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

@jbhiller

😥

Thanks for that, though. Now we might expect some sort of tug of war over what constitutes acceptable bandwidth at power, THD limits, and measuring setups - and how this should all filter down to single power #. It’s perhaps interesting to look back at Heathkit W5 manual from 1959 and all the wonderful measurement curves provided right in the manual (the bandwidth looks very good for a 25 Watt rated tube amp):

To be fair my VAC amps don’t exactly measure stellar either - and I enjoy them regardless.

Thanks @tomic601 

@mulveling , you make good points. It's still a fine little amp.  One of the biggest reasons I purchased it was its ability to drive all sorts of speakers.  I seriously question it can drive a 4 ohm load at 75 watts even at peak power.  But, I'll leave that for the testing experts and true electrical engineers.  

I don't know anything about circuits or amplifier design....this is from the Carver website...take a look at pages 11-13 and their description.

https://9d0691c9-2bb0-4a51-acf2-a4e121ccc931.filesusr.com/ugd/7c4708_fe81ce14b4b54e618bcfd77c7628d241.pdf

What I can say is that I heard the 275 at the Florida Audio Expo...one year playing the KEF Blade 2's and one year playing the Amazing Line Source...and those two combos sounded pretty darn good. 

@snapsc
From the manual specs section, on power:

More than 75 Watts Per Channel, both channels driven at eight ohms, from 20Hz to 20kHz with no more than 1% total harmonic distortion. Distortion decreases at lower levels.

Oh my - it spec’d the rated power at both channels driven, full musical bandwidth, and 1% THD. That doesn’t leave much room for interpretation, and it’s going to be one hell of a tall order for those little OPT’s 😬