Thanks Atmasphere and Snfrosten. I will take my LP12 to the Linn dealer and ask them to try it on their system. I'll keep you posted. |
A ground wire will NOT shield the motor and there will be no effect on the hum. Your Linn dealer will look at you funny for a reason, it will not work and maybe even create a ground loop which will make any cartridge you install hum. The only way to shield the motor is to isolate it, surround it with a magnetic shielding material. |
If the motor is made of a metal that can be soldered, then solder it. Otherwise a wire with a lug, placed under a nut and bolt should do the job. |
Thanks everyone. Does anyone know how to attach a ground wire to a Linn motor? I'll ask my Linn 'mechanic' but I can already see the look on his face. |
Geor, they may have springs but that cannot be considered an adequate ground. The motor must have a wire that does the job, so plinth, motor, platter bearing and arm have the same ground.
The motor may not be shielded, but if you ground it that may not be important! Certainly an ungrounded, unshielded motor *will* be a problem for an unshielded moving magnet cartridge!! So get it grounded right and let's see how it works. |
Dear Geor: I agree with Snfrosten about the Grado cartridges performance.
Regards and enjoy the music,
Raul. |
Its not a grounding problem. The motor is not shielded and most MI will hum a bit. The only way to remove this hum is to shield the motor with some type of material like Mu-metal or add a shied on the platter, between the mat and platter, to shield the cartridge from the magnetic interference from the motor. The Grados are excellent sounding cartridges and worth the effort to fix this problem with the table. |
Thanks Atmasphere. I'm pretty sure there is a ground wire going from the arm base to the bearing sub-chassis. The motor is attached directly to the top stainless steel suspension plate. Is there a missing connection between the top plate and sub-chassis? I thought the springs made this connection, but there are rubber washers on the springs, so I think your idea makes sense. One would think that Linn would have considered this in their design of the LP12. |
There is a fix for the Grado hum... Its a grounding issue - I don't remember what the proceedure is, however if you call Grado, they should know. |
Grados will hum with certain 'tables, like the Rega. Usually this comes from the table not being sufficiently grounded. For example, the Rega needs to have its motor and platter bearing both grounded to the arm ground. I suspect the same is true in this case, based on the fact that if you move the arm, the hum changes. That's not a ground loop!
So this might be easy to fix- have a wire installed that goes from the motor chassis to the platter bearing and then to the base of the arm- make sure that every bit of metal on the 'table is grounded. |
After doing much research on Audiogon and the web in general, I am beginning to realize the problem is a ground loop hum. I have a rooftop FM antenna that is grounded to a single rebar spike. This apparently is not a good setup - too much resistance. It should be two copper clad steel rods, 5/8" x 8' long, 8' apart driven below grade, with the two ground rods connected via buried heavy gage stranded copper wire. The loop is formed by the potential difference between the ground of the FM coax (steel rod) and that of the main electrical service panel (water pipe). It seems that I should also add two ground stakes outside the main panel and connect all ground stakes with the heavy buried copper wire.
Off to the electrical supply store and not the needle shop! |
Sorry, I missed that you have a Lingo.
I think that a cart with a metal body would be less prone to hum.
Sean
|
Thanks Sean. I do have the Lingo. I've only had two cartridges on this 'table (both Grado), so maybe it's time to live dangerously and try something new ;-) |
Whoops, meant to say if it does not hum when it's unplugged then it's the power supply. |
An outboard power supply like a Lingo would most likely solve the problem.
One way to find out is to unplug your Linn, swing the tonearm over the platter, and see if it still hums. If it does then it's the power supply in the deck. You have to unplug because the power supply stays energized even when not spinning.
Sean |
Thanks Coxhaus and Metralla. I did some research on hum problems and tried one suggestion with some success. That was to move the LP12 away from other components, especially their transformers. I realized the turntable motor was about 6-8" away from the preamp (ARC LS2BII) transformer on the shelf below. I lifted the turntable as much as I could - about 18"- with no change. Then I tried rotating it and the hum was almost gone.
The ARC transformer seemed to have a 2-dimensional planar beam (?) running vertically. (The transformer is mounted on the side wall of the preamp). |
I don't have cable, but I do have noisey AC power. I can hear my Braun coffee maker's thermostat cycle on and off! I also have an FM transmission tower about a mile away. |
I have a Grado Signature 8MR on a Sondek using a Linn Basik LVX arm from 1984 - this unit is in storage back in Australia. This has no hum at all into a very high gain preamp (the preamp could handle a moving coil cartridge without a transformer).
Something must be wrong.
Regards, |
I have a Grado "The Statement" on an old Linn LP12 which I bought new in 73 or 74 can't remember. I now have an Itok arm which was not original. I have absolutely no hum. My dealer was a Linn dealer for many years and sold Grados with Linn tables. Do you have cable connected to a device in your system? It is easy to create a ground loop which will cause hum. |
a phono step up transformer is another option if you chose a low output design. |
Thanks All. The Lyra sounds like a good fit, but the Dorian costs about $1100. It must have to do with exchange rates, because I remember it was around $750 a few years ago. Maybe there is presently better value in the Japanese AT for the same reason. (US Dollar) I have German speakers and had a Scottish tonearm that I bought (new) at bargain prices 5-10 years ago when the US dollar was stronger.
Also my phono pre needs higher output. I'm still wondering in general about MM vs MC and especially low or medium output cartridges. Are the advantages worth looking at a MC phono stage. There is a current thread on MM vs MC with 1000 posts but I haven't gotten much out of it yet.
Thanks again! |
Agree with the AT150 for performance and no hum. Bang for the buck is off the charts. |
Yes. I would second the suggestion of a Lyra cartridge for your LP12. The reason they are such a good match for the Linn table is that Lyra used to manufacture all of Linns higher end MC phono carts, including the Troika, if I'm not mistaken. I'm not sure if they still do. |
Might look at a Lyra Dorian I think those are around 700.00I have a Troika on mine and it works well. There is a synergy with Linn. I saw a re-tipped Troika list here the other day. But I have heard the Lyra Skala and Helikon on LP12s and they work well too. I would eventually like to try a Helikon or if extra$$ show up a Skala. The Lyra hous sound is a very open, musical yet detailed sound that I like very much, you might investigate. Lyra had a trade up program that they may run again and in a year or so you could step up. |
