Volume control is achieved by a combination of analog attenuators and high resolution digital multiplication.
When the volume is set in the range -95.5 dB to -12.5 dB, a 12 dB analog attenuator in engaged, and the DSP attenuates (i.e.
multiply the audio sample in 32 bits floating point resolution) by [volume + 12 dB].
When the volume is set between -12.0 dB and -6.5 dB, a 6 dB analog attenuator in engaged, and the DSP attenuates by [volume
+ 6 dB].
When the volume is in the range -6 dB to 0dB, no analog attenuator is engaged, and the DSP attenuates by [volume].
When the volume is positive (i.e. +0.5 dB to +24.0 dB), no analog attenuator is engaged, and the DSP applies a positive gain
corresponding to [volume], whenever possible. If the DSP detects that the upcoming resulting samples will digitally clip (sample
value * volume > 0 dB full scale), it will soft clip this event and automatically decrease the volume to a value that will avoid
clipping in the future.
1.2 Mechanical construction
The C1 D/A controller is assembled from high-quality aluminum and steel elements with no visible screws on the front, top and
side panels. The front panel, base, side panels and top cover are machined from aluminum. The power supply is isolated from the
audio section in its own compartment to avoid any contamination of the audio circuits by noise radiated from the supply. Pin
assembly of all chassis elements provides smooth joints between elements while screws every 6cm ensures protection against
electromagnetic interferences. First class mechanical and chemical surface treatments provide the luxury finish of the C1.
Four steel feet support the unit. Each feet ends with a elastomer ring to sit on delicate surfaces but is also equipped with a height
adjustable steel spike to fine tune unit positioning. Horizontal adjustment is done with the provided screwdriver through the four
adjustment shafts accessible from the top of the unit. In addition to providing convenient horizontal adjustment from the top of the
unit, the shafts also serve as vibration evacuation channels for any stacked unit. Special shaft covers are provided to interface with
the spikes of the stacked unit. Any vibration from the upper unit is transmitted by the shaft cover to the shaft and from the shaft to
the lower unit feet or spike, forming a privileged path for vibrations evacuation.
1.3 Modular architecture and slot-in boards
The C1 benefits from a fully modular architecture. It features separated sections for power-supply, front panel, computing +
signal/clocks routing + central host processor, slot-in boards and monaural conversion boards. This modular architecture combined
to the USB plug for all firmwares (MCU, DSPs and FPGAs) update allows for easy servicing and upgrade should one section become
faulty or obsolete.
The slot-in boards section consists in a vertically mounted mother board with optional boards plugged into it. Optional boards
provide audio functionality and connectivity to other equipment. There are six types of slot-in boards:
• DIGITAL_IN: provides three standard digital audio input plus a proprietary CH-link input
• USB_IN : provides asynchronous USB audio (up to 24bits/192kHz) input. Computer is enslaved to the C1, sending audio
packets a a C1-specified rate
Rev 1.9 C1 User Manual 11
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