Direct connection between DAC & Amplifier

Arthur Salvatore ( recommends that amplifier be connected directly to CDP with volume control bypassing any preamp for the shortest signal path and therefore best sonic quality. I connect a USB DAC to a tubed amp without volume control, and have to use itunes' volume control. Will this digital volume control compromise the sound quality? Is there a better alternative to having an analogue volume control other than a passive linestage or TVC which requires interconnect in the signal path?
EVS Ultimate Attenuators. There's also the Endler Stepped Attenuators that look like the UA's and for a lot less $$$. I've had the EVS and they are excellent. I've never tried the Endler's but have heard many good comments about them here on the Gon.
Good luck!
Yes, the digital volume control does affect the sound. Get yourself a Placette and you'll never look back!