Product: Paradox NDF DAC
Manufacturer: name (local website) - country of origin
Approx. price: £2200 in shops 2730€ (YMMV)
Availability: specialist UK stores or worldwide direct from manufacturer with money back satisfaction guarantee
Reviewer: Mark Wheeler - TNT UK
Reviewed: February, 2013

Introduction

In September your old scribe became aware that Audio Note UK pushed back the boundaries of audiosanity with a multibox cd drive/DAC (Digital to Analogue Converter) that costs £192,000 (240,000€), while another innovative UK specialist introduced a DAC using some similar principles, including No Digital Filter, executed by multiple multibit DAC chips to minimise noise and out of band problems for just 1.15% of that figure. That company is Chevron Audio whose upgrade modifications have been tested here on TNT-audio previously. This is a fully developed product representing a significant step for a small company who undertake all their own research and development and only outsource operations like case manufacture.

There has been much debate, since the inception of domestic digital audio, about how to eliminate all the high frequency junk created by the whole conversion process from analogue to digital and back again, without losing important data from the signal. Oversimplifying, for the sake of brevity, the 44kHz sampling rate allows a reasonable description of analogue frequencies up to half that figure and anything above that 22kHz MUST be blocked to prevent the feedback loops of amplifiers whooping into oscillation or simply wasting amplification and causing premature overload effects. Obviously designers thought of low-pass filters to achieve this and the world has been awash with different ideas about which is the best way to execute this filtration ever since.

Sony built a no digital filter, all analogue brickwall filter CD player model very early on, whose sound was one of the reasons your old scribe was foolishly convinced CD was doomed to failure. Others offered oversampling so that the filters could operate at different points, Bitstream going that little bit further ("Groan," from stage left plebs) etcetera. Some use digital filtering, some analogue, most a mix of both. Your old scribe recalls the fascinating Zero One Ti48HDD & Ar38DAC range of filter slopes, and their dramatic effect on sound quality. The best being no filter at all. At the more esoteric end of the market, DAC designers have been brave enough to omit all but the simplest low pass filters on the assumption that canny dealers and consumers will not pair them with high loop feedback wide bandwidth amplifiers.

Description & tech specs

The Chevron Audio Paradox NDF DAC does what it says on the box. NDF abbreviates No Digital Filter. The simplest single pole 20kHz correction filter is the only place a filter is to be found anywhere except the power supply. The power supply lives in a separate box for better isolation and noise reduction. It features FIVE, yes that's 5 galvanically isolated legs off THREE, yes that's 3 separate toroidal mains transformers. This is the kind of over-the-top power supply architecture Naim offer at the top of their upgrade path for good reason.

The power supply feeds the DAC via a multicore umbilical cord. Hence the demands of any part of the DAC will have no effect on the supply to other parts of the circuit. It has long been argued that no well designed power supply should sag enough under load to affect the regulation of other parts of the circuit. Your old scribe's experiments, experience of other's experiments, and auditioning, confirm that this is probably the most important factor in preserving musical qualities like timing and rhythm in solid state amplifying stages. Your Old Scribe has long railed against privileging any design Parameters above accuracy in the time domain. It is what has raised products like the DAS monitor Active Loudspeakers and Consonance CD player above the merely good. Without good timing, music makes no sense, regardless of how well equipment performs in other parameters. Music is a temporal art.

Inside the DAC itself, conversion is achieved by EIGHT, yes that's 8 chips running in differential mode. This costs more and potentially creates more opportunities for inacuracies, but is the popular contemporary go to solution for improved timing with minimal filtering, in DACs and CD players at the most elevated price points. Local linear power supply regulators in the DAC further preserve supply integrity at all signal processing and amplifying stages. Any analogue audio circuit is nothing more than a modulated power supply; the electrons coming out are not bigger versions of the same ones that went in!
"Eh?" query plebs, stage left.

So 8 dac chips receive identical non-oversampled data (whether 44kHz or 48KHz sample rate at 16 bits resolution), with precisely controlled time differences between each chip. Thus, when the outputs of the dac chips are summed together, there's effectively a 384 kHz sample rate with 19 bit resolution. Inverted data is fed to another 8 dac chips, thus creating a noise and distortion rejecting differential arrangement with the bonus of an extra bit of resolution. Colin Yallop likens the arrangement to lots of small steps on a stairway compared with a few enormous steps. Even without a low pass digital filter, the amplifier is not struggling to reproduce a series of abrupt square-waves (exciting oscillation) as it would for a filterless DAC running at just 44kHz or 48kHz.

In Use

Chevron Audio have had cases made in Italy. The quality is immaculate, the design is neat and the mixture of materials chosen carefully to balance hysteresis, eddy currents and RF rejection. The whole family of contemporary Chevron Audio products share similar casework, so an aesthetically matching system can be produced; the UK small manufacturers have come a long way since the traditional 'made in a shed' aesthetic. This casework represents a significant investment and proportion of the final cost. The circular window revealing the display has retro elements, while the rounded corners will be more pleasant to encounter with fingers than many rivals when reaching for the big selector knob.

For a system based on digital sources, this and a volume control (optional) is all you need with a pair of active speakers. The 'op amps' are all discrete and Chevron's own design using just 4 surface mount transistors in the signal path. The circuit design effectively shunts to cable, hence the Old Scribe's suggestion that it could be ideal for connecting directly to active loudspeakers.

Listening notes

The tonal balance lies on a continuum between the Avondale Audio AA5 and the modified Shanling CDT100. The sound seems to be dominated by the DAC rather than the source drive. The character remained consistent using the Shanling as a disc spinner and using PC and Mac. Whether listening to Miles Davis 'Kind of Blue' from the designer, Colin Yallop's own laptop or Del Bromham's Devil's Highway spinning on the Shanling transport, the timing is right up there with the best. From the highest cymbal strike to the lowest kick drum, the wavefronts arrive at the output terminals as coherent as it is possible to be with these sampling rates. In signal terms, phase is preserved accurately across the bandwidth regardless of load or complexity.

The pace is remarkably close to the Avondale Audio AA5 while listening to Mapleshade's immaculate simple microphone technique recordings. Given that the Avondale remains the ne plus ultra benchmark for pace, this is impressive. Your old scribe has long been suspicious of outboard DAC's because of the potential jitter generated in the cable, the connectors, and the extra clocks. Once again your old scribe's prejudices have been proved wrong by a small manufacturer.

This is a musically engaging product that would have pleased the scribes at The Flat Response with its toe tapping presentation and musical coherence.

Conclusions

With no filters anywhere, except a low-order frequency response correction at 20kHz, with 44kHz sampling by 8 differential DAC chips, this DAC offers a rare approach to conversion. Competitors have tried similar approaches at much higher prices. The absence of brickwall digital filter, indeed any kind of digital filter enables more accuracy in the high frequency domain. This, combined with the minimal analogue filter results in state of the art rhythm and timing. However, it also demands that systems are carefully matched to prevent ultrasonic ringing or provoked oscillation in partnering amplifiers. Even the loudspeaker cables can be implicated in the RF behaviour of some global feedback amplifier designs. Chevron Audio, and their dealers, can advise customers about system matching.

Similar technological formats may be being used elsewhere, but rarely at this sort of price level. Furthermore, the emphaisis on power supply cleanliness and integrity pays dividends in the time domain. CD transport and PC or Mac Digital sources and this DAC, fitted with the optional volume control could drive a pair of active loudspeakers as an economical high end system.

This was a brief 1 day audition due to the built to order nature of Chevron Paradox NDF DAC production. Once again, a small manufacturer overturns some commonly held ideas and produces a stand out product. The brevity of this audition makes confident recommendation unethical, even if that might be the allowed by some of the hifi comics. However, this brief audition demonstrated that this is an excellent sounding product. It is a mature product, of long development, presented in smart casework and future proofed by its multiple inputs.

© Copyright 2013 The Old Scribe - mark@tnt-audio.com - www.tnt-audio.com