Bass distortion-Playing LP's only,,,,please help


VPI Prime----Ortofon Black Quintet (low output moving coil cart)-----Plinius Koru Phono Pre( loading at 20 ohms/gain at 66 db)-----Parasound Halo Integrated -----Martin Logan Montis speakers which have powered bass cabinets.

Using any other source component I have absolutely no issues. When I play an LP and increase the volume past 10 O'clock which is a little loud....but not ridiculously loud-I at times get this huge wave of bass distortion. I do have bass controls on the Montis's...and I have turned them down into the negative, but I still get what I previously described occasionally. 

Any and all help would be appreciated. This doesn't always happen, but its frequent enough to drive me crazy.

Thanks in advance.

krelldog

Krelldog, take heart my friend. By way of encouragement :

  • I use a T/T of almost identical mass/config.

  • It is situated in the worst possible place – a corner.

  • There is an ML active bass cabinet right next to the T/T (Vantage)

  • The stand simply consists of 3x tri-spiked levels, 50mm thick solid oak throughout, set on a solid concrete floor.

Even at peak SPLs of 95db (measured) at 6 metres there is no trace of feedback. (Not that I routinely listen at such volumes, I prefer to retain my hearing! ;)

Bass integration is perfect and the sound completely natural.

Good luck! :)

Best case scenario is that you will solve your problem before adding a subsonic filter, I personally haven't needed them in my systems since moving up from an AR EB101 to a VPI Scoutmaster then a Prime. If you decide that you need the filter search for the Nakamichi SF-10 or SF18 which are 10Hz and 18Hz filters with a 6 db roll off they were my go to filters when needed and they do fix the problem. I sold mine with the AR or I would give you mine. Good luck
The KAB rumble filter uses audiophile grade parts and I can't hear any difference with it in or out other than the bass not distorting and the woofers not going into oscillation..  The quantity and quality of bass remains the same.  You can order one from KAB and have it within a week.  I run mine through the processor loop on my preamp, but a tape loop will do the same thing.  Also I moved my Scout and Prime all over the living room, trying different platforms, even one bolted to the wall but in the end, the rumble filter was the only thing to eliminate.  I have an old house with squeaky floors so perhaps that had something to do with it.