Peeking inside a Carver Crimson 275 Tube Amplifier


So, I just had to pop the hood on the Carver Crimson 275 tube amplifier. I was so curious as to how this little guy weighs so little and sounds so lovely.

  • The layout is simple and clean looking. Unlike the larger monoblocks (that cost $10k), this model uses a PCB.
  • The DC restorer circuit is nicely off to one side and out of the way. It doesn’t look all that complicated but I’m no electrical engineer. Why don’t more designers use this feature? It allows the power tubes to idle around 9.75w. Amazingly efficient.
  • The amp has very good planned out ventilation and spacing. No parts are on top of each other.
  • Most of the parts quality is good. There’s a host of Dale resistors, what look like Takmans, nice RCA jacks, heavy teflon hookup wire, and so on.
  • Some of the parts quality is questionable. There’s some cheap Suntan (Hong Kong mfr.) film caps coupled to the power tubes and some no name caps linked to the gain signal tubes. I was not happy to see those, but I very much understand building stuff to a price point.
Overall, this is a very tidy build and construction by the Wyred4Sound plant in California is A grade. I’m wondering a few things.

Does the sound quality of this amp bear a relationship to the fact that there’s not too much going on in the unit? There are very few caps--from what this humble hobbyist can tell--in the signal chain. And, none of these caps are even what many would consider decent quality--i.e. they aren’t WIMA level, just generic. This amplifier beat out a PrimaLuna Dialogue HP (in my room/to my ears...much love for what PrimaLuna does). When I explored the innards of the PrimaLuna, it was cramped, busy and had so much going on--a way more complicated design.

Is it possible that Bob Carver, who many regard as a wily electronics expert, is able to truly tweak the sound by adding a resistor here or there, etc.? Surely all designers are doing this, but is he just really adroit at this? I wonder this because while some parts quality is very good to excellent, I was shocked to see the Suntan caps. They might be cheaper than some of the Dale resistors in the unit. I should note that Carver reportedly designed this amp and others similar with Tim de Paravicini--no slouch indeed!

I have described the sound of this amp as delicious. It’s that musical and good. But, as our esteemed member jjss [ @jjss ] pointed out in his review, he wondered if the sound quality could be improved further still. He detected a tiny amount of sheen here and there [I cannot recall his exact words.] even though he loved it like I do.

I may extract the two .22uF caps that look to be dealing with signal related to the 12at7 gain tubes and do a quick listening test.
128x128jbhiller

first i would say this thread is nice in that folks raising issues, and @jbhiller and i as current owners of these amps chiming in with thoughts and info, are keeping it positive and cordial - i think that is important, we can see other threads being much less so, and that can be become awfully unpleasant

second, i think to j-b’s comment about pricing of the 275, my own take is that the carver principal(s) were careful to choose their price point, knowing a higher one would considerably reduce their market interest, and i think that is also why they chose to skate on thin ice to write 75 wpc - that was the desired proposition: light amp, kt120’s, $2750 new, 75 wpc, drive most real speakers in real rooms to real volumes - thusly can undercut alot of the competition with a superior value propositon - whether they did this (the power rating specifically) ethically is a fair question -- for me, as an illustration, i bought the amp a touch under $2000 used - had it been a $4000 retail amp, selling for $3000 used, i may well have not gone for it

third, i would just reiterate that in my experience and use, i am not using super efficient speakers - spendor sp100 r2 @ 89 dbwm 8 ohms nominal, harbeth monitor 40.3 xd and shl5+ both @ 86 dbwm 6 ohms - in my 19x17 dedicated room, speakers well away from room boundaries - the amp drives all the speakers very well (i listen at low to mid 70’s db average with 80+ db peaks), has terrific bass response... not bass like a pass or a hegel, but roughly as good as much more expensive tube amps such as my audio research ref series -- how it does it, with xyz feedback circuitry, maybe it is managing the distortion, maybe it is playing some nice sounding distortion, but to my ears it works very well for a tube amp, sounds very good - good detail, excellent warmth and imaging, nice drive/prat - just what one would seek from a tube amp

last point i would add, and a bit of re-emphasis on what j-b said earlier, bob carver has always been an ’against the conventional grain’ type of character/designer in the audio world, he does things differently, thinks very much out of the box, so to speak... if one understands his long history (as i do, i have been at this as an avid hobbyist since the early ’80’s), he is never been shy to push the envelope -- more often than not, he can back it up... so we shouldn’t be surprised this amp with his name on it follows that tradition - importantly, at least in my case, the amp performs, making very good music to real volumes capably

all this said, the stated specs should be honest, and that may well be on bob carver himself, at his current ripe old age, or the folks running the business at present

+1 JJSS49 on how we are keeping it cordial and respectful.  It makes the thread so much more informative and entertaining.  I love the differing opinions, especially those that differ from my own.  

@grovergardner , I didn't know that about console systems of yore.  Very interesting!

The original coupling caps in this unit were really unimpressive.  Take a look on my system page (even though the page is out of date), I have a pic of the original caps. They are the size of a fingernail!  There's a good bit of juice going through them per my tests and the schematic.  I really didn't like seeing that quality on such an important spot on the board. 

Take a look at this--same brand in the 275:   

 

It's a video of a Suntan cap blowing up.  Not acceptable in my book to use these.  You can always find an inexpensive but quality Wima, right?  Nelson Pass stuff is loaded with nice WIMAs and so are many other great brands. Why skimp here? Suntan? I wouldn't put it in an old guitar amp. :)

It's a video of a Suntan cap blowing up.

Those are electrolytics, quite different from what is used for coupling caps in tube gear!

 

Yes, indeed they are Ralph.  It's just an exhibit in support of the point that Suntan caps are super cheap.  If a company's electrolytic blows up so easily how good can their even cheaper film cap be?  But for our education, yes a coupling cap is different than electrolytic AND this cap blowing up is not the same as the coupling caps in the Carver 275.  

The takeaway was supposed to be.... Why use Suntan at $.80 a cap?  Could they not use a better quality cap?  I mean what are you saving by using it versus a Wima or Vishay?  $5-10 per amp?  

Status update--The ASR guys have their Carver 275 now and testing should occur shortly.  The odds do not look good that it will test much much differently on specified wattage, but maybe, just maybe, the distortion results will be better.