Hi all, thanks a lot for all the input!!
I'm sure its not mechanica as I tried the table in diff positions and even holding it down/pressing down on it, but did not change the bomminess. Next to this I can even recreate it in the digital domain by switching of the room correction. That the proof it is the room rather than the table.
Trying to process all of the above and don't understand this. I have an integrated amp with many rca inputs (aux, dvd, etc) it also has a very good phone stage in it (you purchase it separately so it's not a cheap included one). Current setup is table to input, but the pre amp is integrated. So is the loop possible?
If (!) one wishes to adjust equalization
in the analog domain, the equalizer circuitry (e.g., one of those little Schiit boxes) needs to be connected to a line level signal and then route the adjusted line level signal back into the amplification chain.
This is easy with a separate preamp and power amp: preamp -> equalizer -> power amp.
If one is using a reciever or integrated amplifier (preamp and power amp in one box) there has to be a way to get the line-level signal
out to the equalizer and then
back in to the amp or receiver.
Traditionally this was done with a tape monitor loop -- tape inputs and outputs that can function independently of the source selector switch.
TAPE OUT -> equalizer -> TAPE IN
In this case, the (line level) source is selected as usual, but the TAPE MON(itor) switch on the amp or receiver is engaged to listen to the equalized signal.
You can see the
two quads of jacks for the
two tape monitor loops on this Sansui TA-500 "tuner integrated amplifier" (i.e., stereo receiver) for TAPE-1 and TAPE-2. The jacks are labeled REC and PLAY in this case. REC is "IN" and PLAY is "OUT".
On this old Sansui receiver, the ability to "MONITOR" either of the two tape loops is provided by that switch between the FM tuning knob and the volume control.
In the 1970s and later, the use of various "effects processors" (EQ, quad adaptors, noise reduction, dynamic range enhancers, etc.) led to many better components having PRE(amp) OUT and MAIN (or power amp) IN jacks on the rear panel (e.g., a quad of jacks on a stereo amp or receiver). These would normally be connected together with a switch or small, usually U shaped, jumpers. If the two sets of jacks are disconnected from each other, the equalizer may be inserted in between PRE OUT and MAIN IN.
You can see the PRE OUT MAIN IN jacks on these two marantz 1060 integrated amplifiers. The
bottom amp has the original marantz-supplied jumpers installed between the IN and OUT jacks.
Note: It is possble that "modern" multi-zone AV receivers will enable a similar "loop" to accommodate an
analog EQ. I cannot advise on that, though.
A parting thought: IF (!!!) you only want to modify the phono signal, you
could add an outboard phono preamp/EQ, and then connect its OUTPUT to an equalizer box (e.g., the aforementioned Schiit equalizers) and then connect the equalizer's outputs to a line level input (e.g., AUX, TUNER, or CD) on your amplifier to play the custom-equalized signal for playing records.
PS Simple test for acoustic feedback. Put a record on your turntable
with the record player turned off (i.e., platter not spinning)
. Lower the stylus onto the record. With the system set to play PHONO, start at zero volume and slowly raise the volume level. If there is an acoustic problem, a
howl or rumble will appear with increasing loudness. If that doesn't happen, you have no appreciable feedback issue.
Hope this is helpful, or at least
interesting! 
