I received the RCA 5u4gs today and they're plugged in now.  They may need some time to settle, but the first thing I notice is a significantly less impactfull bass and a little vagueness to the sound like a light veil.

I guess I'll see what a weekends worth of burn in/settling time brings.

Gopher, Did you get 5U4G-ST (coke bottle shape like the rubys) or 5U4G-B (straight side, bottle shape.) I have no experience with the B. And my interpretation of the ST may not be like yours, but can see how you could see it that way. I put the Rubies in to check with my current tube set, and with these amp settings. For my system, the bass with the RCAs is more focused and defined, but I would not say there is a lot less.....and everything is more liquid/sweet, the Rubies having an edginess by contrast.

With this setup, the Rubys are way in-your-face. But with a softer/warmer tube set, they might sound quite good to me. Interested, I then put some herbies RX tube dampers on the Rubys, and they became more liquid and balanced, with tighter bass, and less edgy, but still edgy. So I guess it is really relative to everything else. One thing is for sure, if I were using the Rubies, I would play with my amp adjustments and tubes (set now for the RCAs) to adjust to what they bring to the sound. The difference between them and the RCAs are notable, begging for a synergy that this set and settings don't give them.

Also, I find at times that some combinations of tubes can make the qualities of individual tubes change in unusual ways, bringing out different things than expected as some other tube in the setup takes a dominant influence over them.

Finally, if your tubes are NOS, I agree with Lon, they will likely take a while to settle in. I seem to remember my RCAs taking something like 50 hours???? to begin to open up, but can't be sure about that.

If you can run the system while away, and since you have very specific tastes and are playing with new stuff a lot, the Esoteric/Iso-tek Burnin CD may be worth a serious look. It is supposed to shorten burnin a lot in a safe, mathematically calculated way. It took me a long time to get there, but I recently had a lot of new/repaired stuff at once and the burnin was killing me after having really good sound, so I was happy to spend the thirty bucks or so it costs. There is a good review on it out there somewhere.

I suspect they'll change with some hours as well.  It is one 1953 and 1955 coke bottle RCA 5u4g.  I purchased them from tubeword where they tested new but had smudged labels.  

I was just posting some initial findings--I'm not worried about it or anything.  These things probably haven't seen any usage in a couple decades (if they ever did) I'll give them a fair chance to warm up.  The decrease in bass quantity was a little surprising, but I've been in the hobby long enough not to judge a tube (or most equipment) immediately.

I do have the Isotek burn in tones which I will be running over night at a low volume.  Until then I'll leave my system on idling--unfortunately my listening room is also my living room and my wife and kid need to utilize this area--especially on weekends, without listening to burn in tones in the back ground...  they just don't get it!  

Sorry to undermine those underpinnings. I'm sure a nice nap will restore them.

I'm a lover all sort of womanly body shapes, but like my valves symmetrically round and straight.

It is worth a chuckle. I confess it's been long enough, and enough system changes, that I may even prefer the sound of the ST now, it's hard to know. But I really do enjoy my Bs (the ones I'm using came with Bob's Torii Mk II). One of them is giving me problems (it seems to be problematic making contact and glowing, every now and then I have to re-seat it in the socket) and in time I'll be looking for a new one. I used the Electroharmonix 5U4GB for a spell, which is almost as good (a less lush presentation but very dynamic) and those are now in my second system Mk II.

I believe I am using a very similar RCA in my CSP2. I'm telling you, the CSP2 has become an integral part of my system, probably in a similar way that your ZSTAGE has to yours. I can change the entire signature of the amp just by adjusting the gain pots. It's like having several different amps by that method alone, let alone the changes you can make to the Mk III with input bias and speaker settings. Coupled with the electrical accuracy and stability the PS Audio Premier has brought to the scene, I'm just constantly rediscovering my system's playback beauty. It's nothing like real live music but it's glorious.

Will, indeed, tha PSA Power Plant was a great deal at Music Direct. I wish I had just gone ahead and bought two. There is one right now in black on fleabay, (used to be two of them), used, but the price is not bad, starting at 949 with a BIN of 1149. In the alternative, I can attest that the Transcendent Balanced Power Supply is very effective at creating a black background, with no discernible hum or noise. It was also fun to put together. I plan to pair it with a PSA Quintet.

Will, I cannot yet say that the BPS reduces noise, though I believe it does. It does not reduce the THD coming out of the wall socket, but its design should have less noise, and the sense of black would seem to support that. It is definitely "blacker" than the Monster AVS-2000 it has replaced. But if I had to choose between just one—the BPS or the PPP—I would almost certainly choose the PPP. While more expensive, it is more flexible, has more current capability, has the isolated zones, etc.