Designed for the true music lover, the C1’s apparent simplicity hides highly sophisticated technological solutions with the single goal of recreating the full musical experience. This emotion can only be achieved when both level and time information are properly reconstructed from the digital data. And this is what the C1 is all about.
C1 Reference D/A Controller
We describe the C1 as a Controller because it is more, much more than just a digital to analog converter. While creating a world-class DAC could be considered a sufficient challenge on its own, the use of modular component architecture and the power of sophisticated software control opens up opportunities as well as offering solutions: opportunities that transform the role, capabilities and versatility of the C1.
Of course, it is digital conversion that lies at the heart of the C1. The perfect preservation of time and amplitude information is critical to reproducing musical signals stored in digital format. Noise and jitter performance is central to the design of any high-performance DAC, but at CH Precision we believe that the solutions we have adopted for the C1 take digital performance to a whole new level.
We have paid extraordinary attention to the master clock arrangements (as well as providing highly developed clock-sync and external reference clock options) to minimise timing error to unprecedented levels, while our proprietary Polynomial Equations to Enhance Resolution (CH-PEtER) processing delivers incredible sample-to-sample resolution. Input compatibility includes all high-resolution digital formats, whether from optical or file replay sources. Our proprietary CH-Link HD interconnection allows the transfer of DSD data in the digital domain, from the D1 transport to the C1, or can carry PCM data at up to 768kHz/32 bit resolution. The AES/EBU and S/PDIF inputs accept PCM at up to 192kHz/24bit resolution. The DAC itself employs no fewer than four converter chips per channel, in a fully differential, dual-mono topology. The vital analogue output stage is discrete, fully differential, Class-A and DC coupled. The modular input architecture and upgradable software capability ensures that the C1 remains future proof, able to adapt to changing digital standards or system demands.
Having created the C1’s digital decoding core, the next step was to construct the system architecture around it. As well as the established digital input standards (AES/EBU, S/PDIF and TosLink) it was necessary to create dedicated input cards for both Ethernet network and USB music replay, each optimised to deal with the special challenges presented by these computer-based formats. Alongside the multiple digital input and clock-sync options, we also added a by-passable hybrid volume control, operating across both the analogue and digital domains and an A-to-D facility, allowing the C1 to accept balanced or single-ended analog inputs, creating a genuine analog/digital domain control option, allowing the C1 to stand at the centre of any system, irrespective of the source components in use.
With the vast array of user definable parameters on offer, from input identity to input offsets for the analogue connections, overall gain and balance to output level and absolute phase, a comprehensive, non-intrusive display was essential. This requirement led directly to the implementation of our 480 x 272 pixel AMOLED screen, with its user-configurable content, brightness and power down options. Users can even select a specific RGB colour for the content! Although each and every setting in the C1 can be accessed and adjusted from the dual-concentric control on the front-panel, the CH-Control App allows direct, remote access to every parameter from an Android tablet or smartphone, making this one of the most adjustable, configurable and adaptable DAC Controllers on the market – and also one of the easiest to use.
Up to three input boards allows the unit to include many input types. One digital input HD 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 HD board (1x CH Link HD, 1x AES/EBU, 1x S/PDIF and 1x Toslink)
- analogue input board (1x XLR balanced and 1x RCA single-ended)
- USB input (1x USB B-type)
The CH-Link HD interface allows for synchronised transfer of High Definition audio content and control over a single connection and is the optimal link be-
tween the C1 and the matching D1 SACD/CD drive. Audio data on CH-Link HD 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 compatible 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 linearises 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 Cl is based on two ultra low-jitter digitally controlled VCXOs to
support synchronously every available audio sampling rates.
When equipped with the optional synchronisation board, the C1 can be used with external clock generators or it can transmit the D1 SACD/CD drive a synchronisation clock in order to slave it.
The digital to analogue 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 analogue 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 analogue 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 symmetrical design
No capacitors have been used in the signal path to ensure the maximum transparency.
“Neutral, exciting, fast, tons of detail, yet musical in a way that is honest to the source, not gussied up with bloom and decay trails, it is not like the audio we grew up with. This kind of sound did not exist until now. As far as I’m concerned, CH Precision is at the forefront of digital technology. They are the leader of the pack.” – MARSHALL NACK, POSITIVE FEEDBACK (read in full here)
“As it is, the CH Precision D1 and C1 pairing makes it onto my extremely select digital replay top table… It is by some distance the most musically emphatic member of the party and also the de facto recommendation for SACD replay.” – ROY GREGORY, THE AUDIOBEAT (read in full here)
|CH Link HD||
High Definition Link
PCM 16 to 32 bit / up to 768kHz
|AES/EBU||XLR connector, up to 5Vpp, 110Ω
PCM 16 to 24 bit / up to 192kHz
|S/PDIF||RCA connector, up to 1Vpp, 75Ω
PCM 16 to 24 bit / up to 192kHz
PCM 16 to 24 bit / up to 192kHz
PCM 16 to 32 bit (fixed point) / up to 384kHz
PCM 16 to 32 bit (fixed point) / up to 192kHz (384kHz for uncompressed formats)
WAV, AIFF, FLAC, ALAC, AAC, MP3 format supported in PCM
|Inputs type||Balanced, 6V RMS maximum input level
Single-Ended, 6V RMS maximum input level
|Input stage||Discrete fully differential input stage|
|A/D conversion||DSD 1 bit / 5.6448MHz (DSD128) direct conversion|
|Conversion type||Linearised R-2R, 4x PCM1704 per channel, 24 bit / 705.6kHz & 768kHz|
|DSP processing||CH-PEtER up-sampler, synchronous, DSD to PCM conversion
and resolution enhancer
|Outputs type||Balanced (XLR), one pair
Single-Ended (RCA & BNC), one pair each
|Output stage||Discrete I/V stage with ultra-high bandwidth
Active discrete filtering stage
High-current discrete output stageAll analogue stages have a zero global negative feedback
|Output level||5.4V RMS in balanced mode
2.7V RMS in single-ended mode
|Signal to Noise Ratio||Better than 120dB|
|Total Harmonic Distortion + Noise||Less than 0.001%|
BNC, 0.5Vpp to 5Vpp, 75Ω or Hi-Z
44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz, 352.8kHz, 384kHz
2x BNC, 2Vpp, 75Ω
input sampling frequency or clock loopback if externally synchronised
|Display||480×272 pixels, 24bits color, AMOLED|
|Mains operation||Selectable 100V, 115, 230V AC, 47-63Hz|
|Fuses value and location||Standby fuse (black holder): 250mA T (230V AC), 500mA T (100V AC, 115V AC)
Main fuse (white holder): 1.6A T (230V AC), 3.15A T (100V AC, 115V AC)
|Power supply consumption||<1W (standby), 60W average in operation|
|Dimensions/Weight||440 x 440 x 133mm (W x D x H), 24kg|
|Remote control||IR Remote control provided, RC5 codes
Ethernet based system control via the Android CH Control App