After our October 2014 post of Cees Ruijtenberg's Dac One, I'd asked whether, in multi-paralleled current-output with Ω-matching coupling transformer, this Transient module would inform Metrum's next converter. "Yes, we will use it for a new product to hopefully come in December. Prototypes already work very well and I am preparing pre-production units. Our biggest challenge is the housing. We use more aluminium than before and don't like any scratches. The new model will use 8 converters, four per channel in fully balanced operation. 24-bit data will split up over two DAC clusters. The first cluster runs from 0 to about 65dB and is taken over by the next cluster down to -144dB. Summing of these clusters is done in the analogue domain. This gives very low distortion over the entire range. Splitting up the data is the job for our FPGA module. By the way, for me the DAC module was the heaviest job to finish. It held all of my attention almost 24/7 for more than a year and I concentrated mostly on its I/V stage. The Hex DAC was my reference throughout and very hard to beat. Launching the separate Transient modules was due to the enormous R&D costs we incurred in the past. The Transient blocks will reduce our production costs when more companies get interested to use them for OEM applications.


"When using I/V transformers in the current-output scheme, we had to use a lot of electronics outside the DACs due to the two balanced data clusters per channel. Therefore we focused on a very good I/V section. The Lundahl iron on each board is based on Aurix technology to create the single-ended output. Compared to the Hex, there is almost no load on the balanced outputs due to this technique." When I asked Cees whether he'd beaten the Hex, "this will be up to the people and probably is a matter of taste. My first experience was with Norma Winstone's Distances and the cut "Ciant". There was more information present, hence many recordings followed. For that I only have one technical explanation. It's all about speed. The funniest thing was that this approach starting all over from scratch with our own converter chips produced, without yet the FPGA module, a first result very close to the Hex. As a matter of fact, there is not one shared part with the Hex. A recording engineer called it my signature. From my point of view, that is wrong. I am never busy with creating any kind of sound. I can only confirm if the result is closer to my experience with life performances; or whether some info is noticed which was inaudible before."

One needn't even attenuate signal prior to conversion (apply digital volume control) to challenge a DAC chip's low-level linearity. The less and least significant bits already do that at full signal. If we look at the Pavane's published SN/R of -144dB, it's some 15-20dB better than the current standard. Clearly Cees pulled a fast one; as well he should if speed was the thing. In ultra simplistic terms, our man splits his 24-bit data into two clusters. The first gets bits 1-12 as the most/more significant bits, augments them with empty bits below and processes this normally. Cluster two gets bits 13-24 as the less/least significant bits but moves them into its ladder DAC's top segment. This neat trick has them processed just like the first cluster. Once in the analog domain, our (sexist remark alert!) hotter half is attenuated back down to its proper loudness values. Only then is it recombined with the other half. And so our crafty Dutchman applies a temporary dynamic expander action in the digital domain to improve the low-level linearity of the D/A process which naturally wants to get less and less precise as recorded signal amplitude in the lower/lesser bits diminishes and gets mixed up with/in digital noise.