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Carver Crimson 275 Review (Tube Amp)

Rate this amplifier

  • 1. Poor (headless panther)

    Votes: 366 95.6%
  • 2. Not terrible (postman panther)

    Votes: 5 1.3%
  • 3. Fine (happy panther)

    Votes: 4 1.0%
  • 4. Great (golfing panther)

    Votes: 8 2.1%

  • Total voters
    383

Gorgonzola

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I'm no technical expert but this amp seems shockingly bad in just about every respect.

Was this amp really designed by Bob Carver? Wasn't he the guy who said he could design solid state amp that sound like any given tube amp, (or something like that)? What would he be doing designing a tube anyway?

I would like to see some measurements of, hopefully, more competent tube power amps. In particular there are various Dynaco ST-70-inspired amp, a very popular one being Bob Latino's VTA ST70. I'd love to see some measurements for that: maybe there's an owner here who'd step up :) I'd bet it would far out shine the more or less vintage Dynaco Amir tested some time ago.
 

mhardy6647

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You cannot simulate low damping factor amp - speakers interaction :)
Actually, that's extremely easy -- just add a low value (noninductive) power resistor in series with one leg of the loudspeaker cabling. Folks typically use 0.5 to 1 ohm.
voila.

There are folks who actually do this (or at least have tried it... sorta like drugs, I guess) -- so don't laugh too hard. ;)

some goolgled examples (in no particular order nor endorsement from me!):
https://community.klipsch.com/index.php?/topic/173976-tube-sound-from-your-solid-state-amp/page/2/ (this one's somewhat off-axis, but it's Carver-centric, so that's fun)

EDIT: Or you can do it the right way, as suggested by @SIY -- I presume(?) that's the way variable damping controls on vintage amplifiers work(ed).

Has one very unique feature it knows how listen the room. No other amplifier that listens the room and modifies it's signal and soundstage to make the room as glorious that can possible be done with the musical sound stage.' -Bob Carver

What? Was this a joke?

My inferred translation of this prose -- "We gave the amplifier a high output impedance (1.7 ohm, if I interpret the printed specs correctly) so that it's extremely sensitive to the impedance curve of the loudspeakers to which it's connected."

I'll just mention (and @paulbottlehead may know the "right answer") that I believe that my zero NFB, SE DHT (2A3) Bottlehead Paramour amps have an output impedance on the order of 1 ohm. :)
 
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L0rdGwyn

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Many of these commercial tube amplifiers really do feel like cash grabs. Like moths to the flame, the audiophiles are drawn to the glow of the tubes! But when I look inside the mostly empty chassis...where is the power supply regulation? Active loading? Proper layout and grounding? I am no engineering genius, these things are simple to implement, low cost, and drastically improve performance. The best tube amplifiers are being made in the DIY arena, in my opinion, where one doesn't have to worry about profit margins and can afford to add a $20 voltage regulator to a design. Maybe even properly rated output transformers. These commercial tube amplifiers are giving my dear tubes a bad name.
 

DSJR

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This would be terrible for a cheap product, but inexcusable for nearly $3k!. Bob Carver should be embarrassed and ashamed of his name being on this.

From a Brit perspective, I wonder how it compares with an original (1950s) Quad II or Leak TL12.
Neither would be that wonderful, as in the case of the Quad, PW explained in at least one interview that his work in 'listening' to his earlier designs was to try to 'tune' distortions away from our most sensitive frequencies so hopefully they wouldn't be noticed. I have a set of (Glenn Croft) rebuilt Quad II's here and into more lively speakers than the 'Thunderboxes' I current need to use, they sound absolutely 'glorious' I have to say (so does the good-example 303 here, but we're talking valves so shan't go further). The TL12's I borrowed were really odd. Connect to a different speaker and they sounded 'odd' for half an hour, after which they seemed stable enough. Go back to the original speakers and these too sounded less good for half an hour. No idea what was going on electrically, but at the time I found it repeatable, so *hopefully* not merely 'sighted shenanigans.'

My now older Brit perspective wants some of the better E.A.R amps tested and for the subjective based forums, the ever recommended Leben boxes which hide the valves behind a dated looking front panel. PrimaLuna (another bad measuring but popular unintentional? equaliser-amp) seems to have been amply covered in Stereophile.
 

NHL99

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The Carver Challenge


'the listening went on through the whole afternoon and much of the evening, until all of us were listened out. More leisurely listening, refreshed by a good night's sleep, failed to turn up anything. As far as we could determine, through careful comparisons and nit-picking criticisms, the two amplifiers were, in fact, sonically identical. It is a gross understatement to say that we were flabbergasted!'
 

anmpr1

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The Carver Challenge


'the listening went on through the whole afternoon and much of the evening, until all of us were listened out. More leisurely listening, refreshed by a good night's sleep, failed to turn up anything. As far as we could determine, through careful comparisons and nit-picking criticisms, the two amplifiers were, in fact, sonically identical. It is a gross understatement to say that we were flabbergasted!'
There are, however, certain common-sense limitations to the Carver t-mod technique that should be understood. For openers, the amplifier to be modified must have a power supply as good as, or better than, that of the reference (or target)... For example, if the Stereophile people had been smart enough to designate the Krell KMA-200 mono amplifier as a reference unit... Bod would have had to throw in the towel. His amplifier and the Krell are both rated at 200/watts into 8 ohms, and 400/watts into 4 ohms... the Krell, however, can deliver 1600 watts into 1 ohms, and is not bothered by a load of 0.1 ohm... The Carver magnetic-field power supply... gives up the ghost much sooner. Audio Critic #10.

When I first read about Bob's tube amp, and his claimed power rating, I presumed he was using some variant of his 'mag field' operation in order to deliver higher wattage than would normally be the case with a small tube amp.
 

Aperiodic

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What the man in question thinks about it:


Edit:
As I said, as others have pointed out in this thread. If you are going to have a tube amp, buy a well-proven classic like Dynaco, for example, or a brand / model that is sensible and popular in the country you live in.:)

By the way, I think tube amps are best suited for tube amp DIY people, who like to keep on tinkering.:)
Wow. Just wow. To see a man with Carver's track record and reputation stand there and spew grade-A horsesh!t like "it listens to the room" is depressing. On the other hand, perhaps Amir's bench load couldn't 'listen to the room' like a loudspeaker and that explains the poor measurements?
 

Labjr

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Maybe run the AC with the heat on to dry the room out.
 

Koo

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All loudspeakers generate voltage as they play. It’s generated from the driver movement necessary to reproduce music but also all loudspeakers technically “listen” to the room. Did you know that the loudspeakers in prisons are also microphones? It enables the authorities to monitor the prison’s pulse in real-time. All loudspeakers are microphones. You might not want to use one for recording but conceptually, they are microphones in reverse.

Loudspeakers are also electric motors. Electric motors all kick voltage back to the power source whether it’s a loudspeaker, a refrigerator or an electric drill. Manufacturers of line conditioners have a point. Your refrigerator motor not only adds noise to the AC line, they actually send electricity back through the wall outlet. We call this Back-EMF and it's unavoidable, due to the theorem of reciprocity. What's in the back-emf? The room sound!

With a tube type amplifier, when back EMF appears at the output terminals to the loudspeaker, the output transformer’s secondary becomes a primary! The back EMF enters the amplifier through the transformer and affects frequency response downstream. With ordinary tube type amplifiers, speaker matching becomes critical. Our amplifiers are load-invariant. Through decades of experimentation and some pretty heavy mathematics, Bob Carver has been able to use the Back-EMF to increase efficiency in the mighty SunFire subwoofers, and to improve the depth, soundstage and openness of our amplifiers. Solid-state amps discard the Back-EMF.
This is what the product page says about that. If it's true that the amplifier modifies the output based on the speaker kickback, I wonder how does the dummy load affect the system? Would be nice to see if Amir could test with a real speaker if that feature actually does something.
 

audio2design

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The inside looks pretty scary from a safety standpoint. AC wires nicely rubbing against sharp PCBs and untrimmed soldered leads. High voltage leads it looks like soldered to pads, not with a through-hole in some cases. It looks sub-DIY.

@amirm , you mentioned you had to ground the AP to measure. With that bizarre neutral connection in the amp, is there potential that caused issues with the low frequency measurement?
 

SIY

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This is what the product page says about that. If it's true that the amplifier modifies the output based on the speaker kickback, I wonder how does the dummy load affect the system? Would be nice to see if Amir could test with a real speaker if that feature actually does something.
It's not an actual feature, this is just a razzle-dazzle way of saying "it uses ordinary negative feedback." The Carver tradition is taking something simple and standard and dressing it up with fancy terms ("Magnetic Field Amplifier" "Sonic Hologram"), and that hasn't changed even under current ownership.
 

mightycicadalord

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Wonder what the resistor and cap on the speaker terminals are for.

Also is this thing even safe to use? What's with that grounding?
 

sergeauckland

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Actually, that's extremely easy -- just add a low value (noninductive) power resistor in series with one leg of the loudspeaker cabling. Folks typically use 0.5 to 1 ohm.
voila.

There are folks who actually do this (or at least have tried it... sorta like drugs, I guess) -- so don't laugh too hard. ;)
Some loudspeakers were designed to be driven by an output impedance higher than is normal for today's amps. As a specific example, the Quad Electrostatic user manual advises the amp should have an output impedance of 1-2 ohms, in series with 30-40uH, which happens to be the output impedance of a Quad II amplifier, around which the ESL was designed.

There is some anecdotal evidence that Tannoy 12" & 15" dual-concentrics like to be driven from a 1-2 ohm output impedance, but I've never seen anything properly documented, so it may just be internet talk, but again they were designed at a time when amplifiers had that sort of output impedance.

S.
 

SIY

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Wonder what the resistor and cap on the speaker terminals are for.

Also is this thing even safe to use? What's with that grounding?
Stability. It's a pretty standard Zobel.

Not a chance I would use a device like this missing a safety ground. Nor should anyone else. Inexcusable, this is Safety 101.
 

sergeauckland

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Wonder what the resistor and cap on the speaker terminals are for.

Also is this thing even safe to use? What's with that grounding?
That's a zobel network. (SIY beat me to it!) It's purpose is to ensure that the amplifier sees a load at high frequencies when loudspeakers, being mostly inductive, tend to go high impedance. It's especially important with valve amplifiers, as maintaining a load helps with stability, but also to protect the output transformer. That's why valve amplifiers shouldn't be used without a load.

S.
 

AndreaT

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What is the excuse for thin loudspeaker wires? In a $ 2,750 + tax amplifier? It is time for most US manufacturers/designers to wake up to the competition from better engineering, better quality of parts and better prices. Headless panther, maybe even a limbless one. Great to see you back Amir!
 

Labjr

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What is the excuse for thin loudspeaker wires? In a $ 2,750 + tax amplifier? It is time for most US manufacturers/designers to wake up to the competition from better engineering, better quality of parts and better prices. Headless panther, maybe even a limbless one. Great to see you back Amir!
Need to add Roadkill Panther!
 

Steve Dallas

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This review makes me fall in love with my Dynaco MKIIIs all over again. :D

View attachment 179292

Would love to take some measurements of that thing--especially in the realm of channel matching. Carbon comp resistors... Yeesh! With modern components it could be sooooooooo much better!

As a former designer of tube guitar amps, I can confidently say the subject of this review is a broken design and execution. It has no virtues at all--even as a tube amp. The most glaring thing that should not be happening is blowing fuses, which is a symptom of a design problem or at least one faulty component. I would expect to see twice the fuse rating on the mains, unless this is some kind of "low current" design, which is laughable in the tube realm.
 

SIY

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What is the excuse for thin loudspeaker wires? In a $ 2,750 + tax amplifier?
That wire might add 4-5 milliohms to the source impedance, totally swamped by the source impedance of the amp itself. Esthetically questionable, but electrically no big deal.
 
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