Digital audio facilities often require a number of clock sources, which are used to synchronise outboard processors to the system clock rate using external clock inputs. The Drawmer D-Clock is a dual input, twenty output word clock distributor with a 16 character blue LCD display providing a high accuracy reference measurement of the incoming sample rate.
It has both AES/EBU and BNC word clock inputs featuring a zero latency loopthrough output with switchable high impedance to maintain the correct level of the digital signal for onward distribution. Sixteen BNC clock outputs are situated on the rear panel with a further four BNC clock outputs on the front panel for quick patching to other digital devices.
A high-stability TCXO (temperature-compensated crystal oscillator) and microcontroller measure the incoming sample rate with an accuracy of 2ppm. Results are displayed in three selectable modes: actual frequency (to one decimal place), nominal frequency with +/- ppm error, or nominal frequency with percentage pull-up or pull-down.
Overall, the D-Clock works extremely well, and the unique display provides useful reassurance that all is working as it should be. If you can make use of up to twenty word-clock outputs in your digital environment, this is a very cost-effective and useful item to add to your rack.
The D-Clock's outputs can be fed from the word clock input at any sample rate between 32kHz and 768kHz, or derived from an AES11 input or stripped from an AES3 audio signal at any rate between 32kHz and 192kHz. Using an audio signal as the clock source means even devices without dedicated word clock outputs - such as some analogue-to-digital converters or mic preamplifiers with internal A/D conversion - can serve as the master clock for the entire studio.
