Carver Crimson 275 Measurements

[SIY]

Well, wiring insulation has come a long way, and you can fit more turns in the winding window now than you could 50 years ago because the insulation is thinner. This insulation is also far more tolerant of heat stress, so a modern power transformer can be run hot to the touch and the internal wiring still has a substantial amount of thermal headroom remaining. We do have more variety of lam alloys available as well, though some of that stuff gets very expensive very quickly.

Yeah, making the core x-section smaller is... a challenge. I wouldn't expect anything exotic materials-wise from Edcor.

A smart designer might use a modulated high frequency carrier to get the output transformer size down. A really smart designer would use a transformer simulant like switching impedance converters. The only Carver tube schematic I've seen was for the Silver Seven, and the circuit was utterly 1955 conventional (looked like a Mullard variant).

 

[paulbottlehead]

Yeah, the Berning OTL amps are something I'd really like to try out and measure one of these days!

The Crimson 275 schematic is available in the manual which is posted on the Carver forum here:
https://carverstereoforum.com/wp-content/uploads/2018/10/Crimson-275-Owners-Manual-REV100.pdf

 

[SIY]

Yeah, the Berning OTL amps are something I'd really like to try out and measure one of these days!

The Crimson 275 schematic is available in the manual which is posted on the Carver forum here:
https://carverstereoforum.com/wp-content/uploads/2018/10/Crimson-275-Owners-Manual-REV100.pdf

I published a review in AudioXpress of one of the LTA Berning amps, with pretty extensive measurements. Clever concept with some real performance advantages.

Thanks for the schematic. This could have been so much better with some relatively small changes.

 

[Blackdog]

Thanks for the schematic.

I see from the schematic Carver doesn't believe in proper grounding of the chassis.

 

[JRS]

Before I'd go that far I'd make sure the gear is not broken. Bob has been known to use a lot of hyperbole. He's made a career out of it. But he also has a track record of delivering on his promises. If I was the owner of these, I'd contact Bob and ask him about it.

Just to be clear: I'm not saying that these examples are not representative of production. If they are, then that is certainly pathetic. But something doesn't appear totally right, and I'm willing to give Carver the benefit of the doubt until its sorted out.

I'm reminded of the ASR review on one of the Benchmark DACs. If I remember correctly, the measurements were not up to par. John Siau took the device back to his lab, measured it, and it was fine. meeting specs. Not equating Benchmark QC with a handmade Carver tube amp. I just would want to know more before I would say there is fraud.

It is sufficiently unbelievable, I wonder about whether these are even genuine Carver product and not some Chinese counterfeits (or USA for that matter).

 

[mhardy6647]

That might be a stretch Have you seen our 90s product photos???

The R rated days of the site -- I believe I still have a screenshot or two lurking around... and there's always the Wayback machine

 

[JRS]

A number of posts were deleted from that thread, including several of mine. Didn't the site owner involved in the discussion say he's a long-time friend of Bob Carver? I'm sure that's just a coincidence.

That means nothing--say they were fake product, I would protect a friends reputation. One nasty rumor can ruin a life, so shut it down til more is known I'd say.

 

[mhardy6647]

Yeah, the Berning OTL amps are something I'd really like to try out and measure one of these days!

The Crimson 275 schematic is available in the manual which is posted on the Carver forum here:
https://carverstereoforum.com/wp-content/uploads/2018/10/Crimson-275-Owners-Manual-REV100.pdf

Heck, I did not know the schematic was visible in the public domain!
EDIT: Am I reading that schematic right? The center tap on the OPT's at +685VDC?

 

[mhardy6647]

The counterfeit idea's certainly interesting.
I can't imagine an Asian counterfeiter would source EDCOR iron -- although i guess they might knock off a few labels. Obviously, just speculatin', I am.

Presumably there're serial numbers on the amps, and Carver could verify their provenance. That said, it's not in @paulbotthead's court, nor mine, nor "ours" to ask Carver to do so.

The owners of the two amps know how they got them -- although they don't owe us that information, either.

 

[JRS]

Yeah, the Berning OTL amps are something I'd really like to try out and measure one of these days!

The Crimson 275 schematic is available in the manual which is posted on the Carver forum here:
https://carverstereoforum.com/wp-content/uploads/2018/10/Crimson-275-Owners-Manual-REV100.pdf

Ugh, wt is listed as 17#. Now I am fearing this is real.

 

[Larry B. Larabee]

You'll have to PM me what you're after, as I suspect you're three steps ahead of me and I need to catch up!

Maybe not, I usually associate the striped green wire with a center tap so I thought for some reason he was trying to establish some kind of virtual ground. Only when I went back to look at the photos of the power transformer did I see that wire is part of the primary. I can assume the clipping is symmetrical and so the duty cycle is okay. I just can't get over the low frequncy output not resembling a sine wave even at low output levels? As you say those output transformers just don't cut it. Is that a resonant circuit to flatten out the low frequency response on those transformers? Anyway, you've convinced me that he's made some deliberate design choices. Choices that I find confounding since their was no doubt in my mind that Carver was a genius, 30yrs ago. It is what it is.

 

[paulbottlehead]

It is sufficiently unbelievable, I wonder about whether these are even genuine Carver product and not some Chinese counterfeits (or USA for that matter).

I mean one of them is signed by Bob with a personal note, so...

Also Dan Santoni of Black Dog Audio has confirmed my measurements on an another 275 provided by Carver as a sample to a potential dealership.

You could do some investigating ask Edcor who they made those parts for. They would not sell stuff custom wound for one manufacturer to anyone else.

If I need to find a third one of these to satisfy any doubts, I can go to work on that.

 

[JRS]

I mean one of them is signed by Bob with a personal note, so...

Also Dan Santoni of Black Dog Audio has confirmed my measurements on an another 275 provided by Carver as a sample to a potential dealership.

You could do some investigating and Edcor who they made those parts for. They would not sell stuff custom wound for one manufacturer to anyone else.

If I need to find a third one of these to satisfy any doubts, I can go to work on that.

Well I am sad to say this looks like the real deal. He was a minor hero of mine for taking on the tube folks and offering up the Carver Challenge, which as far as I know, nobody collected on. Wonder why. Oh those side firing speakers were a bit of genius too.

 

[paulbottlehead]

The willingness of people to change their minds on this forum is something rather exceptional, am I still on the internet?

 

[LTig]

The willingness of people to change their minds on this forum is something rather exceptional, am I still on the internet?

Are we all politicians?

 

[SIY]

EDIT: Am I reading that schematic right? The center tap on the OPT's at +685VDC?

It's a cool thing about some pentodes- as long as you watch dissipation (especially screen!), you can really run up the B+. That's how I get 40+ watts out of EL84s. Another Modjeski trick; I miss the guy, he was really creative in a field that runs on same old same old.

Ironically, with some jiggering around of the Carver circuit, the transformer distortion could have been made much lower, but... Also, I'm surprised/disappointed that the screens aren't regulated. A Maida-style reg would have only added ten bucks at most to the BOM.

 

[Blackdog]

It's a cool thing about some pentodes- as long as you watch dissipation (especially screen!), you can really run up the B+

Not to add to a derailment, but I've seen over voltaged plates before. Check out Musicman guitar amps.
6L6GC tubes with 700V on the plates, only 350V on the screens. They use a rather interesting way to bias them too.

 

[anmpr1]

The willingness of people to change their minds on this forum is something rather exceptional, am I still on the internet?

I must say, contrary to my original skepticism, IMO the OP has sufficiently proved his point. With two samples, and a supporting report of a third sample, from another poster, claiming similar measurements, there doesn't appear to be a lot of wiggle room left for doubt. If it can be cleared up, the only way that can happen is for Carver to rebut the claims, which he should do if he is able to. Without his input, or without someone somewhere with another sample that meets advertised specs, I don't know that there is anything left to say.

It's too bad, really. Bob was a guy who did a lot for 'blue collar' consumer hi-fi. Even if you didn't much care for his products, he always seemed to have the end user in mind--first and foremost offering value for the dollar. If instead of this, Bob simply decided to build a lightweight, 15 watt/ch tube amp, hand made and with a five year warranty, that looked cool, then no one would view it as much of a problem. But now? How can anyone explain it away?

 

[Larry B. Larabee]

I must say, contrary to my original skepticism, IMO the OP has sufficiently proved his point. With two samples, and a supporting report of a third sample, from another poster, claiming similar measurements, there doesn't appear to be a lot of wiggle room left for doubt. If it can be cleared up, the only way that can happen is for Carver to rebut the claims, which he should do if he is able to. Without his input, or without someone somewhere with another sample that meets advertised specs, I don't know that there is anything left to say.

It's too bad, really. Bob was a guy who did a lot for 'blue collar' consumer hi-fi. Even if you didn't much care for his products, he always seemed to have the end user in mind--first and foremost offering value for the dollar. If instead of this, Bob simply decided to build a lightweight, 15 watt/ch tube amp, hand made and with a five year warranty, that looked cool, then no one would view it as much of a problem. But now? How can anyone explain it away?

I think so.

I may have previously read something about Carver basing his designs solely on the results of listening tests. If that's the case we could be the only people who actually care about the measured performance of this amp. As it is, we're talking about a tube amp where there is only varying degrees of bad measured performance. To the credit of tube fans I agree that having friends over to listen and enjoy some music seems to have more credibility as far as making a good choice goes than not listening and showing them the blown-up graphs I have taped to the wall showing how great the specifications of my system are. Some would prefer to have Bob over for dinner and some would prefer to have Floyd over for dinner but all of us are glad when they finally leave.

 

[anmpr1]

I may have previously read something about Carver basing his designs solely on the results of listening tests. If that's the case we could be the only people who actually care about the measured performance of this amp.

Could be. But Bob has no excuse. He knows how to measure, and he knows circuits. He's based his entire audio career on innovation, and offering a certain value for the dollar (with the possible exception of his Silver Seven--but he used that as a transfer function model for his cheaper SS designs). Bob always tried to offer something you couldn't get in the marketplace, for less money than you'd normally expect to pay. With this, you get a lot less than you thought you were getting, for more money than you should be paying. Just the opposite of his history.

That's what makes this thing so unbelievable. It's just not something anyone would expect from him. At least I didn't expect it.