Chevron Audio Paradox 8i DAC

England's Chevron Audio Developments has an interesting proposition for its Paradox 8i DAC.  Rather than using the usual over/upsampling techniques, or just going plain Non-oversampling ("NOS").  They interpolate incoming data using 8 dac chips driven with the same original data but at precise time differences. When the output of the DAC chips are summed together the result is an increase of data bit depth from 16 to 19 and increase of sample rate from for example 44.1KHz to 176.8 KHz. This is achieved without digital filtering which is considered by many to produce unsatisfying sound quality.

"Key to the design is the elimination of digital filtering used in most CD systems, as part of the over sampling or up sampling process. The effect of digital filtering is to blur the sound such that it sounds somewhat bland and lacking in dynamics. This is the main reason that reproduction of music via LP records has retained a large following. 

The reason for digital filtering is to remove the alias signals that occur at ultrasonic frequencies as a direct result of the analogue to digital recording process. For example with (redbook) CD the conversion is done 44,000 times per second (44KHz) which allows information to be recorded up to 22KHz but when reproduced there is also a mirror image of the recorded information from 22KHz to 44KHz. This sounds like a bad thing but actually human hearing does not extend beyond 22KHz and it is able to effectively filter out the unwanted information. There is also the risk that the 22KHz-44KHz signals will adversely affect reproduction equipment indirectly leading to sound degradation but in practice this is extremely rare."

To reduce jitter they have developed their own reclocking circuitry "ChronoClock" with ultra low noise power supply. This process reduces jitter nearly as low as can be achieved with crystal oscillators but allows different sample rate data to be received. The DAC can receive any data rate up to 100KHz.

The dac chips output current signals are passively converted to a voltage signals. The voltage signal is however buffered by an active circuit to provide a low output impedance signal capable of driving any interconnect cables.

USB interface is also developed in house. Starting with a low noise power supplies to power the USB interface via the DAC rather than via the computer. Ground isolation is also used to prevent possible ground loop noise. The signal is passed through its jitter reduction circuit (mentioned earlier) to clean up the signals before feeding to the dac chips.

Multiple torroidal transformers power the Paradox DAC, there are 5 isolated power supplies to minimise undesirable interaction between circuits. All voltage regulators are fast high bandwidth types combined with low impedance capacitors to give low noise at audio & Radio frequencies.

• Inputs - USB type B, SPDIF coax 75R and Toslink optical. Balanced input is optional.
• Outputs - RCA unbalanced stereo.
• Contols - Phase can be inverted 180 deg. Some recording give a better sound-stage with phase inverted.
• The Paradox DAC is available in 4 versions, its possible to upgrade to the better versions at a later date:

1. Standard Paradox DAC uses a high performance opamp output stage. Price - £520.
2. Paradox 8i DAC adds 8 times interpolation. Price - £610.
3. Paradox 8i Plus DAC uses a non opamp output stage powered by Hypex regulators. Price - £750.
4. Paradox 8i DAC Deluxe same as Plus DAC but with an external power supply. This arrangement isolates any electrical noise radiated by the transformers or rectifiers from the DAC circuits. Also included in this power supply are additional active ripple reduction circuits which allow the voltage regulators in the DAC to work more effectively. Price £970.