How make my Ayre system "warmer"?

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. I personally own a tubed CDP, tubed power amps, and still enjoy very transparent(coloration and distortion-free) music. Some tubes, most generally from Britain (ie:NOS Mullard/Brimar), will provide a much "warmer" or more "sugary"(think, "glazed") coloration. Many obviously like that sound, as these tubes are very popular. Should you decide to add a tubed component to your system: Try some of those, and you'll probably be well pleased.

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.

I've got six NOS(pre- 1968) CCa's in my CDP(BAT VK-D5) and enjoy their presentation very much. Like you said, "It's also the gear into which the tubes are placed." My goal has always been to recreate(as much as possible) what I hear and feel in the live venues I visit/work a couple times, every week. It's been my experience that most people blame excellent components for shortcomings elsewhere in their audio chain. Again- Everyone has their own tastes also(I believe I mentioned, "subjective evaluations"). BTW- What was the manufacturing date on those CCa's you had? The ones made after '67 could singe your ear hairs with their stridency.

Mr T: You're right about the getter supports on the later CCa's being shiny metal. Also- They had the date code on a plate inside the tube. Mr N: The VK-D5 is also somewhat sensitive to the impedance it sees at it's output. It's bass will roll off slightly more(about -2.5db at 20Hz) at 1kOhm as compared to 100kOhms(-.2db), which will seem somewhat thinner, but- better defined with some speakers. Increase the impedance to, say 200kOhms, and things can get a bit warmer/bloomier. In my system, and with the CCa's, I've been enjoying a great deal of accuracy/realism from the 'ol BAT.