Help Diagnosing a Feedback Loop Issue

Hey all.

I set up an Aiwa Mini Component 50 series (preamp, amp, cassette deck), along with a Rega RP1 (performance), a bluetooth receiver, and a set of AR 18b speakers. All of the components are plugged into the switched outlets of the amplifier.

The turntable and left channel speaker are connected to the amp through in wall wiring via patch panels.

I'm getting a pretty noticeable feedback loop through the speakers and I'm trying to narrow it down. I'd appreciate some help/suggestions.



So far:

• Disconnected the Rega but left RCA cables connected to the amp- feedback
• Disconnected the RCA cables- feedback is actually worse
• Tried other components- Tape Deck, no feedback
• Wired the speakers directly to the amp- feedback
• Tried R.S. feedback loop isolator RCAs between the phono and amp and between the phono and pre- feedback both times
• Completely disconnected the bluetooth receiver thinking there was some sort of interference- no difference
• Tried changing polarity of unit by flipping the plug

Two last things to note, the RP1 is internally ground. The AR speakers were previously used with a Sony STR-50 with no feedback issues.

Seems like it's narrowing itself down to the RCA in the amp. But, is there anything else I should give a try before calling it a day and looking into the internal connections?

Thanks all.

I guess I would start simple.
Amp with speakers connected only. Nothing plugged into the switched outlets either.
Next the preamp 9turning all off of course).
Then try a source etc,.

Also, before you connect the preamp RCA's plug in only the power to the preamp, then if there is no hum turn all off and connect the RCA's.