This is a review and detailed measurements of the Carver Crimson 275 tube stereo power amplifier. It was purchased new by member
@paulbottlehead and given to me for testing. It costs US $2750.
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I really like the way the amplifier looks. The burgundy color is attractive as is the handle. On the latter, the unit is very light though so the handle while handy, is not necessary to lift the thing. Back panel shows high quality connectors:
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The tubes, four Tun-sol KT120, pair of 12AT7W and 12AX7 can in their original boxes for the owner installation. Went to open one of the small tube boxes but found nothing in it! Worried, I looked around and it had come out of its box and was just floating in the larger box that they all came in.
Prior to installation of tubes I had something to investigate: there was clearly something loose in there, rattling around. So I took the back panel off to find a metal screw rolling around in there:
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Not sure where it was supposed to go. There is a hole for something above the second fuse from the bottom but I think that would for a nut.
I did not like lack of safety (earth) ground from the IEC terminal:
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Instead, there is some kind of local, star grounding referenced to neutral using a resistor. That naturally won't work for safety purposes. With that power supply board mounted vertically with voltages as high as 300+ volts, I sure as heck would want this metal case grounded. I don't care what audio/electrical problem they were trying to solve there. I want a safe product first and foremost. Naturally there is no safety/regulatory certification which I expect a company with the name "Carver" to be able to afford.
I got a kick out of the beefy speaker terminals but ultra-thin wires leading to it! Yes, the lengths are short and at this wattage is probably fine but from "optics" point of view, you would want to use something better than hair thin wiring (see gray and red wires).
I was sad to see the VU meter glued to the case:
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I realize welding a couple of threaded stand-offs to the case costs money but at this price, I expect such. The meter is not backlit which was another disappointment. But was useful for checking bias which was right at the spec at 100 milliamps.
So nice looks but under the skin, a number of concerns.
Carver Crimson 275 Measurements
I usually let amplifiers warm up some and watch their behavior and also let things stabilize before measurements. Manual states that bias can be checked after 20 minutes so I let it run for that long and a bit more:
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Note that the vertical scale is only 3 dB so don't be alarmed by the variations. Generally speaking, unit is table after a couple of minutes of warm up. But it is fascinating to see performance gradually get worse as it kept warming up (again, at micro level).
So next comes our usual dashboard. My Audio Precision analyzer by default has floating (non-earth connected) RCA terminals. But I had to override that by grounding it as I observed oscillations (frequent occurrence with some amplifiers). No other attempt at grounding made a difference in power supply/mains hum:
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The power supply noise really dirties up the FFT spectrum but looking past that, we see that the low SINAD (sum of noise and distortion) is dominated by distortion. Unlike the common reputation for tubes, distortion is third harmonic for the most part, not second. Naturally the high level of distortion places the 275 very low in our scale, second only to one other amp ever tested:
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Company spec is quite good for noise level relative to full power. I could not get that without a-weighting:
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But applying the a-weighting filter and with it, getting rid of power supply noise, we do essentially get there:
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Crosstalk was poor:
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Frequency response has an odd shape and good bit of loss at high frequencies with 4 ohm load:
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Output impedance is high enough that is combining with the load to change the high frequency roll off. Things get better as such with an 8 ohm load:
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There is an RC filter on the speaker terminals. Wonder if that is what is providing the roll off.
Using 32 tones to simulate "music" we see a high level of "grass" which would obscure any low level detail:
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Notice how the worse performance is in low frequencies.
There has been controversy regarding ability of the 275 to produce its rated power of 75 watts so let's start with 4 ohm load as I usually do:
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The amplifier produced 29 watts after which it blew its 3 amp mains fuse. Fortunately two spares were provided, allowing me to continue testing. Company specs distortion at "less than 1%" so let's see power at that rating:
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Very dramatic difference between 1 or 2 second power (used for left side) vs short bursts. There is clearly a capacity problem to produce sustained power. Note that this is at 1 kHz as is industry convention. Note that allowing just 1% THD reduces the power even more than what I allowed in my power sweep.
I was surprised to not see selectable output impedance for 8 ohm load so proceed with the test as is:
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We blew the second fuse but now power is much more healthy at 60 watts.
Hoping to not blow the last fuse, I kept the max power level lower as I changed frequencies:
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Performance was "reasonable" (for at tube) but once we got down to 20 Hz, it became super erratic and blew the third fuse.
It produced only 14 wats which is well short of 30 watts it produced at higher frequencies. I would have wanted to test at more frequencies but it was past midnight and I did not feel like hunting around to find my own replacement fuses.
Conclusions
As a Carver owner of 40 years (solid state), I have a soft spot for the designer. Alas, while I like some things about this amp like the nice looking paint, I am very disappointed in the QC and construction of the unit with respect to safety. Loose screws and glued meters should not be part of a nears $3,000 amplifier. Measured performance is awful of course and one would expect that for many audiophile tube amps. But having third harmonic be dominant blows away the story of why that is audibly a good thing. Clearly the specifications of the amplifier is incorrect for 4 ohm load (company even allows usage for 2 ohm loads!). And low frequency behavior is very poor.
Unless you are going to buy the Carver Crimson 275 to just look at it, I can't recommend it for many reasons stated above. I expect more from the man, the legend....
P.S. It was nice to take a break from drying up our flooded home and get back to some "normalcy" with testing this amp. It cheered me up to be "working" again and doing what I enjoy.
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