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

In connecting a cartridge in balanced mode, to a balanced phono stage, ground is left to "float".  As you know, the cartridge has no ground connection, per se, except for a very few older designs, like (I think) old Decca cartridges, and those cannot be hooked up for balanced drive. The shield on the phono cable itself, if there is one, can be attached to phono stage ground lug, but I have three TTs operating in fully balanced mode, and in no case has it been necessary to ground anything to anything. I don't see any problem with Mitchell's wiring scheme, certainly not one that can account for the phenomenon. And it's not confusing.

Someone else very early on mentioned the Hall Sensor, which is very likely used in the drive system of the Yamaha, because it has a DC coreless motor.  On my Kenwood L07D, also coreless and also DC, the Hall Sensor is fixed to the plinth surface under the platter, but there must also be a signalling device built on the underside of the platter itself that rotates with the platter and triggers the sensor if there is a speed error.  It seems possible that in balanced mode the phono stage is picking up a signal from the cartridge, as the Hall component that is fastened to the platter rotates under the cartridge. This is causing an impulse from the cartridge to push the woofer in concert with TT speed.  But why this happens only with platter mat and LP in place, I do not know.

One idea why the problem only occurs in balanced and not in SE mode might be that in the latter case, both channels ARE connected to audio ground, so maybe the signal never gets to be amplified to drive the woofers.  It would be interesting to hook the output to a 'scope and see if one can detect the spurious signal on hot or ground in SE mode.

In connecting a cartridge in balanced mode, to a balanced phono stage, ground is left to "float".  As you know, the cartridge has no ground connection, per se, except for a very few older designs, like (I think) old Decca cartridges, and those cannot be hooked up for balanced drive. The shield on the phono cable itself, if there is one, can be attached to phono stage ground lug, but I have three TTs operating in fully balanced mode, and in no case has it been necessary to ground anything to anything. I don't see any problem with Mitchell's wiring scheme, certainly not one that can account for the phenomenon. And it's not confusing.

I don’t see a problem either, but to attach the shield to ground, seems worth taking a lark on trying?

Someone else very early on mentioned the Hall Sensor, which is very likely used in the drive system of the Yamaha, because it has a DC coreless motor.  On my Kenwood L07D, also coreless and also DC, the Hall Sensor is fixed to the plinth surface under the platter, but there must also be a signalling device built on the underside of the platter itself that rotates with the platter and triggers the sensor if there is a speed error.  It seems possible that in balanced mode the phono stage is picking up a signal from the cartridge, as the Hall component that is fastened to the platter rotates under the cartridge. This is causing an impulse from the cartridge to push the woofer in concert with TT speed.  But why this happens only with platter mat and LP in place, I do not know.

Yep -it wakes little sense how the mat and LP could contribute

One idea why the problem only occurs in balanced and not in SE mode might be that in the latter case, both channels ARE connected to audio ground, so maybe the signal never gets to be amplified to drive the woofers.  It would be interesting to hook the output to a 'scope and see if one can detect the spurious signal on hot or ground in SE mode

If the signal was sneaking in on the ground, then the SE is tying the phono stage to the TT. And the pin-1 being disconnected, is not tying the XLR to ground.
But this also would suggest that the XLR at the TT side may not be wired as push/pull and maybe has the out of phase side tied to ground?

sound like your cartridge/arm wiring is specific for SE output.

the correct wiring for balanced wiring supposely take (+) and (-) pins to pin 2 and ping 3 in XLR connector. if you want to use external grounding wire between TT and phono stage, leave TT side pin 1 of XLR connector idle (floating). Otherwise, connect TT ground to pin1 of the XLR connectors. 

Above balanced wiring assumes that on Phono stage side the pin 2/3 is connection to positive/negative side of balanced input (such as step up transformer primary), would not work for SE inputs (negative grounded).

"If the signal was sneaking in on the ground, then the SE is tying the phono stage to the TT. And the pin-1 being disconnected, is not tying the XLR to ground.
But this also would suggest that the XLR at the TT side may not be wired as push/pull and maybe has the out of phase side tied to ground?"

You lost me there, but I am not suggesting or even thinking that the signal is coming in on the ground connection. Quite the contrary, the balanced connection is floated (not attached to audio ground), and the phenomenon only occurred in balanced mode.

I ended up with a snow day so I assembled two XLR to RCA adapters. I also wired a conductor attached to pin 1 in each XLR that exits at the connector base. Think XLR with an external ground wire. I made a junction for the two ground wires ending in a single wire.

So let’s dive in:

Woofer Pumping in balanced mode is present and unaffected by the presence of a pin 1 tonearm ground connection. I tried first with the XLR ground extension attached at the preamp tonearm ground lug along with the conventional tonearm ground wire and second with the XLR ground and tonearm ground attached to each other but not attached to the preamp tonearm ground lug. Neither arrangement made the slightest difference.

It would appear the pin1 theory is exploded, which is sad because the solution would have been as simple as a reconfigured cable set.

Next up, Static Electricity. I forget who (sorry) but it was suggested that wiping a record with a dryer sheet might affect the pumping. I observed the pumping with only the mat  to get a visual baseline, then applied the dryer sheet while the platter was spinning. The amplitude of the woofer excursions diminished visibly while I was wiping the mat, I’d say by 80 to 90 percent.

It would appear that the correct answer is, levels of static electricity not enough to arc but enough to influence the Hana ML while operating in balanced mode.