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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

Showing 5 responses by cleeds

cleeds
6,072 posts
 
gibsonian
Rumble filter is simple and easy, no big deal. Get one and move on. They’re in most all phono pre’s, for a reason.
A rumble filter is a Band-Aid. While they are common on older receivers and lower-end equipment, you’ll find they are much less likely to be included on better gear, where the manufacturers expect the user to be using a properly setup quality turntable. For example, the phono stage I use is spec’d to be within ± .2dB at 10hZ and down just 2dB at .3hZ. My speakers are relatively flat in-room to below 25hZ. No woofer flapping, no rumble filter needed.
cleeds
6,072 posts
 
mijostyn
Cleeds, the problem is your room is not flat down to 20Hz.
My full-range speaker system is essentially flat in-room to below 20 hZ. It’s odd that you believe otherwise without knowing anything at all about my room.
It is easier and safer to correct a subwoofer than a full range system without overloading either the speaker or the amp.
That depends on so-ooo many variables. I’ve used my speaker system safely for years with no issues.
... If I delete the subsonic filter from the program it ia mass pandemonium. It looks like the drivers want to jump right out of the cabinet. It is just inherent in vinyl if you have a good system capable of reproducing deep bass.
Oh no, that’s not inherent to LP at all. It’s true that woofer pumping can be common with improper setup or inferior equipment, but it’s not inherent to LP playback.

I have no subsonic filter at all in my system. The bass goes down below audibility to frequencies that can only be felt, not heard. No woofer pumping. Ever.
cleeds
6,072 posts
 
tablejockey
... members who have their table setup dialed in, no rumble filter and use sub(s) ... you can actually play any LP, CRANK the volume, and you have ZERO woofer pump?
Yes.
To be fair, I don’t use subwoofers - I use a full-range speaker system that is essentially flat in-room to below 20hZ.
cleeds
6,072 posts
 
mijostyn
Many amps roll off below 20 Hz so you won’t see woofers pumping.
Not good ones.
Your system is doing exactly what it is supposed to do. Moving the turntable won’t change a thing. Anybody who uses subwoofers aggressively and plays vinyl will need a subsonic filter ...
Oh no, that’s mistaken. Completely.

I don’t use a subwoofer, but I do use a full-range speaker system that is essentially flat in-room to below 20 hZ. It’s awesome. My phono stage, line stage, and bass amplifier (this is a bi-amped system) are all rated to far below 20 hZ. The system can produce bass that you can’t hear but can only feel.

No rumble filter. No woofer pumping. Ever.
The best subsonic filters are digital.
I think the best subsonic filter is no subsonic filter.
cleeds
6,072 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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