Up to three input boards allows the unit to include many input types. One digital input board is provided in base configuration, while two slots are kept free and can be fitted from factory or after product installation with the following board types:
- digital input board (1x AES/EBU, 1x S/PDIF, 1x Toslink and 1x CH Link)
- analog input board (1x XLR balanced and 1x RCA single-ended)
- USB input (1x USB B-type)
The CH-Link interface allows for synchronized transfer of High Definition audio content and control over a single connection and is the optimal link between the C1 and the matching D1 SACD/CD drive. Audio data on CH-Link is cyphered when protected content is transmitted.
The ethernet streaming board option replaces the ethernet control board in order to add the C1 a uPnP/DLNA compatibe input. It should be noted that this input can be added even if the three available input slots are fitted.
For each channel a fully programmable 2.4GFLOPS DSP engine is used for the following processes:
- proprietary CH-HiD processing for data over-sampling at 705.6kHz/768kHz
- DSD to PCM direct conversion at 705.6kHz with selectable low-pass filters
- resolution enhancement for data streams of less than 24 bits resolution
- D/A converters data scrambling
This DSP engine also linearizes each of the four R-2R converters - its absolute output level as well as DC offset is taken into account - thanks to a calibration process which is done at factory but can also be performed by the user afterwards to maintain optimal operation over time.
Timing & clocking
Extreme care has been given to the timing of the audio conversion. The clocking section of the C1 is based on two ultra low jitter digitally controlled VCXOs to support synchronously every available audio sampling rates.
When equipped with the optional synchronization board, the C1 can be used with external clock generators or it can transmit the D1 SACD/CD drive a synchronization clock in order to slave it.
The digital to analog converter boards are full dual mono with one board per channel. A dedicated set of regulated power supplies has been built for each channel in order to keep the channel separation at its maximum. Each channel is using four R-2R converter in a balanced design to create directly from the D/A conversion process an analog balanced signal.
An integrated volume control is embedded into the C1, which can be turned off in case an external analog preamplifier is used. It has been done with a mix of analog and digital steps to ensure the best possible resolution at all listening levels. Coarse steps are done with relay-driven resistor-based dividers, while the fine steps are done into the DSP engine in floating point.
All analog stages inside the C1 are built only with discrete components, no operational amplifier have been used into these sections. This deliberate choice warranties the shortest path for the audio signal and allows the use of custom-made building blocks. All analog stages have the following features:
- no use of global negative feedback
- operating mode in pure class A
- fully symetrical design
No capacitors have been used in the signal path to ensure the maximum transparency.