Bombaywalla - The reason my response came off as defensive was because I made an effort here to convey my observations; these descibed the strengths and weaknesses of the two preamps under test. Never did I refer to either as terrible. That (dis)hono[u]rable title belongs to a few other preamps that I have auditioned over the years and noted here on A'gon.
I do indeed take a manufacturer's or an audiophile's suggestion for a starting point to use a specific cable, tube, matching component, etc. But the road to refinement on a per-system basis is only possible if we experiment with other options, and some of these will likely be contrary to the initial suggestion/advice we got. The Mullard tube is a classic example here. It did not work for you - but it worked for me ... if nothing else, as a significant improvement over the stock tube used to "voice" the product.
Another factor is that my tests were with the UII and yours with a Mk III. Besides our very different systems, could the difference in the CAT preamp models be a factor for our opposing conclusions with the Mullard 6922? .... very possible. And the same for the Tele 12ax7? .... again, very possible. Can you imagine that one brand of 12ax7 might lock in for the CAT line stage and another lock in for the CAT phono stage? ... And swapping these two could be a worse result that what we had with the stock tubes? This is exactly the case between the Io and Callisto for both the 6922 and 12ax7. Afterall, they were designed by the same engineer and also voiced with Sovtek tubes. And yet when other tubes are tried, the two components react very differently to the same 12ax7 or same 6922. Even Mr. Spock would be perplexed by such a outcome.
I think that if we evaluate a tube's performance, or anything else such as a cable, with a specific product, all of our conclusions about that specific tube or cable are relative to the one product under test....and in the context of that system. We can not judge the performance of that tube or cable onto another product until we repeat the test process for the product.
What I was trying to do with the resources available to me, was to max out the CAT UII and max out the Io/Callisto and in the final analysis, the results for each was very impressive. But through so many changes to each, tubes and cabling, a "house" sound for each became very evident...and the design engineers' priority in a resultant sound for each became evident. We can tweak and refine a product to get it to be a little more to our liking, but if we still find something lacking, we must continue our quest to find a more suitable product; expecting a $1200 pair of golden tubes to save the day is not realistic.
Btw, I did a lot of playing of 6922/12ax7/12au7 with the JL-3s. With Mullards and Teles here, the JL-3's performance took quite a step forward - hardly a surprise. And this was long before I ever had the UII here. I have paid a lot more money for a component change and gotten less improvement than I have with some of these $200-300 tube "upgrades".
I don't mean to get so philosophical here, but so many people here, as shown by the multitude of "best of" threads on A'gon, are obsessed with what is best.....and there is no such thing.
Bart - I get the DAC and Io back from GNSC tomorrow. Once I burn these in for a couple weeks, then try out a matched octet of Brimar 12ax7's for the Io's first stage, the pair in the Callisto and pair in the DAC, I will be ready to borrow some Stealth cables. Hopefully the JL-3s will return very soon too. I am very excited to try the Steath products. I will keep you posted on this.
John
