Owners of Carver Crimson 275 -Caution/Warning--Potential Increased Risk of Electric Shock

@lowrider -Interesting.  I’m not an expert but, at minimum, I would like to see that all of those power hook up connections were totally insulated so in the event one of them came loose they would be shielded from conducting with anything by the insulation wrap. But that is not done either.

@daveyf , Yes, and I have read books that cover the subject.  Most authors are very serious about this and seem to say what you say here--that many designers get it wrong. 

Bob Carver has a PhD in physics so maybe he can explain how it is safe.  

@erik_squires , 

I found it out by looking at it--literally opening the unit up.  Also, the folks at AudioScienceReview.com saw it too.  To be honest, I wasn't quite sure upon initial discovery whether the grounding scheme had some other means of protecting users because I don't have the true education, training and experience in the field.  I've also confirmed this is a problem from at least one electrical engineer.  

And, Carver Corp. has not denied it. Instead, the amp is under engineering review after I emailed them.  

By "wide open" I mean the ground post on the IEC is not attached to anything at all.  

You bet @jjss49 

I’m hoping, but not optimistic, there is an explanation for this situation that explains away the potential problem.  Time to unplug and let this unfold. 

@wfarrell, Bill, you are welcome. I debated posting something at all on the issue. Then I thought--you know, even though it would probably be unlikely that a wire would come lose from its solder weld, it’s possible. Not to mention that the build quality on these amps varies. Amir at ASR has a copy of the amp that has like 26 gauge wire going to the speaker terminals, whereas mine has heavy duty wire. His had a lose screw rolling around the chassis and the power transformer loose.

So, I thought: How do I know the welds in these amps are solid? There could be owners who have units where things were rushed in assembly. No one deserves to get zapped in 2022 from just touching the machine in operation!

@jea48, You certainly have more knowledge and expertise than I do.  If I get motivated today, I could open the unit again and post phots of the grounding scheme.  

@jea48 , it makes total safety sense that proper grounding would require a mechanical connection--not just a solder connection--because that wire to the chassis could still come lose.  I think I get it. 

Carlsbad, I would think that any tube power amplifier using power transformers, output transformers, which has 600+ volts going on in some sections must use a grounding scheme that grounds to chassis and to earth prong so that if something happens the current goes into the 3rd prong and your wall wiring and trips a breaker. 

Stuff happens. People drop amps. Wires age, And so on.  

Maybe an electrical engineer can chime in on this.  

Disclaimer:  I am not taking the position that this amplifier is a "Widowmaker" or "Widowermaker".  Could it be? Yes.  That's the sole point.

@jea48 , THANK YOU for the education.  Seriously.  

Note: the photo above is from AudioScienceReview.com.  My amp is built a bit better than this one, which is also odd and slightly disturbing.  But, the lack of ground on the IEC and grounding scheme looks similar if not identical to mine.  It looks like the power supply side of things is grounded to the fuse holder. 

As an aside, my amp does not have the film capacitor and resistor linked to the speaker output terminals. Bizarre. 

@carlsbad, I would ask you to re-read my post. I talk about an "increased risk". I cannot quantify it, but I would agree that a good strong weld should not come loose. But they can and do come loose. While it may not be probable, it is entirely possible.

Not to mention, Carlsbad, there are questionable things going on in the amp. I actually did have the line running to the meter come lose and I re-worked and resoldered that. In my amp, some of the welds (not many) could have been better so I touched them up.

The other thing to note is that the DC Restorer circuit and its PCB are mounted vertically and some of it appears to be glued into place as opposed to being bolted or connected with a standoff. If that glue were to come loose due to heat, age, etc., that vertically mounted board carrying many hundreds of volts of power (per Carver’s own schematic available on their forums) could touch the chassis or other component parts. The hookup wires holding power have bare leads exposed before they attach to the solder welds.

So I don’t think I’m exaggerating the risk. I say numerous times its a potential increased risk.

@czarivey ,  Thank you for your courtesy.  Lovely. 

@jea48,  Thank you once again.  Yes, I was wondering about that neutral hookup to the power fuse.  I built a very very simple single ended amp about 4-5 years ago and the plans came from a book.  I remember the author saying something just like you are about this being a big no. 

Still waiting on @FMalitz to provide an update on his engineering department's review of the issue.  

At some point, I'll just call Music Direct. 

@raysmtb1, many of us respect Bob and love what he’s done for hifi. He’s a legend in my book. Go read my posts about this amp. You’ll see we’ve given him the benefit of many doubts. But anyone saying the lack of proper grounding on this amp is not a problem, is incorrect. There’s no room for accepting this grounding scheme as acceptable in 2022.

I used to take electricity less seriously than I do today. I’ve incidentally rubbed up against a beefy Lundhal power transformer. I’ve touched a 120v AC line. I cannot imagine what 300, 400, 500 or more volts would feel like. If an amp design has issues with ground loops, this is not the way to handle it.

Paulbottlehead is spot on here.

Also, maybe it’s not so bad that the meter and the big electrolytic caps on the DC restorer circuit are literally held in place with glue--with no mechanical bond. But that method coupled with heat and a terrible, or shall we say non-existent grounding scheme, makes it utterly foreseeable that the amp could result in injury.

I think if anyone makes a post that says this isn’t an issue or it’s being exaggerated should have to take a basic electronics test before posting. If you’re reading this post, please make your decisions on the side of caution. The voltages in tube amps are seriously high. Some caps can hold super high voltages hours after power is shutdown.

On a lighter note...Maybe the shocks I have taken have caused my hifi Gear Acquisition Syndrome.  :)

I saw that.  I'll email him now. 

Just sent him a message asking...

1. Update on Lack of Chassis Ground

2.  Whether Bob Carver specified the 15w Edcor output transformers in the design?  (noting OPTs and PT now have hum and buzz). 

@jea48 ,  I wish you were in my town and I could take a class from you. Thank you. 

It seems we may be seeing an update from Carver Corp. on this soon per Jim Clark.  However, @jea48 , if Carver Corp.'s offer is to chassis ground the scheme would you say that is not enough?  Specifically, they must remove the neutral to fuse connection too?  That would be my understanding.  

Still no response from Frank Malik.  

I would think that knowing they have a loose bolt rolling around in an amp with a loose power transformer (the one ASR bought), they would want to issue a statement sooner than later.  They have now been alerted (they have actual knowledge) that there's a grounding scheme problem that could result in serious injury/death.  

All this raises the question:  Wouldn't Wyred4Sound see the wonky design issues that relate to grounding, securing the meter and the DC restorer circuit PCB, etc., when they build these things? I'm not trying to be critical.  I'm just thinking if Jea48 and others can see this so simply, would W4Sound?  Something is off here. 

And we wait....

Hi @jea48 , can you explain the takeaway for us from this observation?  Are you saying the B- is properly handled so we do not have to worry about other means of chassis grounding? 

I have asked EJ Sarmento of Wyred4Sound the following questions on the ASR thread where he chimed in: 

"Folks have raised these salient questions to which there has been utterly no response--just conclusory statements by Malitz and now Bob. Maybe you could help answer them as your firm looks to have built a good number of copies.

1. Is mounting the DC restorer circuit by gluing it vertically to the chassis part of the design?

2. Is mounting the meter to the chassis by gluing it part of the design?

3. Are the Edcor 15w OPTs part of the design?

4. What gauge hookup wire is supposed to be running from the PCB to the speaker output terminals?

5. Does the design-manufacturing process allow for substitution of Panasonic film caps with Suntan brand or other lesser known caps?

6. Have there been reports of transformer hum? I have owned two units and both hum/buzz at the transformers with no signal and volume totally attenuated (not a sound coming from the speakers, but buzz/hum coming from the transformers (all 3)?

7. Frank Malitz stated there was a problem with transformers when the vendor deviated from specification, and that resolved. Would that vendor be Edcor? What can be done to silence the transformers for those with those issues?

8. Grounding. Are you aware of what many of us view as a problem with the grounding scheme in this amplifier? Specifically, several of us have the neutral running to fuse and no chassis grounding or ground to earth. Do you believe these scheme is safe and acceptable?

This unit is supposed to have a 5 year warranty and many of us are just trying to figure out where things stand.

I'm not trying to come at anybody. I like the amp. I'm just trying to navigate through this and Frank Malitz and Bob just say: (a) the amp is awesome; (b) the amp is totally safe: (c) everyone who hears it loves it; (d) Amir and associates test it incorrectly.

I'm sure you can appreciate that when a consumer spends $3k on something they want to know they bought what was sold to them and it is safe."

Carver Corporation Refund:

By the way, Bob Carver (by handle) chimed in on ASR offering a full refund to consumers who bought the amp if they want it, directing consumers to email info@bobcarvercorp.com

@daveyf , Agreed. Personally I like the sound of the amp quite a bit through high-efficiency speakers. However, this whole thing is a dog and pony show. I really respect Bob and what he has done for the hi-fi community. However, the responses from him and others associated with this, including Bob Carver and Wyred4Sound are just bizarre. 
 

I would be quicker to believe Bob Carver and his associates, saying that the amp is safe, if they actually gave a basis as to why. Specifically I mean, just tell me why from an engineering perspective this is safe. Instead they just make a blanket conclusion that it is safe and saying that you can have a full refund if you want it. They also do say that they will ground it to the chassis if you would like. That’s good. I was just looking for a little more transparency what is going on, especially from the folks that designed, manufactured and market of the unit.

Team Audiogon,  

Trying to put this into perspective...

If the amp measures 15W continuous at 4ohm with <1% distortion, it might be fair to say that when driving 8ohm nominal Klipsch Cornwall IVs at 102dB efficiency, the amp sounds or can sound sublime.  Wasn't it David Manley who said that distortion under 1% is not really audible? 

The facts remain though that they likely misrepresented its power (by a bunch) and it has a wonky, outdated grounding scheme. 

Finally, would a GCFI outlet/plug truly make the unit safe? 

Thank you @imhififan 

I'm sure there are more people who have been hurt by poorly designed grounding schemes and we don't hear about them in the news. 

Wait, didn't Keith Relf die from an improperly grounded amp?  

At any rate, science tells me it is absolutely possible.  Probable? Maybe not, but....I'll take my amps grounded to chassis and to earth.

Can someone show me documented case where injurie resulted from an ungrounded piece of equipment?

I know Keith Richards was shocked on stage and same with the guitarist from Kiss when their guitars created a circuit due to lack of proper grounds.  Keith passed out I think, but of course he survived! He's Keith. :)

But in all seriousness,I would think the number of serious injuries and fatalities might be low, yet finding you a "documented case" could be tricky.  Medical histories are private. It might be just as hard as finding injuries/deaths by hairdryers.  

The potential for injury or death is real.  What that potential equates to probability wise, who knows? 

Not a tube amp situation per se (microphone, but a tube amp is potentially involved)...

Les Harvey electrocuted by unearthed microphone on stage.  while on stage with Stone the Crows at Swansea Top Rank in 1972, that he was electrocuted after touching a microphone that was not earthed while the fingers of his other hand were holding the strings of his guitar.  

Oh my. Get it all out! 

I love the product. I wish it was built with a better grounding scheme though. It’s 2022. It’s not 1955.