Turntable on a speaker - I thought that was not advised.
replies(3):
If you sum the stereo channels into mono then feeback present but inverted on each channel is cancelled out and the problem goes away like magic.
This seems to be lost knowledge but it's how old school sound systems[1] were able to have their turntables basically on top of a collection of speakers without feedback.
Many mixers back in the day, from people like Pioneer, used to have a mono/stereo switch for this purpose.
It's very easy to demonstrate this by placing a stylus on a stopped record, then tapping the record surface directly
The speakers are right next to each other so it's not like you're loosing stereo image.
1. I'm talking old school Jamaican and UK Sound Systems here. https://en.wikipedia.org/wiki/Sound_system_(Jamaican)