Click on the picture to get a larger view. The printed circuit board of the QSX Mark III Amplifier.
Why is it so important with the phono amplifier in order to get good sound quality?
See the page about QSX Mark II.
How does this particular amp sound? First of all, I'm amazed how similar this one sounds compared to my "monster". I have listened to this amp rather much now, mostly with headphones connected directly to the output. The amp can drive headphones at very high levels with a crystal clear sound.
It's a pure pleasure to listen to my old (but not worn out) vinyls. The bass is surprisingly firm and deep. The mids are very detailed "this haven't I heard before"-like. The treble sounds also good and the "clicks" aren't so clear. I think this is caused by the fast amp, high open-loop gain (creates descent feedback at all frequencies) and the high current output stage. The amp can take high frequencies into low impedance load without choking.
What is the difference between the transistor buffer (BD139/BD140) and the monolithic one (LT1010). Very little, in fact I can't hear any difference. Transistors are cheaper but the buffer is more advanced. I gather also that LT1010 can be a little harder to get compared to regular transistors. I recommend the LT1010 as output stage.