How make my Ayre system "warmer"?

Mullard and Brimar tubes sound different enough to me that I
would not put them together under the same "sugary and glazed" umbrella.

I have rolled Mullard Blackburn production tubes with Amperex 6922 white
label tubes and Siemens CCa, ECC88, E88CC and E188CC. To my ears, these
tubes sound more alike than not. The Siemens have the least coloration, and
the Mullard have the most coloration, but the differences between them are
not nearly as pronounced as between even the Mullard and Brimar (which to
my ears sound quite colored and rolled-off).

I like Mullards. They round off the sharp edges with a very slight burnish
while still maintaining the air and detail of Siemens and Amperex.

IMO...but this is a bit off topic.

Back on topic, perhaps Tje experimented with a tube preamp that did not
have an output impedance that was a good match for the Ayre amplifier. This
would explain the lack of dynamics. Using a properly matched tube preamp
with Mullard tubes could definitely warm things up a little (but not a great
extent). Installing Brimar tubes could warm things up a great deal, but the
sound is going to be very different than the clean and neutral SS Ayre sound.

Tubes don't add distortion until they are driven to distortion. Then they produce even-order harmonics rather than the odd-order harmonics that SS devices produce when over-driven.

Then why, to cite what I admit is probably a somewhat extreme example, would the CJ PV15 line stage preamplifier have a thd spec of 1%? And why would some older ARC power amp designs that I can recall have thd specs of 3% or so? I'm sure a little research would turn up a considerable number of other examples as well, of highly regarded tube designs that have highish thd numbers, when operated within rated limits.

Obviously I was not referring in my previous post to the major distortions that would result from overdriving or clipping. Any non-linearity that occurs within the normal operating range of a tube or other amplifying device will result in small amounts of distortion, that may be sonically significant, especially in low feedback designs. Distortion that I believe would likely be a significant factor in what is perceived to be the particular tube or the particular design's sonic "signature."

Regards,
-- Al

You might keep in mind that tubes are not the only components in those pieces of equipment, and that designers of SS equipment have historically taken vastly more drastic steps to minimize distortion figures(ie: typically 40db of negative feedback), usually to the detriment of actual sound quality. Tubes are innately very linear(into RF frequencies), but unfortunately, provide relatively little gain/transconductance(low output current) and high plate resistance, hence the need for matching transformers. A great deal of the distortion inherent in tube amp design results from the use of transformer output coupling, not the tube itself.

Hi Tvad- Like most subjective evaluations with regard to this hobby: One person's candy will be another's poison. My first Mullards(CV 4004) were tried in a CAL Alpha DAC, when I had a much less resolving system than now. Their warmth was much more than I could accept even then, and they were quickly replaced with Tele's(ECC83's). No problem with soundstage, imaging, etc., but the coloration was simply not natural. I agree with your ranking, RE coloration levels: Brimar, Mullard and Amperex(the "pinched waist" I could probably live with). To me the Siemens and Telefunkens(whatever family of nine pin miniature) are the most transparent, extended and uncolored(natural) out there. Let me narrow that last statement to the pre-1968 tubes manufactured for the German Telephone Services, and branded as "Specially Selected"). One nice thing about Mullards is that, once tried, if not appreciated: they are easy to sell. I do love their voltage rectifiers though.

To cut long story short, try Kubala-Sosna Emotion powercords, and when your budget allows it add IC's na SC.
You will not lose any resolution and balance will lean more to the bass.