amp clipping or low freq causing pumping speakers

It sounds like you have 2 problems...

1- not enough gain just for the system with that cartridge if you crank and don't get the volumes you want, but ....

2- You need to read this thread below and it will solve the woofers pumping basically guaranteed with no sonic effect, but again will not solve problem #1, your other preamp has a subsonic filter most likely, and the other does not, its basically just capacitors in a certain value directly connected at the phono input RCA's in most preamps with built in active phono statges that gets rid of the surface noise off an LP pumping the woofers, take it from experience.

Not sure but possibly the good outboard subsonic filters can add a tad of gain due to most of them are active designs, being it will need to be plugged into the wall I believe. If your really concerned I would call KAB acoustics U.S.A and see if they will let you try one, might be a restocking fee however. Its possible Mr. Doshi since being a custom preamp most likely hand built can put the cutoff Capacitors in the preamp for you on the phono inputs. But the value would have to be determined in order to get the right cutoff... Fact is most of this noise is likely down around 10 to 3 hz.. Were taking its the Wind blowing effect with the groove going thru your cart puffing away, the preamp is just amplifying it, no sonic benefit, nor is it a benefit to your woofers working out on a daily basis for nothing! And of course this is an in-efficient power loss too, so might up your dynamics in the real music eliminating it.

By the way your speakers obviously don't play that low, but this energy goes somewhere and its in a pulse effect causing your speakers to act this way, I have first hand experience and solution on this.See thread

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1267683244&openusid&zzUndertow&4&5#Undertow

thanks guys

seems the record with the most trouble was a slightly warped one. I went back and lowered the volume a little and haven't had the pumping effect. It's mostly very demanding passages - doesn't get overloaded on jazz like it does on some rock records

I have a ZYX Artisian outboard phono pre and will try that in one of the line imputs on the doshi - perhaps there is a roll off in the low freq end of the phono stage

it doesn't do this with cds

I'll touch base with Nic Doshi and get his comments on gain and low end frequency

I believe I do have that test record

thanks

Tom

Have you tried repositioning your turntable? You might have it placed in a room node peak.

woofers only seem to be over-extending on fairly loud playback or warped records

could be a room mode 15' depth - speakers 3
from back wall

Hi Audiotomb, What did Nick have to say about this?
Perhaps you are just listening too loud? How loud are you listening?
Bob