So Weird- No Stylus Contact Woofer Pumping with Hana ML and Elac PPA-2


I observed the weirdest thing I have ever seen in audio. With the cartridge positioned above the record, tone arm locked up and platter spinning, the woofers were pumping on my system. I googled every permutation of query I could think of but came back with no hits. That’s when I decided to video the problem- link below:

Mystery Woofer Pumping

I could type out all the details but the video pretty much covers everything. I thought ya’ll might be interested in this.

 

mitchellcp

most likely this TT/Phone inputs w/o a grounding wire between them, so it is sensitive to 33 1/3 electro-magnetic  radiation.

It’s kind of reproduced except mine needs a record or synthetic mat or both.

So it pumps with a record and not a mat, but no pumping with just the platter?

 

 @byang12  I’m confused, could you restate that

There is pretty much electrical field and magnetic field.

I am having a hard time with an electrical field that is at 1/2 RPM… and a magnetic field should not be affected with just a piece of vinyl on top of the alloy platter.

It is either coming out of the cart itself, or it needs to be tied to the ground wire, like making some differential voltage between the ground and the cart, which is tied to the platter phase.
But those mechanisms should not be tied to rely on a mat or piece of vinyl.

I could imagine Lewm’s idea of electrical being tied into the electrical side.
@mitchellcp previously I think that you mentioned that there NO ground wire running to the electronics… and the PIn-1 is not tied to ground.

I am wondering if pin-1 should be tied to the ground at the TT end.

@holmz 

The wiring rundown is here.

Wiring for the tonearm to the preamp was as follows:

  • Pin 1- no connection
  • Pin 2- + positive
  • Pin 3- - negative
  • Shell ground- cable shield

Why was it wired like that? I agree the typical connection is pin 1 for the shield. See excerpt from the Elac PPA-2 Manual:

"Typically a balanced connection will be more immune to hum, so it would be the preferred connection. However, you must be careful that the shell of the XLR is not connected directly to the ground line within the XLR connector ( That sentence is a little confusing but I take it to mean that the shell of the XLR should not be connected to pin 1). They SHOULD be independent. The shell is the external shield of the cable and connector, and should be the CHASSIS connection. The ground wire within the XLR is twisted with the (+) and (-) balanced and should be the signal or tonearm ground. This can all be confirmed with an Ohm meter. "

The PPA-2 has two ground lugs, one for tone arm ground (labeled ground) and one for chassis ground (labeled chassis). Since there is no chassis ground on the GT2000, that lug remains unused. The tonearm ground is connected via the other ground lug.

The cable shield is NOT connected at the TT end, but is connected via XLR shell to the chassis ground.

 

I’m still thinking you are putting a static charge on your records. That charge won’t universally distribute evenly across the record, as the vinyl itself is an insulator. Something you are doing is leaving a charge, and that charge is concentrated (possibly) at the last place you touched the record. That concentrated, persistent static charge is inducing a periodic, low-frequency signal via your cartridge.

I also still think the conversion from balanced to single ended isn’t what resolved your issue. You created a better ground path to dissipate the static charge. I’d bet that if you ran a very thin wire from your head shell to ground you would have resolved the issue as well.