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
@jjss49, 

Sure thing.  

1. Output Coupling Caps:  

Four (4) .68uF 630v ClarityCap CMR
Four (4) .1uF 630v ClarityCap CMR

Available at PartsConnexion.

2.  2 Caps on Pre/Gain Tubes.  Note, I don't have a schematic so I'm taking my best guess as to what caps ore on the signal input side of things. 

Available at VCap. 

Two (2) .22uF V-Cap CuTF 300v (matched to at least 5% or lower)

3.  Resistors 

Two (2) 36k ohm (36kR) 5watt. Kiwame
Two (2) 39k ohm (39kR) 5 watt Kiwame

Available at PartsConnexion. 

***********

Some notes:  

If I did this again, I might use VCap ODAMs throughout.  They are so amazing.  ClarityCaps are very good to excellent too and I adore their sound as well.  ODAMs can sound better than even the VCap CuTF to me. 

Your tech is probably better and smarter than I.  But, those two sets of 36k and 39k resistors right in the middle of the board are placed counterintuively.  They do not seem to be symmetrically placed to the circuit.  Even though I took photos in case I needed to see the original layout, I still installed one channel's 36k and 39k resistors incorrectly--I swapped them.  Well, that channel was super faint as an extra 3k ohm of resistance (I had a 39k where a 36k should go) made the output too low.  Takeaway--be sure to follow exactly how they are in there to begin with.  It's easy to do one side/channel and mirror it on the other, which is incorrect.  You won't blow anything up, but it won't work right and you'll know it.  

Here's a photo from my virtual system for your tech. https://systems.audiogon.com/systems/9364#&gid=1&pid=7

PS--There's no need to duplicate exactly what I did.  Any decent cap will be an upgrade over the cheap, generic caps that were in there.  

There's a couple of giant Dale dark grey/black resistors on the input side of things.  I suppose you could look at Mills, Ohmite, etc. 
many thanks jb... info and your points all noted  👍🏻👍🏻👍🏻

@fmalitz Frank thank you for this response.. however I’d like for you to respond to why the 275 does not even come close to its specs? Why does an amp spec’d for 75 watts per channel only put out 17 wpc? Why are the transformer covers very large fake covers over very small transformers that are only capable of 15-18 wpc?

I almost bought a 275. I am glad I did not, seeing how I know from experience that my speakers need at minimum 75 to 100wpc. Can you imagine how angry I would have been finding out it can only put out 17 wpc?

 

I visit Audiogon often but hardly ever post.. I was moved to post this question. I’d like an honest answer.

The 275 is under scrutiny on at least four other audio forums as we speak. Interestingly on one, the negative comments are largely removed. I’m happy here we can have a warranted inquiry without censorship. I’m not sure why the forum mods are protecting truth on this other audio forum.. but the real measurements and specs are all over the internet like wild fire. Multiple sources sharing the same failures to meet published spec in epic proportion.

As a previous fan and owner of Carver products I’m anxious to hear the other side. My confidence has waned and I’m becoming bias with facts that will be tough to refute or explain.