M9 Phono


The M9Phono pre-amplifier in gold and black

Why Did We Design the M9Phono?

Being a major record collector, I have always felt the need for a top flight pre-amplifier which was focussed on getting the absolutely best from the LP, whether mono or stereo, the M9 is therefore designed as a proper record collector’s control centre and features a stereo – mono switch and the most direct and cleanest signal path possible, with no tape input or loop, it is really designed to maximise the quality of all LPs made with the RIAA curve, whether mono or stereo.

The Technical Stuff, Circuit Description Etc.

The line stage is used a 5814a/12AU7WA/ECC82 first stage and a 7044 second stage with each channel amplified by one side of these double triodes, the 7044 is coupled to a specially designed fully silver wired output transformer on a core made from 55% nickel AN Super Perma double c-core providing both balanced XLR and single-ended RCA outputs.

All the boards in the M9 are point to point hard wired by hand, the boards themselves are made from a special Phenolic wood, which has extremely good resonance absorption and internal self damping properties and is an ideal base to place parts on.

The volume control is an in house designed and hand made stereo attenuator with silver contacts and ½ watt Audio Note™ tantalum resistors throughout.

On the input side the M9 also offers some novelty in that, apart from the MM phono input, it has 3 line inputs one of which is a transformer coupled XLR balanced CD input, to allow for fully balanced connection to our best transformer coupled DACs., the most linear and lossless interface possible.

The M9Phono is very time consuming to make and requires a very high degree of skill to put together, it takes about 140 man hours to manufacture, as a result production output is strictly limited and delivery time is almost always inevitable.

The M9 is unusual in most respects, it’s main features are described, but now over to Andy Grove for the full low down,

“The M9 Phono stage uses a new concept, that of the “Virtual Component”. Real reactive components, whether inductors or capacitors exhibit losses due to DC resistance, hysteresis and other energy storage effects such as dielectric absorption. The M9 Phono stage uses a specially designed “RIAA Transformer”, where the usually unwanted leakage inductance between primary and secondary is utilised as a component in the RIAA equalisation. This inductance is essentially loss less, and has no stray capacitance associated with it, which is the downfall of conventional inductor RIAAs as used in the original M10, and requires such circuits to function at a low impedance level of 600ohms requiring cathode follower drive, or suffer severe problems with unwanted resonance’s. In contrast to this the M9 Phono operates at 50 kOhms, unheard of until now.

To keep the size and cost to a reasonable level the circuit still requires some silver foil capacitors to function. The forthcoming M10Phono, however, will utilise the “Virtual Component” concept throughout. The RIAA transformer is hand made with the finest nickel-iron alloy core and a very large number of turns of extra fine silver wire. The fine tolerances gained from the careful crafting of the transformer ensure an accurate response, however the surrounding capacitor and resistor values are then tuned to give a response within +/- 0.1dB within the RIAA specified frequency range.

The Philips SQ E80F is used as the input valve, it is a low noise, low microphony pentode, specifically designed for audio. It is used as a transconductance element, and impresses a current proportional to it’s input voltage upon the LCR RIAA network, the signal is passed via the aether to the secondary of the RIAA Transformer and thence to an E80CC double triode which is used for second stage amplification.

The overall gain from phono input to single ended line output is 60dB, 66db to balanced outputs.

The line stage uses one ECC82 and one 7044/E182CC and is transformer coupled via a nickel-iron cored silvered wired output transformer to the outputs. The volume control/attenuator is a hand assembled shunt attenuator, where the signal only traverses a single extremely high quality resistor before reaching the input to the line stage. All switch contacts and other components are in the shunt leg of the attenuator.

The power supply unit is housed in a separate chassis, this minimises hum interaction from the mains transformers and is necessary due to the size of both the supply itself and that of the line and phono stages, housed in the audio chassis. The power supply itself uses two stabilised units using a 6X5 rectifier, an ECL82 stabiliser and an OB2 reference glow tube. The stabiliser is of proprietary design and uses a similar technology to that of the M10 power supply.”

What Will You Hear from the M9Phono?

What I found really interesting when playing 1950’s mono records through the M9Phono’s transformer RIAA correction, is the way that records which were obviously cut with the original choke anti-RIAA correction system suddenly stand out in terms of dynamic integrity, medium and timbral vividness, this truly leaves anything digital standing as the medieval medium we all know it was, despite advances in CD transport and DAC technology, but put into stark contrast the way that every other pre-amplifier presents the information embedded in the grooves of our records.

The M9Phono will reveal greater depths of information of all kinds from your collection of LPs, it will separate the great performances from the merely good in a way that unearths the greatness of many performances that you found less exciting on earlier auditions, I found on pretty much every record I played that the M9Phono opened up not just further insight into the performance, but improved many less than great recordings considerably.

The M9Phono is only suitable for the very best systems, in my personal system I use it with a TT Three Reference with IoGold cartridge and AN-1s/SOGON50 tone arm, AN-S9L and a pair of KEGON Balanced power amplifiers into the AN-E SOGON, this is the main benefit of making this stuff yourself, you get to live with it at the highest level for free (well almost!).



Side view of the M9 control unit with the output transformers near the front of the unit at the top of the picture with their distinctive copper shrouds, the RIAA correction transformers are seen in the middle of the unit and the balanced CD line input transformers at the bottom of the picture, the overview gives a good idea of the amount of silver parts involved.



Back of the M9 shows the two power supply connections on the left, the two RCA outputs with the balanced/single-ended switch to their left, the 3 single-ended line inputs, to the upper right the balanced CD input, below which is the input to the phono stage and above right the balanced pre-amplifier output, with the ground connection immediately below.

Picture below shows a close up of the wooden board holding the RIAA correction circuit showing in detail the 2 E80F input valves, the two watt Audio Note™ tantalum resistors and the serious number of silver foil signal capacitors and the two RIAA correction transformers at the top right.



Two close ups of the RIAA board this time from inside the unit, one showing in greater detail the E80F pentode and the other below, showing the E80CC second stage, Both show the N-Type Black Gate™ capacitors and all the through connection on the board being solid silver as is everything piece of signal carrying wire and component in the M9PHONO.

Close up of the RIAA transformers.

PQ 01.02.2008

All material copyright Audio Note (UK) Ltd., unless otherwise stated. Audio Note (UK) Ltd. reserve the right to change, modify, add to, or remove any of the content of this site at any time without prior notice. Further, images on this site may differ from current models or specifications.

Product Brief

Product Specification
Name:
M9
Inputs::
6
Outputs:
2 plus Balanced
Coupling:
Transformer
Code:
ZZ118

Product Specification
None
Audio Note M-9 Phono Valve Hifi Preamplifier