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What finally set the course for the TotalDac design was listening to a discrete R-2R DAC made from a simple 1% resistor ladder without the usual chips. Vincent enjoyed this for its stunning musicality whilst remaining upset by its lack of resolution. Nevertheless this architecture provided him with a new goal for this project.

The R-2R ladder DAC is an alternative to the binary-weighted input DACs and uses fewer unique resistor values. Resistors for the more significant bits (MSB) must be proportionally more accurate than those possible with other delta-sigma DAC designs. This is true even for the lower bits. The upshot is that  resistor ladders can become very expensive if the goal is true high-end performance. Hence this approach is quite rare in DIY. To illustrate this, the raw cost of Vincent’s Vishay precision resistors in the TotalDac exceeds 30% of its sell price. The resistors in his R2R network are printed directly onto a single substrate using a single film to share similar electrical characteristics. They also are laser trimmed to achieve the required precision. These monolithic networks are said to have an inherent accuracy advantage over discrete solutions because of the tight ratio tolerances and low temperature coefficient of resistive tracking.

The TotalDac board is optimised to listen to a digital source with minimal conversion artefacts and without synchronous or asynchronous sampling frequency alterations. Instead of converting a source to 24-bit/96kHz, the TotalDac recalculates the delay length and the filter coefficients adapt themselves to the incoming signal’s data density.

Like many other DIY projects the TotalDac was compared to several competitors during its R&D and thereafter. As part of the French Melaudia audiophile circle, Vincent had opportunity to assess the competitiveness of his creation to high-end references by MSB Tec, Metronome and Zanden. Purportedly these encounters each time had the DIY contender perform as a serious rival to this crème of the crop.

To approach the performance of indecently priced machines for ten or five times less is obviously compelling. That said, Vincent Brient’s creation has neither the versatility nor the sculptural beauty of a Zanden or MSB Diamond DAC. Ownership of the TotalDac should only flatter those who focus on its sonic abilities. Certain limitations like 24/96 max compatibility and a single S/PDIF input also confine this device to very particular use which in certain ways is a far cry from recent market trends and the promotion of high-resolution digital. Having just one S/PDIF input could seem unreasonable in fact.

It thus depended heavily on just how good this input would prove relative to the remainder of the audio chain...