[jdandy]

Stephen.......Had I left the stock McIntosh tubes in the phono stage of the C2300 the Pass Labs XP-15 would be quieter, but with the Telefunken 12AX7's in the C2300 phono stage the noise floor is much quieter than stock, and quieter than the Pass Labs XP-15.

The XP-15 has been energized since 6 PM last night. There is no power switch, so it stays on continuously. I have 11 hours of music played through it from last night to now. It is a fine sounding phono preamp. The dry edge has melted to some degree from last night to today, but the noise floor is still higher than the C2300 phono stage and I don't believe this is going to change. When music is playing, the difference in the noise floor between the XP-15 and the C2300 is not noticeable, but with no signal it is apparent the XP-15 is not as quiet. This is what bothers me, and has dampened my enthusiasm for the Pass Labs phono preamp.

I went through all the different connections schemes suggested last night. Serge suggested I lift one of the two ground wires on the SME interconnects. Lifting either one introduced a low level hum, and both needed to be grounded for this to disappear. Shane suggested I try single ended interconnects, so I swapped the balanced Wireworld Silver Eclipse for single ended Wireworld Silver Eclipse. This made no difference in the noise floor between the XP-15 and the C2300 so I returned to the balance interconnects.

Perhaps I should be less concerned about the difference in noise floor between the XP-15 and the C2300 if I cannot hear it while music is playing, but my nature will not accept this, and certainly not for the cost of the XP-15 versus what I already own and is included in the C2300. The Pass Labs XP-15 is not living up to my expectations, so I am returning it. I will continue to use the C2300 phono stage preamp, at least for now.