Anybody blow a ceramic woofer with an OTL amp?

I would appreciate anybody's experience with transients (such as a tube blowing) in an OTL amp that results in breaking the ceramic driver in a Kharma 3.2. I just had this happen to me - a driver tube blew, terrible noise from the woofer and it broke. The Kharma distributor said this was only the second he had heard of with an Atma-Sphere amp, but that it was much more likely with an OTL amp because of the lack of transformer. Ralph is interested in the frequency with which this occurs, as he feels it only happens with ceramic woofers, which are much more likely to blow than non-ceramics. Have any other OTL owners had this happen to Kharmas? I guess the lesson is to keep testing tubes or keep a careful eye on them to prevent this happening, but I would like to know if this was a freak happening or more common than has been generally accepted? Judging from the number of Tenor-Kharma combos out there, it should be more common than I thought if the combination of OTL and ceramic woofers is a problematic one.
"Ralph is interested in the frequency with which this occurs, as he feels it only happens with ceramic woofers, which are much more likely to blow than non-ceramics."

Sorry for your loss but the frequency is DC. By the way that is a stock accuton driver so it's like $230 to replace it.

Using open ended amplification will lend itself to tempramental behavior and occasionally the speaker system takes a hit.

I think Springbok is asking about the frequency of occurrence, as in number of events, as opposed to audio spectrum frequency.
"the frequency is DC"
Springbok, sorry to hear that a blown tube took out your driver. It's rare for those Russian 6AS7Gs to blow rather that simply shorting their internal fuse with little other fuss.
I think he means how frequently it occurs.(not the frequency of the signal that did the damage.)
Actually, it was a 6SN7 that blew. (RCA Black plate NOS) Very unusual. Yes, I am enquiring about occurrence frequency.
I'm also sorry to hear this news, Spingbok10.

I have had 6AS7G and 12SX7 tubes go bad on me. The 6AS7 continually builds up blue gas inside until they pop (and REALLY violently), which relieves the pressure. Then, the whole thing repeats. The fuse arrangement provides no defense. However, neither the amp nor my speaker was damaged in the slightest way. Replacing the tube corrected the situation, and bias was still spot on.

This being the only 6AS7G go down on me, I have been fortunate. Others have told me about the potential, ala the Soviet era QA/QC mindset. This being the reason several at the old ASOG site developed means of testing, run in, and burn in for the tube.

The 12SX7GT would send a really disconcerting pop through the loudspeaker at turnoff. Ralph's initial diagnosis was an output tube, but after going through each, I was still experiencing it. Trying the same thing with the input tubes found the culprit. I'm just glad it wasn't a capacitor or some of the other things we discussed.

For the record, I have never had a 6SN7 go bad on me.

As far as ceramic, in this case, alumina (Al2O3) drivers go, despite being very hard, they are brittle. It is not unknown for them to be easily damaged via shipping, handling, and now this reason. The one advantage a more conventional paper or polymer driver would have in this situation would be their compliance and resilience.
Would not a bias resistor have prevented this?? Meaning the resistor takes the hit??
I used tube circuitry for several decades and never had a tube "blow". In my experience when a tube "went bad" there were symptoms like audio distortion, noise, oscillation, blue glow and the like but never anything catistrophic.

One of the disadvantages of transistorized amps is that when they lose an output device bad things do happen. (Fortunately it is rare).
When you say "pop (and really violently)...", do you mean the glass bottle actually explodes, sneding glass flying everywhere?
I bet Paris Hilton's done that...wasn't it on that video tape?

I am a bit leery of OTL's. I know that if a tube does fail, they will not actually pass D.C. because they are coupled by a capacitor, but still, I worry. A friend borrowed a Joule Electra OTL and it was subject to intermittent popping. On his horn system, popping meant a sound that rattled windows and could send someone into cardiac arrest.
Cinematic_systems- The drivers used are not stock accuton drivers, kharma modifies them in house. So your right its not expensive but it can be time consuming and difficult to find the right replacement driver.
Not to be a wiseguy, Honest1, but if you read the next sentence, "Then, the whole thing repeats.", you will find the answer to your question...
This is very disconcerting to hear. I've read how much you enjoy the sound of the Kharma and Atma-Sphere combo. I was just digging up the thread where Tireguy *cough* was telling some stories about blown drivers :P and I see that you've already found it.

I trust what Jtinn said fully. If your speakers did not have ceramic drivers, it might not have blown, but it probably would have been damaged without you knowing it (not sure which is better). It is nevertheless a cause for concern since it can happen, but like anything else, there's a great deal of luck and chance/freak occurence involved. How many times have we read of a bad review sample? Considering the relatively small number of reviews and perhaps the importance of these reviews, you would think that the frequency in which a bad review sample is sent would be small but it isn't.

I've been lucky so far with my 3.2s. I don't normally play at great volumes but do turn up the volume now and then. I don't have extensive experience with tube amps but did for a time run a pair of Bryston 7Bs SSTs on them, so the ceramic drivers can definitely handle lots of power.

Keep us up to date on the process of getting your speakers fixed.
Howie- As I understand it the issue is not power handling but distortion/amp cliping which causes the driver failure.
Tim. Ya I know. I'm simply saying that ceramic drivers aren't exactly fragile in the strictest sense. That if the same thing occurred with another speaker driver, it would most likely still be damaged. Either way, this is indeed unfortunate and very worrying.

Lowrider over at AA had his speakers damaged by his Bryston amps (yes I know this is quite a different scenario). But Bryston agreed to cover the speaker damage as well. Since the amp is at fault here, perhaps Atma-Sphere would be willing to pay for the damages?
Ralph has had enough trouble, financially, without my compounding it! But I appreciate your concern and comments, Howie. We Atma-Sphere owners are blinded by the sheer brilliance of the design and sound, and will go to any lengths to keep them and not blame the designer:)I would rather change speakers than amp, if push came to shove. Hopefully, by checking all my tubes regularly, which Andy at Vintage Tubes will do, this won't happen again. All I need do now is replace the driver without burning it during soldering. I would rather just put a crocodile clamp on it but doubt the contact will be good enough (see thread under speakers)
Tireguy is right. It can be easier to damage a speaker with a 20 watt amp than it is with a 400 watt one. On the other hand, it's true the ceramic drivers are more fragile - damage most often occurs in transit.

Ralph is doing well, and sales are way up in the past month or so.
Springbok10- Don't worry about the driver replacement it really is very easy to do. If you have little to no experience soldering ask a friend to help you, if you can't find that practice on some scrap wire until you get the hang of it. Have a friend hold the driver and you solder it, should take less then 15 minutes, even if you work really slow.
Springbok10. I hope you keep us up to date on the repair process. I for one remember my work with a soldering iron *shivers* I do believe that there are some things that are worth the effort in dealing with the inconveniences and music is one of them.
Soldering is done. 15 minutes. So far, so good...........:)Thanks for the interest.
I'm sorry to here of you lose Springbok10.(belated)Hope all has been well since.

I'll have to stay in touch with this issue as I poses newly updated Atma-Sphere MA-1 Silvers that Ralph and his fine crew just updated. I feel the new caps are finally burned in, and could not be a happier camper than with Ralph's OTL's. Simply brilliant! But I'm running them through... Coincident PREt's with the Accuton's. Again, Israel Blume and his speaker designs, have just brought the whole thing together. At this point, no problems and no need to expect any... the music and performance is lovely.

I too am unwilling to part from my Atma-Sphere's, I'm OTL hooked.

Never had one of Andy's choice Sylvania 6SN7's go yet either, but have had two 6AS7G/6N13S Svetlana power tubes go, in over seven years of faithful service, but when they did, it was absolutely frightening! Yet, no damage.

Happy Listening! ;^)>