3.1. 12VDC input
This is the power input for the Pace-Car USB. It powers everything, except the USB
interface, which is powered from the USB cable. The power from this goes directly to
the standard clocks, Superclocks or Ultraclocks, so the quality of this power is critical.
Upgrades here make an immediate difference in jitter. Average power consumption is
up to 500ma, depending on clock options, but much higher transient currents are
possible. The standard AC adapter included with the Pace-Car USB supplies 5.5 Amps
@ 12VDC. The connector is center positive, 2.5mm and protected from reverse voltage.
To power-on the Pace-Car USB, plug in the AC adapter and then connect the DC power
cable to the Pace-Car USB. The included AC adapter grounds the chassis of the Pace-
Car USB to earth ground. Any other AC supplies used with the Pace-Car USB should
also have the ring or minus of the connector tied to earth ground and AC ground.
3.2. S/PDIF Coax input
The S/PDIF input is for use in Modes 1,2 or 3. It should be connected to the source
device S/PDIF coax output using a 75 ohm digital coax cable. This input supports only
PCM data, not AC3 surround. All sample-rates are supported, but must be selected in
two groups using the Sample-Rate switch on the back-panel. The S/PDIF input is
isolated, so the ground return is not connected to the chassis ground of the Pace-Car
USB. The input is terminated in 75 ohms characteristic impedance.