Audio Note Kit2
Integrated Single-Ended Triode Hi-Fi Amplifier - 12W per channel
The Audio Note Kit Two 6550 stereo amplifier yields about 12 watts in pure unblemished Class A, single-ended operation. It uses a single 6550 pentode per channel, one of the most popular and reliable pentodes ever designed in a single-ended arrangement. Each stage of the amp is operated in class A.
We chose a simple circuit, where both channels of the input fed directly to each half of a 6SN7GT double triode operating in an unusually high current mode, the gain control potentiometer is placed AFTER this first gainstage, to allow the amplifier to be driven by any source with a minimum of noise introduced by this first stage.
The 6SN7GT inut stage feeds a 12AX7 driver stage. The 12 AX7 is a miniature double triode of high gain and in our circuit is configured is a SRPP (Shunt Regulated PushPull), which gives a gain stage with a very wide dynamic swing, low impedence and outstanding drive capabilities.
For the output stage we chose to use the popular and very rugged 6550 pentode. In our kit it is used within its limits and coupled to an oversized in-house designed and manufactured Audio Note output transformer with 4 ohm and 8 ohm taps.
No real compromises have been made within the component choice in the audio circuit, each component being of the best quality and being operated most conservatively, ensuring reliability and long life. Despite the low price of the kit the chassis and PC-boards are of a high standard.
...Oh, the sound? It is a bit early but I can tell you that if you need a bit more than the 8 watts a 300B provides and 12 watts will drive your speakers, this may be the best 12 SE watts one can obtain. Even right off the bench, the Kit 2 has a beautiful, extended upper end and as a few others than came in and heard this amp commented, very impressive bass. The midrange is so real, you may feel obligated to offer the artist a glass of wine...
|Bill Baker - Response Audio|
Brian in Perth Australia
Paul Hefer in USA
I bought the kit2 as I needed to drive 88db Meadowlarks and the 300B kit offerings available were just not going to cut it. I favor the 'SET' sound as the normal push-pull unltralinear/tetrode amps have a transitory flavor that just doesn't float my boat. Brian convinced me to go for the 6550 SE (not SET mind) amp. The kit 2 runs single ended but in tetrode (or pentode?) mode.
When I fired her up I was amazed at the sound. The Kit2 is not a compromise, but seems to combine the best of a SET amp and a ultralinear/tetrode push pull. Strings, brass and vocals are amazingly detailed, lifelike and vibrant, yet the amp is extremely extended on both end and has a prostigeous bass. I was absolutely amazed when I heard the the bass -it really slams! My current reference is a (highly modified) 6C33 based SET from ASL and the kit2 was giving it a good run for it money, with std tubes and with no uprated parts.
Flo - Sweden