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Woofer pumping possibly due to tube amp when playing vinyl

I am moving this issue  to this forum because of what I discovered this weekend.

I’ve been trying to figure out why I have woofer pumping when I play vinyl, and for the last two weeks I’ve been messing with my vinyl rig trying to figure out what is causing the issue.  The woofer pumping seems to be more prevalent with the vertical up-and-down movements of the tonearm regardless of which turntable is being played. It appears it happens more at the outer edge of the record then the inner grooves.  I assume this is because record is more warped at the outer edges. The woofer pumping happens even in quite passages, so it’s not noise induced vibration affecting the turntable. 

 I have used two different turntables to try to figure this out, one is a pioneer PL 530, and the other is a VPI prime. both with different carts. Also, I have verified that all the carts being used on these turntables work well together with their respective arms.

However, it is not the turntable or cartridges. 

Things I can say for certain, it is not the turntable because I switched turntables with different cartridges to confirm this, and I still get the woofer pumping.  It is not a phono preamp because I’ve switched several phono preamp‘s, solid state and tube, and I still get the woofer pumping. It appears it is the tube amp that may be at cause. It’s the only component left of the chain. 
I have a Audio Research  Classic 60 amp. I got the amp used but it came with a new set of power tubes I don’t recall if I changed the four smaller driver tubes,  I also change the four large capacitors to new capacitors and biased the amp. 
The interesting thing is, with the TT’s I tried, it is the right channel that pumps more than the left channel, regardless of the variety of different cartridges tried, all aligned with AS Smartractor.

To be certain it was limited to vinyl playback, I plugged in a CD player and I do not get the woofer pumping at all. So I have a couple theories (1) the TT is just transferring subsonic frequencies from the records, ALL records I play do this.  Please remember, this is from the two different turntables being used, one a VPI prime belt driven, and the other a pioneer PL 510 Direct DrIve,  or (2) there’s some weird thing going on at the amp that I cannot explain. 
My question is, if there is something going on with the amp could it be a tube issue, or capacitor issue, or a biasing issue.  If so what is the most likely culprit.  Or I guess something else altogether. 
In the end I’m rather tired of chasing this ghost, and I would rather not use a subsonic filter if possible. If I do have to use a subsonic filter I want the most transparent one if such a thing exists. I’ve heard mixed results about the KAB unit. 
last_lemming
stereo5's avatar
stereo5
6,497 posts
 
@last_lemming,

It is not the turntable.  I tried my VPI with 3 different clamps and none made any difference.  I still use the KAB with my Technics SL1200G and even though the noise was less it wouldn't go away until I used the KAB.  I used every type of isolation platform known to man on the 2 turntables I had, the VPI Prime and the Technics SL1200G, no difference.  I believe the stylus is picking up the sound from the speakers and re-amplifiing it.  The KAB filter is around $180-190.00 and it uses all audiophile approved high end parts inside.  Using it I am very much enjoying my vinyl collection again with no loss of sound quality.  To add one more thing, my Audible Illusions Modulus 3B had a subsonic/rumble filter and it did nothing, hence the KAB.
last_lemming OP
639 posts
 
Well it’s not the music making the woofers pump since the pumping happens in the quiet passages as well. 
stereo5's avatar
stereo5
6,497 posts
 
I never tried it without music so that is what I always thought, I was wrong on that one.                                                                                     
millercarbon's avatar
millercarbon
12,531 posts
 
Wrong on all of it. You tried three different clamps. If none of them are designed like I said you could try a hundred more and it won’t prove a thing- other than that a lot of record clamps are of poor design. Which is why I made my own.

There are some good ones out there. I described exactly how they should look and work. Get one and use it. Problem solved.
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cleeds
6,033 posts
 
stereo5
It is not the turntable. I tried my VPI with 3 different clamps and none made any difference. I still use the KAB with my Technics SL1200G and even though the noise was less it wouldn't go away until I used the KAB ...
If it's not the turntable, or the match between cartridge and pickup arm, then it's the set-up. Rumble filters are really a Band-Aid. They work, but treat the symptom, not the root cause.
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