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.
I question whether it was as much about "cheaping out" as it was about creating a *lightweight* yet powerful tube amp. Small couping caps notwithstanding (they've gotten a lot smaller these days due to better manufacturing techniques), I'd propose that the amp is an experiment in just that. The design isn't sloppy, as Gordon pointed out at AK, there's a lot of tailoring to accomodate the small output transformer. Another point of speculation over at AK is that the lower octaves are reinforced by harmonic doubling, much in the way that old console stereos used small, low-wattage amplifiers coupled with large, highly efficient woofers in a resonant cabinet to create the feeling of low bass, albeit at higher distortion levels.
I'm firmly on the side of honesty in marketing. I've also been building my own tube amps for 20+ years now and finally learned to use an oscilloscope to see what's going on and improve my projects. If I set out to build a 75wpc amp I certainly wouldn't be happy with those measurements, and would seek to improve them. *That said* I'm curious to know if jbhiller has actually tried the amp in his big room, and if so, how it sounded. Maybe the damn thing works, I don't know.
first i would say this thread is nice in that folks raising issues, and @jbhillerand i as current owners of these amps chiming in with thoughts and info, are keeping it positive and cordial - i think that is important, we can see other threads being much less so, and that can be become awfully unpleasant
second, i think to j-b’s comment about pricing of the 275, my own take is that the carver principal(s) were careful to choose their price point, knowing a higher one would considerably reduce their market interest, and i think that is also why they chose to skate on thin ice to write 75 wpc - that was the desired proposition: light amp, kt120’s, $2750 new, 75 wpc, drive most real speakers in real rooms to real volumes - thusly can undercut alot of the competition with a superior value propositon - whether they did this (the power rating specifically) ethically is a fair question -- for me, as an illustration, i bought the amp a touch under $2000 used - had it been a $4000 retail amp, selling for $3000 used, i may well have not gone for it
third, i would just reiterate that in my experience and use, i am not using super efficient speakers - spendor sp100 r2 @ 89 dbwm 8 ohms nominal, harbeth monitor 40.3 xd and shl5+ both @ 86 dbwm 6 ohms - in my 19x17 dedicated room, speakers well away from room boundaries - the amp drives all the speakers very well (i listen at low to mid 70’s db average with 80+ db peaks), has terrific bass response... not bass like a pass or a hegel, but roughly as good as much more expensive tube amps such as my audio research ref series -- how it does it, with xyz feedback circuitry, maybe it is managing the distortion, maybe it is playing some nice sounding distortion, but to my ears it works very well for a tube amp, sounds very good - good detail, excellent warmth and imaging, nice drive/prat - just what one would seek from a tube amp
last point i would add, and a bit of re-emphasis on what j-bsaid earlier, bob carver has always been an ’against the conventional grain’ type of character/designer in the audio world, he does things differently, thinks very much out of the box, so to speak... if one understands his long history (as i do, i have been at this as an avid hobbyist since the early ’80’s), he is never been shy to push the envelope -- more often than not, he can back it up... so we shouldn’t be surprised this amp with his name on it follows that tradition - importantly, at least in my case, the amp performs, making very good music to real volumes capably
all this said, the stated specs should be honest, and that may well be on bob carver himself, at his current ripe old age, or the folks running the business at present
+1 JJSS49 on how we are keeping it cordial and respectful. It makes the thread so much more informative and entertaining. I love the differing opinions, especially those that differ from my own.
@grovergardner, I didn't know that about console systems of yore. Very interesting!
The original coupling caps in this unit were really unimpressive. Take a look on my system page (even though the page is out of date), I have a pic of the original caps. They are the size of a fingernail! There's a good bit of juice going through them per my tests and the schematic. I really didn't like seeing that quality on such an important spot on the board.
Take a look at this--same brand in the 275:
It's a video of a Suntan cap blowing up. Not acceptable in my book to use these. You can always find an inexpensive but quality Wima, right? Nelson Pass stuff is loaded with nice WIMAs and so are many other great brands. Why skimp here? Suntan? I wouldn't put it in an old guitar amp. :)
Yes, indeed they are Ralph. It's just an exhibit in support of the point that Suntan caps are super cheap. If a company's electrolytic blows up so easily how good can their even cheaper film cap be? But for our education, yes a coupling cap is different than electrolytic AND this cap blowing up is not the same as the coupling caps in the Carver 275.
The takeaway was supposed to be.... Why use Suntan at $.80 a cap? Could they not use a better quality cap? I mean what are you saving by using it versus a Wima or Vishay? $5-10 per amp?
Status update--The ASR guys have their Carver 275 now and testing should occur shortly. The odds do not look good that it will test much much differently on specified wattage, but maybe, just maybe, the distortion results will be better.
The takeaway was supposed to be.... Why use Suntan at $.80 a cap? Could they not use a better quality cap? I mean what are you saving by using it versus a Wima or Vishay? $5-10 per amp?
Fair and intelligent question , ×hat are you really saving in cost?
That aside, even with its hundreds upon hundred of crystal clear watts (it tested ridiculously well), it couldn't beat out a nice Creek Evo Integrated of lesser power, driving all sorts of loudspeakers.
What do you mean by beat out?
Buying on stats alone wouldn't tell me that. Why ASR's zealot faction (not all of them) refuses to listen at all is beyond me.
Buying on stats alone won't tell you which amplifier you might prefer. I've read a lot of posts on ASR and I'm not aware of anyone especially Amirm that says buy on stats don't listen. Now if you make a claim that one amp measures or sounds better you will be asked if that's a personal opinion applicable to you or a general statement about the amplifiers themselves, if the latter you will be asked for your testing procedure. That's what a lot of people get wrong about ASR. There are members there who prefer tube amps, class A amps, lousy measuring speakers and DACs but they don't make universal claims about those products they know they're simply personal preferences.
Hi djones51, Yes, you are correct. I think that I was suggesting there are measurement zealots who don’t put much stock in the subjective side.
By "beat out", I meant in my room, my system, my music, my ears. These amps were not bad, and, in fact, I said that I would recommend them in that post. The point was supposed to be (and I probably didn’t make it all that well), but testing and stats can be very important or, sometimes, not that helpful. I’ve owned a few products that tested in the tail of excellence side of the bell curve--yet I didn’t keep them because they were "beat out" by other things.
For instance, take the glorious and wonderful KEF LS50. I loved them and wish I had them around still to play with. But they didn’t work quite as well in my particular application than did the much less expensive Wharfedale Denton anniversary. This is why so many of the folks here always say try to audition or get a forgiving in home demo.
I have certainly seen folks chime in on ASR (who are new to those parts) and make a comment or ask about sound and they get pushed aside because that’s subjectivity and the product in question already tested poorly per their results. I was also pretty certain that in the ASR testing thread of the Carver that there was no talk or commentary on how the machine performed in use. Maybe I am mistaken and someone on that thread who tested it used it with a couple of different speakers/preamps. I like hearing about people do that.
Some old British roadsters test poorly but are a joy to drive! Same can be true with hifi. Sorry if I’m not great at making such points. Not trying to litigate this just explaining what I meant.
@Charles1dad, I'm glad you understood what I was trying to convey. I mean I have no beef against a great cap like WIMA. Aren't they littered throughout nice products, like Audio Research, Pass, Vincent, and the list goes on.
A Suntan? Come on! I bought WIMAs and AmTrans for the first tube amp I built and they hardly broke the bank.
QUESTION: Bob, A guy is claiming a 275 makes 17 watts with strange distortion numbers any thoughts?
ANSWER: Thats ridiculous, a 75 watt amp.. Isn’t it obvious? It is being test wrong or its damaged.. My amps can be difficult to test, difficult to get the grounding correct. I’ve been dealing with people testing my designs wrong and getting grounding errors effecting measurements, most of my life.
Well, Bob has opened a can of worms. Grounding systems can be wily. I’m going to sit back and watch what ensues out there.
I do wholeheartedly agree with Bob in that the amp sounds big and sweet. It’s a fun ride regardless of what wattage it puts out. [I do question that it can reach anything near 75 watts based on my teardown.].
I bought one of these amps 6 months ago and absolutely love it-- great amp with a hefty bottom end and no complaints on power output but my speakers are 102db @ 1 watt in a 14x18 room. 95% of my listening is around 75db so I'm barely using any power.
@jjptkd, Glad you are enjoying it. Same here--my speakers are Cornwall IVs so my listening is not likely indicative of how the amp can pair with less sensitive speakers. It had no problem though driving Wharfedale Linton Heritage speakers.
No one will tear it apart. It will be measured to see if it meets advertised specs. Those who like the amp why wouldn't you still like it? Still interesting to see how it does on the bench.
Please note: this post is not related to testing but improving the amp.
Bob's response on the Carver forum identified R53 and R26 as doing the following:
"Note that one end of the resistor is connected to amplifier ground, the other to the negative binding post. Now just imagine what would happen if you connected the some test equipment to the negative binding post that turned out to be grounded to the amplifier ground. That resistor is important. It senses current going to the speakers and provides a signal into the feedback network that, among other things, reduces distortion in the amp."
As these are important resistors, I may swap them out and put in .1 ohm 5w Mills resistors, which are $4 each. Why? Because I'm nuts. :)
I’m bothered by the view point that we should just gloss over the big covers over little 15w trannies or it making less than 25% of what its advertised to make because a few can still enjoy it with super efficient speakers in little rooms. So their false advertising and sneaky use of big fake covers should excuse its non performance for those who may buy this amp and have it totally not work for them because of the misrepresented specs.
What about the guy in a 30 x 40 room with 3 ohm speakers rated at 84 sensitivity? Think he feels this amp is “sweet sounding”? There is just no excuse for it.
I have no doubt that it isn’t a wonderful 15 or 17 watt amp.. thats not the issue. The issue is All the other people who spend their hard earned cash only to receive something thats a lie and not help them or worse harm their current equipment.
Maybe Bob can remarket it as the Crimson -120 since its missing 120 watts? or how about the Crimson 2-60. I suppose the Crimson 215 or 217 could work.
I’m bothered by the view point that we should just gloss over the big covers over little 15w trannies or it making less than 25% of what its advertised to make because a few can still enjoy it with super efficient speakers in little rooms.
Who is glossing over anything? Responses on this thread have been virtually unanimous in condemning the misrepresentation of amplifier output power? Even those who own/like the amplifier have been openly critical.
@funky54 , you are correct in that misrepresentations are unacceptable. If someone is buying a 75w push pull tube amp for 84dB speakers with nominal impedance of 3 ohms I doubt they would ever look at this thing. But the Company did market it as going into 4 ohms at 75w.
I'm just not sure how this thing could test out near 75w with that 15w Edcor OPT in mine from MusicDirect. I have my doubts. But Bob has pulled rabbits out of the hat before and it indeed sounds good.
I have only 3 audiophile friends within an hour's drive. They all have sensitive speakers. Does anyone with less efficient speakers live in Chicagoland and want to have me bring the amp by for a listening test? You could bring speakers here too, yet that's more work than lifting this light amp. :) I'd be curious to hear it with more demanding loads.
@jbhiller That’s a great offer. I live in Florida so not feasible. As mentioned I came super close to buying this amp. My speakers are 86db 3 ohm and in a 30 by ..60ish room with 13 ft ceilings. It would have been a disaster. I came from two Carver C-500 amps vertically bi-amped. So while they were grainy on top and not the end of my road.. I was all bought in on Carver. Bitter sweet to see where its led. I was still keeping my eye out on used to see if I could pick one up, not now. Do love my current tube amps.. but there will always be that what if Changitis with this hobby.
I'm just not sure how this thing could test out near 75w with that 15w Edcor OPT in mine from MusicDirect.
It won't.
As far as I can tell from the photos, that output transformer is a custom unit.
But its still a 15 watt device and will saturate when pushed beyond that level. The laminations in the transformer play an important role in how much power it can pass. The laminations are the magnetic core of the transformer and determine when it will saturate (no greater magnetic effect can occur). The wire plays a role too- it has to be able to handle the current at the power levels involved. But its mostly the laminations that say what power the OPT will be able to make. That is why higher power transformers are bigger and heavier.
I wouldn't think so, but Bob has a PhD in physics. His response suggests it will. I'd bet it won't, but who am I?
It will be sad if he goes into retirement making this representation--that it, it will exceed 75 w per channel, both channels driven at 8 ohms.
The question I have is this-- if this thing can only put out 15w per channel at 8 ohms, wouldn't we hear of folks finding they have little headroom before the thing starts getting blurry and smeary? Was the room where they demonstrated it with KEF Blades so small that 15 watts was enough to get the KEFs singing?
jbhiller, don't swap out those resistors. They provide "current feedback" from the output transformer, you won't gain anything by changing them. To the contrary, some feel the amp might be improved by bypassing them. Many amps in the 50's offered a similar arrangement, except with a variable resistor, to adjust the "damping factor," a way to "loosen" the amp's grip a bit to accomodate speakers with poorer bass response.
No 75 wpc tube amp is going to deliver into a 3 ohm load and 86 db sensitivity. Especially in a room like you described. It just shows how foolish you are to consider it.
jbhiller, what you could do is run clip leads from each negative speaker terminal to the corresponding outer shells of the inout jacks, thereby bypassing this feature, and see if it sounds different.
My custom-built Will Vincent SET 45 amp has way bigger Edcor trannies than in the Crimson! Without the proper size iron the Crimson is dead in the water! No swapping caps or resistors can redeem it!
The ASR test and review really nails it! This is a broken amp that can't make its specified power and distorts terribly at 35hz and below! What was Bob Carver thinking when he chose those small 15 watt Edcor trannies?
I had a crimson 275 in my system for about 2 weeks. To be fair, the unit appeared to offer more power and headroom than my lowest wattage amps on hand at the time (35 watt Latino ST-70 and Muzishare X7). The sound of the Crimson 275 was fine, not great, not terrible. Fine. However, I didn't feel it was worth the price given the ST-70 is half the price and also made in the U.S.A.
In the end, I sent the unit back because the transformer buzz was clearly heard from 10 feet away. JCS honored their return process for which I'm grateful. I'd hate to be stuck with one of these given recent drama since most secondhand buyers will probably be turned off at anything but fire sale pricing.
For an industry and hobbyists obsessed with specifications, and wary of snake oil, this unit seems like a major gaff.
The speaker ground vs. audio ground issue was brought to my attention and I tried the suggestion of connecting my FFT to the audio ground instead of the speaker ground and it made no appreciable difference. Amir is also aware of this and I believe he will be posting his measurements very shortly.
To be fair, the ASR measurements show it performing a lot better into 8 ohms: 60 Watts/ch sustained at 1kHz, and at less than 1% THD. The really bad numbers, where it greatly underachieves its rated power (< 20 Watts/ch), are into 4 ohms. Without multiple taps this amp can only be optimized for one load, and it looks like it’s 8 ohms.
It did better than I expected at 8 ohms, but then 60 is still clearly under rated power, and it blew a fuse on top of that. And power bandwidth is clearly a big shortcoming here, probably much more than with other tube amps.
It’s probably not filling any necessary market slot with this performance.
Haha, good point. I'm sure putting in a larger fuse value might allow Bob's circuit magic to be unleashed. Of course you have to insert the fuse JUST right, because as we all know now, the grounding in this amp is very complex 😂
Actually my 1961 MC240 will run my 3 ohm Apogee Stage just fine. It’s probably not a combo for the deaf or AC/DC duty, but it’s solidly musical. I guess 40 wpc at Binghamton meant something, well actually last time I measured it was 52 wpc. No puppies died in the informed writing of this post.
of course it’s 50# of beefy transformers at work, Phd in ? Be fanged..,.danged, whatever…
Sad results. The machine Amir at ASR reviewed had worse build quality than mine, in the form of super high gauge wire going to the speaker output terminals, a missing bolt, and so on. Disgraceful.
Mine also has no chassis grounding, which is a touch scary given the voltages in the unit.
Mine has the slots on the PCB, C4 and C19 (going by memory), missing the actual caps. The ASR review sample has caps in those slots, but they are mounted on the other side of the board. ???????
Whatever wattage this thing makes sounds good into super sensitive speakers. But thanks to the teardown, we can see the OPTs are just 15W Edcors.
What is going on with the differences in build quality?
Why is Music Direct (and other retailers) no longer selling the product? Hmmm...
Why is Jim Clark, a dealer, defending the product, but there are circuitous and scant responses from Frank Malitz, Wyred4Sound, and even Bob Carver?
I questioned the build quality on certain areas, as a hobbyist. Now, it is more than confirmed that there are multiple more questionable things going on, and the marketing of the product is totally wrong and misleading.
Why is Jim Clark, a dealer, defending the product, but there are circuitous and scant responses from Frank Malitz, Wyred4Sound, and even Bob Carver?
I questioned the build quality on certain areas, as a hobbyist. Now, it is more than confirmed that there are multiple more questionable things going on, and the marketing of the product is totally wrong and misleading.
I'm off to Discogs to do some "retail therapy", and buy some nice pressing that will make me smile and stop thinking about what a mess Bob Carver's amp appears to be.
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