Carver Crimson 275 Measurements

[paulbottlehead]

Idle chit chat for now. This will sit on the floor in my garage till Amir is ready.

Eventually I will get back to some scope traces of the amp with a cap across the outputs.

 

[Zackthedog]

Are you here for idle chit-chat or an update on 'the status'?

We're *all* here for idle chit-chat, Larry. This is hardly a life-or-death matter. It's a hobby.

 

[Travis]

I stopped listening to solid state amps permanently about 15 years ago. The turning point was a dirty, unrestored $20 tube amp from the '60s that blew my Luxman M120 into the weeds. And I can tell you, the Luxman was no slouch. I might not be able to hear the difference now (I'm almost 70), but I know it exists, I've heard it repeatedly, and I'll never go back.

Jack

A man who knows what he likes. Refreshing.

 

[anmpr1]

I have to admit I had a similar experience. Although I find measurements extremely important, they don't always correlate with my preferences for whatever reason.

The weird thing is, David Hafler, a man who sold more tube amps than probably anyone ever did, and probably ever will, always claimed that as long as his SS amp was used in a commensurate manner as his tube amps, they would sound the same to the end user. He told that to Gordon Holt, right after Gordon had praised his SS design. Dave always seemed sincere in his statements, but perhaps it was just the practicality of a businessman.

Fifty and sixty years on, his tube amps (many of them just corroded rust buckets, cosmetically) are selling for a premium, and any number of new circuits/parts are available to keep them going.

I won't get into the argument about 'sound'. But I'll admit that if I had the choice between an ancient PAS and a PAT, I'd take the PAS any day. But if I had the choice between an ST-70 and Jim Bongiorno's Ampzilla kit, I'd ride with James (who, incidentally, had a major hand in the Dyna 400 SS amplifier).

I really like the idea that Hafler's work continues, in today's throw-away world. It is a lasting testament to a time when audio was certainly a different animal than it is, today. I think you can also say that, to a lesser extent, about Dyna's SS state designs, but more so with his eponymous amplifiers, which have a continued following, and a ready upgrade path.

PS: On a lark, and because I thought it could be time, I took out the Fluke and checked the bias on my Mk IV amps. After three years of use, a move across the country, and work in two different systems, they both were pretty much spot on. 1.4 V. A tiny twist of the knob and they were back up to 1.56. In the days of analog, you calibrated your meter with a Nine Lives or Ray O Vac 'D' cell, before making adjustments.

 

[paulbottlehead]

Here is the 10kHz square wave on the 275 with no load.

Here is the same square wave with a 0.047uF cap across the speaker terminals.

 

[MakeMineVinyl]

Here is the 10kHz square wave on the 275 with no load.
View attachment 177980
Here is the same square wave with a 0.047uF cap across the speaker terminals.
View attachment 177981

Measurements with no load at all are kind of unfair.

 

[egellings]

Pentode output tube amplifiers need a correct load on them in order to work properly. An unloaded test is an invalid one on that kind of amplifier.

 

[Zackthedog]

Pentode output tube amplifiers need a correct load on them in order to work properly. An unloaded test is an invalid one on that kind of amplifier.

It was just a test for stability, as requested, and I'd say it passes. That's pretty stable.

 

[Zackthedog]

Measurements with no load at all are kind of unfair.

That's the point. If it remains stable into no load or, even tougher, a purely capacitive load, you know that your compensation networks are working as they should. In that respect, the amp seems well-designed.

 

[mhardy6647]

We're *all* here for idle chit-chat, Larry. This is hardly a life-or-death matter. It's a hobby.

That would be, like, a good motto... or something.

 

[mhardy6647]

Pentode output tube amplifiers need a correct load on them in order to work properly. An unloaded test is an invalid one on that kind of amplifier.

I think @paulbottlehead knows this.

 

[paulbottlehead]

I'm just taking measurements that are asked for.

Having said that, I would expect something like a Western Electric 124 to be quite happy with no load on the OT.

 

[mhardy6647]

I'm just taking measurements that are asked for.

Having said that, I would expect something like a Western Electric 124 to be quite happy with no load on the OT.

I don't think we're likely to get @amirm to review one, though.
Now... I might (might!?!) be able to get him access to an RCA/Disney Fantasia amp... but I think he'd have to make a road trip. It'd be tricky to ship.

 

[Zackthedog]

I'm just taking measurements that are asked for.

Having said that, I would expect something like a Western Electric 124 to be quite happy with no load on the OT.

But it doesn't use global feedback, does it? I think there's some feedback between the output plates and the drivers. But once you bring the transformer into the feedback picture, it's a lot trickier, don't you think?

 

[paulbottlehead]

But it doesn't use global feedback, does it? I think there's some feedback between the output plates and the drivers. But once you bring the transformer into the feedback picture, it's a lot trickier, don't you think?

Yes, but both are still pentode amps!

 

[TriodeLuvr]

Considering all those bandaids, I would expect it to be stable driving a Leyden jar.

 

[mhardy6647]

 

[Zackthedog]

Considering all those bandaids, I would expect it to be stable driving a Leyden jar.

LOL

 

[Head_Unit]

b) risk dealing with an FTC complaint (is the FTC rule still in effect?)

(a) I don't think so
(b) Even if so, enforcement = nada, zilch, zero
Funny right below this is appearing a thread "Monoprice "Pure Tube" 15 wpc stereo vacuum tube amp - worth review?"

 

[anmpr1]

There are at least two issues that are soon to be resolved. First, Bob's claims. Does his claim match reality? Second, apart from that, how the amp measures on the bench, regardless of his claims.

The first issue will (or should) be pretty cut and dry.

The second? When doing comparisons, it is (in my view) important to compare like with like. Measuring this 275, and then superimposing the power/distortion graph of the best SS amps measured so far, as is usually done here at ASR, is to me idiotic. I don't mean that disparagingly, since I appreciate the work that Amir is doing, generally. What I mean is that it tells us nothing interesting.

That is, tube design should be judged by what is possible within the universe of tube amplifier design. That would be the 'objective' measure of any tube circuit. How any tube amplifier measures against any SS device is pretty irrelevant at this late stage of the audio game. No one expects any tube device to match what is possible with a SS design.

The exception would be 'hybrid' designs, which utilize tubes and the various types of SS circuits. Those form an altogether different category.

In this case, what would be interesting (again, to me, and I dare say, to others) would be how the 275 compares with, say, the 9 watt Bottlehead amplifier, which, on their Website states is capable of 8 watts per channel in stereo configuration and 16 watts of 300B magic as a monoblock. That would be something fascinating, and worthy of comparison. I'd also suggest something like a refurbed and/or modified ST-70. That might be good for comparison--not the old and rusty thing that was measured a year ago on ASR. I mean a 'newer' build, maybe from Bob Latino or from Curcio.

I can't speak for anyone else, but does anyone need to know how the Caver will compare against the AHB2 on a four ohm load? It's not like we already don't know that, without actually knowing it.