CAT Preamps vs Amps

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.

Bombay, if you followed Ken Stevens advice you would still be using the stock tubes. Have you considered the cost differential between the stock tubes and Teles or Amperex may be the deciding factor in Ken Stevens tube selection?
The 6922's or 12ax7's have certain output parameters that are the same regardless of the tube manufacturer. That is why they are measured by classification (6922, 12ax7, 12at7, etc.) not by manufacturer. So for you to say that Ken's design was optimized for the Sovtek is absurd. Does it sound optimized to your ears or any other ears on this post with the Sovteks? Bart

Bart,

>> So for you to say that Ken's design was optimized for
>> the Sovtek is absurd.
I'm merely conveying to you what he told me. For a clarification you should call Ken & ask him yourself what he exactly means.