CAT Preamps vs Amps

Hi Rayhall & Jafox,

Jafox: good to read your review of the CAT UII after having played w/ it for 3 months. I guessed, when I spoke to you earlier this year, from your choice of words, that your review was not going to be favourable towards the CAT UII.

Rayhall cites my experiences w/ the tube rolling correctly from the other thread.
The Tele 12AX7 definitely is a winner in the CAT. It should come as no surprise - the Ei12AX7 is supposed to be a copy of the Tele smooth-plate 12AX7. I believe that the Ei factory even has some original Tele tube making equipment. Of course, it does not mean that it has to work. However, it comes to me as a major surprise that the Tele 12AX7 does not work in the CAT UII.
I'm using this combination at present - Tele 6922 & Tele 12AX7 & am enjoying it immensely.
It looks like we are hearing things/music in totally different ways!
Also, Mullard tubes are wrong, wrong, wrong, wrong, wrong, wrong tubes for the CAT!
Of course, one is allowed to tube roll any & every tube that one has on hand - nobody is there to stop the user from doing this. However, I've found it worthwhile to solicit an opinion from the designer/manuf before doing so. If nothing, I take his words under advisement. More often than not I follow his guidance 'cuz I feel he knows more about his design that I do.
One minor communication w/ Ken Stevens will tell you how wrong Mullard is for any CAT!
It is indeed unfortunate that you had Mullards for the 3 month audition period! I feel that you severely hobbled the CAT UII by using those tubes. The CAT *should* have performed terribly w/ Mullard tubes & it did, as you stated!
2ndly, talk to the designer/manuf of the CAT before you try the Tele 6DJ8. From my conversations w/ Ken Stevens, DO NOT use 6DJ8 in the CAT. They'll work but the bias is not set correctly for that tube. If memory serves me correctly, the 6DJ8 tube takes more bias current than a 6922. The bias in the CAT is set for a 6922 & it'll not let the 6DJ8 perform to its max/best. It'll hobble the CAT UII (once again).
I think that the correct tube complement(s) need to be used in the CAT UII before a conclusion can be made vs. the Aesthetix.
I cannot believe that Ken Stevens, who is absolutely behind the 8-ball on dynamics, timbral accuracy of instruments & voices, attack of instruments, soundstage width & depth, would make a preamp that lacked these qualities.
If he did (consider this for grins), then, how did the CAT power amps, all of a sudden, get these qualities???
A man/designer who has no knowledge of dynamics, timbral accuracy of instruments & voices, attack of instruments, soundstage width & depth for his preamp can, suddenly, discover these qualities for his power amp??
You do not see the inconsistency of this??

Thank you Bombaywalla for your response. Let me addres your issues one by one. And yes, I knew my comments would get people's blood boiling.

First of all, as stated before, I have not heard the Tele 6922/6DJ8 tube in the CAT. I have no doubt it would work very well here; every place I have tried the Tele 6DJ8, including the Counterpoint NPS400 amp, there was a marked improvement in tonal coherency. I am 110% sure of one thing: Tele 6922 tubes in the CAT UII are NOT going to rescue this line stage from its weakness in portraying space and decays. This tube was a very nice refinement in the Callisto and Io, but it did not take either of these units to a new level in this sonic area. So if anyone thinks they are going to get the Aesthetix strengths by putting Tele 6922 tubes in the CAT, they are in for quite a disappointment. No tube change is going to do this. The differences here are inherent in the respective designs here.

As I have heard the Callisto vs. the Calypso many many times now, they are so very much the same except in one key area - the issue of dimensionality. And the two designs are quite similar except one key factor - the Callisto has a tube PS. Hint, hint. This could very well be the reason why the UII lags behind the Callisto like the Calypso does in this manner.

Obviously, our experiences on how the Tele 12ax7s worked in the CAT are polar opposites. I like this tube very much, but so far only in the Io. What it does in the CAT UII, Callisto and Manley Ref DAC is consistent - the soundtage and dimensionality are greatly diminished in my system. Perhaps there is "synergy" between the Tele 6922 and 12ax7 in the CAT, but this too sounds more like a leap of faith rather than a reality.

I am not going to get into a pissing match over what tubes are right or wrong in any product. To lecture me that Mullard tubes can not work is nonsense. They might not be the ultimate tube here, but for $100, just one pair in the line stage took the UII into far greater sonic performance. This is the tube I had at the time, and with it, I observed a significant improvement over the Sovtek. If nothing else, it is a wonderful starting point if it is the only available tube at the moment.

That Ken Stevens shared with you that the Mullards were not a got tube here is fine - I accept his opinion here. Let me be frank - he does not want any of us to even change the stock Sovteks. And yet it is a consensus here - until we get rid of them, one has not begun to hear the potential of this product.

As for me hobbling the UII experiment with only Mullards indicates to me that you're getting a little ahead of yourself with coming to judgement here.

"I cannot believe that Ken Stevens, who is absolutely behind the 8-ball on dynamics, timbral accuracy of instruments & voices, attack of instruments, soundstage width & depth, would make a preamp that lacked these qualities."

You are not paying attention to what I have written in this thread at all!!!!! In the context of dynamic contrasts and initial attack of notes, I have repeatedly stated the UII line stage outperforms the Callisto by a significant margin. And this is very evident with the JL-3s. From my amp listeneing sessions, no amp can touch the JL-3s in this regard. And we are driving some very resolving speakers here: SoundLab A1s. So nobody needs to lecture me about dynamics or transient speed. It is why I bought the JL-3s and it is what I immediately noticed was the UII strength.

I have been very kind to simply state that the Io was far beyond the UII's phono stage. And this was why I did not put anywhere near the effort between these two as I did with the line stages. As stated before, I threw everything at the UII but Tele 6922s and the kitchen sink to bring on the magic and it just did not happen. I suspect very few people would have done so much with this unit as I did.

"The CAT *should* have performed terribly w/ Mullard tubes & it did, as you stated!"

And again - you were not paying attention. I never said it performed terribly. I stated the UII's strengths over the Aesthetix. And I then followed through where the Aesthetix excels over the CAT, i.e., harmonic textures, layering, decays, ambience, etc., etc. Rather than you scold me for my incompetence and/or lack of responsibility for sharing my experiences here with the Mullard tubes, I suggest you get on down to your Aesthetix Io/Callisto dealer, and take a box of Mullard, Tele and Brimar tubes, and hear for yourself the areas where the UII falls behind. Oh, and so there will be no bias on lack of dynamic contrats from the audition, maybe you can also borrow a pair of JL-3s.

As for the issues of soundstage, decays, body of the instruments, etc., even the CAT amps lose out to some of the competition here.....the Atmasphere amps driving the SoundLabs bring on a most incredible performance in these key areas over the CAT. And this was observed with a direct comparison between the amps. When I heard this at the dealer, I remember telling him I wanted both amps in one. And the same holds true with the UII and Aesthetix. But this is not possible so the best I can do is pick one from each side of the fence. And to me, the Aesthetix/JL-3 pairing is incredible. Everyone who has heard this with the A1s, has said the same.

Perhaps the UII and the Atmasphere amps would be the flip side of this success. But a CAT/CAT setup is just too much into the neutral zone for me. Other people love it and I respect that. I just need a little more direction into the dimensional zone.

"You do not see the inconsistency of this??"
Not at all, and maybe you won't either once you pay more attention to what I have written all along. There is no perfect product in the CAT nor Atmasphere nor Aesthetix nor whatever camp. The key is to assemble a system in such a way that brings on the strengths of certain pieces that stand out and try to improve on that component's weaknesses through other changes in the system. And this is what I have done.

The post by Bart(Poswbp555) where he spoke with Ken Stevens is interesting. This ought to be very exciting when the Legend comes along. But the full function preamp by Michael Elliot is also much on my mind. We all benefit when these very talented engineers continue to improve on their past great achievements.

I think I have shared all that I can here to convey the pros/cons of the products under evaluation. For me to continue here will only result in rehashing the same information through and through. And as exhibited by Bombaywalla, my instincts were correct - people get upset when their reference product is put under a microscope.

John

John,

Thanks for your update. Appreciate your time to write a detailed rebuttal post.

>> And yes, I knew my comments would get people's blood boiling.
NO! my blood is not boiling. Far from that, let me assure you & double assure you, if I may.
When I wrote my post earlier today, my intention was to invoke a debate & not a screaming match.
At no point did I "lecture" you about Mullard tubes - it was 1-line statement.
At no point did I "scold" you for your "incompetence" or "for your lack of responsibility for sharing my experiences here with the Mullard tubes".
You have become way defensive & aggressive than, I think, my post called for, if I may say so.

>> And as exhibited by Bombaywalla, my instincts were
>> correct - people get upset when their reference product
>> is put under a microscope.
Let me say again, I'm NOT upset that you put the CAT UII under the microscope. On the contrary, thank you for doing so! My ego is not hurt, my sentiments are not hurt. OK?
I'm not here to convert you to a CAT preamp person & my post was not intended to do so either.

I will say this: you & I are hearing music *very* differently. There is a wide gap.
Maybe I'll conclude the same as you when/if I get to hear an Aesthetix product? Who knows.....

I have to agree with John (Jafox) on the sonic qualities of the CAT U2. I am hearing similar strengths and weaknesses to those he describes. I value a liquid, musical, melt in your ear three dimensionality over dynamic slam (it would be nice to have both obviously). I may try the Atmasphere in combo with the CAT U2 in the future to split the difference between their strengths. Bombaywalla,
I haven't read your thread on all the tube rolling combos you have tried in the CAT yet but I'll bet you that the Amperex 12AX7 D getter long plate (circa 1950's at 200 to 300 a pair)will significantly outperform the EI 12ax7. John is also correct about Ken Stevens adamantly rejecting swapping the stock tubes in the CAT U2, so why are you referring to his rejection of the Mullard as a suitable replacement for the stock tubes when we all agree the stock Sovteks are dreadful. Anyway, thanks for doing the tube rolling, these are the kind of experiments that can save us money in a very costly hobby. Bart

Bart,

>> but I'll bet you that the Amperex 12AX7 D getter long
>> plate (circa 1950's at 200 to 300 a pair)will
>> significantly outperform the EI 12ax7.
maybe so. The $ amount is a bit too extravagant for me - I cannot convince myself to spend this much on NOS tubes!
I also tried the Telefunken 12AX7. I think that I had a smooth plate pair (if memory serves me correctly). Like Rayhall wrote, I found the Tele 6922/Tele 12AX7 combination the best. The Amperex 7308 USN-CEP/Ei12AX7 combination the 2nd best.

>> John is also correct about Ken Stevens adamantly
>> rejecting swapping the stock tubes in the CAT U2,
Having spoken to Ken Stevens several times at length, he informs me that he has "optimized" the CAT preamp design for the Sovtek 6922. That's why he's so insistent on retaining those tubes. I didn't ask him specifically what he meant by "optimized" but I surmise that he means creating the bias specifically for that tube to run it in its most linear region + the power supply filtering for its heater supply.

>> so why are you referring to his rejection of the
>> Mullard as a suitable replacement for the stock
>> tubes
Again, speaking at length w/ Ken Stevens informed that the Mullard tube was ill-suited to the design on the CAT. As you know, certain tube types work well with certain tube preamps i.e. if a certain preamp uses a 12AX7 then not all brands of 12AX7 will suit this preamp. The CAT is no different - the Mullard tubes make the CAT perform at its lowest. I found the same when I tried a Mullard pair generously lent to me by Jafox.
However, I did write the following in my original post:-
"Of course, one is allowed to tube roll any & every tube that one has on hand - nobody is there to stop the user from doing this. However, I've found it worthwhile to solicit an opinion from the designer/manuf before doing so. If nothing, I take his words under advisement."

I'll have to listen to an Aesthetix Callisto & determine for myself how its sound compares & contrasts to the CAT preamp. I'm not convinced that the CAT can be faulted for the lack of portraying space, decays & harmonic textures.