HELP Sudden Phonomena II Groundloop Hum

Hi. I have a Musical Surroundings Phonomena II Phono amp and a nuded Denon DL-103R which sounds great. I was planning to send the Denon to Soundsmith for a retip. In the meantime I purchased a Nagaoka MP-200 MM cartridge to hold me off until the retip was completed. It arrived today and when I reset the input load switches to 50K and gain 40db to match the Nagaoka I suddenly heard feedback hum (the buzzing noise a PA system makes). It gets louder as the volume goes up. I played with the connections on the cartridge and nothing changed. Then I adjusted the load switches and that affected the hum but it also affected the sound quality, dramatically. I then put everything back to the Denon mode and the noise disappeared. What really kills me is that even with the noise I heard a better sounding Nagaoka than the Denon.
I have never had feedback noise buzz in the past. This is new and began today as soon as I adjusted the dip switches on the back of the Phonomena II. Any suggestions on removing the noise is highly appreciated.
DIP switches are 'notoriously' fragile.
I would think yours are having issues.
Try using some other settings on the switches?
If only the one bunch of settings is the culpret, then it is the switch (or switches) which is bad.
Perhaps one of the switches has a bad or over soldered bit on it?
Or, the switch is just bad at that other setting.
If the setting put back to the Denon work, try adding in the new cart, but leave the Denon's settings. If the new cart will play without causing hum, then it is the DIP switches, if not, then it is the cart.
Good luck.
I would think that if the DIP switches are the cause it would be in only one channel. There's a set of switches for each channel on the Musical Surroundings.
My Phonomena Nova is dead quiet with Grado and DL103r
Double check the wires on the cartridge. The left channel blue and white, and right channel red and green are rotated from top to bottom between these two cartridges. If they are reversed, you can get a loud hum. If the colors do match, you could try switching them with care. Swap the blue and white, then swap the red and and green. Start out with a *low* volume to see if it is better or worse. Be *careful* with the volume at first, encase it hums a lot worse. Links for them
Pardon grammar.
Thanks for your advice. I contacted Michael Yee the designer of the Phonomena and explained what was happening with the sound. He believes the problem could be located in the 50k output resistors. He asked if he should send me a pair to install or if I should send in the unit. That is customer service.
I'll report back on the results.
Check the input L&R cables of the TT. If you put your hand around the neck of both of them, and the hum decreases or disappears, then you have a problem with the cable shielding, or the core fibers of the either the left or right input are broken. How old is the table?? Also check out condition of output cable from the P-2 to your pre-amp. Jim