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Posts by Donald North

Think of the Stratus as an integrated amplifier for headphones. The preamp duty is handled within the amplifier by the 6N1P. Now if you were to listen to vinyl through the Stratus, then you would need an external phono stage preamp.
Bypassing the internal volume control and using an external active preamp is not a good idea, in my opinion and experience. You will be adding more gain to the signal path, when there is already plenty with most sources and reducing the usable range of the volume control before it is too loud with dynamic headphones. You will also be adding noise. Of course you are welcome to try by turning up the Stratus volume control to maximum, thereby effectively taking it out of the...
Thanks, the design is not yet final and there are some more features I am considering to add to further improve performance. Stay tuned
I just received the Audio Note input transformer samples. I do not know their price yet. Once I receive it I can calculate the amp price difference.
The 20A amp needs to be driven from a low source impedance, be it a DAC/disc player with variable output or active preamp. Volume attenuator can be analog or digital. Transformer volume control can also be used but not a traditional resistive passive preamp because their output impedance will be too high and cause high frequency attenuation.
It's always a cost versus benefit trade off and to attain that last few percent of performance the added cost is exponential. These custom input and output transformers made by Audio Note in England are not inexpensive to put it mildly. Take a look at their website for reference.
The 20A is a concept headphone power amplifier from an idea of creating a minimalist, ultimate single tube DHT amplifier intended primarily for the HD800 and other higher impedance dynamic headphones. It is a special unit for a select audience. I first demonstrated it to some friends back in December 2014.The Solaris is more an all-rounder, like the Stratus, with improvements in all aspects of the listening experience.
I will look into this possibility. Space inside the Stratus is tight and I need to see if there is room to fit the balanced input transformers.
Thanks for your voice message Paul. I was in meetings all day and will call you tomorrow. To answer your questions, the Solaris is a dream I have had for the past 6 years. I first reached out to Audio Note about some custom 2A3 headphone transformers back in July 2009. They are very busy but after 6 years of patience and persistence, they finally developed a custom pair of output transformers to my specification. I received them earlier this summer and they sound...
I would like to test your speaker. Let's exchange your unit for a new one. Kindly PM me with your details and I will make arrangements.
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