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

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 

@fsonicsmith1 Wow

@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)?

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.

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