All I can really say definitely right now is. . . it's a damned fine preamp for the price!  Gets out of the way, offers precise control of volume, doesn't cloud or really add much of a signature of its own.

Amazing value for the price in that respect I feel.

I've introduced so many variables to the system along with it (another power cord, another tube and actually lots of tubes swapped in and out, two sets of interconnects now because I've gotten the Decware interconnects in place now, replacing my TARA Labs interconnects) that I really can't speak to how it may be "sweetening" cd playback. . . . It may be.  It may be smoothening the top end a bit compared to directly into the Monoblock amps.  I'll have to reconfigure and do direct comparisons at some point in the near future.

I'm definitely keeping mine, because it is nice to have a preamp and this is one fine preamp!  Glad you are enjoying yours so much Grant!

I am using the DEC 685. . . it puts out near 4 volts I think.

Currently I am running the Monoblocks completely 100% up.

I am using the preamp at about 25% to 35%.

Did I miss something along the way, I thought the Z-Box was a cathode follower-buffer with no gain and an attenuator (aka volume pot) on the input side, not a pre-AMPLIFIER.  Nevertheless, they sure must sound nice, lowering all that nasty impedance and what not.

dr._sleep

Just wait a bit.... I 'think' it's starting to do nice things to the sound.  ie. more detail, weight and distance between instruments....  it does roll the highs a bit methinks however it is emenently listenable, or not as the sleeping seems to attest....

Cheers!
Grant

You are correct about Zbox Lon. If I had a 4V source I would keep it too.  :)

Corey I have NEVER been happy with a JJ input tube before, and as I have a number of Mullards and other NOS tubes to use, I'm not going to bother with the JJ except as a last resort. (I'm picky about input tubes and have a lot to choose from; old guitar amp habits die hard).  I am positive that the "liquidity" in the machine is not due to the JJ tube.

The point I guess I haven't made too clear is that I was enjoying liquidity (whatever that really is) before the Zbox with the tubed output of the DEC685 and it's major benefit to me is that it serves very well as a simple preamp.

Corey, Steve ships with tubes that a person can buy new with no hunting and searching, that's his purpose there.  He even mentions quite clearly that the Zbox is designed for easy tube rolling.  

I may try the JJ sometime but I'm in no hurry to, because I know I have better tubes.  All the other JJ input tubes I've used have been mediocre compared to the Mullards I'm using.  I'm using right now a Mullard 12AT7 that has been cryo'd and is a notch above anything else I've used.  (You might even try experimenting with tubes in your DEC685 because the Ruby that was sent with that was one of the lamest input tubes I've ever used sonically; who knows, you may enjoy the sound of the tubed output with a better tube).

Not to belabor this but I just can't yet qualify what I hear because the machine is not but ten days in use and because I've introduced a lot of varialbles to the system along with it.  I'm not going to just gush over this when at this time the main thing it is doing is allowing me a preamp.  It may be doing a lot more but the fact of the matter is I was extremely happy with my system without the Zbox and I'm still  extremely happy with my system, and the Zbox is not hurting the sound in any way.  It may improve further, I'll note that fact if it does.  But, unlike others perhaps, I bought this machine to act as an inexpensive but compatible preamp for my system, and it is indeed doing so far a smashing job for that purpose.  You probably want a Zbox or want to hear about a Zbox improving digital playback.  I feel I've already accomplished that with the DEC685 tubed output section.  Maybe you should order one and see if it will work for you as a digital improver, either allowing you to use the excellent tubed outputs of your DEC685 or sweetening the sound of the (as far as I am concerned) inferior stock outputs.