Ground loop hum and audio isolation trasformers

[nkg]

Hi All
I built a reverb unit and rebuilt an old Knight Pa head both use tubes both work , but together I get ground loop hum . Can someone recommend any 1:1 isolation transformer they have used to get rid of this problem .
Thanks
Nigel

 

[Enzo]

Before you do that, have you explored internal methods? You rebuilt an old Knight, fine, does it have a cap from either mains lead to chassis? And have you tried removing it? Same in your reverb unit? Have you measured the difference in chassis potentials?

 

[nigelwright7557]

Sometimes disconnecting one earth from zero volts line will get rid of hum.
But don't disconnect earth from chassis !

 

[nkg]

Hi Enzo and NigelWright 7557 thank you for answering . With the Knight I put in a aluminium chassis as it was badly bent like somebody jumped on it , I put in individual transformers for the tube rectifier , input , phase splitter , power tubes and B+ as over here is 50hz rearranged the lay out as the original was messy and left out the cap on the mains side same with the reverb . I have tried removing the circuit ground but with no success chassis to ground was less than the leads on the multi meter but they still produced a loud buzzing sound . I wasn't happy with the job I did on the reverb and currently rebuilding it hence wanting to try an isolating transformer on the output of the reverb .
Nigel