Here's one for ya Part 2

Dave, try relocating your TT onto a stand. This may change the nature of the vibrations that are reaching your platter. It is also possible that the TT is in a place in the room which has alot of bass excitation. Having the TT on a stand would allow some movement to experiment with the placement, and perhaps cure or reduce the problem. You might try just moving your speaker(s) temporarily to different areas of the room, and see if this cures it. If it does, then the feedback is related to the location of the TT with respect to the speaker location. Then you could move the equipment rack and TT to a spot that does not seem to cause the problem.

Tom-here's my room/setup
Room 15x20x7.5
At the long end of my room is a area that extends 3 feet longer than the room and is 6 'wide with same ceiling height of 7.5' There are treated windows.
The speakers are 4 feet from each side of the extention and 4 feet from the front wall.
The rack is in the extention as is all my dedicated outlets.The TT wall stand is 4.5 feet up over the stand.The steel support is bolted through my house wall and the nuts are on the outside siding.Every TT I've had I had acoustic feedback but was able to eliminate it with added weight on the TT shelf.3 TT's were non suspention and this is the 2nd suspention TT I've had.
I cant move my rack/stand d/t room setup.
I may need better advice how to set up the Delphi.
I have a ground from the interface box on the back of the delphi to the Creek.I added another ground tonight from the box to the TT steel support and it lowered the hum ~25% more.
Could the 65 gain from the Creek cause the hum?
I have a cheap linestage (tubes) could some better tubes (NOS) lower the hum?Its dead quiet with CD/tuner.
Without the clamp the acoustic feedback is really a non issue.I have to crank it louder than I would normally to get feedback.I would like to figure this out though so I can use the clamp.
Any other tricks to lower the hum with better grounding? Cheater plug maybe?
BTW Tom,The Denon is a special p.u. It reminds me of a Ortofon MC-20 super I once had,only smoother and more transparent.

Dave, the feedback issue is based upon whatever frequency vibrations are getting through the shelf into the TT. You might try using various weights on the shelf, and see if you can find a particular weight that brings it into a zone the TT suspension can handle. I think the reason that using the clamp makes it worse, is that the record is somewhat de-coupled when not using the clamp, so it doesn't get affected as much. From what you describe, the vibrations at a certain level and frequency are defeating the suspension and getting right up to the platter.

I think that there will always be somewhat more noise with a high-gain phono stage, but it shouldn't be a "hum". I don't think your Creek is the problem. But even a small grounding issue in the TT area will be fed through the high gain phono section and sound alot bigger than it might be otherwise.

Your room extension seems to be a "funnel" for reflected waves from the room, and focusing them on the equipment. This could be a large part of the problem. Try some standing diffusors or maybe even a bass trap in front of the TT/equipment. Even a couple of high back chairs in there to see if you can break up the wave-fronts, so you can see if there is any improvement.

Just a few guesses to try.

thanks again Tom..problem fixed!