The new mono design TVC is getting some very positive feedback from audiophiles who tried it. I am not sure about the return policy.
Another option would be Bent Audio passive - based on TVC (have not heard it. But if it is as good or better then original TVC, worthy contender).
Dodd and RWA both battery powered. Both great. Bought them for similar reason - zero noise or feedback. Ultra quiet, transparent with pitch black backgrounds.
I am sure others might have more interesting recommendations.
Good luck...Oh yea, if you have only one source: a better source with volume control could also make perfect sense....if you want to get the most from that approach, get yourself $50 Goldenjack attenuators.
Just my 2c.
Good luck
Mariusz