I've lived with three TacT units - 2.0s, 2.2X and 2.2XP. I didn't like any of the internal DACs and used them with external DACs, mostly non-oversampling. I thought the Altmann was terrific (still do) but it didn't mesh perfectly with the XP. Ultimately the Lessloss was the choice for a number of reasons, though it's an oversampler. I definitely wanted one that could work directly from the XP's 24/96 native output.
TacT is quiet about their clocking scheme but I'm pretty confident it's complex. I think there are multiple clock circuits driving the DSP works in addition to the main audio signal. When I asked them about clock slaving to use the Lessloss as the clock master I got the idea that there's a LOT going on in there.
Whatever digital source you feed, it's going to be upsampled to 24/96. Somehow, the 24 bits are necessary for transparent digital volume control and the sampling frequency is beneficial to signal processing. If you're feeding an analog source the first operation will be digitizing to 24/96. Feeding analog to a TacT doesn't make much sense to me as I believe every ADC/DAC/sample rate conversion takes a toll on sound quality but I'm sure argument could be made there.
Condensed, my thought is while digital transports probably do make a difference through the TacT, the degree of difference will be minimized by the unit's processing versus going straight to a DAC.
The last setup I had was the Lessloss which works perfectly from 24/96 straight to a Yamamoto A-08s, 45 SET amp. This is a GREAT amp, assuming you can live with 2 watts which I can. As an aside, I had to sell that amp but I kept the 45 bottles and my SET star will rise again. This should have been a terrific combination - high quality SS output as "preamp" to a truly superior, hi-gain tube amp. But, something was not right. I began to think I could hear all that processing as dropouts in quiet passages and though I was using SET amplification to paper drivers I was still missing organic richness.
Moving to a tubed Lamm preamp (the baby one) fixed all that and then some. I still am using a DSP processor but only below 120 hz. I believe the TacT units have "a sound" that cannot be escaped. That doesn't mean it's a bad sound or that it can't work or that it's not your sound. But like everything else it does put its signature on a system. I don't write this to discourage you from keeping it, rather as a data point since I've traveled a similar road.
IMO, a DAC has much more potential for gains than the input digital. If you're running the 2.0s or 2.2X, an Altmann DAC with 24/96 encoding might just seal the deal for you. If it had worked with the XP I might have stopped there for quite a while. You'll give up some resolution sometimes those edges do need a bit of smoothing. A few folks I corresponded with on the TacT/Altmann combo had the s and X and all reported they worked very well together. The XP is a major departure in architecture and even TacT themselves were not able to get them to play together.
Sorry for the rambling, hope the itch gets scratched!
