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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
 

as per previous post 

A- Pumping exists when the system set up is: Balanced output from tonearm to balanced input at phono preamp and:

  1. Stylus is over the play surface and the platter is rotating- not off to the side (it also persists with the stylus on the record).
  2. There is a just a record on the platter (rotating)
  3. There is a just a mat on the platter (rotating)- the mat is a synthetic material.
  4. There is a mat and a record together (rotating)

B- Woofer pumping stops when:

  1. There is platter rotation and the platter is empty, no record, no mat
  2. There is no rotation regardless of what on the platter.
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karl_desch's avatar
karl_desch
442 posts
 

Any way this could have something to do with the 6db boost in balanced configuration compared to the single ended?  Does the woofer pump in balanced mode if the speaker is much farter away from the table?

mitchellcp OP
86 posts
 

Take a look for yourself

 

ejb14
37 posts
 

A few questions;

1. Isn’t woofer pumping caused by infrasonic frequencies (below 20hz)? A John Atkinson quote from 2009 Stereophile seems to support this, though he was referring to record warps in that quote;

https://www.stereophile.com/content/bass-cone-flap-1

2. The PPA-2 has a rumble filter and I believe that I saw it turned on when the woofer pumping is occurring - doesn’t a rumble filter filter out these frequencies precisely for this reason - to prevent large woofer excursions? If so, it would seem the rumble filter is not working on this phono stage - you may want to look into a warranty repair if we can assume the woofer pumping is being caused by infrasonic frequency.

3. Not sure how static would cause the cartridge to output signal in the infrasonic range. Even so, the Funk Firm mat claims to be static free, yet with just that mat on the platter still exposed this issue; so if not static, then what?

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