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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
last_lemming OP
639 posts
 
Larry,

I know it’s the TT per se, but it seems like some sort of interference is ramping up the pumping, because it doesn’t pump in the other room in the same set up - TT, cart, rack.

to you comments:

1. I have bought the ring. Hasn’t arrived yet
2. I have bear claws on a maple shade wood block, with the original prime feet secured to the wood block.  I have removed all these feet and tried various racks and also a concrete floor and carpet. Pumping is exactly the same in this particular room. Even on quiet passages. 
3. The TT is FURTHEST away from the right speaker where the pumping is worse. BTW the right speaker pumps more on all three TTs with 5 different carts and 3 different alignment methods. The pumping is exactly the same in all the different configurations. 4.  I did download a vibration program, but it must not be sensitive enough since the line is perfectly flat even on the most sensitive setting. 
tony1954's avatar
tony1954
1,143 posts
 
“When you have eliminated the impossible, whatever remains, however improbable, must be the truth?” — Arthur Conan DoyleTime to call in an exorcist.(Sorry for the flippant reply, but you have me stumped on this one.)

ditusa's avatar
ditusa
1,908 posts
 
@ last_lemming, What, atmasphere said yes!. Plus component three the (room.) As you said, the same equipment and rack in another room doesn't cause pumping.  :-)
last_lemming OP
639 posts
 
I agree it has to do with the TT, but something is going on in one room that is not happening in the other and it has nothing to do with room or rack resonance. I’ve always had a weird hum coming from the electrical line in that room that I’ve always thought was a ground loop issues, but what if it is something else?
The only thing I can thing of is maybe there is some kind of electromagnetic interference that might be interacting with ll the different TT’s cart’s magnets. 
I do have a preifereal ring coming in, so we will see what happens there. 
ditusa's avatar
ditusa
1,908 posts
 
@ last_lemming, I have a funny question, do you have a fireplace in that room where the woofer pumping is going on. Because a fireplace can cause low resonant frequencies in a room. The flue pipe is the culprit. I hope you have good luck with the preifereal ring. Mike  :-)
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