Second failure of new amplifier

Two weeks ago I burned my new amplifier equipped with eight 6L6 tubes. I had been using the amp for one week before that and everything was OK. The failure occurred when I was switching the amp to the standby position and then to the "off" position (two small tubes and two central power tubes flared, so I switched it off and disconnected from the mains immediately). Switched on - no sound. I found out then that the failure was caused by one damaged 6L6 tube and one burnt fuse.

I replaced the fuse and one tube and everything was OK, until I decided to listen to the music today. I listened to it for 15 minutes, then the same problem occurred - when I was switching it to the standby position and then to the "off" position, there was a clapping sound, one 12AU7 tube ignited (flared strongly) and the tubes do not glow after switching on. I will explore this problem further when I come back from work.

When I was purchasing this amplifier (I would prefer not to disclose the manufacturer), my local dealer claimed that the amp had a "stabilized power supply design" or something like that. One of my audiophile friends dissuaded me from bying this amp, saying that 4 output tubes per channel may cause a problem. The dealer said "don't listen to him - he does not know what a "stabilized design" means."

I think I know now what is "stabilized design" - it's burning fuses and tubes every second day. My dealer is reluctant to take it back even for resale (I suggested that he took it for repair and sold it and only after that give me money), but he claims that the guarantee is void because I replaced the stock tubes (12AU7 and 6922) with my own (vintage)tubes and that I should have waited for a couple of months (while it was burning-in) and should have used it with stock tubes without replacing them for other tubes. He added that according to the European ISO standards, changing the tubes would void the warranty.

My questions are:

1. Does tube-rolling in a new amplifier always void the warranty?
2. Is it true that the auto-bias function (especially when the amp is powered with so many (8!) output tubes is unreliable as compared to manual bias adjustment (like my other amp - Cary SLI-80)?
3. Is it normal when a brand new amplifier behaves like this?

I will appreciate all comments, opinions and suggestions.
I wouldn't do a thing until I cleared it with the Dealer you bought it from..As far as I am concerned they ( dealer ) should take responsibility from here..There is something going on internally ( my guess ) that is causing this to happen..You shouldn't have to mess with tubes for at least a year or two..I also wouldn't start rolling tubes until you realy give your ears and your new piece a good chance..
No it is not normal..and rely on your Dealer for help!!!!You can find out how he can Stabilizes the situation!!!
Does the amplifier exhibit the same behavior with the stock tubes? I would suggest putting them back in and seeing if the problem occurs again--if so, then the problem may not be attributable to the NOS tubes. I would not think tube rolling with tubes of the same type should necessarily void a warranty, but you'd have to read the warranty to be sure, and this sounds like a European law question with which I'm not familiar anyway. In any event, I agree with Thorman, your dealer should be fixing this problem for you; just make sure that it in fact is a problem with the amp and not with your tubes. This does not sound like normal behavior for an amp. As far as autobias circuits, Jadis has had them for years with their amps; I never had a problem with my JA80s relating to that circuit.
As long as you rolled the tubes with tubes of the exact same family(IE: 6DJ8/6922/6H23/7308/E88cc/E188cc/CCa) it should not void the warranty. Burn-in time has absolutely nothing to do with an amps affinity for blowing tubes. Sometimes the translation from another language can make a warranty sound like tube changing will void it. The Lector CD player warranty SOUNDS that way(via translation), but the designer is a veteran tube roller himself, and rolling does not void their warranty. Contact the manufacturer, and request that info directly. I don't believe the driver or phase splitter tubes would be taken out by a problem in the auto-bias circuit. It sounds more like a power supply/transformer issue. Again- Contact the manufacturer. Solid state servo bias adjusters that tweek each output tube's bias on the fly, on a continuous real-time basis("Auto-Bias Circuitry") are great in that they 1)free you from having to buy matched sets of output tubes 2)eliminate the possibility of you mal-adjusting the bias 3)keep the tubes running exactly where they should.
You weren't clear if the tubes you installed were the the same type as the factory installed. If you replaced the 12AU7 and 6922 with the same types it should NOT void the warranty in my opinion. In the close to 40 years I've been an audio electronics hobbyist (building, repairing and modding - I've got the scopes, distortion analyzers, meters, freq generators, etc.) I've never heard anyone else state that changing a brand of tube voids a warranty. I'd strongly question that. I'd want to see a copy of the "European ISO" regulation with my own eyes.

Now if you were experimenting with different types of tubes there could be an issue - the pin-out or operating characteristics could be different and cause a problem.

However, step 1 is to figure out what is currently wrong with the amp. If putting the original tubes back fixes the problem, you may have had nothing more than a defective tube. If something more is wrong, it still needs to be found. No manufacturer has 100% quality control and it could be that while a part passed the initial QC tests it might have been marginal and was doomed to fail in a short period of time no matter what you did or didn't.
This is a question of dishonest dealer, for sure. If I were in his place, I would make my best to maintain good reputation.
Quickly ditch the unit back to the dealer for a fully 100% refund and stay away from the brand. Make it a dealer problem. Move on, quickly.
Replace the burned tubes with the stock units. See if the problem goes away. If it does, you're finished. Also, why is everyone so reluctant to provide the name of mfgrs. here? It isn't as though you said anything libelous.

Give us the mfgrs. name, please.

#1 - Fact is you had no choice but to replace the tubes since the first unit took them out in the first place..

#2- no it should have nothing to do with a warranty putting different but correct tubes in the unit.

#3- at the VERY least the dealer should provide you with a brand new set of Stock tubes free of charge, as the manufacturer does have at least a 90 day warranty or so on tubes period I would assume, you have done nothing wrong with trying to correct a problem from the get go and make it better considering the only reason you put NOS tubes in the unit was the originals turned to toast on a brand new unit which you would not even considered doing it this early I am sure..

It seems if the dealer is giving you an issue on this then it is not explained to them correctly that THEIR Stock unit was toasting itself in the first place, and you just tried to rectify it, however you need to realize your loss in the NOS tubes is not their responsibility.. But the Stock Tubes absolutley are, and they can take the unit back, re-tube with stock, and refund you and take their chances on selling it again on their own.. You should have a 30 day return policy with them anyway.
Undertow: While your analysis would normally be correct on the above facts, the poster had an earlier thread where he said that he had used the amp for a week with no problems with the stock tubes, then decided to tube-roll and started having the problems after he did that--the amp failed only after he put in the NOS tubes. Hence my advice, which was based on knowing about that prior thread. And for those of you who are interested, you can get the name of the manufacturer from that thread too.
, No I think I read the STOCK tubes welded themselves in place he was able to actually remove them and replace the fuses etc... After that with the NOS... I might be wrong
OK. To resolve the second failure, I replaced the fuse and installed the stock pre-amp tubes. The amp sounds terrific, by the way (which makes me think that some modern amplifiers are optimized for modern tubes - if you replace them with NOS tubes, you sometimes hear "mushy" sound and a loss of focus)... I will see how it behaves with the stock pre-amp tubes.
Transl, sounds like nothing more complicated than one of your NOS tubes was defective. That certainly can happen.

As such, I'd just run it stock for a while to make sure nothing else is going on. If it continues to work well, then you can continue with your tube rolling experiments.
I suppose it's also possible that even like-type NOS tubes may have caused the problem even if they were good. But that would presume the amp had no autobias, or that it was not rebiased when the NOS tubes were put in, AND that a scenario like that would cause just such a problem. Hard to imagine for anything with a reasonable design, but if it's even likely that the amp would become so unstable with anything other than the manufacturer's specified tubes then I might reconsider owning that piece of equipment.
I'm surprised by those who think tube rolling wouldn't void the warranty. Why would a manufacturer stand behind a product with parts he did not supply? That's crazy. Some waranties are void if you simply remove the equipment's cover, let alone exchange original parts.
I'm surprised by those who think tube rolling wouldn't void the warranty.
I gather you don't have much technical experience with tubes. You can get a tube data manual and find that any given tube - say a 6922 for example - has to meet a set of specifications unique to that tube. See
for this particular example. It doesn't really matter which manufacturer makes the tube; if it is a 6922 it should meet those specs and be safe to use in any circuit designed to use that tube.

Any differences in sonic characteristics will be due to slight differences in physical construction - say one manufacturer's screen or plate may differ slightly even though the raw electrical specs are the same.

As noted before, any manufactured product can be or become defective. It is far more likely that the tube that caused your problem was simply defective (or headed that way) when you installed it.
Mlsstl is 100% correct. like # tubes are the same, whether they be NOS or current production and use of NOS tubes should not void a warranty. what happens if the supplied maker of the tube closes? a tube is much like a lightbulb, a 60watt Phillips is the same as a 60watt GE.
Contact the manufacturer, and tell them how the dealer is treating you. AND you should tell us how its resolved.
If you used the wrong tubes though then its a learning curve.
Tube rolling is part of the fun...
I think your dealer is full of it. I have never heard rolling tubes can void a warranty and if this particular amp will not allow for tube rolling than it should be noted in the warranty or this unscrupulous dealer should have stated it to you. Usually unauthorized modifications or abuse will void the warranty. If possible speak to another amp manufacturer to get an idea of their thoughts on tube rolling in their amps. I know my amp calls for 6550 tubes and I wanted to use KT88's. I called Conrad Johnson and although it wouldn't void my warranty, I was told that I would be unable to bias the KT88's, but that is a far cry from voiding a warranty. I also contacted Cary at one point because I wanted to replace the 6SN7 tubes in my SLP98 preamp with 5692 tubes. The Cary tech told me that it would be no problem and that I would probably like the 5692 tubes very much. This has to work out for you, as you have done nothing wrong. If you cannot get satisfaction from this dealer, then you should contact the better business bureau. Good Luck to you!!
Is it always the same tube socket? If it is, check the socket under a bright light. Look for burn marks, carbon deposits or mechanical damage in the pin holders and solder points. Use a magnifying glass as even a carbon coating could cause an arc short - and it does seem like there's a short somewhere. Could have been initially caused by a bad tube and replacements may suffer the same fate.

Rolling tubes may have an effect in causing tube failure if the amplifier has a fixed bias setting. Even if the tubes are compatible substitutes, there could be a slight change. But not enought to result in a short IMO.

Curious... why use the standby switch to power down? Is it recommended? Using the standby does not allow the tube B+ voltage and power supply caps to power down gradually. Also, the bias settings may be affected when you roll tubes which may cause the plate current to increase. These may be reasons why the first tube and fuse blew in the first place or just pushed it to premature failure. I'm just going by my experience with guitar amps - power on with standby but power down with just the power switch - but whatever your manual says overrides.
'Curious... why use the standby switch to power down?' - how can I avoid the standby switch? Shall I make two quick clicks - standby and then immediately to the "off" position?

By the way, the amp is working now. I replaced the fuse and installed the stock EH 6922 and 12AU7 preamplifier tubes. Sounds very nice! I will watch how it behaves with stock tubes. Afraid to roll tubes forewer (but not with the second amp - Cary SLI-80).
I gather you don't have much technical experience with tubes. You can get a tube data manual and find that any given tube
That made me chuckle as I began my life as an electronic technician back in the days of tubes. Used to have a tube tester in my garage. I fully understand the principle of suitable substitution.
That being said, I'll admit I don't know much about warranties for tube electronics. It still would surprise me if a manufacturer is obligated to replace a defective unit when the defect was caused by a faulty tube (not supplied by the manufacturer) being placed in the equipment by the new owner. Just an assumption as I haven't read the warranty agreement, I could be wrong.
If the product had a defective tube socket that wasn't apparent until the original tube was removed that's a different issue and Transl was fortunate to discover it. This needs to be discussed with the dealer.
Timrhu, what would you say if Ford or GM voided your car warranty because you put in Bosch spark plugs instead of the Champions (or whatever) that it originally came with? Or limited your brands of gasoline to Exxon/Mobil only. ("I'm sorry, your warranty claim is denied since you used BP/Amoco gas.")

Another problem with that logic is the brand of tube used is often meaningless since many tube manufacturers are no longer in business even though the brand may still exist. Those tubes are being made elsewhere.

I have to say that in 40 years of involvement with the technical end of audio this is the first time I've ever heard someone trained in audio electronics claim a warranty was likely to be voided based on the brand of vacuum tube used. Interesting.
Mlsstl and Timrhu, FWIW, a warranty covers exactly what it sez it covers (so long as it conforms to any State laws regarding warranties), not what you would like to speculate it should or should not cover. I don't see that Transl has ever told us what the warranty actually said.

While I'm a bit confused by the multiple comments regarding tubes initially rolled in, it looks to me as if the only tubes were the small tubes, not the power tubes, and I agree with those who have said that substituting brand A 6922 for brand B 6922 (for example) should not affect the operation of the amp and the failures experienced by Transl. Had Transl identified the actual amp perhaps someone here with hands on experience could have helped him. FWIW, something tells me that the problem lies in the standby curcuit's operation.

- I was not given a warranty and I don't know what it says. The dealer, or, rather, the distributor, prefers not to give a warranty saying "I myself am a warranty". Perhaps he wants to conceal the original price by all means and to prevent a buyer to contact the manufacturer directly. He succeeded in it - the company's president stopped to answer my queries.
Transl, Unless the dealer and the manufacturer are thugs and will come out and do you harm, why not identify them so that others will be warned and will not duplicate your unfortunate experience?
"I myself am a warranty"

Really now!? To state it rather bluntly. . . You have been had!
Is this a Nightingale product?
Mlsslt, who said anything about the brand of tube voiding the warranty? What I'm saying is if a user installs a DEFECTIVE part in a piece of gear which damages the piece, he just voided the warranty. If that doesn't void a particular warranty the manufacturer needs to hire better lawyers to write his warranty.
Timrhu, thanks for the clarification. That condition wasn't specified in your first message. It was simply described as "exchang[ing] original parts."
There's a strong possibility that you have made a grey market purchase, so there won't be a warranty from the manufacturer or perhaps your guy is not an authorized dealer, which also would mean that there will be no warranty from the manufacturer, or he is just an unscrupulous person, which seems to be the case!

I don't think that a defective tube should destroy an amplifier. Even a brand new functioning tube will one day become lifeless and defective. At that point, will it destroy the circuit? I guess it is possible, but it never has happened in my experience. I don't think there are too many threads on this topic either, which would seem like this is a rather unique and unfortunate incident for Transl.
I still don't think he has done anything wrong, except that he purchased this amp from some loser!
I want to thank all guys for compassion and understanding. I haven't decided yet what to do - the dealer keeps (and will obviously continue to keep) silent, while the amp is working OK with the stock tubes, except that I installed the Mullard CV4110 tubes in the 6922 position (tomorrow I expect NOS TungSol 5881 tubes to arrive and I am not sure whether I will install them or not under the circumstances). I will be watching for the amp's behavior.
I have a new amp and have had tube failure. I am new to tubes an did not replace the tubes. These things can happen. But the service I expect is the service I'm getting - the importer came to my house, replaced the tube (and the other one in the pair for a match) and the fuse. Unfortunately it seems to have taken something else with it so the amp is in for repair. I understand that tubes which test fine can become defective, it's just bad luck. But you should expect the sort of service I'm getting - no questions asked, it's being fixed.

Just for information - the tube in my amp arced inside the tube and although I turned the amp off in a hurry it was dead after this (fuse blown). Now if a replacement tube is put in there is a big orange glow in the tube in the position the offending tube came from. Hope it's back soon though.

If it works fine with the stock tubes, then I do think that have to look elsewhere for the problem (i.e., something wrong with the NOS tubes (a short, etc). I can't imagine that the amp would work fine with new tubes and not NOS. I also agree with those who said that rolling in identical NOS tubes should not/cannot void the warranty. Tubes wear out and they also fail occassionall. They are a normal replacement item. This would be like a car manufacturer telling you your warranty on the entire car is void because you replaced the brake pads at Sears instead of the dealer.
Amp failure update:

Yesterday I received an octet of brand new NOS/NIB TungSol 5881 tubes (60s vintage). Trembling with fear, I inserted them in proper positions and listened for a couple of hours. Even in half an hour, the sound was fantastic. I switched the amp off without a problem.

Today in the morning I switched the amp again and very soon heard some noise (cracking sound) from the left speaker. Switched the amp off, let the tubes cool down and swapped the output tubes from left to right and vise versa (exchanged the channels). The problem did not appear again. Went to work. Will resume the listening in the evening. What could have caused the cracking sound? Gas burning inside the tube(s)?
Something to consider, and which presents itslef in one of my mono amps, on start up and for the first 5 minutes or so there is a light crackling (heard when you are standing near the speaker). I thought it was the drive tubes and changed them - it went away and came back. I eliminated the power tubes. It turns our the problem is the driver tubes sockets don't grip the pins tightly enough until the metal heats up. I figured this out by simply pushing the small tubes down/sideways and noticed the crackling sound went away. Don't know if that could be your problem. Wrong pin size in power tubes has been a problem for JJ Tesla and that can be a major problem for users. FWIW.
Look this thread has no meaning if we don't know the manufacturer of the amplifier in question, otherwise this whole thread is just speculation and that is NOT what I thought Audiogon was about.
The manufacturer's name transpires from the previous posts, so this thread is not a speculation.

Here is the response I received from the manufacturer:

'I understand your disappointment for a malfunction of a new equipment. But let me tell you that I don't agree with your request to return the equipment to the dealer, loosing money. I believe you buyed the amplifier as you liked it, and you have the right to own a perfectly working equipment.
Our goal is the customer satisfaction and if you were in Italy I should have requested you to send the unit to our factory for a careful control: this is the first time an ADM35 or ADM32 has such a problem and we are interested to investigate the causes.
Unfortunately the distance between Russia and Italy does not allow it.
Anyway, please let me be informed about the operation of your amplifier: I hope the malfunction was a temporary problem, and you can enjoy the ADM 35 and the CTR-2.'

Rather vague and inconstructive...The amp is now working with vintage TungSol tubes, by the way.
>> The manufacturer's name transpires from the previous posts, so this thread is not a speculation. <<

WHAT? Why don't you just come out and state, CLEARLY, the name of the Mfgr.? All you have done is waste our time and good will...

I wrote - Nightingale.