January 19 2015

Happy New Year!

Recently with the D5000 DHT DAC we were replacing right channel 3A5 NOS RCA tubes at an abnormal rate. Stereophile’s John Atkinson thoroughly tested the D5000 last fall and reported a number of poor and puzzling measurements. KS Park and Colin Shin at Waversa Systems confirmed that the measurements Mr. Atkinson obtained were due to 3A5 tube failures. Replacement of the tubes solved the problems. However, it was difficult to understand how the age and delicacy of the DHT 3A5 tubes could lead to problems so consistently. KS Park thought there might be an underlying issue. He had relied on a vintage Polish tube manual produced in 1942 for the voltage parameters of the double triode 3A5. The Polish publications have always been accurate, but in this case, upon researching the tubes further and cross-referencing with other sources, he realized that the document he used reported the upper voltage specification incorrectly. That led him to design the DAC to run the tubes above their actual upper voltage limit. What a frustrating result for our customers, for which we are very sorry - and also a frustrating and very humbling one for us!

Since this error was discovered, we have redesigned the circuitry of the D5000 to reduce the voltage to proper specification. Resistor kits for the voltage reduction have been sent to pre October 2014 D5000 customers. Included in this kit are new 3A5 tubes that have been tested and burned in on our new tube tester shown in this picture. Once the new resistors are successfully installed, please remove all the old tubes and replace them with the new ones supplied. Please dispose of the old tubes. If we have missed any customers, please contact Hammertone Audio for immediate assistance and financial reimbursement.

Last year, tube resellers New Sensor imported and introduced a marvelous version of the venerable KT88, KT120, 6550 power tube - the KT150 from Tung Sol. These new tubes might be drop in replacements for the earlier versions in some amplifiers but can require circuit changes in others. Run to spec, the KT150s have tremendously attractive sonic properties and enhance the sound of Allnic’s T2000 integrated and M3000 mono block amplifiers. The KT150s can be run in existing Allnic amplifiers using the KT120 tube but require bias to be set at the top of the range, just inside the right hand parallel line on the bias meter. Having tested this new tube for sonics, stability and longevity, we will now use the KT150 as OEM equipment on a new 200 Watt M3000 Mk2, KT150 version of our most powerful amplifier. This new version of the M3000 will operate strictly with KT150s due to increase of plate voltage from 450V to 500V maximizing performance from this soon to be legendary tube. Expect March 2015 deliveries. The highly popular T2000 integrated will continue to be a flexible unit, utilizing the 6550, KT88, KT120 power tubes as well as the KT150 with no modifications required, only the previously mentioned bias adjustment for the KT150. It can be ordered with KT150s at additional cost. Due to new interest, we are also reviving the A2000, a 70-90 WPC stereo amplifier, with the same flexibility as the T2000. Chassis will be available April 1st, 2015.

For L5000 DHT owners, inventory of the KRON KR3A tubes is now available to replace the existing NOS 3A109/3A110/MROPT8 gain tubes. Benefits include sonic improvements, dependable supply and reduced microphonics. Contact your dealer for pricing and details.

As always, thanks for your continued trust and kind feedback!