OK- here is why not an SUT and basic phono section.
In a word: transparency.
We have auditioned every SUT we could get our hands on and they all have a signature. We also identified several other problems.
One of them was the use of feedback to equalize the RIAA curve. This often contributes to enhancement of surface noise. In addition, we found that if we used single-ended circuits we had more noise per stage of gain than if we went balanced (actually, balanced differential). Further, we found many differences in the sound of interconnect cables that connect between the tone arm and the preamp; since the cartridge is a balanced source we found that by accepting the signal in the balanced domain at the input of the preamp, we could reduce the artifacts imposed by the cable.
So we built a zero feedback, fully differential, passively equalized LOMC phono section. It has two stages of gain, so the signal path is actually simpler when compared to many preamps.
So far we have only built our phono sections into our preamps- there are two reasons for this. The first is connectivity- we don't have an interconnect between the phono section and the rest of the world so there is less artifact on that account. The other reason is that our line section has a direct-couple vacuum tube output (that is also balanced). This not only gives the line section more transparency and bandwidth on account of no coupling cap at the output to mess things up, but it also allows the preamp to drive really long interconnect cables (100 feet being no worries) so the power amps can be placed close to the speaker to minimize artifacts from the speaker cable.
If you get that we are concerned about the effects of cables then you have an important understanding about why our designs are the way they are. That is why everything is balanced, as balanced cables, if driven correctly, have essentially no artifact at all.
