Carver Crimson 275 Review (Tube Amp)

[SIY]

On another point on the grounding. Although not entirely safe. As a 3 prong IEC cord and connector was used, the connection was properly polarized, whereby the neutral side of the line was connected to the chassis. As the neutral side of the line is bonded to ground at the panel entrance, a path to ground is available. This itself will lessen the shock hazard. The ground connection was added as additional safety.

Class 1 requires the ground to be attached to the chassis and any other metal parts that the user can touch. We've been through this extensively and the relevant documents have been linked to.

If the neutral side of the line were connected to the chassis, that would be insanely bad practice.

 

[NTK]

If the neutral side of the line were connected to the chassis, that would be insanely bad practice.

A simple wiring error in the wall plug will make this a death trap.

 

[GRBH]

You can't just look at current, but need to look at voltage as well. It's the power that counts. Here is a simple calculation.

Not taking account the Reactive Load P=E x I = 120V x 3 amps = 360 Watts Input
Tube Heater Power = 4 x (6.3V x 1.95 amps) = 50 Watts
360 Watts - 50 Watts = 310 Watts theoretical max for audio power. Assume worst case 50% efficiency = 155 watts for 2 channels, 77.5 each.
This is only for rough demonstration purposes only. Just to show 120 volt 3 amp input should be capable to handle a 75 watt/channel amp.

Class 1 requires the ground to be attached to the chassis and any other metal parts that the user can touch. We've been through this extensively and the relevant documents have been linked to.

If the neutral side of the line were connected to the chassis, that would be insanely bad practice.

As the neutral side of a 120 volt circuit is bonded to ground at the entrance panel, the grounding of the chassis by way of the ground pin also ties the neutral side to the chassis.

 

[AudioTodd]

The amp is a push-pull design. The circuit is there to ensure the 'not active' tube draws less current than it would otherwise and thus load the transformer a bit better (lower current, lower DC difference, longer tube life and lower distortion).

Thanks for the response. What I'm curious about is how it does that. I've looked at lots of schematics, but do not always get the way all of the parts work together at the same time. It would appear to me, though, that - taking the "positive" side of the pull-pull output right now - when the input turns negative, the diode in the bias network would start to conduct and essentially parallel its series resistor with the other larger resistor that goes from the bias supply to the series grid resistor, reducing the combined value of the resistance to the parallel combination of the "main" resistor and the combination of any internal resistance of the diode plus the resistor in series with the diode. Does this act as a variable voltage divider? Wouldn't this actually raise the instantaneous grid voltage to a less-negative level closer to the negative bias supply voltage? Doesn't this keep the "positive" output tube from going deeper toward or into cut-off?

Feel free to PM me it that is easier! I may be the only one who is curious how a couple of diodes makes a guy a genius in the minds of many and perhaps his own.

 

[GRBH]

A simple wiring error in the wall plug will make this a death trap.

Well you can only go so far to protect people that don't know what their doing

 

[SIY]

Well you can only go so far to protect people that don't know what their doing

I gather that you have no experience in product safety. Nor have your read ANY of the compliance documents linked to in this thread.

This is BASIC stuff.

 

[SIY]

A simple wiring error in the wall plug will make this a death trap.

Which is why devices like All American Fives are a thing of the past. The compliance standards were created and implemented for a reason. Arguing that they're all wrong and Carver is right is... beyond insanity.

 

[SIY]

Thanks for the response. What I'm curious about is how it does that. I've looked at lots of schematics, but do not always get the way all of the parts work together at the same time. It would appear to me, though, that - taking the "positive" side of the pull-pull output right now - when the input turns negative, the diode in the bias network would start to conduct and essentially parallel its series resistor with the other larger resistor that goes from the bias supply to the series grid resistor, reducing the combined value of the resistance to the parallel combination of the "main" resistor and the combination of any internal resistance of the diode plus the resistor in series with the diode. Does this act as a variable voltage divider? Wouldn't this actually raise the instantaneous grid voltage to a less-negative level closer to the negative bias supply voltage? Doesn't this keep the "positive" output tube from going deeper toward or into cut-off?

Feel free to PM me it that is easier! I may be the only one who is curious how a couple of diodes makes a guy a genius in the minds of many and perhaps his own.

Overload recovery for when the grid drive goes positive. The idea is to not interfere with normal operation but reduce the time constant for blocking.

 

[Joe Smith]

So we are now onto the *sixth* entity making the Carver Black Beauty/Cherry/Crimson amps?

1). Bob Carver making the amps and winding the output transformers himself and selling on eBay pre-2011;
2). Bob Carver and Bob Farinelli founding Bob Carver LLC and building the amps in Washington sometime in 2011, and carrying into 2013;
3). Emotiva buying Bob Carver LLC and building the amps in Tennessee, later in 2013;
4). Emotiva and Bob Carver split later again in 2013, Bob starts The Bob Carver Company, although I am not sure where the amps were built;
5). Frank Malitz becomes involved with The Bob Carver Corp. in 2015; at some point, Glass Audio is started by Malitz with E.J. Sarmento/Wyrd4Sound to manufacture the amps in California; Malitz purchases The Bob Carver Corp. in 2019; in late 2021/early 2022, Glass Audio is dissolved;
6). Bob Carver and his wife start a new company to subcontract manufacturing of the amps to unannounced entities, with Jim Clark handling online sales.

I think I have it down, but the twists and turns are a little hard to follow between 3,4,5.

This see-saw history would certainly make me NOT want to buy any products from iteration 6.

 

[GRBH]

I gather that you have no experience in product safety. Nor have your read ANY of the compliance documents linked to in this thread.

This is BASIC stuff.

What are you disputing? This comment - "Well you can only go so far to protect people that don't know what their doing"
If so, it's up to lay persons adding in receptacles to do some research before installing them, or hire an electrician
I have an Electrical/Electronics background and am well aware of electrical product safety.
No I have not read any of the documents you have pointed to.
No I'm not defending Bob Carver.
Everything I have stated about house wiring is correct. Check it out
I see it's pretty popular here to attack people when they don't like what the hear!

 

[dfuller]

You can't just look at current, but need to look at voltage as well. It's the power that counts. Here is a simple calculation.

Not taking account the Reactive Load P=E x I = 120V x 3 amps = 360 Watts Input
Tube Heater Power = 4 x (6.3V x 1.95 amps) = 50 Watts
360 Watts - 50 Watts = 310 Watts theoretical max for audio power. Assume worst case 50% efficiency = 155 watts for 2 channels, 77.5 each.
This is only for rough demonstration purposes only. Just to show 120 volt 3 amp input should be capable to handle a 75 watt/channel amp.

Wow, I never would have known that!

As for efficiency, considering that power tubes are generally idled well above 50% of maximum dissipation at idle for audio amplifiers... And also waste an enormous amount of the input power as heat... I would say 50% is being awfully optimistic.

Regardless, 3 amps is very small for 2x75 watts on 120V. A typical 2x40W stereo amp uses a 2.5A mains fuse - that's definitely more the ballpark output wattage I expect for a mains fuse of that value.

 

[Xulonn]

I see it's pretty popular here to attack people when they don't like what the [sic] hear!

Unfounded assumption, and a statement that appears to be defensive.

You were not attacked, but your positions were - and your support for the concept of caveat emptor will not be popular with many people..

"Awareness" of consumer electrical safety issues is not the equivalent of "experience".

Jumping into a long written conversation without reading what has already been discussed and referenced is a path to controversy - and will draw criticism.

You are arguing with other technical experts here who also have electrical engineering backgrounds and careers - and have established their credibility with ASR members and visitors over several years.

 

[amirm]

What are you disputing? This comment - "Well you can only go so far to protect people that don't know what their doing"

Depends on who doesn't know what they are doing. Our first home was a townhouse and it had incorrectly wired outlets (and light switches). In our current home, there was an outdoor light in the remote workshop. Flip it one way and it would light fully. Flip it the other way, and it would light dim! I forget how the owner had wired it before I ripped it out but it was so stupid.

We also used to have a boat. Pulled into a marina once and plugged in. The boat had polarity indicator and it lit up that the wiring was reversed! Immediately disconnected and used the adjacent dock power.

So yes, we do need protection from people who screw this stuff up. It is not like it is readily apparent that something is miswired. Billions of dollars spent on power safety is not done for kicks and grins. It is there because mistakes happen and risk of life so high. It is not too much to ask an audio designer to take advantage of redundancy in home wiring in the form of safety ground.

And why would we take a risk here? For the privilege of own this amp when there are so many safe and performant designs out there?

 

[paulbottlehead]

General question: Just curious, has anyone who tried to get a refund received it?

I did receive mine!

 

[GRBH]

Wow, I never would have known that!

As for efficiency, considering that power tubes are generally idled well above 50% of maximum dissipation at idle for audio amplifiers... And also waste an enormous amount of the input power as heat... I would say 50% is being awfully optimistic.

Regardless, 3 amps is very small for 2x75 watts on 120V. A typical 2x40W stereo amp uses a 2.5A mains fuse - that's definitely more the ballpark output wattage I expect for a mains fuse of that value.

Points well taken. I'll have to do a bit more thinking on this.
Carver did have a novel circuit, that claimed to reduce idle current well below the norm. If I recall it was called the DC Restorer Circuit. This circuit was the main reason he claimed a much longer life for the output tubes. I have a pair of Carver Black Beauty 305 Monoblocks by the way, and a fair amount of Carver vintage solid state gear.
I don't profess to be a Carver fanboy, and I don't care much for his cavalier comments on the 275's. Senility maybe?

 

[SIY]

Points well taken. I'll have to do a bit more thinking on this.
Carver did have a novel circuit, that claimed to reduce idle current well below the norm. If I recall it was called the DC Restorer Circuit. This circuit was the main reason he claimed a much longer life for the output tubes. I have a pair of Carver Black Beauty 305 Monoblocks by the way, and a fair amount of Carver vintage solid state gear.
I don't profess to be a Carver fanboy, and I don't care much for his cavalier comments on the 275's. Senility maybe?

Low idle current has a long an partially honorable history. My last big tube amps (150 watt monoblocks) idled at 4mA per output tube, but I could get away with that by using a grounded control grid and driving current into the screen. Amps by Audionics, Berning, and LTA use the same method. There was nothing like that in Carver's circuit, he just turned down the idle current in a conventional grounded cathode output stage.

The "DC Restorer" is likely the diode used to reduce blocking, but given a fancy name and description (the carnival barker).

 

[GRBH]

Depends on who doesn't know what they are doing. Our first home was a townhouse and it had incorrectly wired outlets (and light switches). In our current home, there was an outdoor light in the remote workshop. Flip it one way and it would light fully. Flip it the other way, and it would light dim! I forget how the owner had wired it before I ripped it out but it was so stupid.

We also used to have a boat. Pulled into a marina once and plugged in. The boat had polarity indicator and it lit up that the wiring was reversed! Immediately disconnected and used the adjacent dock power.

So yes, we do need protection from people who screw this stuff up. It is not like it is readily apparent that something is miswired. Billions of dollars spent on power safety is not done for kicks and grins. It is there because mistakes happen and risk of life so high. It is not too much to ask an audio designer to take advantage of redundancy in home wiring in the form of safety ground.

And why would we take a risk here? For the privilege of own this amp when there are so many safe and performant designs out there?

I agree with everything you say Amir.
My comment was only aimed at some DIY's who failed to do research on basic home wiring before tackling the job of installing a new receptacle.
Sounds like you may have been the unfortunate victim of such a person.
I as well am somewhat dismayed at Bob Carvers cavalier response to the findings on your forum.

 

[GRBH]

Low idle current has a long an partially honorable history. My last big tube amps (150 watt monoblocks) idled at 4mA per output tube, but I could get away with that by using a grounded control grid and driving current into the screen. Amps by Audionics, Berning, and LTA use the same method. There was nothing like that in Carver's circuit, he just turned down the idle current in a conventional grounded cathode output stage.

The "DC Restorer" is likely the diode used to reduce blocking, but given a fancy name and description (the carnival barker).

It was actually a 6AL5 tube.
As you have alluded, Bob Carver has always been very good at marketing, with a long list of colorful names assigned to his patents!

 

[TitaniumTroy]

Thanks for the review Amir, I have always wondered about his new line of tube amps. Also I had to change my vote, I misread the choice’s and thought it said “Happy Fire Panther” instead of fine, oops

 

[GRBH]

Unfounded assumption, and a statement that appears to be defensive.

You were not attacked, but your positions were - and your support for the concept of caveat emptor will not be populzr with many people..

"Awareness" of consumer electrical safety issues is not the equivalent of "experience".

Jumping into a long written conversation without reading what has already been discussed and referenced is a path to controversy - and will draw criticism.

You are arguing with other technical experts here who also have electrical engineering backgrounds and careers - and have established their credibility with ASR members and visitors over several years.

Semantics, my position, not me, may have been the victim, but please point out the "error" on my position regarding house wiring and grounding if you can.