Regarding the lengthy technically oriented post which Ralph provided yesterday, I of course agree 100%. At the same time, though, I believe his post is not at all inconsistent with mine that preceded it, in which I said:
If:
1)The output stage of a source component can drive whatever power amp is being used and the associated interconnect cables without compromise, or, alternatively, at least as well as whatever preamp might be inserted between those components, AND
2)The volume control in the source component, assuming it has one, is EITHER:
(a)As transparent in the range of settings that would be used in the no preamp configuration of the system as it would be if set for use with a preamp (i.e., at or near max in typical cases), OR
(b)As transparent as the volume control that is provided in whatever preamp might be introduced into the signal path,
then it seems to me that the only way inserting a preamp into the signal path can result in sound quality that is subjectively preferable would be by producing an output that is less true to the source material (i.e., less accurate) than the signal that is provided to it by the source component.
And it would seem, on paper at least, that in the specific case of Rustler's PS Audio DAC both of the criteria I listed above should be met. Essentially, the output section of his DAC **is** a preamp, or so it would seem.
Which means, IMO, that if he finds insertion of a preamp to result in improved sonics, chances are the sonic effects of the preamp would be compensating for an issue elsewhere. Which is not to say that there would be anything necessarily wrong with introducing a preamp as a solution, but the possibility should be considered that changing something else in the system, perhaps the power amp, might be a more optimal solution.
Best regards,
-- Al