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The S1 shares the same solid aluminium chassis as the current A1 but offers higher levels of performance by utilizing 4 x ESS Sabre 9018 eight-channel DAC chips (two per channel). This arrangement delivers 16 paralleled DACs per side as compared to the single Wolfson WM8741 DAC per channel of the A1. This modern Sabre multiple Delta Sigma or MDS architecture confers on Lumïn’s new flagship comparable D/A conversion to the Accuphase DC-901. MDS is a technique for reducing conversion errors to improve the measurable performance of D/A converters. The result is higher dynamic range, better linearity, lower harmonic distortion plus further improvements in other areas.

Because the outputs of the paralleled converters add up, overall output increases by a factor of 16. However, conversion errors in each converter have different properties (they do not have a fixed phase relationship) and therefore do not add up x 16. Rather, the error increase here operates as √16. On the other hand, the relationship between output level and conversion error is 1/√16. Hence all important performance characteristics of the D/A converter are improved. A major advantage of this technique is the fact that its improvements are obtained uniformly throughout its operation range, that is, regardless of the signal frequency or level. This elegantly solves one of the major problems inherent in conventional multi-bit D/A converters - linearity at very low signal levels. With the analogue output signals from their 16 D/A converters per channel being added up, Pixel Magic needed an ingenious arrangement to get exactly the same clocking and phase signal to process the same audio data at the same time. The voltage multiplier in the amplification section also operates separately for normal and inverted phase. This has the effect of distributing and smoothing the addition process for excellent circuit stability and extremely low noise levels.

Accuphase for instance now use a technique called MDSD which allows straight D/A conversion of DSD signal. Multiple DSD signals delayed through digital processing in an ultra-high-speed FPGA are converted with separate DACs. After D/A conversion, summation of the parallel data results in a moving-average filter circuit with double-speed accuracy. An important characteristic of MDSD is the use of MDS-type D/A converters to keep conversion errors to an absolute minimum. At the same time, an MDSD circuit acts as a high-pass filter with completely linear phase characteristics. Accuphase claim that the end result is an overall improvement of the potential of DSD.

Mind you, Pixel Magic did not explain to me in such detailed manner what exactly they do within their FPGA and overall implementation of the 4 x ESS Sabre chips. They just explained that their FPGA code was adapted to take into account the further complexity of their sixteen DACs, the related clocking system and new circuitry. Mentioning Accuphase’s implementation of their DC-901, my intention was merely to highlight that clever use of these still affordable ESS Sabre parts can lead to very sophisticated engineering.

The S1 also gets a new clocking system with 6 x NZ2520S Nihon Dempa Kogyo crystal clock oscillators where the A1 used four; 24-bit/192kHz compatibility; 1-bit DSD running at 5.6MHz that can be output over HDMI; and an upgraded twin toroid power supply. The S1’s oscillator base frequencies (input sampling rate x 256) are 11.289MHz for 44.1KHz signal, 12.288MHz for 48KHz, 22.579MHz for 88.2KHz, 24.576MHz for 96KHz, 45.158MHz for 176.4KHz and 49.152MHz for 192KHz. The A1 used the lower 4-values oscillator. This clocking system is said to exhibit extremely low phase noise (-151/-157dB @ 20MHz). Related phase jitter should be around 55fs (femto clock value of 0.055ps) according to the manufacturer. As was already the case for the A1, the digital output via USB is disabled. The CPU chips used in both devices don’t support USB audio output. All Lumïn network players share the same CPU chips.

Pixel Magic seem to have adopted a very pragmatic approach of retaining the maximum number of components of the original version and modifying only what could be improved. What you thus acquire with the S1 over the A1 is only improved circuitry, no marketing or cosmetic artifacts that would lead to further cost increases without added sonic value. Hence the S1 looks exactly like the previous A1. The sole visual difference is a small golden plate inserted in the chassis à la Goldmund. Another external difference that can be observed only if compared directly is the PSU depth. The new PSU is almost 2cm deeper than that of the A1. Looking at the internal circuitry, the main changes to the digital board are related to the new clocking system and internal routing which was matched to the new layout. The analogue board is a completely new design based on the four Sabre chips. Many parts were upgraded. Only the output transformer stage with the famous Lundahl LL7401 transformers remains similar to the A1.