Building high-end 'tables cheap at Home Despot II

Ok, I'll attach it to the top of the plate. Thanks again - and for the revised notes as well. Chuck

Hmmm. That makes some sense. I will fool around with it later this week and see what happens. Thanks.

Hi everyone - thanks to Mario and all the rest for the restart of this incredible thread - although from the looks of ebay, for all those on the outside looking in, finding a usable Lenco seems to be getting pretty hard.

I have a pretty significant hum, sort of like a ground hum, that begins when I turn the table on. It only impacts one channel, and it lessens significantly when I move the arm (VPI 10) from its rest - although it does not fully disappear. This makes me think it is vibration being absorbed into the base - the pivot is indeed close to the motor as the table is turned 90 degrees (but the arm never crosses over the motor), but it seems to come throught the cartridge or arm, because when I remove the connection from the arm to the pivot, the hum stops. The hum remains the same when the platter is removed, but immediately ceases when I turn it off. The fact that only one channel picks up this hum is confusing.

Anyone have any suggestions? Thanks as always, Chuck.

PS: The thing still sounds stunning, even with this little hum - just stunning.

Oregon & Jean: thanks both. I will try both ideas and let you know. The power of this thread is so formidable that when I was fooling around yesterday (with my wife's help listening) she was the one that said "you should post the problem on your favorite thread."

Ladies and gentlemen, for my wife to reach this opinion, well let's just say we've penetrated well down into the masses!

In the original thread there was considerable conversation about hum that originates if the arm/cartridge crosses over the the motor. I think I am experiencing this.

I (finally) took the time to experiment with this low frequency hum from my VPI/giant Lenco/Decca (Grado now, as the Decca had to be sent off for repair).

It is coming from the cartridge interacting with the motor - either the electrical/magnetic field or amplifying the motor noise. When I de-couple the arm from the table, the low frequency hum remains audible, growing especially loud when the cart passes near the motor. Move the cartridge 6-8" away from the motor, and the hum disappears. I tried various grounding wires from the chassis and arm, and none of these made any difference. It's gotta be from the motor.

I don't think I can reset the arm - and when I move it to another corner, the hum remains about the same. The base is at the corner where the motor is, but the arm doesn't really cross over the motor directly. It seems to be more about how close the cartridge is to the motor than anything else. I have been using a grounded plug with this motor, but I doubt that's the cause. But maybe, as I am using the same motor from an earlier version but changed the cord, adding the ground. I suspect I have to somehow shield the motor better, but can't imagine how. Maybe something beneath the platter?

Any suggestions? Many thanks, and happy Thanksgiving. Btw, this baby still is magnificent, hum or no hum (it's not that loud, not nearly as annoying as, say, a ground hum).

Mike, as I imagine an electro-magnetic field to work, the waves are not absorbed but are deflected by mumetal. If I am right, then the waves would flow out and emerge around the edges of the motor - still interacting with the cartridge as it plays the record. When the shielding is done for the platter, this flow around the barrier would also happen, but shielding the platter would disperse the field to the outside of the record and the interference would occur outside the playing surface of the record.

I had also thought of shielding the bottom of the platter rather than the top - this way you won't have to be so particular at adhering it. But I'll have to wait until I see the material in the flesh. Mario, is there any reason for doing the top versus the bottom?

Of course, I may be full of hot air here and this is a guess based on my extensive ignorance of electro-magnetic fields.

If anyone wants mumetal to shield their platter as per Mario's approach, I just ordered some and will have about 4 sets of sheets that I will sell you for my cost. The kit cost $140, so each set would be about $30 (round #, including postage). If you've got the same hum I do, this is how Mario got rid of it. Email me if you're interested.

Tsatalia, I experience that hum, and after testing the possible causes, mine is caused by the electro-magnetic field the motor emits. Like Johnnatais mentioned, Mario has found a solution that is in this thread.

(For those of you I owe mumetal sheets to, every weekend I plan to do this, and somehow it hasn't gotten done. My apologies. Maybe this weekend....)