Peeking inside a Carver Crimson 275 Tube Amplifier

I question whether it was as much about "cheaping out" as it was about creating a *lightweight* yet powerful tube amp.  Small couping caps notwithstanding (they've gotten a lot smaller these days due to better manufacturing techniques), I'd propose that the amp is an experiment in just that.  The design isn't sloppy, as Gordon pointed out at AK, there's a lot of tailoring to accomodate the small output transformer.  Another point of speculation over at AK is that the lower octaves are reinforced by harmonic doubling, much in the way that old console stereos used small, low-wattage amplifiers coupled with large, highly efficient woofers in a resonant cabinet to create the feeling of low bass, albeit at higher distortion levels.

I'm firmly on the side of honesty in marketing.  I've also been building my own tube amps for 20+ years now and finally learned to use an oscilloscope to see what's going on and improve my projects.  If I set out to build a 75wpc amp I certainly wouldn't be happy with those measurements, and would seek to improve them.  *That said* I'm curious to know if jbhiller has actually tried the amp in his big room, and if so, how it sounded.  Maybe the damn thing works, I don't know.

jbhiller, don't swap out those resistors.  They provide "current feedback" from the output transformer, you won't gain anything by changing them.  To the contrary, some feel the amp might be improved by bypassing them.  Many amps in the 50's offered a similar arrangement, except with a variable resistor, to adjust the "damping factor," a way to "loosen" the amp's grip a bit to accomodate speakers with poorer bass response.

jbhiller, what you could do is run clip leads from each negative speaker terminal to the corresponding outer shells of the inout jacks, thereby bypassing this feature, and see if it sounds different.

I'll suggest some evaluation at this point.  IMO, the amp is cleverly designed to provide 17wpc continuous across the bandwidth at low distortion, with some pretty fair peak power into 8 ohms.  It's a "concept" amp, and as such it succeeds, IMO--a clever design, light weight, large under-biased output tubes that will last for years, current feedback to adjust for low-frequency speaker impedance swings.  Many people say it sounds great--and it probably does in many circumstances.  My old ProAc Response 2's only need 15 wpc to sound really nice in my room.  With the peak reserve, they'd probably be very happy with the Crimson (now Raven, apparently).

The problem is that the amp is sold at 75wpc 20Hz-20kHz at less than 1% distortion.  The amp clearly cannot meet those specs.  Jim Clark claims that only the sound matters--and he's right in some respects, but audiophiles aren't stupid.   Sound matters, but so do honest specs.  So Jim is in a terrible position.  An example of honest marketing from the days of yore was posted above, with an eye on the intelligent buyer (and he had to have some deep pockets back then) who valued technical competence as well as sound.

jbhiller, the only answer is, does the amp work for you at the price you paid?  

Many years ago, I built a pair of single-ended 845 monoblocks for a friend.  He uses them with some old Gallo towers (remember those?)  By any technical measure they shouldn't have worked--but they do, and he still uses them with great pleasure.  No less than David Berning actually paid me a compliment on the amps.  So there are anomalies in this world of audio.

OMG!  I just noticed you have a Doge DAC 7!  I LOVE mine.  I only know one other person who has one.  What tubes are you using in it?

But regarding the Crimson, I'll bet a case of nice Oregon wine that a classic Williamson--like the Heathkit W2, W3 or W4--would beat that Carver hands down on your Cornwalls.

@jbhiller I also use Brimar 12AT7s, and the Gold Lion 12AX7s.  No noise problems yet.  I *did* have an issue shortly after purchase--one channel developed distortion.  After some inital hassle (Covid was just appearing in China) I managed to get the schematic, and our technician at work repaired it for me.  It had some bad current-source transistors at the output.  He ordered a batch and replaced them all with matched ones.  So if you ever have trouble with yours I do have the schematic.