T1 10MHz Time Reference

Timing in digital systems is the key to carry and to faithfully convert digital audio content. Why so? Let’s imagine that a digital to analog converter chip is fed from a clock containing a high level of phase noise, otherwise known as jitter in the time domain. Instead of being evenly spaced in time, the digital audio information converted to the analog domain is spread randomly around the ideal time, introducing undesired artifacts. The better the clock source, the lesser the phase noise, the more precise the conversion.

An ultra-low phase noise, high accuracy 10MHz oven controlled oscillator (OCXO) forms the heart of the T1, CH Precision’s first clock generator.

Products Fertures

Modularity

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)
  • analog input board (1x XLR balanced and 1x RCA single-ended)
  • USB input (1x USB B-type)

The CH-Link HD interface allows for synchronized transfer of High Definition audio content and control over a single connection and is the optimal link be-
tween the Cl 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.

Processing

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 Cl is based on twoultra lowjitter 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 syn- chronization clock in order to slave it.

D/A conversion

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.

Volume control

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.

Analog stages

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.

Specificatons

Frequency
TESTNominal frequency 10MHz, +/- 20ppb typical in internal mode, factory adjusted
10MHz, +/- 1ppb maximum with GPS option locked for 1 hour
Tuning range +/- 0.1ppm via BNC input
Phase noise performances better than -105dBc/Hz @ 1Hz deviation
better than -125dBc/Hz @ 10Hz deviation
better than -145dBc/Hz @ 100Hz deviation
better than -155dBc/Hz @ 1kHz deviation
better than -165dBc/Hz @ 10kHz deviation and above
10MHz Outputs
Output level 500mV or 1V, peak to peak, loaded with 75Ω termination, adjustable for each output
Waveform type Sine or Square wave, adjustable for each output
Output impedance 75Ω, 6x BNC coaxial connectors
External BNC Input
Input level 5V TTL level
Input impedance 47kΩ, BNC coaxial connector
Accepted signal frequencies 1 PPS
44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz
100kHz
Reference signal frequency deviation maximum +/- 0.1ppm around the above signal frequencies
General
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 max in operation
Dimensions/Weight 440 x 440 x 133mm (W x D x H), 26kg
Remote control Ethernet based system control via the Android CH Control App
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