I posted this problem last month but the ansewers that I received (thank you both very much) indicated that I had failed to make myself clear.

I have three turntables with moving iron cartridges.a B&O 3404, a Denon 62L and a VPI with EPA tonearm

I have two preamps with phono inputs...a very vintage Marantz 7T and a 12 year old Coda Fet01

All three tables are dead silent with the Marantz 7T and an equally old Marantz receiver in my bedroom

The denon and VPI are dead silent with the Coda

The B&O produces a very very very loud hum with the newer Coda when the 3404 is turned on but is dead silent when playing LPs

When the recording ends the very very very loud hum comes back and continues as the arm returns to its resting position

The hum does not cease until the 3404 is turned off

This 3404 does not have a built in phono pre

HELP !
please

Bob

It does have a ground wiire that attaches to the preamps