[earwicker7]

Hey, all. I recently got a Transrotor Apollon 40/60/M turntable. So far, everything is going pretty well as far as setting it up, but there is one problem I'm having. There is some rumble that seems to be related to the motors (there are three of them, and they are outboard, so they don't touch the plinth, but they do share the block of maple that the whole shebang is on). It's not really loud (it's not noticeable until about 50% on the volume knob) but it's enough to drive a perfectionist like myself mad

. Basically, when everything is hooked up and the turntable isn't moving, the output is silent. When I turn the table to 33RPM (without dropping the needle) there is a rumble in the 30-40 Hz range. When it's on 45RPM, it stays at about the same level, but is more in the 60-70 Hz range.

Todd from TTVJ said that it was probably vibrations from the three motors being transferred to the pickup, and that I could try isolating the motors by placing something underneath them (he recommended starting with mousepads). I also read somewhere that poor cartridge/tonearm compliance could cause rumble; does anyone know if the Dynavector DV-507 Mk2 goes well with the Grado Statement? I've also got a Dynavector DRT XV-1S cartridge that I was going to eventually set up (the tonearm has detachable headshells and I have two of them), so that may help.

Anyways, if anyone else has any recommendations, I'd love to hear them.

Thanks!!!

 

[casouza]

I suggest that you remove the belts and turn on the motors. If the rumble stops it is caused by a bent or defective platter main bearing/spindle.
If the rumble continues, keep the belts off and adjust the arm to zero weight, no anti-skating. Unlatch the arm from its rest stop, float it in mid-air and turn on the motors.
If the rumble continues, it is coming through the arm base. If it stops, it was coming through the arm rest, no bid deal.
Re-adjust the arm weight and anti-skating to the usual settings (still with belts off), place a record on top of the platter and place the stylus in play position. Turn on the motors.
If the rumble continues with a static platter, the motors need damping and isolation (or maybe one of them is defective).
Mouse pads are a good idea, a sorbothane sheet may be better.
The ultimate solution is to make a large cutout (with a wide gap) in the maple block in order to isolate the motors from the platter/TT base. I recommend Stillpoints or Herbie's vibration dampers under the separate blocks.
I hope this helps

 

[earwicker7]

Quote:

Originally Posted by casouza /img/forum/go_quote.gif I suggest that you remove the belts and turn on the motors. If the rumble stops it is caused by a bent or defective platter main bearing/spindle. If the rumble continues, keep the belts off and adjust the arm to zero weight, no anti-skating. Unlatch the arm from its rest stop, float it in mid-air and turn on the motors. If the rumble continues, it is coming through the arm base. If it stops, it was coming through the arm rest, no bid deal. Re-adjust the arm weight and anti-skating to the usual settings (still with belts off), place a record on top of the platter and place the stylus in play position. Turn on the motors. If the rumble continues with a static platter, the motors need damping and isolation (or maybe one of them is defective). Mouse pads are a good idea, a sorbothane sheet may be better. The ultimate solution is to make a large cutout (with a wide gap) in the maple block in order to isolate the motors from the platter/TT base. I recommend Stillpoints or Herbie's vibration dampers under the separate blocks. I hope this helps

Wow, your first post and you've already been super helpful!

Hold on a second... you're not God, are you?

 

[Lazarus Short]

Have you tried detaching the drive belt(s) and turning the platter slowly by hand, with a stylus in the groove? It could show you a lot. Otherwise, casouza's suggestions seem to cover most of it.

 

[earwicker7]

Well, some interesting stuff has happened. I took off the belts and ran the table; the hum was still there. When the arm was in the armrest, the hum was still there. However, when I moved it halfway to the platter, it stopped. I moved it back to the armrest, and it came back. I moved it from the armrest to the platter, and this is when it struck me...

The rumble disappears completely when the cartridge is directly above the motor. As it moves away from the center of the motor, it gets louder.

So it seems like there is some form of electrical field interference. I didn't have much time to screw around last night, so that's as far as I got. Tonight I'm going to completely remove that specific motor from the stand and see what happens. I hope there is some way to deal with this other than making it a two motor table... I really like the speed stability of a three motor table.

 

[Publius]

You're using a Grado? Try a different cartridge. Grados are rather notoriously sensitive to interference.

 

[earwicker7]

Quote:

Originally Posted by Publius /img/forum/go_quote.gif You're using a Grado? Try a different cartridge. Grados are rather notoriously sensitive to interference.

I just did some googling, and not only are they notoriously sensitive to interference, they are specifically notoriously sensitive to interference from having motors underneath them.

D'oh!

Good thing I've got the Dynavector, which is in all likelihood a better cartridge... I just wanted to set up the Grado first, as it's newer. Hopefully switching cartridges will nail the problem and only present me with the issue of what the hell to do with a $2500 cartridge that won't work with my setup

.

 

[nikongod]

it sounds crazy, but have you tried rotating the motor?

Just a few degrees each way (max 1/6 turn) may help. It may not, but it dosnt cost anything to try.

Also, is the grado a low or high output? If its a low output, you may have the same issues with the dynavector. Grados are hum-magnets, but if your motors are leaking that much noise you may get noise across the board.

If you do have a low output grado, what phono-stage do you have?

 

[earwicker7]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif it sounds crazy, but have you tried rotating the motor? Just a few degrees each way (max 1/6 turn) may help. It may not, but it dosnt cost anything to try. Also, is the grado a low or high output? If its a low output, you may have the same issues with the dynavector. Grados are hum-magnets, but if your motors are leaking that much noise you may get noise across the board. If you do have a low output grado, what phono-stage do you have?

I haven't tried that, but I will.

And yes, I have a low output Grado, actually the lowest output they make (I think it's 0.5 mv). There don't really seem to be any horror stories immediately available on Google about Dynavector hum, so I'm hoping it will make a difference.

As to phono stage, it's a Ray Samuels XR-10B.

 

[earwicker7]

Good news and bad news...

The good news is that it was indeed the Grado causing the hum, not the turntable itself. The Dynavector works just fine.

The bad news is that I now have a cartridge that is basically worthless to me. I only have one tonearm, so I can't use it on the old SOTA without buying a new tonearm. Maybe it's time to sell the SOTA and the Grado; it could make a good package for someone, all they'd have to do is buy a decent tonearm and they'd have a killer setup.

 

[BobMcN]

Too bad - I was hoping that the Grado turned out fine for you and you'd be willing to part with the very excellent XV-1S catrridge at a significant discount. Damn!!!

If you really like the Grado sound you could also try putting some ERS paper over the motor, in an attempt to shield it from the cartridge.

Enjoy,
Bob