@markimiller - good question. Came across Yamamoto when doing research on a new DAC and their design struck med a beautifully minimalistic with a focus on letting specific types of tubes do what they do best. But I’ve no listening experience with them - so just fascination & curiosity + some very positive reviews.
I have the CS-600 with different tubes in the driver stage (6CS7s). I just tried connecting a high-output DAC to the preamp in. The input does not seem to bypass the boost function and the balance contro, so I’m doubt as to which degree the pre amp mode makes the amplifier function as a (pure) power amplifier.
If the driver stage is not bypassed, there might not be much to gain by running it with a separate preamplifier.
But I might be missing something here. Theoretically, adding a preamplifier might worsen the sound as the signal chain gets longer both in terms of through the amplifier circuits and the extra interconnect.
Some people report great results running the input signal through the tape in instead of one of the line level-ins. This, however, does not seem to bypass parts of the driver stage either though.
