I’m sure that’s the case. I successfully downloaded the Service Manual from here: PANASONIC CQ-TX5500W SM 1 Service Manual download, schematics, eeprom, repair info for electronics experts (link text says “Get Manual” under the preview image. I’m not familiar with this site; I use Adblock and didn’t see any annoying/malicious crap on it at all, YMMV). The manual has ALL the schematics, part numbers, wiring diagrams, and everything else. Here’s the main block diagram: Imgur: The magic of the Internet . I’ve looked at it and have to admit I’m not knowledgeable enough to say for certain what all those components are doing, but it LOOKS to me like the vacuum tube (lower left) is pretty much separate from the power amp section (top right) – looks like CD L/R line goes into the tube, comes back out, then heads over to the “Electronic Volume” control and a power amp IC before going to the speakers. So, additional transistorized amplification, I think. Since it looks to me like only the CD channels even go to the tube (the radio goes direct to volume and amp ICs), I suppose its only function really is to provide some supposed “warmth” to the CD/MP3 audio.
“Warmth” is one of those beautiful terms that audiophiles love to use.
I never understood how a term used to describe heat could be applied to sound sensations.
I too, suspect the tube was only there for visual effect.
BTW-is Mark Levenson audio stuff all that good? They seem to have a decent reputation-what is their schtick?
Yup. As I expected - a simple cathode follower in the audio path. This is a roughly unity gain buffer, and is actually a pretty low distortion circuit, so whilst it might add a little even harmonic distortion, it isn’t going to make much difference. In a car you would be very hard pressed to hear any difference unless they really tortured the circuit. (I don’t have time to do the load lines and work out what the transfer function would really look like - by cathode followers are usually quite linear.)
Warmth is a word you would use the moment you heard it. Just one of the human traits. Like talking about a sharp taste. Mostly warmth is indicative of low order even harmonic distortion. Think a nice fat cello sound. (And there I go using another simile.)
Mark Levenson sold his company long ago and it is now part of the Harmon group. They still make stupidly expensive top end audiophile gear. Harmon also brand their top end in-car gear as Mark Levenson. My Lexus has Mark Levenson branded audio, it is pretty good. Most car manufacturers have a tie in with a name brand audio company now. For some it is little more than badge naming, others it is more serious.
I can make a sound “warm” by some careful EQing in the middle-low range. Adding a tiny bit of echo will help, too.
there are tons of audio descriptors which use words that don’t seem to apply to things you’d hear. “tinny,” “thin,” “tubby,” etc.
a “warm” sound usually means the upper midbass is enhanced relative to the rest of the spectrum. and people say tubes sound “warmer” because the distortion they add is mostly 2nd harmonic.
yes, but it goddamn well better be for those prices.
they appeal to people who buy their audio equipment by the lb.
But made a very nice radio when detached from the car. Power supply rejection was exceptional, noise rejection was exceptional.
Tell me about it. I dropped a modern radio into my 68 Mustang. It’s on the same circuit as the dash lights so I’ve go no console displays at night if I turn on the radio.
I’m working on it.
Huh? Does not parse at all.
Besides being factually wrong – see the links above to tube radios – it’s conceptually wrong too.
The world is full of dumb-shit ideas and products that make millions of dollars. One would think that a product being really dumb would be a barrier to manufacture and sale, but no. May I remind you of Billy Bass, the wall-mounted singing fish. 
were any of them offered as factory equipment? 'cos that’s what I took the OP as asking.
I took it to be the manufacturers of the stereos, but it makes for another interesting question. Suppose Porshe made one of these things standard equipment in their models. I wonder how much overlap there is between supercar buyers and obsessive audiophiles? If it was me, and I learned that my hundred thousand dollar plus car had a radio with tubes, I’d start shopping for another car.
My sense it that if this fact became widely known, Porshe dealers would have to spend more time selling their customers on the radio than the car.
Porsche is probably the wrong example. Rolls Royce, Bentley - closer. As an option of course. Those cars are built to order and the options and customisation list is so long and so expensive you can literally spend hundreds of thousands. The audio systems they offer are already insane - and include things like a custom DSP system from Dirac that alone would cost a few thousand just to licence the software. Offering a tube based amplification package would probably work. They would only sell a few, but would also charge tens of thousands for it. It would need to be a top end name brand system. Marketing wise - it would probably work. When your car is already well over two tons, who cares about the additional mass?
I’m pretty sure I have a couple of old Blaupunkt VW radios that have tube amplifiers.