Carver Crimson 275 Review (Tube Amp)

[Gringoaudio1]

I have been... the kitchen was gutted and redone to code. Family room as well when it was done. The issue now is I need a new panel installed, and that is way above my pay grade.

A new 100Amp panel installed at my 1957 house was less expensive than a Carver Crimson 275!

 

[john2017]

A new 100Amp panel installed at my 1957 house was less expensive than a Carver Crimson 275!

I need a 200 amp service relocated from where it is, plus a whole house rewire

 

[Gringoaudio1]

I need a 200 amp service relocated from where it is, plus a whole house rewire

So basically gut your house interior. Huge.

 

[amirm]

Do those Carver 275's have bottom cover plates on the chasses? I would hope so. My home brews do.

Yes, they do.

 

[Billy Budapest]

Wowow. ASR is becoming tubular.

I would actually like to see a tube circuit that measures decently well in most commonly-tested parameters. Is that possible?

 

[Urib]

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.
View attachment 179227
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:
View attachment 179230

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:

View attachment 179235

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:
View attachment 179238

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:

View attachment 179239

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:
View attachment 179241

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:


View attachment 179242

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:

View attachment 179243

Company spec is quite good for noise level relative to full power. I could not get that without a-weighting:

View attachment 179244

But applying the a-weighting filter and with it, getting rid of power supply noise, we do essentially get there:

View attachment 179245

Crosstalk was poor:
View attachment 179246

Frequency response has an odd shape and good bit of loss at high frequencies with 4 ohm load:
View attachment 179248

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:

View attachment 179247

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:

View attachment 179249

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:
View attachment 179250

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:
View attachment 179251

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:

View attachment 179252

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:

View attachment 179254

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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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Thanks! Good you're back.

 

[Doodski]

I would actually like to see a tube circuit that measures decently well in most commonly-tested parameters. Is that possible?

I have no idea. I justtt missed the entire tube era when it was common. I never serviced a tube amp in my life.

 

[Blumlein 88]

I would actually like to see a tube circuit that measures decently well in most commonly-tested parameters. Is that possible?

The McIntosh MC275 isn't solid state good, but pretty good in general.

McIntosh MC275 power amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

Wolcott power amps supposedly measured near good solid state though I've never seen a complete set of measurements.

Dick Olsher: Wolcott Audio “Presence” Monoblock Tube Amplifier

Enjoy the Music.com Review Magazine

www.enjoythemusic.com

Tube Amplifiers - Vacuum Tube Amplifiers - Loudspeakers - Wolcott Audio Research

Tube amplifiers, vacuum tube amplifiers, distortion-free speaker systems and more are the specialty of this boutique electronics firm renowned for its innovation in audio research.

www.wolcottaudio.com

 

[Blumlein 88]

Though I am not aware of them ever being used for audio, they did make vacuum tube op amps. Seems one could recreate them and create a very low distortion wideband amp if one chose to do so. These were made in the 1950's for use in analog computer circuits.

http://www.philbrickarchive.org/k2-w_refurbished.pdf

The Philbrick Archive

 

[Zackthedog]

I would actually like to see a tube circuit that measures decently well in most commonly-tested parameters. Is that possible?

Well, It depends on what you mean by "commonly tested parameters." Are there tube amps that measure well? Sure there are--lots of them. You're almost always going to get higher THD and S/N ratios, to some degree, but I don't think that's a disqualifier. They're also very ineffiecient, of course. In terms of flat response across the audible spectrum, a well-designed tube amp can do very well.

Here's a triode Williamson with a Peerless OPT I just built for a friend, measured at 1 watt.

Square waves are very handsome at 10kHz and 40Hz, respectively:

It's very stable and has great realism and authority on efficient speakers. Transient response is good and low-frequency stability is very good. Power is 12wpc in the midband and 10wpc at the extremes, but that's the Peerless OPT. Some would consider this a poor weight-to-power ratio. But then look at the Carver. ;-) An Acrosound OPT will do better in terms of HF power bandwidth, but the Peerless has a sonic heft and solidity that the Acros don't. The Acros are also *much* harder to tame on the high end--multiple peaks and anomalies threatening stability.

For more power, look at the Macs, Eicos, ARCs, Fishers, Conrad-Johnsons and other well-made amps. Properly restored (and sometimes tweaked) they measure very well where it counts. ;-)

These amps I built, wired for ultralinear, will measure just as well with 22wpc. And these are VERY honest measurements, mind you. I don't count when they go into clipping, as harmless at that might be in a tube amp. ;-)

The output transformers are the key to any good tube amp. Without a good OPT nothing else really matters.

ETA: By "triode Williamson" I mean a classic push-pull, triode-wired KT66 amplifier. For those who are interested, here's the exact model for my amp with the same output transformer and a slightly modified power supply (one choke less, a higher B+), some stabilizing circuitry added, and using KT66's instead of 807s. You can see the fuller measurements here:

http://oestex.com/tubes/mus_amp%20.pdf

This was the first American adaptation of the Williamson design--an outstanding amplifier for it's day and holds up very well now.

 

[Zackthedog]

Oh, and here's a pic of the products--Delrin top plates on my "inimitable" home-made oak bases (I am NOT a woodworker). ;-)

 

[Zackthedog]

Though I am not aware of them ever being used for audio, they did make vacuum tube op amps. Seems one could recreate them and create a very low distortion wideband amp if one chose to do so. These were made in the 1950's for use in analog computer circuits.

http://www.philbrickarchive.org/k2-w_refurbished.pdf

The Philbrick Archive

This is marvelous!

 

[Zackthedog]

Oh, and here's a pic of the products--Delrin top plates on my "inimitable" home-made oak bases (I am NOT a woodworker). ;-)

View attachment 180107
View attachment 180109

Oh, and BTW, that Sprinkle and Sarser article I linked to is another example of HONEST marketing back in the day--even when they had nothing to sell! The specs they cite are completely realistic and will correspond to any measurement you want to make of this amplifier. They treated their fellow audiophiles with dignity and respect.

 

[Zackthedog]

The McIntosh MC275 isn't solid state good, but pretty good in general.

McIntosh MC275 power amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

Wolcott power amps supposedly measured near good solid state though I've never seen a complete set of measurements.

Dick Olsher: Wolcott Audio “Presence” Monoblock Tube Amplifier

Enjoy the Music.com Review Magazine

www.enjoythemusic.com

Tube Amplifiers - Vacuum Tube Amplifiers - Loudspeakers - Wolcott Audio Research

Tube amplifiers, vacuum tube amplifiers, distortion-free speaker systems and more are the specialty of this boutique electronics firm renowned for its innovation in audio research.

www.wolcottaudio.com

Wolcott!! I'd forgotten all about him. Now there's an esoteric designer who pretty much delivered what he promised.

 

[Zackthedog]

The McIntosh MC275 isn't solid state good, but pretty good in general.

McIntosh MC275 power amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

Wolcott power amps supposedly measured near good solid state though I've never seen a complete set of measurements.

Dick Olsher: Wolcott Audio “Presence” Monoblock Tube Amplifier

Enjoy the Music.com Review Magazine

www.enjoythemusic.com

Tube Amplifiers - Vacuum Tube Amplifiers - Loudspeakers - Wolcott Audio Research

Tube amplifiers, vacuum tube amplifiers, distortion-free speaker systems and more are the specialty of this boutique electronics firm renowned for its innovation in audio research.

www.wolcottaudio.com

Interesting! Now compare all those to the original Williamson I posted above, tested at the same output level (2.8 volts RMS or 1 watt). The Williamson, despite it's low power and hefty weight-to-power ratio, was an astonishing achievement. Of course, you got a lot more for your money, powerwise, with a Mac, but still, the Williamson was really something. The first truly wide-bandwidth consumer amplfier.

 

[anmpr1]

Wolcott!! I'd forgotten all about him. Now there's an esoteric designer who pretty much delivered what he promised.

My experience with Wolcott was limited to a colleague who was 'dealered' out of a lot of money. But I think he was happy. I guess we need more happiness in the world, in spite of whether happiness is based on naive stupidity.

He bought a large set of Doc West's Sound Lab electrostatic speakers. Huge panels. The dealer convinced him that the 'only' way to listen to them was through Wolcotts. But not the 'stock' amps (they were mono). Those weren't 'good enough'. Had to be re-tubed with special high performance glass (don't recall the brand). Not only that, in order to get the full magic, he had to buy 'special' wire to 'match' the amp to the speakers. Plus... (it gets better), the special hook-up wire had to be 'lifted' off the floor (carpet) using x-tra special 'risers', which looked like ceramic insulators you used to see on telephone polls, back in the '50s.

How did it sound? Nothing special. Listening position was too up close; the speakers were too large for the room, so it was kind of like listening to headphones.

Tell me why I hate tweako dealers?

The amp itself had some sort of self-biasing circuit that worked its magic when you turned it on. LEDs flashed (as I recall), and a minute or so later your system was ready. I have no idea what it cost. But retubed, and with the rest of the ancillary package, it certainly wasn't cheap.

 

[Blumlein 88]

The Wolcott P280 was $7k. As for dealer adding to that with goofy stuff, you can't blame the amp for that.

 

[Zackthedog]

My experience with Wolcott was limited to a colleague who was 'dealered' out of a lot of money. But I think he was happy. I guess we need more happiness in the world, in spite of whether happiness is based on naive stupidity.

He bought a large set of Doc West's Sound Lab electrostatic speakers. Huge panels. The dealer convinced him that the 'only' way to listen to them was through Wolcotts. But not the 'stock' amps (they were mono). Those weren't 'good enough'. Had to be re-tubed with special high performance glass (don't recall the brand). Not only that, in order to get the full magic, he had to buy 'special' wire to 'match' the amp to the speakers. Plus... (it gets better), the special hook-up wire had to be 'lifted' off the floor (carpet) using x-tra special 'risers', which looked like ceramic insulators you used to see on telephone polls, back in the '50s.

How did it sound? Nothing special. Listening position was too up close; the speakers were too large for the room, so it was kind of like listening to headphones.

Tell me why I hate tweako dealers?

The amp itself had some sort of self-biasing circuit that worked its magic when you turned it on. LEDs flashed (as I recall), and a minute or so later your system was ready. I have no idea what it cost. But retubed, and with the rest of the ancillary package, it certainly wasn't cheap.

Ah, well. Speakers too large for the room is a very common problem with a lot of audiophiles, IME. And I've heard a lot of very expensive systems that sounded "just okay"...or worse. Dealers who constantly upsell, well beyond the customer's ability to even begin to understand what he or she is buying, is also common, unfortunately.

I have an audiophile friend who is constantly buying tweaky things and adding them to his system. When I lived nearby, he would call me and say nothing was sounding right, so I'd go over and remove all the tweaky gadgets and things would sound okay again.

 

[anmpr1]

The Wolcott P280 was $7k. As for dealer adding to that with goofy stuff, you can't blame the amp for that.

I certainly don't blame Wolcott for the dealer's actions. I understand they have to keep the doors open, but really... (I rank high-end dealers just a tad above car dealers, and probably below most politicians. I'm not sure what is worse, spending extra dollars on fancy cables, or getting the undercoating and nitrogen? Speaking of, would helium and/or hydrogen make your tires lighter? )

Here's a funny addition (I thought it was funny, at least) to the story. Along with the rest of the gear, the dealer sold him a special CD player made in France. Why anyone in the US would want a French CD player was a mystery to me, but he did. We were listening for a few minutes when he left the room in order to answer a phone call, leaving me alone. I had brought with me a backpack holding some demo CDs, and inside was a Panasonic battery powered 'discman'. (I think I still have that in a closet, somewhere.) I don't know the model #, only that it had MASH on the flip top cover. MASH was some kind of 1-Bit noise shaping thing. I guess proprietary to Panasonic. Marketing 101.

I also had an RCA to mini plug in the bag, so on a lark I connected the little CD player to the pre (I honestly don't remember what preamp was in the system--I want to say it was a plebian B&K). When the owner came back he started to extol the sonic superiority of his French CD player. I actually felt sort of bad for him, once I told him that he was listening to a portable Panasonic.

 

[Blumlein 88]

I certainly don't blame Wolcott for the dealer's actions. I understand they have to keep the doors open, but really... (I rank high-end dealers just a tad above car dealers, and probably below most politicians. I'm not sure what is worse, spending extra dollars on fancy cables, or getting the undercoating and nitrogen? Speaking of, would helium and/or hydrogen make your tires lighter? )

Here's a funny addition (I thought it was funny, at least) to the story. Along with the rest of the gear, the dealer sold him a special CD player made in France. Why anyone in the US would want a French CD player was a mystery to me, but he did. We were listening for a few minutes when he left the room in order to answer a phone call, leaving me alone. I had brought with me a backpack holding some demo CDs, and inside was a Panasonic battery powered 'discman'. (I think I still have that in a closet, somewhere.) I don't know the model #, only that it had MASH on the flip top cover. MASH was some kind of 1-Bit noise shaping thing. I guess proprietary to Panasonic. Marketing 101.

I also had an RCA to mini plug in the bag, so on a lark I connected the little CD player to the pre (I honestly don't remember what preamp was in the system--I want to say it was a plebian B&K). When the owner came back he started to extol the sonic superiority of his French CD player. I actually felt sort of bad for him, once I told him that he was listening to a portable Panasonic.

Oh no you didn't do that to your friend or is he an ex-friend?

I think one of my friends had the same CD player. It was pretty as I recall, but they had their own damping on the disc table they were using, and the bearing went out after a couple years. A common problem for those players. I can't remember the name of it though. It was definitely French and had some review in the English hifi mags.