Audio Note M10 Signature - Manual (Page 8)

I created a working model of this power supply at Audio Note (UK), and we
assembled a very high-end version of what was essentially an M8 preamp to be
powered by it, and the results were really mind blowing.
At the same time I designed a special input transformer to received balanced signals,
this transformer has exceptional noise rejection powers, yet has an equally
exceptional bandwidth and very low distortion. Of course this component is also
wound using silver wire and assembled using the highest quality laminations and
materials.
The M10 uses the finest materials and components available, even down to the use
of a special ‘densified’ wood circuit board material.
We know what happened when the M10 was released to market. What was intended
to be just a special preamp for a few chosen customers became a phenomena in
itself...
If we fast-forward to today, then we can discuss the M10 Signature. The concept is
essentially the same, but I have further optimised the PSU by changing valves and
utilising their characteristics.
In the M10 Standard, we have an EL34 as the shunt valve and a 6SL7 configured as
a current reference, which in turn defines the output voltage. In the Signature I have
substituted a 12E1 for the shunt, and a 6SJ7 as the current reference.
The 12E1 is a Special Quality beam tetrode, similar in some ways to the KT88. It has
considerably more power capacity than an EL34 so I can increase the shunt current.
The fact that it's a beam tetrode lends a harder clarity to the sound, which requires
some modification further down the line. I replaced the 6SL7 current source with one
built around a 6SJ7, this was done so I could pass more current in the C.S., and
because I could create a bootstrap circuit around it and feed a more accurate AC
signal to the grid of the 12E1.
AN INTRODUCTION FROM THE DESIGNER continued…