I was quite surprised to find this;
http://www.stereophile.com/amplifica...47/index4.html

It sums up at the bottom, in case you don't get that far, "In some areas the
lack of intermodulation distortion, the superb squarewave performance, the
wide bandwidth the 4706 Gaincard offered excellent measured performance. In
fact, almost all the measured problems I encountered can be laid at the feet
of the Humpty power supply"

Gaincloners have solved this by using two transformers, one for each
channel, hardly rocket science and not a very expensive solution either.

For those who would like to see the circuit including the power supply
please use this link;
http://gainclone.com/phpBB2/viewforum.php?f=2
and scroll dowm to the bottom of the page, there are links to the diagrams.

Jem