This is a job for "Superwill"! will has the ZStage and really understands its use. I hope he'll weigh in here.

I have had the ZBox in two systems. It will add that "warmth" you wish with the right tube and if you don't need added dynamics, it may be all you need. I have had problems with the ZBox and hum going into my 25 wpc Torii amps, very little hum issues when going into the lower wattage amps I've owned from Decware. . . .(And I confess it's really not a necessary component for any of the larger Decware amps. It's best applied to solid state amps and the smaller Decware amps when used with average to good sources. Mine I had Steve add an additional input to, and its best use was as a basic "preamp" for a system built around a pair of Decware SE34 Monoblocks.)

Though I have not heard the Zbox, I would say they are two different things. The gain stage of the Zstage is useful for more than just gain. When riding the volume with your amp, it adds or subtracts weight, density, dynamics, brightness/darkness and so on. I found this particularly helpful for adjusting various recording qualities to my system and tastes. I guess, for me, that this gain adjustability is equally, if not more important than the tube alone. But if you need the tube interface only, the Zbox may just be the ticket.

My experience is similar to Lon's. The tube choice matters, but you have plenty to choose from, and rolling one tube for refining the sound to taste is pretty fun.

At the same time, I have been using a Tranquility DAC for a while and it is not compatible with the Zstage as-is, presumably because of the DAC's greater than 2 volt output. I get distortion.

Steve said he can mod my Zstage to handle the higher voltage and for my other wish...to have two inputs like Lon has on his Zbox. But I am using the Zstage as an often necessary gain for my DVD player, and I am quite happy with the Tranquility sound, so I am waiting for a good time to send it back where I won't miss it. I do want to hear how it acts with my Tranquility, but can't say if it would benefit it or not. It has a very refined sound and the Zstage may or may not get in the way, but since recordings are so variable, I suspect I will like it with the Tranquility. I like the Zstage quite a lot with my ZDAC and Oppo.

I also have the option to use the ZSTAGE with the power amplifier inputs of the HK990, therefore using it as a straight tube preamplifier.

In theory, it sounds very promising - S.E.T tube preamplifier into a decent solid state power amplifier; but in practice..? Remains to be seen & heard...!

Fireblade,

Not knowing electronics, I will try to answer your questions as best I can.

I did not do extensive testing with the higher output Tranquility. And my favorite tubes in the Zstage (with the ZDAC) are a particular few NOS 12AT7 variants as opposed to the stock 12AU7. If I recall correctly the higher output 12AT7 was more prone to distortion with the Tranquility. In my system, the ZDAC and Oppo do not distort at all with this tube.

Since it has been a long time, I just hooked the Tranquility through the Zstage with a 50's, D getter, Siemens 12AT7 (nice transparent and solid tube!). I had not checked it since I got an updated output stage in the Tranquility, and HMMMM....less, but still discernible distortion with hot source material. Presumably the output is less of a push for the Zstage.

I think your thoughts on the Zstage function in riding the gains are correct. But the Zstage is an independent stage between source and amp with its own electronic input, gain, and output parts. So I would speculate that at some point, a too high input voltage going into the Zstage effects some Zstage part(s) electronically, overloading something within the Zstage signal chain, and in turn, shows up in the Zstage gain. Perhaps resolution is as simple a putting in a slightly higher value resistor in the tube stage??? Whatever it is, my experience with my very early Zstage (Serial #002) indicates a threshold over which one might experience distortion. And for effective gain riding, though I tended to hang out in the middle ranges with my gain, I don't think you would want limitations as to Zstage gain adjustment.

If you want real answers though, since your DAC has a higher output voltage, if you get to wanting to order one, I would call Steve and ask him. He knows, and if necessary, could very likely build the Zstage so that it definitively accommodates your input voltage.

So I would not "conclude that high output DACS may not benefit from the ZStage given possible distortion issues." I would say that higher output DACs might benefit greatly from the Zstage as a tool, and perhaps the Zstage parts have changed a bit since mine, but if not, just be aware that my personal experience indicates that THIS Zstage, in THIS system, needs a little modification to accommodate my current source.

Fair enough, Will.  Thanks for your explanation. I think I'll do just that once the gear is broken-in.

meraklya,

I agree. For me engaging is an ultimate determinant, but when I look really closely, as my system develops, there are so many things that contribute to this seemingly esoteric quality.

The Zstage is definitely capable of bringing about yet another elusive quality...authentic warmth. Seems to me warmth has many, many shades. I guess I would call it comforting body and depth enlivened with the sparkle of unobstructed, but smooth and real sounding detail throughout the spectrum.

Seems to me that all of the Zstage's attributes and tools could be used to fine-tune your source toward the end of engaging warmth. From Steve's parts synergy and their tendency toward subtle warmth; to the many tube choices (both type and individual characters within the types); to the gain with its impact on weight and body; to the bias switch and how it works with the tube to accentuate (or not) "warmth."

I guess I am observing that, as a whole, the Zstage offers many meaningful adjustments toward refining "warmth" to personal tastes. And this does not even consider power and IC cables!

I hope it brings a good synergy to your system, and I will look forward to your thoughts once you get used to it.

Fireblade,

First, I think Steve's and forum member's observations are very informative and worth considering carefully. But with these very good amps, all designed with the thread of Steve's interpretation of exploiting the benefits of tubes toward real sound...though each will have characteristic qualities, they will all be great amps with excellent tube sound.

So though the differences in the amps are real, I suspect you may very well find your amp to have plenty of SET qualities in the midst of its individual traits. And with the amazing array of tube choices it allows, after breakin, I may be wrong, but I doubt your decision for a Zstage will come of a strong need for SET qualities, even though it might help flesh that out further.

As to the Zstage getting in the way, I think this is a hard one to answer. I think it was designed by a purist with transparency and musicality in mind. And with appropriate cables and tube, in my very revealing system, it fits that bill for me, but I definately hear it. As to whether it "is in the way" or is a sweet addition in a given system must depend on tastes, power, gear, tubes, cables and their synergy.

Liking what the Zstage does, if there is a potential issue, I think this might depend a whole lot on your source, especially along with using an excellent tube amp and gathering tube benefits there. I suspect that an extremely lucid, warm, and subtly detailed source could possibly get a bit smoothed out by the Zstage's "signature" and the extra hit of 2nd order harmonics. Maybe. But then the question becomes whether the benefits of gain tuning, bias adjustment at the pre level, Zstage tube rolling, and cable tuning balance things to the positive.

For me personally, with the ZDAC and the Oppo, once I got the Zstage tuned to taste, there was no question of benefit in the balance. My Tranquility, with its very good micro detail and micro dynamics may or may not be the same. But I have been listening today to the Tranquility through the Zstage with an RCA cleartop 12AU7 (no notable distortion with that tube) and like it. I need more time to get the sound deeper in me, but first impressions are "different" but great... excellent texture and detail, solid bass, fast and tight dynamics, very saturated sound stage, liquid and musical...it sounds really good to me! Not as relaxed as without, but ...my system/room/tastes...I like it today.

Knowing my tendencies to tune to taste, once I get the Zstage modded, I will mess around with tubes, cables and feet and likely keep in after the Tranquility, but not having gone there, I can't say for sure.