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Posts by Donald North

The Stratus chassis have all been made to fit a 9-pin tube socket. More importantly, I looked up the specs and plate curves for the 6N7. While it has a mu of 35 the plate impedance is 22k, which around 3 times higher than the 6N1P, and makes it much more difficult load with a high resistive load while attaining an optimum bias condition with a 300V supply. 2A3s run at a lower voltage than 300Bs, for example, so there is less voltage available with which to work for the...
The Stratus (and Stellaris) use the 6N1P for driver duties and has more than enough gain (mu of 35) to drive the 2A3 to full power. The 6J5 and 6SN7, for example only have a mu of 20. The 6SL7 has too much gain, in my opinion, combined with a high plate impedance with associated complications.I like your suggestion for him to max the volume control on both amps and use the variable out from his DAC and compare.
I think there is a misunderstanding: The unbalanced inputs go directly to the volume control and 6N1P input/driver tube. The balanced inputs are received through the Audio Note input transformers, then sent to the volukencontrol, etc. Some amp send both the balanced and unbalanced input signals through the input transformers - I don't do this in the Stellaris.
The balanced input option adds a pair of custom Audio Note input transformers which accept and convert the balanced signal to unbalanced. From there the amplifier is single ended.
In my experience a proper silver transformer provides unmatched transparency, allowing you to clearly hear all of the nuances and layering within a recording. In order for you to hear its ability, everything else within the amplifier (power supply, coupling, and cathode bypass capacitors, resistors) needs be of the same calibre otherwise you won't hear the full benefit. I experienced this firsthand while working on a phono stage. Once you have an amplifier which is built...
A Silver Stellaris features silver-wound Audio Note input and output transformers, silver foil coupling capacitors, and silver internal wiring. Chassis will be blue.
A stage is an active stage of amplification, which are then cascaded. A tube gain stage can be a simple cathode-biased triode or SRPP or cascode or mu-follower, as examples, and can consist of a single tube section or multiple tube sections or hybrids (tube & solid state). The Stratus and Stellaris are 2-stage amplifiers: The first gain stage is provided by the 6N1P; the second stage is provided by the 2A3. How these 2 stages are coupled (direct, capacitor, transformer)...
Hopefully sooner. I may be able to build the first one in 2-3 months.
You need to adjust the hum nulling potentiometers each time you swap 2A3s. With no music playing, set the volume control to 0 and use your most sensitive headphones. Carefully listen and adjust until it is inaudible.When using TRS headphones the -6dB setting changes the secondary grounding from the - end to the center tap, thus reducing the output voltage by one half or 6dB. Output impedance is also reduced from 8 to 3 ohms. This settings is useful for low impedance...
A head-fier recently brought the KEF Muo to our office to compare to the Turbo X and S. When listened individually I was surprised to find that the Muo operates as a mono speaker. They have some explanation for this on their website. You need two for stereo.
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