Good morning!

With a SE84UFO2.1 and DAC/SACD player...  should I use a ZBIT or ZSTAGE? Which will provide the most improvement to a digital front end with XLR out?

Thanks!

I like both... the ZBIT for pretty transparent gain-lucidity/dynamics balancing, really nice for optimizing the level of the higher voltage balanced out of DACs. To me, the voltage adjustment and those high-bandwidth transformers work really nicely together for system clarifying tuning and gain balancing for different recordings...

And the ZStage, the tube is the thing, good or bad depending how you look at it. Long time since I have used it in my main system, but I got to really enjoy tube tuning. With it, you can tune to system and tastes with the tube influence being your sonic enhancement filter rather than the transformers of the ZBIT, giving quite a lot of potential sound tuning. I used 12AU7 types, 12AT7 types, and some of those in between. I suspect you can still use all those with the new ones??? Mine was early. If tube rolling is intersting, the bias switch on the ZStage also changes the character of each tube sound in pretty nice ways, though I personally was always going for clean revealing sound, so left the bias punch off. But it is a good sound as I recall. Guessing they might end up somewhat similar in feel of a useful range from voltage tuning, using the lower output of the DAC RCAs with the ZStage, but the ZStage having some gain.

All that said, and my heavy ZStage period having been a long time ago (got caught by the CSP3), so memory rather than direct comparison, but my gut is probably like Tony if I had to choose one or the other... I would probably want the ZBIT more with my DAC and amp. And my DAC sounds really good with RCA out, so I speculate it is more the ZBIT sound qualities than balanced out being the main player here. But I also have lots of tube rolling potential with my amp's many tubes, and hyper tuned ZRock2 and CSP3.