Having guarantee issues with KR Audio?

I had the same issue with KR and Coincident, one of tubes broke after 150 hours or so. Coincident refused to replace the tube and asked to talked to KR. They said I should ask Coincident. After several e-mail exchange I gave up.
A few months later I met owner of KR personally at Audio Show in my country. She promised me to replace the tube and after a few days I receive the matching tube.

Beware that not every 300B tube would work with Frenkenstein and for some of them its dangerous. There is no information about it at Coincident site. Here are parameters of Frenkenstein, You can consult it with a technician or compare to recommended by manufactures max values.
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Plate Voltage 580 Volt
catode Voltage 97.5 Volt
Plate Current 97.5mA
Plate Disspation 56,55 Watt
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Anyway, I'm going to sell Frenkeinstein, I still prefer my second amp, ASL Cadenza (modified). For me Frenkeinstein suffers of typical 300b limitations.

I love the Frankensteins. They just flat out please both the audiofool and music lover in me. These tubes were recommended (and sold to me) by Israel Blume himself, and he hasn't steered me wrong as of yet. I can't believe he would make an error and then not rectify the situation, so I have to assume that KR Audio has issues.
Funny though, I'm at 150 hours or so.

After speaking with Eunice Kron( owner of KR) over dinner in Las Vegas, she advised that KR no longer has any intention of selling KR 300Bs to any outside source, instead opting to manufacture tubes solely for use in their own amplifiers. However, right after this conversation, she doubled the price of the 300B tubes over night.

As for reliability and warranty of KR 300Bs, their longevity for those tubes manufactured in the last 18 months has deteriorated. They seem to be more prone to premature demise. Coincident has received back about a half dozen 300Bs that have gone bad within 6 months of use. KR does offer a 6 month warranty. Well this is not really a warranty at all, as it turns out. After sending back to KR all the defective 300Bs, KR denied offering replacements because " the tubes were misused by their owners and therefore not subject to the warranty". In other words, KR offers a warranty but if a tube becomes defective it is the user's fault and not KR's.

In the case of 2 customers who had their KR 300B balloons expire within 2 months of use, we replaced them free of charge inspite of the fact that we only offer a 14 day warranty on tubes.

Due to all of the above, we no longer stock nor sell KR 300Bs. Our standard supplied EH Gold Grids have proven to be extremely reliable( not a single failure in the field) and sound superb. For those who wish to upgrade, we highly recommend the Sophia or TJ carbon plates. They sound great and their manufacturers extend a genuine up to one year replacement warranty. We no longer offer for sale, any 300Bs other than the EHs since we are confident in their reliability and sonic performance.

As for using differing 300B tubes in the Frankenstein amplifiers, all of them will work as the operating voltages and bias current of our amps is within spec for all of them. Stereomojo used the Frankenstein as the reference amplifiers in a 6 tube 300B comparison with no tube failures. If the 300B is properly manufactured and falls within the specs required for a 300B, it will work without incident in the Frankenstein amplifiers. Some tubes are better constructed then others and will last longer but that is a tube issue nothing to do with the amplifiers.

Israel Blume
Coincident Speaker Technology