Issue with my TADAC balanced outputs...?

Greetings,

After a couple of years I lucked out and found a Tube Audio Design TADAC - tube dac/preamp

I sent it to my local audio guy to clean volume pot and replace broken headphone plug. I then replaced tubes with nice pair of NOS paired Telefunkens

Here's the weird part: when I drive my Sophia Baby tube amp all is well but when I drive my Bryston 2B-LP via the TADAC's balanced out puts I get a loud and immediate hum!?

How is that possible? I thought balanced connections were supposed to be quieter than single-ended?

I have clean balanced power and pricey Ridge Street cables...

Speakers are Gallo Ref II's [ yes the Martian ones ;-) ]

Any advice will be much appreciated

Party On!