Questions about original Cal Alpha DAC

Hello all, I just yesterday recieved a Cal Alpha DAC from an A-Gon member to upgrade from my CAL Sigma II DAC, and I have been using the CAL Delta transport since I bought new, the Delta-Sigma II Combo for about 6-7 years now.

I'm very happy with it so far, and it's condition is beautiful, but I do have just a couple of minor issues I'd like to resolve.

The sound of this Alpha seems very analytical, very bright, very "trebley", and over-detailed at the high frequency end. It makes you sort of cringe with it's brightness.

While I haven't tried other tubes yet, I understand there's two Phillips-JAN 12AX7A's inside, and I'm hoping I'll perhaps be able to round, and smooth the sound a bit with pair of Sovtek 12AX7A's? Mark