EAR V20 question maybe tubes question?

Folks,

I just purchased a used EAR V20 amplifier. I've never owned tube gear, and I've never auditioned the V20 (I've auditioned other tube amps though) (as to why I bought it: it was on ebay, auction was ending and the price seemed very right.)

The amp sounds great, but there is a slight problem and I have also one question about what I should be expecting from a 20-W tube amp.

-- When the volume control is used, there is audible hiss/scratch coming from the speakers. How can this be remedied? Is it a big problem or just a matter of changing some tubes?

-- The amp replaces a Creek 5350SE in a setup that uses Triangle Antal speakers and a Philips 1000 SACD source. Even though on classical music and voice the V20 sounds much better and seems to set the Triangles free in a way, the base sounds quite a bit leaner: tighter and cleaner but also with less body. Is that to be expected? Is that what I'm giving up with the tubes?

Thanks in advance!!