Carver Crimson 275 Measurements

[paulbottlehead]

You probably should put at least 470 ohm load across the outputs of a xfmr coupled tube amp like that. Normally you don't want to run one with no load connected.

There's an 8 ohm dummy load visible in the photo in the bottom right.

 

[Zackthedog]

Have you seen the replies to this thread on the Jim Clark forum? They claim there's a special way to test them?

Carverfest Amps and how to measure them. A note from Bob. – Carver Stereo Forum

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.

Jim, Frank or Bob could lay this whole thing to rest by posting some o'scope shots of the amp performing as advertised. That's all they have to do.

 

[jjptkd]

Jim, Frank or Bob could lay this whole thing to rest by posting some o'scope shots of the amp performing as advertised. That's all they have to do.

Yes I agree 100% I've contacted Jim Clark without reply then noticed the posts on his forum. I don't know anything about testing amplifiers myself just want to pass this info along so that hopefully the final results are not disputed as a result of improper testing. From the forum:

"Turns out that there is resistor in line with the negative binding post that MIGHT get bypassed if your test equipment is grounded exactly wrong. The trick is to NOT use the negative binding post for ANY of your test equipment (except the dummy load). That means ANY test equipment, Distortion analyzers, DVMs, spectrum analyzers or oscilloscopes. Instead, use the amplifier ground, which is available on the shell of the input RCA connector. Just use the ground on the RCA shell and it won’t matter."

 

[anmpr1]

While we await the definitive Carver test, a few thoughts on thoughts:

I haven’t ever seen one with a bad finish or poor inlays. Not that I’ve seen all that many. The Epiphones were more in my price range. My first acoustic at age 14 was an Epiphone.

Anything hand made is going to have flaws, or variance in fit 'n finish. On a three thousand dollar guitar there is no excuse for sawdust in the pickup cavity. Just like on a two thousand dollar preamp, the top panel should be the actual top panel (when Peter Aczel received his JC-2 preamp, the top was for one of Mark's crossovers!). But even automated machine produced items can have problems, if the operators aren't watching. Check out the Guitaristas on YT. Last weeks video. A big run of the latest Epiphone '61 SGs have their back bevel miscut--and this is an $850.00 guitar! Generally Epiphone is good value for the dollar (I own a couple), but mistakes can happen.

1) But I also believe the audio industry has produced an overwhelming amount of solid-state equipment for all the wrong reasons...

2) I know this is a contentious subject, and 3) I don't wish to debate it with the masses.

1) If it was not for SS, many music lovers would never be able to afford gear. That in itself is a net positive. 2) It is certainly contentious, among some. However, it's just a hobby for most of us, so no need to become contentious. 3) Who are the masses? Are we the masses?

Hey, let's talk about pressure washers.

Will the debate between electric and gasoline pressure washers ever be decided?

I think the draw of S.S. was its reliability, low heat output, and compact lightweight size; no tubes to fizzle out & need regular replacement and no bad backs caused by heavy transformer-laden chasses.

In the early days of SS, horrible failures were frequently reported. I recall one of the major hi-fi magazines planning to review one of the first SS integrated amps, but before the review could run, so many were defective, blowing up, that the company went out of business. Generally, if a tube failed, your loudspeaker was probably safe. Can you say Quartre Gain Cell?

 

[mhardy6647]

Hey, let's talk about pressure washers.

I could write a book...

passee. Ultrasonic cleaners are where it's at

Kind of hard to prep a house for exterior painting or clean a deck that way, isn't it? Besides, how would the neighborhood hounds feel?

 

[mhardy6647]

I did try hooking just my scope up to the speaker terminals and no analyzer with my scope running on its internal battery (so completely floating), and this did not change the waveform appreciably. ...
Tomorrow I will drop off the production unit to Amir.

You may have to help with bucket brigade there(?)

Please do tell him we all said "hi" and we wish him & his wife the best, @paulbottlehead !

 

[HammerSandwich]

Jim, Frank or Bob could lay this whole thing to rest by posting some o'scope shots of the amp performing as advertised. That's all they have to do.

Prediction: "We're very embarrassed about it, but the specs have a typo. They should read 2 channels at 7.5W."

 

[BDWoody]

Hey, let's talk about pressure washers.

Finally, something I might be qualified to speak on...

 

[paulbottlehead]

"Turns out that there is resistor in line with the negative binding post that MIGHT get bypassed if your test equipment is grounded exactly wrong. The trick is to NOT use the negative binding post for ANY of your test equipment (except the dummy load). That means ANY test equipment, Distortion analyzers, DVMs, spectrum analyzers or oscilloscopes. Instead, use the amplifier ground, which is available on the shell of the input RCA connector. Just use the ground on the RCA shell and it won’t matter."

Been there done that. This did not make any difference. That's why I posted the image in post #461.

 

[raindance]

I'm waiting for someone to trot out the old argument about tube watts being mysteriously bigger/better than solid state watts and provide some sort of imaginary conversion factor...

 

[atmasphere]

I'm waiting for someone to trot out the old argument about tube watts being mysteriously bigger/better than solid state watts and provide some sort of imaginary conversion factor...

That's simply because tube amps have a more graceful clipping characteristic. So they can be overloaded and produce a bit more higher ordered harmonic distortion, which the ear interprets as greater sound pressure (the ear uses higher ordered harmonics to sense sound pressure). So as long as the amp doesn't outright break up, its higher distortion will make it sound louder than it really is.

 

[jjptkd]

Been there done that. This did not make any difference. That's why I posted the image in post #461.

Unless I'm missing something I'm looking at the picture and I see you doing exactly what the text provided says not to do-- you used a speaker binding post for the ground of your test equipment instead of the RCA ground.

"The trick is to NOT use the negative binding post for ANY of your test equipment... Instead, use the amplifier ground, which is available on the shell of the input RCA connector. Just use the ground on the RCA shell and it won’t matter."

 

[SIY]

That's simply because tube amps have a more graceful clipping characteristic.

Blocking?

 

[SIY]

Can you say Quartre Gain Cell?

And Rappaport? Of course, the SWTP Tigers were the Kings of Flame.

 

[mhardy6647]

Prediction: "We're very embarrassed about it, but the specs have a typo. They should read 2 channels at 7.5W."

I am now rolling on the floor here.

I'm waiting for someone to trot out the old argument about tube watts being mysteriously bigger/better than solid state watts and provide some sort of imaginary conversion factor...

I am almost certain that the conversion factor involves either √2 or π. Or maybe √π -- I'm a little rusty on my tubonics.

That's simply because tube amps have a more graceful clipping characteristic. So they can be overloaded and produce a bit more higher ordered harmonic distortion, which the ear interprets as greater sound pressure (the ear uses higher ordered harmonics to sense sound pressure). So as long as the amp doesn't outright break up, its higher distortion will make it sound louder than it really is.

Grace is one of those quantum mechanical properties of quarks, like truth and beauty, if I recall correctly.

In a (slightly) more serious vein, is this @atmasphere Mr. (or Dr?) Ralph K. of that Atma-Sphere fame? If so howdy! Didn't know you were a member here.
If not, then, my apology, and, as Emily Litella so aptly said:

 

[Zackthedog]

Unless I'm missing something I'm looking at the picture and I see you doing exactly what the text provided says not to do-- you used a speaker binding post for the ground of your test equipment instead of the RCA ground.

"The trick is to NOT use the negative binding post for ANY of your test equipment... Instead, use the amplifier ground, which is available on the shell of the input RCA connector. Just use the ground on the RCA shell and it won’t matter."

That is if the test set-up is itself grounded. A floating scope such as Paul's should not make any difference. The 8-ohm test load and the scope are both floated from AC ground, the same as a speaker would be.

IMO this is just a lot of hand-waving from Jim and Bob. If I understand how that resistor works, it's similar to the old Fisher "Z-Matic" system that compensates for dips in woofer impedance and provides a corresponding boost in the bass response. It may well do that, but when testing into a constant fixed load it shouldn't make any difference. But I could be wrong about that.

Regardless, it's pretty much a given that a 15 watt output transformer simply cannot produce 75 undistorted watts at 20Hz. If Jim and Bob want to post some scope shots proving otherwise, I'll be the first to eat my words.

 

[egellings]

You could also use a dual channel scope, place a channel on each speaker terminal with the probes' gnd clips attached to chassis, and then have the scope take the difference (subtract mode) between the two channels & display that.

 

[amirm]

The amp is here....

 

[Blumlein 88]

The amp is here....

Have the flood waters receded that is the pressing question?

 

[JayGilb]

The amp is here....