I am the US importer for KR. It is hard to know where to begin.
[1] KR Enterprise has been out of business for years. No printed documentation exists about these amplifiers, other than what we have recreated here in the US.
[2] No new 300B balloons have been imported into the US since July 2008.
[3] KR has had issues with dealers selling out of warranty tubes as new. As importer, when these tubes fail, the most I can do is offer new tubes at my cost, because I never received any money for the tubes in the first place.
[4] There were a bad batch of tubes that came through Coincident when I first started, but these were more than two years past the manufacture date at the time they hit customer hands, so these should have been marketed as NOS unwarranted by factory.
[5] The KR 845 does have sensitivity to heater voltage. As the tube heater draws substantially less current than a carbon plate 845, unregulated heater supplies will go to almost double the rated heater voltage. This is a recipe for tube failure. We screen all 845 sales to avoid this issue. Further, we have driven some design mods into KR 845 tubes and KR has renamed them 845M. Their reliability is now world class.
[6] It sounds like there is a lot of concern about the tubes. If you find a KR tube for sale, get the serial number off the crown of the tube, the tube type, and the vendor. Email that info to: tubehist@renaissanceaudio.com with KR Question in the subject field. We will let you know if the tube is legit, black market, or NOS and if the vendor is known legit within 48 hours of the receipt of the email.
[7] Lastly, unless you purchase tubes from me directly, please send in your warranty registration card, with a copy of the the purchase receipt within 30 days of purchase of the tubes. This is required to get warranty service on the tubes.
Unfortunately, by the time that we joined this party in 2008, a lot of damage was done by some importers/dealers with less than scrupulous intentions. This really was out of KR's control because the firms servicing the US and Canada are not owned or directly controlled by KR in Prague.
Since late 2009, we have bi-weekly quality meetings with KR in Prague to advance quality and reliability. The Mark II amplifiers were designed here in the USA and are assembled here in Michigan with the best and most reliable parts we can find.
Lastly, if you have an issue with a KR tube or amplifier, please email me at tubehist@renaissanceaudio.com.
We are trying to clean up the chaos, but trust is easy to lose and takes forever to rebuild.
