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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
mitchellcp OP
86 posts
 

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?

holmz's avatar
holmz
2,328 posts
 

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

lewm
13,806 posts
 

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.

mitchellcp OP
86 posts
 

@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. 

 

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