October 10, 2020

How to pimp your Audio Note M2 Phono

1. Personal taste: the knobs
Usually the Audio Note M2 Phono will be delivered with golden knobs. Honestly speaking I do not really like this appearance as I prefer it more unpretentious. Most of you might not be aware about it but Audio Note also offers various DIY components, indeed control knobs, too. Consequently I ordered a set of four black knobs via Germany´s official distributor. I have chosen gloss black types (not matt black) as these perfectly match with the reflecting front. Nominal diameter of the knobs is 26 mm, furthermore you need to check the positions of the screw borings in relation to the knob markings (there are two different types available: "aligned" = boring and marking at the same position and "not aligned" = boring and marking turned 180° to each other). You even can order new components with knobs in your preferred color. Later - as in my case - the knobs can also easily be changed by means of a hex wrench as they are fixed with simple grub screws only.
My Audio Note M2 Phono, now with black knobs
comparison: black knobs vs. golden knobs

2. Mandatory: short-circuit plugs and dust protection plugs
Personally I just would need a pre amplifier being equipped with balance and volume control, 1x Phono input and 1x output to the power amp. I neither do need a selector for line inputs nor a separate  source/tape selector as I only listen to vinyl. I am very dogmatic in that regard... What a slim design that would be! But what a waste of time, material, resources and money indeed on the other hand if you do not need all these inputs. Anyway, I deal with it!

From the technical perspective all these unused inputs potentially might act as a sort of antenna. But hey, don´t get me wrong, I am not expecting to receive Radio Jerewan or so. On the other hand, you never know... To be on the safe side and to avoid any interfering signal straying in via these unused inputs I am usually shorting them. Of course the unused outputs must not get a short-circuit plug but a dust protection plug only! Both, short-circuit plugs as well as dust protection plugs, can be ordered just for a few bucks at any good audio equipment dealer.
Easy to distinguish: short-circuit plugs with golden cover, dust protection plugs with silver cover

3. Obligatory: tube rolling
Out-of-the-box - after a reasonable burn-in time - the Audio Note M2 Phono sounds really good. Ok, very good. But of course the tube roller in me strongly insisted to have a look what kind of tubes were plugged into the sockets. As far as I know Audio Note delivers the M3 Phono for instance with finest New Old Stock (NOS) tubes. But in the significantly cheaper M2 Phono this is not the case. 
The tubes of the M2 Phono: 6SN7GT (line section, top left), ECC83 + ECC88 (phono section, top right), 6X5 + ECL82 (power supply, down middle)

3. a) Line section
The line section contains only one tube: the famous 6SN7GT. I found a Russian Electro Harmonix type in my pre amp which is therefore satisfactory at best, but honestly speaking it does not really meet my demands and allows for significant improvement. I replaced it by a JAN CRC-5692 redbase tube made by RCA which is a premium industrial military type.
EH 6SN7 vs. RCA redbase JAN CRC-5692

3. b) Phono section
Well, the phono board contains two tubes, both being covered to protect the sensitive phono section from microphonics. What I found under the covers was a PSVANE 12AX7 (=ECC83) and an Electro Harmonix 6922 (=ECC88, 6DJ8), a fact that does not really make me happy.

Left tube: PSVANE 12AX7, right tube: Electro Harmonix 6922

Fortunately even nowadays there are various excellent NOS tubes of the ECC family available on the market. For reasonable prices! You do not necessarily need to look for overhyped tubes like the Telefunken ECC803S Goldpin for instance to achieve excellent results.

ECC83 by Amperex (Philips), Siemens & Halske and the PSVANE

I love the logo of the Philips made Amperex ECC83 (Heerlen, Netherlands) which have been produced from 1963 - 1969. But this time I chose a Siemens & Halske made ECC83 with double getter fixation (Munich, Germany, 1962 - 1969) for the phono section and left the Amperex in my stock. All these tubes have symmetry matching for both internal systems.

The same appears for some ECC88 types which I have on stock. The left tube is a very interesting E188CC tube made by Mullard (UK) with gold pins and frame grid. 
The second tube labelled "BEL" (E88CC) has been produced in India on original Philips machines (which the manufacturer bought from Philips) with original Philips raw materials. It also has gold pins.
The third tube is a RCA branded 6922 with gold pins which indeed has been manufactured by Siemens (Munich plant)! This is the one which I chose as replacement for the Electro Harmonix.

3. c) Power supply unit
Honestly speaking I was not worried about the tubes which were placed in the sockets of the power supply unit but really satisfied! The 6X5 GT rectifier made by RCA is a military grade tube even. So there was no necessity to replace it by one of my "standard" RCA 6X5 GT.
The usual purpose of the ECL82 was the use in TV sets. This is a tube which combines a triode system and a pentode system. In the power supply of the M2 (Phono) it is used as stabilizer.
The ECL82 made by EI (Yugoslavia) is not too bad but I replaced it by one of my Valvo made types. Generally the tubes of the power supply unit the M2 Phono comes along with are no show stopper...
In conclusion, I can say that Audio Note´s M2 Phono is worth to be pimped! For sure the replacement of the tubes in the phono section and in the line section have the greatest effect. Finally you make a step from Level 2 to - let´s say - Level 2.5!

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