[Premium-Rx] A query about Cubic Dual Rx R2411/U audio

[Dan Rae]

I have one of these fine dual HF receivers and am a bit puzzled about 
the audio output in stereo phones mode.
 
Both receivers work fine on their own with no hum heard using mono 
headphones.  However if I use stereo headphones in either socket to hear 
both receivers at the same time, one in each ear, as per the manual, I 
get a nasty 60 Hz mains hum from the ground loop caused by the way these 
are wired.  Looking at the schematic it seems that this is inevitable 
due to the way the two Audio amps are connected to the phone sockets.

So has anyone else been bothered by this and is there a solution?  I 
think it might be possible to improve things if the feed to the ring on 
each phone socket from the opposite side receiver were run through a 1:1 
transformer, which would break the ground loop.

This is the first Cubic I have owned, and while I am very impressed by 
the performance overall, this seems an odd thing to find in an expensive 
radio.

Dan

ac6ao / g3ncr