Audio Note UK launches the flagship preamplifier, the M10 Line Signature, which is based upon the M10 Line with the following refinements:
- Larger and “significantly” improved 55% Nickel Double C-Core output transformers and input transformers
- Dedicated input transformers for each pair of the two pairs of XLR inputs
- “Significantly” improved power supply providing greater stability, clarity and refinement
According to Andy Grove, Designer in Chief at Audio Note UK: “….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… 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 a 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 12E1for 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
The preamp unit of the Signature is also upgraded, I redesigned the output transformers, this time using a much larger core of the same 55% nickel iron material C-Cores. This allowed me to increase the bandwidth and lower the distortion of the output transformer as compared to the original.
To further improve things I designed a new input transformer, again on a larger core. The results are the same as for the output transformer. However here I have used a double screen between primary and secondary to separate the grounds internal to the preamp and external to it.
These improvements to the transformers are akin to having larger windows on your house, more light is allowed inside so you can see more clearly. The upgrades to the power supply and to the transformers made an incredible difference to the absolute clarity of the machine. However, we are not in the business of making lab instruments: The M10 is about musicality.
So, the next step was to tune the circuitry by ear, and for an audio component of this quality level that requires time, knowledge, good ears, patience – and a good system in which to insert the unit and listen to it.
In the end not too much was required to be done, the incredible clarity meant that I had to slightly rebalance the voicing of the preamp (I have a box of “magic components”!). It took some time to get it exactly right, but the results were absolutely worth it.
Not only were we hearing into recordings to an unprecedented depth, but the sound had a beautiful organic tone, for example wooden instruments felt like they were wood, you could feel it inside yourself, not just hear it. Percussion was tidy, but not blunt, rigid and “square edged”: Drums had a defined dynamic envelope and resonance.
What really left us with open mouths, and a tear in our eyes, was the representation of voices. It seemed that before, even with the M10 Standard, you heard a voice, but there is a thin veil between the sound of that voice and the communication with your soul. The Signature lifted that veil, and Ella was singing to each of us personally.
We know what it means when you look at a pretty girl across the street, and then she turns and looks in your eye…”
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