I am the KR importer and have the only two new KR 845M's on the continent. My next shipment arriving in a few weeks should have four more 845M's.
While, I would love to say the KR's sound the best, they are not totally compatible with all amplifiers. This is why I insisted that KR reclassify their 845 as 845M.
At issue is the heater current requirements for the 845M. They draw dramatically less heater current than a traditional 845. Yes, they are way more efficient to heat, but the heater power is minimal when compared class A operation.
Many amplifier designers, to cut costs, do not use a regulated filament supply. When you use a KR tube, in these amplifiers, the voltage rises substantially above the rated heater voltage and the KR tubes burn up. This, unfortunately, is a misapplication and is quite visible in the tube and warranty replacement is difficult to defend.
An additional issue with the KR tubes is their plate coating, which is the most durable on the face of the planet (remember, metal plate tubes need an oxide coating). KR tubes need some run time to "sound proper," like 80 hours.
In a 10000 hour MTBF tube, this is small, but for flipping tubes, makes a judgement call difficult on short order.
If you would be interested in trying a pair of 845M's and your amp can handle it, email me at [email protected] and we will see what we can arrange.
While, I would love to say the KR's sound the best, they are not totally compatible with all amplifiers. This is why I insisted that KR reclassify their 845 as 845M.
At issue is the heater current requirements for the 845M. They draw dramatically less heater current than a traditional 845. Yes, they are way more efficient to heat, but the heater power is minimal when compared class A operation.
Many amplifier designers, to cut costs, do not use a regulated filament supply. When you use a KR tube, in these amplifiers, the voltage rises substantially above the rated heater voltage and the KR tubes burn up. This, unfortunately, is a misapplication and is quite visible in the tube and warranty replacement is difficult to defend.
An additional issue with the KR tubes is their plate coating, which is the most durable on the face of the planet (remember, metal plate tubes need an oxide coating). KR tubes need some run time to "sound proper," like 80 hours.
In a 10000 hour MTBF tube, this is small, but for flipping tubes, makes a judgement call difficult on short order.
If you would be interested in trying a pair of 845M's and your amp can handle it, email me at [email protected] and we will see what we can arrange.