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

That’s actually pretty funny 

This may be the first in AudioGon history - a thread with a resolution! Good stuff!

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.

"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.

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).

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?

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.

@nrenter I will be addressing the static issue as well, later this week.

@byang12 The pin 1 ground to tonearm is the only missing piece of the puzzle, however since the tonearm is already grounded to the phono preamp via the external ground wire, I felt that sending the tonearm ground down the left cable, the right cable and the external wire was not a great idea. My assumption at the time was that the tonearm ground lug was most likely connected at the same circuit point as the two pin 1 connections. 

We'll find out latter this week. 

Just to clarify one point, the TT is grounded to the preamp. The question being is it the correct point?

Actually, this phenomenon states a fundamental fact:  electro-magnetic energy broadcasting as waves/Strings not as particles. So the great Einstein could be wrong right here. 

your statement:

Wiring for the tonearm to the preamp was as follows:

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

is very very confusing.

This tonearm is for custom mono cartridge? For stereo cartridges, 4 color coded pins (same four pins from arm) are:

positive 1

negative 1

positive 2

negative 2

There is no ground pin for cartridge.

My experience is that ground loop hum/electro-magnetic noise has nothing to do with RCA or XLR plugs if ground wire was connected properly.

remember, Tesla proved a long long time ago that electro-magnetic energy could be transform from source (turn table/cartridge) to receiver (phono stage inputs) if no ground shelling to short the energy.

You have a relative humidity of 25%?!?!

Way too dry.

40% to 50% should be a your target. 

BTW, I’m running balanced from cartridge to speakers (and have been for 17 years). Soundsmith Aida -> OL Enterprise -> AudioQuest Leopard (balanced) -> Ayre P-5xe (balanced) -> AudioQuest Colorado (XLR) -> Ayre AX-5/20 (balanced).

And I can tell a difference if my table bearing is properly grounded or not, particularly on dry days. 

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.

@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.

 

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.

@byang12  I’m confused, could you restate that?

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

My oscillation hypothesis is officially in the toilet, if the frequency of the woofer pumping is equal to the TT rpms.  Over and out.

@ejb14 

When you were spinning by hand, was the turntable power on?

No, when the power is on you have two choices, 33 or 45.

Powered items were amp and pre amp.

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

Yeah, @mitchellcp you said this in an earlier post - "Woofer pumping is tied to rotation speed, the pumping is faster at 45 than 33 also spinning the platter by hand will excite the woofers."

When you were spinning by hand, was the turntable power on?

Also, when you tried 33 and 45 did you turn anything off in between? I ask because @lewm talked about turning on and off equipment can yield different results with the oscillation idea.

Not sure this below is representative, but it is interesting:

I managed to reproduce woofer pumping, with my old Dual 701/V15III (direct drive) unplugged from wall power, the platter on or off, and just having the stylus near the motor housing and spinning the housing or platter by hand. More pronounced with the platter off. I can go real slow and get real slow woofer pumping, or faster and get fast woofer pumping. Move the stylus further away and no pumping. I had to turn the gain almost to full to see anything though; increasing the gain on the phono stage increased the extension of the pumping (makes sense).

I also reproduced this, but it was much more mild woofer movement, with my old Technics SL-D20 (also direct drive), again unplugged from wall power and just spinning the platter by hand.

It pumps to the rpm of the platter. 33 at 33, 45 at 45, and slowly if I spin it by hand.

Bear in mind, that isn't happening now because I'm in single end mode.

 

Not everyone is focused on magnetism. Have you read any of my posts? I’ve just grown weary of contradicting Holmz, who IS focused on magnetism. I let his last fantasy stand as is, because I did not want to appear to be picking on him.

Like I have said three or four times, my best guess is that the system is oscillating at a very low frequency when the preamplifier is hooked to the cartridge output in balanced mode. When the OP switched to single ended mode, the problem went away. The bit about the platter mat and LP is a red herring, as per my earlier definition. The fact that it seemed to make a difference can possibly be due to the fact that when you power down an oscillating electronic device (in this case, the preamplifier or the amplifier would be oscillating due to input from the TT), the oscillation of course ceases. When you then restart or power up the same electronic device, even with the same input and output loading, the isolation may or may not reappear. In order to remove the platter mat and LP, in this instance, the OP had to shut down power to the TT and then power it up again in order to demonstrate the "no platter mat, no LP" condition. So lets say the cartridge is picking up something from the TT motor that intermittently causes either the preamp or the amplifier to oscillate but only in balanced mode. The intermittent nature of an oscillation is what confounds the investigation of its cause, let alone trying to fix the problem. And beyond that, we really do not have enough data to speculate further. Maybe the OP will eventually come forward with some additional information, but I don’t blame him if he does not want to be bothered and is perfectly happy to operate in SE mode.

Magnetism, shmagnetism.

Yeah @lewm I am guilty as charged.
Your posts are usually pretty thoughtful, so I would probably be OK with being picked on.

WRT the air currents and wind, just blowing on the stylus would be more that it would see from currents, and if that does not move the stylus then to get LF movement would be pretty hard.

And resonance of the stylus/cantilever should be much higher freq, that the <1 Hz.

So I am thinking the causal mechanism is doubtful to be mechanical… which leaves electrical and magnetic as two forces.

@mitchellcp I have lost that ball a bit, but we may want to see of it pumps moving the TT patter by hand, or as the thing is spinning down right after the motor stops getting power.

If it does it with only the motor being on, or regardless of whether the motor is powered, then that would be “more clues.”

@lewm I am starting to come around to your hypothesis, as it seems like it what is known as motorboating.

It looked like it was sync’ed to the platter position, and platter speed.
I am wondering if the pumping is faster at 45RPM than at 33-1/3?

I mentioned that I would be re-wiring my tone arm this weekend and I have completed that. I'm going to start a separate thread about the why of the rewire and it's results. For the purposes of this thread, I'm enjoying the improved sound so much there may a hold on converting back to balanced mode.

Kidding I’ll try that next go ‘round

I think it would smell very fresh!

I wonder what would happen if you rub a dryer sheet over the rubber mat?

In the post above, the word "isolation" which appears in line 9 of the second paragraph, should be changed to "oscillation".  I thought I fixed that within the time limit for editing, but apparently not.

Not everyone is focused on magnetism. Have you read any of my posts? I’ve just grown weary of contradicting Holmz, who IS focused on magnetism. I let his last fantasy stand as is, because I did not want to appear to be picking on him.

Like I have said three or four times, my best guess is that the system is oscillating at a very low frequency when the preamplifier is hooked to the cartridge output in balanced mode. When the OP switched to single ended mode, the problem went away. The bit about the platter mat and LP is a red herring, as per my earlier definition. The fact that it seemed to make a difference can possibly be due to the fact that when you power down an oscillating electronic device (in this case, the preamplifier or the amplifier would be oscillating due to input from the TT), the oscillation of course ceases. When you then restart or power up the same electronic device, even with the same input and output loading, the isolation may or may not reappear. In order to remove the platter mat and LP, in this instance, the OP had to shut down power to the TT and then power it up again in order to demonstrate the "no platter mat, no LP" condition. So lets say the cartridge is picking up something from the TT motor that intermittently causes either the preamp or the amplifier to oscillate but only in balanced mode. The intermittent nature of an oscillation is what confounds the investigation of its cause, let alone trying to fix the problem. And beyond that, we really do not have enough data to speculate further. Maybe the OP will eventually come forward with some additional information, but I don’t blame him if he does not want to be bothered and is perfectly happy to operate in SE mode.

Magnetism, shmagnetism.

Everyone is focused on magnetism. This phenomenon is not magnetic. Something else is causing the cartridge to output a very low frequency signal. The cartridge is a very sensitive vibration measuring device. To output a signal all you have to do is move the cantilever. An unloaded cantilever hanging in the breeze might be sensitive to air currents. Blow gently on the cantilever and watch the woofers. For some reason the spinning platter with either the record or mat loaded produces an air current that the plater alone does not. Loading the cartridge differently by going from single ended to balanced configuration could change the damping on the cartridge enough to bring this out?

@mitchellcp , I also run balanced but other than blowing on the cantilever, I can not replicate your situation. 

Ok I tried the compass- nothin’

It is super interesting.
Do you access to a compass like hikers use?
I think even an iPhone with its magnetometer built in might work as a way to see if the mat is somehow magnetised.

Sure, it is possible, that it is somehow related to wiring… but I doubt it.

When I had a 50 Hz hum it was also from a magnetic field, and the coils in a MM or MC cart are effectively a magnetometer.

If it is only doing the pumping when the mat is on, then I would think that removing the mat would be a possible strategy to use to ameliorate the pumping.

@lewm 

No problem. You are one of my favorite contributors on this Board so I'm glad to have that cleared up.

fsonic, Mea culpa. A thousand apologies.  It was Holmz who wrote the sentence I quoted (and responded to), not you.

@lewm you may be correct about the oscillating- not enough information right now. I’m re-wiring the tone this weekend with Audionote Silver and silver clips- I’ll have everything apart anyway so I might as well try again. 

@lewm 

lewm

11,075 posts

02-16-2023 at 09:46pm 

fsonic, I don’t know what I said to make you so angry, but you DID write, ..."or degauss the current mat, or put a blocking capacitor somewhere." And this is what led me to believe that you were supposing that a capacitor can block a magnetic field. Even Sherlock Holmes could testify to that fact.

You have me confused with someone else. I did not write that. 

fsonic, I don’t know what I said to make you so angry, but you DID write, ..."or degauss the current mat, or put a blocking capacitor somewhere." And this is what led me to believe that you were supposing that a capacitor can block a magnetic field. Even Sherlock Holmes could testify to that fact.

Mitchell, I apologize if you felt that I was discounting the thoroughness of your analysis. I was not, although your report as it is does suggest a few other experiments that could be done to investigate the matter further, rather than for the rest of us to just keep on guessing. The first of those would be to re-install the XLR connectors and determine whether you can reproduce the original phenomenon. But I also understand what a pain it is to change the connectors on your ICs, and if you don’t want to be bothered, that’s fine.

My point was and STILL is that it could be that some piece of gear in your signal chain (originally I mentioned the preamplifier, but it could also be the amplifier) is induced to oscillate under certain conditions. And this may have nothing whatever to do with the platter mat plus or minus an LP on top of it. (Hence, I used the term "red herring" in reference to the bit about the effect of the platter mat/LP) Oscillation can be very capricious, intermittent, and nearly impossible to reproduce when you want to investigate its cause. Turning a unit off will stop its oscillation, and when you apply power again, the unit may work fine under the exact same input and output loads. Like I mentioned, I have had a personal experience with an unstable amplifier that vexed very competent repair persons and then vexed me for another year when I took on the job of fixing it because no one else wanted to touch it. This amplifier oscillated when fed by a certain CDP but not when fed by another CDP, for example. On other occasions, the amplifier worked fine for months before it would go into oscillation solely due to music input. From a pragmatic point of view, if you are happy with SE operation, and if your particular problem never recurs, you really never have to know what was going on. Just enjoy the music.

@jpaulfreeland74 Great question and the answer is yes, it’s both and in phase.

Just to be clear, I’m not changing anything else until I have time and another excuse to play with wires, which will probably be tomorrow.

My primary reason for posting this was to see if anyone else had seen this and perhaps knew a solution. Google search yielded no results for this specific problem so I thought, why not? I can run it single ended with no trouble until I have time to dig back in.

@mitchellcp  I think this problem is super interesting and part of what makes the hobby so fun (I think we're all gluttons for punishment).  Thanks for posting this, I've enjoyed learning from the other folks who are posting ideas. I am not sure if it has been asked and I couldn't see in the video, but does the woofer movement happen on both speakers and in phase with one another at the same time (both channels)?

@fsonicsmith1 Wow

A capacitor does not “block” a magnetic field.

__ ____ Sherlock… but it blocks 33-1.3/60 Hz, as well as DC

but that’s not so much of a problem, because there cannot be a magnetic field generated from the Funk Firm Acromat, because it is completely non-metallic, let alone non-ferrous.

Those fridge magnets are also plastic.

(See the FF website.) I know there are some who believe that records can become magnetic and need to be degaussed periodically. I am not one of them, but even if it were so then we would all be having this kind of problem, and we don’t.

Agree

Furthermore, a magnetic LP would attract the magnets in a cartridge, and could be disastrous for the suspension, but that doesn’t happen either. Furthermore, if LPs could be magnetized, they would become uniformly magnetic; the magnetism would not be patchy across the LP circumference so as to cause the phenomenon the OP observed.

As I said above and still believe, I think the story that goes with the observation (removing the platter mat and LP cured the problem, etc) is a red herring. If the phenomenon was to be further investigated, in other words, all that bit would be seen to have had nothing to do with the actual cause.

The OP could for an instance use a compass to see if it has the periodic needle jiggle. Or hold that mat next to the compass.

For example, it is possible that the phono stage has the potential to oscillate at a low frequency when in balanced mode. Such an oscillation can easily be a some time thing; in other words it comes and goes. In the story, the OP had to shut down the turntable to remove the platter mat and LP. This might stop the oscillation that is really going on in the preamp, just by chance alone. When he switched to SE operation, that too would require shutting down the phono stage, and it could easily be the case that the premp does not oscillate at all in SE mode. If you have ever tried to chase down and cure an oscillation in a piece of audio gear, as I have done, you would know what a royal pain in the arse it can be. Took me over a year with an amplifier, and that was with help.

this is possible, but the mat suggests that it 

@mitchellcp

Have you noticed any movement of cantilever during woofer pumping?

That with your balanced connection.

@lewm  You appear to be under the impression that everything I tried with that problem was shown on the video, that I just happened to be shooting a video as I was listening to records, as we all do, and shared this comic little problem because I'm off my meds.. 

That is not the case, what you see in the video; for you, the first time, was for me the umpteenth time. It was a problem that persisted over many hours, restart cycles, wiring checks, different records, different mats, disconnections and reconnections. If it's a red herring, it's extremely reliable.

Once I realized it was not going to go away, I shot the video because just explaining it in writing would stretch credibility past any reasonable point. 

A capacitor does not “block” a magnetic field.
but that’s not so much of a problem, because there cannot be a magnetic field generated from the Funk Firm Acromat, because it is completely non-metallic, let alone non-ferrous. (See the FF website.) I know there are some who believe that records can become magnetic and need to be degaussed periodically. I am not one of them, but even if it were so then we would all be having this kind of problem, and we don’t. Furthermore, a magnetic LP would attract the magnets in a cartridge, and could be disastrous for the suspension, but that doesn’t happen either. Furthermore, if LPs could be magnetized, they would become uniformly magnetic; the magnetism would not be patchy across the LP circumference so as to cause the phenomenon the OP observed.

As I said above and still believe, I think the story that goes with the observation (removing the platter mat and LP cured the problem, etc) is a red herring. If the phenomenon was to be further investigated, in other words, all that bit would be seen to have had nothing to do with the actual cause. For example, it is possible that the phono stage has the potential to oscillate at a low frequency when in balanced mode. Such an oscillation can easily be a some time thing; in other words it comes and goes. In the story, the OP had to shut down the turntable to remove the platter mat and LP. This might stop the oscillation that is really going on in the preamp, just by chance alone. When he switched to SE operation, that too would require shutting down the phono stage, and it could easily be the case that the premp does not oscillate at all in SE mode. If you have ever tried to chase down and cure an oscillation in a piece of audio gear, as I have done, you would know what a royal pain in the arse it can be. Took me over a year with an amplifier, and that was with help.

Has anyone here read the OP’s previous thread?

What is your point here @deKay?

It is almost surely a magnetic field.
I would do the test with the mat alone, and the record alone, but cannot fathom a mat being magnetic, however the fridge magnets are plasticy.

One could put a mark on platter and mat, and then try the mat at a few phase angles.
Or get a new mat, or degauss the current mat, or put a blocking capacitor somewhere.
A new mat is what I would suggest

Finally!! Someone who runs balanced!! Did you read this?

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. "

I did not connect the tone arm ground to pin1. The tone arm to preamp cables are shielded star quad, so there isn’t an available wire from the arm to run the tone arm gnd. That's running externally, like a regular turntable cable. The shield ground is connected to the shell at the preamp end and floats at the other end.

That’s my deviation from the manual and although I doubt that is the issue, my doubts generally have no effect on the real world.

What do you think?

Right. Is there a gain difference between balanced and single ended? Run a meter across the cartridge right and left channel negative terminals. It should be open. 

You said it pumped with either the record alone and the mat alone as well as both. It only does this when wired for balanced operation which floats the ground.  I assume you will maintain single ended operation so further experimentation would require rewiring the connectors again which is a PITA. I will bring it up with a few friends and see if they have any ideas.

I run balanced all the way and can not replicate the problem. May be time to call the Ghostbusters.

@mijostyn take a look for yourself