough gain or the right loading to work with the AT-F7, which is a low-output moving coil cartridge. With the AT-F7 into the LP-120's phono stage, you'll have to really crank up the volume, which will amplify any background noise and could be the source of hum when using that cart.
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Re: Audio Technica lp120 USB

Postby Joja » 15 Dec 2013 11:51

Hello Tedrick, thanks for your comments!

I completely tore off the built-in preamp+usb:)The signal goes directly from the cart to the female RCA plugs and ground plug mounted on on the rear side. My preamp is Pro-Ject phono box SE II sitting on Denon PMA-1500R integrated amp. The distance between the cart (mounted on turntable) and the amplifies is 60-70 cm. I use occ double-shielded good wires (1 meter) and a good ground wire (1 meter).
Plug/unplug ground gives almost no effect:(
Surprisingly, AT 440ML cart works silent (no hum at all), Shure 97 is quite silent too.
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Re: Audio Technica lp120 USB

Postby cafe latte » 15 Dec 2013 22:59

Grado can hum on DD, idler and belt drive TT's as they can pick up EMF from AC motors or even from the turntables transformer if it is not well shielded. I am not convinced that the LP-120 has a shielding plate under the motor hemisphere that is connected to the platter like a Technics does so this is probably your hum. Also the mains transformer is likely to be not well shielded if at all so this will be another source of hum.
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Chris
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Re: Audio Technica lp120 USB

Postby thommo_work » 18 Dec 2013 13:16

On my ATPL120 (non-usb)

Grado Red = hum.

Shure, Ortofon, Nagaoka, AT = no hum.
Introduce me to the big blonde, she's got a touch of Tuesday Weld.
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Re: Audio Technica lp120 USB

Postby Joja » 19 Dec 2013 17:38

cafe latte wrote:Grado can hum on DD, idler and belt drive TT's as they can pick up EMF from AC motors or even from the turntables transformer if it is not well shielded. I am not convinced that the LP-120 has a shielding plate under the motor hemisphere that is connected to the platter like a Technics does so this is probably your hum. Also the mains transformer is likely to be not well shielded if at all so this will be another source of hum.
Regards
Chris

Hello Chris
Could an amateur like me shield the AT LP120? What could be some simple and practical steps, materials?
Sergey
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Re: Audio Technica lp120 USB

Postby Joja » 19 Dec 2013 17:39

thommo_work wrote:On my ATPL120 (non-usb)

Grado Red = hum.

Shure, Ortofon, Nagaoka, AT = no hum.

Hello
Do you use MC or MM AT cart?
Sergey
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Re: Audio Technica lp120 USB

Postby cafe latte » 20 Dec 2013 00:14

Joja wrote:
cafe latte wrote:Grado can hum on DD, idler and belt drive TT's as they can pick up EMF from AC motors or even from the turntables transformer if it is not well shielded. I am not convinced that the LP-120 has a shielding plate under the motor hemisphere that is connected to the platter like a Technics does so this is probably your hum. Also the mains transformer is likely to be not well shielded if at all so this will be another source of hum.
Regards
Chris

Hello Chris
Could an amateur like me shield the AT LP120? What could be some simple and practical steps, materials?
Sergey

Not easily no. EM fields are like water and are very hard to shield. I tried to shield the motor of a Lenco using a cart that hummed. I tried completely covering the hole on the metal chassis that the idler wheel of the lenco poked through after removing the idler wheel first and to my surprise I still had a hum. The em field was being deflected by the steel plate I put in (steel is a good material to shield EM) and by the steel chassis but it was leaking up and round the sides.
I dont know what causes the EM field in LP-120's but my guess is the transformer and the direct drive motor itself. The simplest way to eliminate EM problems from the transformer is to remove the transformer from the TT and put it in a box away from the TT (only attempt this if you know what you are doing though). If the DD motor is unshielded it is not so easy to fix. Remove the platter and look at the underside of the platter. You will see half of the motor attached to the platter, if the motor is shielded (I am fairly sure it isnt) behind the motor half you would have a circle of steel between the platter itself and the motor a bit larger than a record label would be. You cant just remove the motor and fit a shield unless you are confident you can get the motor EXACTLY back in its position that it is in factory. If you put it back slightly wrong you will increase the wow and flutter big time and it is already quite high on an LP-120 so unless you are confident you can get it right dont try it.
The LP-120 has more issues than just hum from a grado, my advise is to live with the hum for now and save up for a better TT. For about what you will have paid for your lp-120 you can get a Technics sl1600mk2 which is the automatic version of the sl1200mk2 with a suspended sub chassis. You basically get a sl1200mk2 for a lot less money and you wont have any hum issues and they have far far far less wow and flutter too.
Regards
Chris
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Re: Audio Technica lp120 USB

Postby Joja » 20 Dec 2013 12:54

Thank you, Chris, for your time and comments. I believe that saving for a better TT is the best idea:)
Best regards, Sergey
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Re: Audio Technica lp120 USB

Postby Willem54 » 13 May 2014 21:43

Sergey,

Try this before you stop using your turntable:

Cut a piece of paper the size of the top of your cartridge, place it between the head shell and the Grado. Make sure there is no electrical contact between the outside of the cartridge and the head shell. My AT-150 MLX cart also hummed in my Technics SL-1200's. Piece of paper did the trick!

The Audio Technica has a heavy metal plate in its belly, this acts as ground, that's where the funny spring is for, it makes contact with the metal plate. I hope you didn't remove the spring, if you did, any cart will cause hum. Or you must install a ground wire and connect the wire to the amplifier. I have one too and it doesn't hum, a AT-120e is on it, it has a plastic top ( essentially the same cartridge as the AT-440MLa ) thus isolating the carts' metal housing from the head shell. I hope this works and please let me know!

Good luck!

Willem.
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Re: Audio Technica lp120 USB

Postby cafe latte » 13 May 2014 22:57

Willem54 wrote:Sergey,

Try this before you stop using your turntable:

Cut a piece of paper the size of the top of your cartridge, place it between the head shell and the Grado. Make sure there is no electrical contact between the outside of the cartridge and the head shell. My AT-150 MLX cart also hummed in my Technics SL-1200's. Piece of paper did the trick!

The Audio Technica has a heavy metal plate in its belly, this acts as ground, that's where the funny spring is for, it makes contact with the metal plate. I hope you didn't remove the spring, if you did, any cart will cause hum. Or you must install a ground wire and connect the wire to the amplifier. I have one too and it doesn't hum, a AT-120e is on it, it has a plastic top ( essentially the same cartridge as the AT-440MLa ) thus isolating the carts' metal housing from the head shell. I hope this works and please let me know!

Good luck!

Willem.

A good idea that works with some carts but Grado carts are different, they are unshielded. A grado will hum on many turntables, there has actually been a list compiled of turntables you can and cant use them on. Sadly there is no way a Grado can work on the AT for a number of reasons.. On a Technics the platter side of the motor is shielded with a steel disc, but on the AT it is not. It is also not really viable to to put one there either as you would need to remove the motor half from the platter and the alignment and spacing is critical. Also the transformer in the AT is unshielded too which is another source of EM which will cause hum. The problem with chasing hum caused by EM is it is almost impossible for the reasons I stated before. The Grado cart is a special case regarding hum and it will hum whatever you do due to the design of the AT and lack of shielding. I have a grado in my collection so I know how little it takes to set of a hum.
Regards
Chris
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Re: Audio Technica lp120 USB

Postby Willem54 » 13 May 2014 23:16

I have no experience with Grado's. But I do see some resemblences with Stanton and Pickering regarding hum. Stanton and Pickering carts all have a small copper strip. This strip is connected to the blue earth terminal of the cartridge and the metal housing. If needed one could remove this strip in an attempt to eliminate hum. On most tables though, it has to stay in place. It is also important what the level of hum is. If it is well below the -50 dB level near the spindle of the turntable ( here hum is loudest on most turntables ) I'd say one could live with it.

Greetings,

Willem.
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Re: Audio Technica lp120 USB

Postby cafe latte » 13 May 2014 23:26

Willem54 wrote:I have no experience with Grado's. But I do see some resemblences with Stanton and Pickering regarding hum. Stanton and Pickering carts all have a small copper strip. This strip is connected to the blue earth terminal of the cartridge and the metal housing. If needed one could remove this strip in an attempt to eliminate hum. On most tables though, it has to stay in place. It is also important what the level of hum is. If it is well below the -50 dB level near the spindle of the turntable ( here hum is loudest on most turntables ) I'd say one could live with it.

Greetings,

Willem.

This is because the Stantons and the Pickering are shielded (metal body) and this metal body is connected via a foil strip to the right ground, on some turntables if the body of the cart is not insulated from the headshell or the strip removed you will get hum normally on the right channel. My Stanton 881 and my 681 will both hum on my Lenco for this reason, but the Grado is different there is no shielding of the coils so any em will set off a hum. The AT has so many sources on EM the Grado will hum for sure and it is not fixable.
Regards
Chris
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