When dealing with media converters, it was noticeable that the one installed in the Melco S100 switch could keep up with even the audiophile Sonores in terms of sound. When asked whether the converters from the S100 would also be available separately, Alan Ainslie, Melco's European representative, asked for patience: Now the first Fibre Kit from ADOT - arrived at the editorial office.

The fact that optical transmission paths with two media converters and one optical fibre can be sonically superior to electrical Ethernet connections in digital playback chains has already been explained in detail in Hifistatement in four articles about media converters and accessories. Therefore, I will not mention the advantages of the complete galvanic isolation of the audio components from the Internet and of reclocking - provided the media converter has a good clock - again here and refer to the reviews mentioned. By the way, the Audiophile Digital Optical Technology - ADOT - Fibre Kit mentioned in the introduction is ideal if you want to use it together with the Melco S100, which was awarded a Statement In High Fidelity, or another switch with a built-in media converter such as the SOtM sNH-10G i. Of course, I would also like to try out the Fibre Kit with the PowerSwitch from Ansuz for example. For this, you need a second media converter, which Alan Ainslie also brought on the way to Gröbenzell some time ago. The second ADOT Media Converter and power lead is supplied in the ADOT accessory kit allowing ADOT fibre kits to be used with any dataswitch even if there is no SFP port. Probably thanks to Brexit, however, it has been flickering around for more than a month in the UPS warehouse in Nuremberg or at customs. I fear that we will have to get used to such delays. So for the time being we will make do with one media converter and in a second part we will compare the second converter from ADOT with the one built into the Melco switch.

When I asked Alan Ainslie last year about media converters that could be purchased individually, I assumed that Buffalo, the Japanese computer peripheral specialists, of which Melco is a subsidiary, had such converters in their portfolio. That is indeed the case, as I later found out from the Amazon Japan website. But it is not a Buffalo media converter that has now arrived in my place. The manufacturer is ADOT, or by its full name "Audiophile Digital Optical Technology", and our test object trades under the name "Audiophile Grade Optical Fibre Kit". The company's organisation is based in England, where the concept for the products was also developed. The manufacturing is, how could it be otherwise, in China. That the kit is intended for use with a Melco switch is already suggested by the scope of delivery: In addition to the one media converter, there are two SFP adapters - SFP stands for "Small Form-factor Pluggable" - which convert the electrical signal provided by the media converter into light waves. As described in the first article on media converters, there are different adapters for single or multimode optical fibres, each with different wavelengths. The SFP adapters included in the kit carry a label identifying them as ADOT products. Alan Ainslie notes that it was not easy to find adapters with good characteristics for audiophile purposes, as they were usually designed for IT applications. The optical fibres also had to be of good quality to avoid transmission losses and jitter. Duplex multimode optical fibres with a wavelength of 850 nanometres were chosen because they were more reliable at a reasonable cost. However, jitter increases with short multimode optical fibres due to path length differences or modes. Measurements have shown that jitter above one metre is reduced to an acceptable level. Therefore, the fibre optic cables of the kits have a standard length of 1.5 metres. Lengths of up to 50 metres are available from stock, and lengths of up to one kilometre are available upon customer request. Each fibre optic cable is supplied with an individual test report, after all, it is impossible to use an ohmmeter for an optical cable! At a later date, a single-mode update will be offered for a fee. ADOT ist still looking for a reliable provider for short connections. 

ADOT offers three different kits: The cheapest version, the MC01, is available with a plug-in switching power supply. Although this affects the sound quality of the media converter and also has a negative effect on the rest of the system, the overall sound advantages of the fibre-optic transmission path outweigh the disadvantages, says Alain Ainslie. The MC02 kit comes with a linear plug-in power supply powerful enough to feed two media converters. MC03 kit is the top version and in some markets comes with a custom build Plixir low noise power supply with three stage noise reduction. In Germany the Melco Distributor sells the MC03 with the Sbooster power supply. Finally, the MC Accessory includes a media converter without SFP adapter and optical fibres, but with a Y-cable that enables the supply of two media converters by one (plug) power supply unit. The Y-cable is not the only indication of where ADOT sees the Fibre Kit's field of application: It is not primarily intended for loss-free signal transport over long distances, but to interrupt the electrical Lan connection and thus act as a filter for jitter and high-frequency interference.

A special feature of the ADOT media converter compared to all those presented in Hifistatement so far is the possibility to limit the transfer rate from the usual one gigabit to 100 megabits per second, providing that the other components support it. Also in the Melco switch S100 the transfer rate for four of the eight Lan ports was reduced to 100 megabit. This is said to be one of the main reasons why the audio components connected to it sound so excellent. With the ADOT media converter, these settings can be made with DIP switches. To gain initial experience with the media converter, I set the four switches as recommended by the manufacturer for audiophile operation.

I could not use the enclosed SFP adappters because of the long duplex single-mode optical fibre with a wavelength of 1310 nanometres that is laid between my router and the switch; the ADOT adapters are designed for duplex multimode optical fibre with 850 nanometres. So I'll stick with my Finisar adapters. How reassuring that Alain Ainslie has already mentioned that singlemode SFPs can be a welcome upgrade for ADOT media converters. For an initial functional check, I put the ADOT in the place of the 10Gtec media converter near the Ansuz PowerSwitch. There, the two boxes are much easier to access than the converter near the router. My 10Gtec is powered by a five-volt SBooster, the ADOT has to make do with its linear plug-in power supply for the time being: And you seem to hear that from the brand-new media converter. It plays a little rounder and, yes, also more ingratiating than the 10Gtec, but lacks a little openness and spatial depth. But the larger power supply could still change that.

Before I switch to the SBooster, however, an hour or two passes with intensive writing - and a tea break. After that, I listen to the 10Gtec again with Shostakovich Symphony No. 15 and then continue with the ADOT. Although the ADOT still draws its power from his mains adapter, it is almost indistinguishable from the 10Gtec and SBooster in terms of airiness and three-dimensionality. The 120 minutes of warm-up time have done it audibly good. Actually, I don't want to hear play-in effects in products that can also be counted as computer peripherals. Nevertheless, they are unmistakable here. Even with the standard plug-in power supply, I like the ADOT a little better than my previously tried and tested combination because of its greater suppleness in the high-frequency range. When the media converter from the Fibre Kit is also fed by the SBooster, it suggests an even larger imaginary stage than the 10Gtek, proves to be even more playful and dynamic: excellent!

Now the 10Gtek and the Ansuz PowerSwitch have a break: the Melco Switch takes over, on which - if I understand correctly  - the Fibre Set was developed. It is connected to the Melco N1Z/2EX-H60 and the Aries G2.1 via the Ansuz Ethernet cables supplied with various voltages by the Ansuz PowerSwitch and to the router via the fibre optic cable. It is always amazing in how many disciplines the Melco switch comes extremely close to the one from Ansuz. The only thing I wished for here was a little more smoothness in the high-frequency range - a really outrageous wish, considering the huge price difference between the two switches. After listening two or three times to one of my test tracks, I switch the 10Gtek for the ADOT near the router - and hear nothing. The Aries complains that it can't make contact with the network. This only works when I remove the restrictions on the ADOT media converter to 100 megabits. Then the Melco N1Z/2EX-H60 also wants to be restarted. Despite the delay, it is clear from the first bars of Keith Jarrett's "God Bless The Child" that the ADOT provides more joy, pressure and openness. No wishes remain unfulfilled! But let's go back to Symphony No. 15: Here the high frequency range comes across a touch softer - very nice.