Carver Crimson 275 Review (Tube Amp)

[paulbottlehead]

The ground was floated to avoid the possibility of ground loops and 60Hz hum (and its multiples).

Floating ground would mean that the chassis is earthed and the audio ground has no connection to the chassis. This is not what has been built.

 

[Billy Budapest]

Question: is it possible that the power supply in the Carver 275 has a mechanism that provides leakage current protection?

 

[Billy Budapest]

Floating ground would mean that the chassis is earthed and the audio ground has no connection to the chassis. This is not what has been built.

I am speaking of a floating ground as a ground that is not connected to earth. In the 275, the star grounding point is connected to the negative conductor, not to the grounding pin ( i.e., to earth). My understanding is that is correctly called a ”floating ground” in electronics.

Not as if Wikipedia is the most dependable source of knowledge, but it agrees with my use of the term:

Floating ground - Wikipedia

en.wikipedia.org

 

[john2017]

It is not.

I have explained how the loose screw that came with this amp could lodge between the power switch and the chassis and energize the chassis to 120V AC. This is not safe. The fuse will not blow under these conditions and you would have to rely on your interconnects to carry enough current to pop the circuit breaker in your home. There is no mystery here or lack of understanding on the part of anyone with experience in the industry who has posted about this issue. In fact I suspect if you went over to DIY Audio and proposed that this was a proper technique for manufacturing that you might get banned for doing so!

You are not going to find a manufacturer who disagrees with this, and BC coming here to say otherwise is alarming. It's also worth mentioning that the fusing issue is drawn properly in the schematic but not built properly in the amplifier!

The grounding scheme, absent the loose screw is not a problem. The poor attention to detail during assembly is the real issue here. Classic tube amps from back in the day were floating ground, just as Bob designed these amps. Bob, for good or bad, is on a nostalgia kick when it comes to these amps. What you guys are seeing, IMHO, is not an attempt to be a fraudster, or willfully designing a bad product. It is simply a physical manifestation of an 80-year-old man wistfully going back to the days of his youth.

Prior to my amps being constructed with an EIC connector, the Cherry 180's as they were then known, had captive power cords. The most powerful variant was the cherry 260's. During my build, I was struck by the joy Bob got out of putting an amp on the bench and bringing it to life.

By extension, I am inclined to think he sees these tube amps as an extension of himself and knowing a bit about the man from having spent time with him, I can say that he is probably more than a little hurt by what has happened. I am confident that he will do as he promised in his post here, and might even do what he can to improve the performance if he were asked to... These amps were really nothing more than a hobby for him, and he wanted to share that love of tubes with others. I am saddened by the way the 275 turned out.

 

[Larry B. Larabee]

I have seen insome non-audio applications where the correct fusing involves the neutral and not the hot terminal as one would normally expect. As far as I'm concerned neutral is ground. The resistor connected from neutral to ground, I guess, would shunt the neutral leakage current since typically you would have <1vac to get rid of since it is seldom at 0v like it should be. Just speculating.

 

[Billy Budapest]

Question: is it possible that the power supply in the Carver 275 has a mechanism that provides leakage current protection?

@paulbottlehead @amirm would that change in any way your opinion of the safety issue of not having a chassis ground?

The reason why I am asking is twofold:

1). Bob Carver himself posted that the amps are safe as wired and assembled. My initial reaction was “of course Bob would say that as he would not ever admit to liability in a public forum.” That was my risk management brain speaking. However, I then stepped back and thought that there had to be something more to his statement. Bob is one of the legendary figures in audio design, and has been selling products for a long time. That makes me think he had a reason for making that statement.

2). If you look at the back of the Carver Cherry 180 (photo attached), there is a two-prong, ungrounded IEC (required for for IEC Class II wiring) and the symbol for IEC Class II wiring. So, it has been in his past practice to design amplifiers to the IEC Class II standard. Admittedly, it is odd that in the 275, a three-pin IEC was used with a disconnected ground pin, and neither IEC Class I nor IEC Class II symbols are on the chassis.

 

[MerlinGS]

People found my insistence to be patient to be egotistical, passive aggressive and a miriad
of other adjectives. Multiple members have prefaced their comments with a list of their professional
accomplishments. They should know that companies respond to allegations in a logical and
(unfortunately due to frivolous law suits) a legal manner. This takes time. I proved to be correct
on my assertion.

There are only a few people in this discussion that actually own the equipment in question.
It is their opinion, the owners, that is of most significance. Bob Carver has given them unprecedented options.
If they are happy with the output of the amplifier (irrespective of measurements) they can choose
to have it modified for 'safety issues' at no expense to them. If they feel that they no longer want to own their product they
will be refunded their purchase price.

Who wrote Bob's release is of no consequence.
@amirm - I may be wrong but, I would assume (my opinion) that the engineers didn't write the final press releases at MSFT.
That is usually handled by people with English or Law degrees, with the input of the technology team.

Actually, your insistence for patience was not proven correct. The amp is clearly poorly designed and the specs provided are clearly deceitful. The response provided by Mr. Carver was a canned response that only takes a few minutes for a lawyer to produce and gave no valuable information to the purchaser. The response does not ackowlege any of the clear failings in the amp design, the deceitful marketing strategy, and it does not even provide a clear statement of refund to purchasers. A brief visit to the BobCarvercorp website makes no mention whatsoever of the problems identified in this review, it makes no mention whatsover of the potential hazards the amp may present the user, and it makes no mention whatsoever that purchasers may return their amp for a full refund for the failings identified in this review. Needless to say, the website makes no mention that the purchaser can return the amps no questions asked for a full refund if they express any concerns regarding safety or deceitful advertising.

The grounding scheme, absent the loose screw is not a problem... Bob, for good or bad, is on a nostalgia kick when it comes to these amps... By extension, I am inclined to think he sees these tube amps as an extension of himself and knowing a bit about the man from having spent time with him, I can say that he is probably more than a little hurt by what has happened.

Shilling is one thing, trying to perpetuate a dangerous misrepresentation is another. @atmasphere 's post below clearly explains how this amp can present a dangerous hazard to the user. As to the waxing poetically about Bob's nostalgia, that does not explain why he misrepresents the facts about the amp's amplifier power output, and its potential hazard to the user. In the post below, Mr. Carver describes the amp as powerful; however, he provides absolutely no specs to support this claim, why not present the specs in an honest fashion? Why hide under the cloak of "musical". Mr. Carver is clearly aware of the dishonesty in high end audio, he called them out himself, yet the design of the 275, and his description and defense of the 275 amp are clearly taken out of the pages of deceitful "high-end" audio discourse. From an engineering perspective, which he should care about, the statement "high quality design, one that does not disappoint in any respect" is clearly false. It disappoints from a safety and performance perspective. His statement that @amirm 's measurements fail to "do justice to the sound engineering of the 275" is clearly disingenuous. Notice Mr. Carver does not provide evidence to refute any of the measurements, yet he claims the 275 is an example of "sound engineering". A lot of hand waving, and not facts to back any objective claim, not exaclty the hallmark of someone arguing from the perspective of "sound engineering".

I am compelled to say that the 275 is safe as it is wired and assembled, and performs as it was designed...The 275 is a powerful, easy to listen to amplifier... If for any reason a customer is disappointed in the performance or sound quality of this amplifier, they may return it for a full refund. The general reception of the 275 to date has been that of a high quality design, one that does not disappoint in any respect. The performance as it was measured by Amir does not do justice to the sound engineering of the 275... For any person with a 275 wanting to change the grounding or get a refund, email [email protected].

Over and out,
Bob Carver

Not only is there apparently no mention of the option to get a full refund at the website, the above note statement merely states that if the purchases wants a refund they can contact the corporation. No guarantees that a refund will be provided, under what context will the purchaser be entitled to a refund, and whether the refund total would be for the full amount paid for the 275 amp.

This statement:
"We know that the 275 is perfectly safe the way it is currently wired. If you want it grounded another way, send it in and we can rewire it so the earth ground connects directly to the chassis, us paying shipping both ways. We stand behind the product and its quality.”

-is problematic! They may think its safe, but it isn't, plain and simple. The power switch is located at a corner beneath the transformers; if this unit received bad handling in shipping (imagine that...), the switch could take a whack and short to the chassis. Apparently its on the neutral side of the line, which means that the power fuse will not blow. This means that the chassis will be at or near ground potential if all goes well (no problems at all anywhere else in the system) since the neutral and ground are the same thing at the breaker box. However, things don't always go as planned! You would not want to be in contact with the audio system ground while barefoot on a basement floor...

This practice does not meet EU Directives for electrical safety.

 

[paulbottlehead]

2). If you look at the back of the Carver Cherry 180 (photo attached), there is a two-prong, ungrounded IEC (required for for IEC Class II wiring) and the symbol for IEC Class II wiring. So, it has been in his past practice to design amplifiers to the IEC Class II standard. Admittedly, it is odd that in the 275, a three-pin IEC was used with a disconnected ground pin, and neither IEC Class I nor IEC Class II symbols are on the chassis.

Some basics on double insulating:

"The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation."

https://www.draelectricals.co.uk/double-insulated-electrical-appliance/

For the 275, the wire going from the IEC entry module to the power switch would just need to break at the power switch or come off from the power switch, and that one loose wire could touch a chassis screw or the metal body of the power switch right next to it and you then have 120V AC on the shells of the RCA jacks. No bueno.

 

[BlackTalon]

Well stated, @MerlinGS . That email had no real content.

 

[Gringoaudio1]

He never said anything about making the amplifiers meet its power specification.

Federal Register :: Request Access

It is in fact the law to meet rated power specifications!

 

[Larry B. Larabee]

Some basics on double insulating:

"The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation."

https://www.draelectricals.co.uk/double-insulated-electrical-appliance/

For the 275, the wire going from the IEC entry module to the power switch would just need to break at the power switch or come off from the power switch, and that one loose wire could touch a chassis screw or the metal body of the power switch right next to it and you then have 120V AC on the shells of the RCA jacks. No bueno.

Did the production unit have CE certification or not? Dangerous and within regulatory limits are two different things. Is CE saying it's not dangerous?

 

[amirm]

Question: is it possible that the power supply in the Carver 275 has a mechanism that provides leakage current protection?

Don't see how. It would need a relay shut off to disconnect mains on such leakage as GFCI outlets do. If such a thing existed, I would have expected Bob to mention it and he did not. I also haven't heard of such a mechanism in an audio product.

 

[Blumlein 88]

I don't know if it would be legal for them to have a sticker on the back saying the amp should only be used with a GFCI outlet or not. That is more or less what they do with hair dryers.

Still doesn't fix the 15 watt amp masquerading as 75 watts.

 

[Larry B. Larabee]

Some basics on double insulating:

"The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation."

https://www.draelectricals.co.uk/double-insulated-electrical-appliance/

For the 275, the wire going from the IEC entry module to the power switch would just need to break at the power switch or come off from the power switch, and that one loose wire could touch a chassis screw or the metal body of the power switch right next to it and you then have 120V AC on the shells of the RCA jacks. No bueno.

If it was only a matter of using shrink tubing on the exposed AC terminals why was it still certified by CE?

It may be that the double insulation label is restricted to the use of two prong AC connectors. The ungrounded 3 prong connector is obviously used to maintain the correct polarity at the plug end on this component.

 

[Larry B. Larabee]

Don't see how. It would need a relay shut off to disconnect mains on such leakage as GFCI outlets do. If such a thing existed, I would have expected Bob to mention it and he did not. I also haven't heard of such a mechanism in an audio product.

I don't see how either. That doesn't mean that Carver hasn't come up with some rudimentary GFCI like protection none of us understand since he is still smarter than all of us put together.

 

[jbhiller]

Interesting interview about this amplifier here.

https://www.facebook.com/permalink.php?story_fbid=2150225165013361&id=919522768083613

In the interview, Malitz says if you have a problem or question you talk to him. That would be great, but he needs to respond to make it true. responded.

 

[jbhiller]

I suppose I need to go the refund route. If Malitz will not answer my questions, how do I trust that I will get a refund after I ship this thing to him?

 

[Blumlein 88]

I suppose I need to go the refund route. If Malitz will not answer my questions, how do I trust that I will get a refund after I ship this thing to him?

Ship it COD?

 

[john2017]

I suppose I need to go the refund route. If Malitz will not answer my questions, how do I trust that I will get a refund after I ship this thing to him?

You are more likely to get birds to fly out of your ass than get anywhere with Malitz...

 

[Chazz6]

I suppose I need to go the refund route. If Malitz will not answer my questions, how do I trust that I will get a refund after I ship this thing to him?

It's customary to get an RMA number before returning a product. Request one from Frank Malice, excuse me, Malitz. If nothing else, his response or non-response will strengthen your legal case.