Pace-Car USB User Manual Empirical Audio Rev. 1.
Pace-Car USB User Manual Empirical Audio Rev. 1.0 1. Function/Technology The Pace-Car USB is a versatile hi-res compatible USB interface combined with a reclocker that can be used with an array of devices including various WiFi devices and some CD transports. The object of the Pace-Car USB is to reduce jitter in the digital data stream of streaming audio. Digital data goes into the Pace-Car USB and digital data comes out, only with lower jitter.
The Pace-Car USB is a reclocker, meaning that the timing of the data flow into the device is retimed using an internal clock. The Pace-Car USB reclocker inserts between your source device or computer and your DAC. The Pace-Car USB buffers the music data stream in a memory and then reclocks it out with an ultra-low jitter clock. The data is not modified an any way, it just passes through.
The switch on the backpanel must be in the correct position to match the samplerate of the incoming data-stream. The two positions are: 44/1/88.2/176 and 96/192. Optionally, the second position can be 48/96/192. 1.3.3. Mode 2: For Mode 2, the source device must have a Slave-Clock input. This can be added to Sonos, Squeezebox, Duet, Tascam US-144, and other devices. The customer must order a modification to add the Slave-Clock input to their source device.
2. Front-Panel: 2.1.1. Input Select Switch Input selector for S/PDIF coax in, Toslink in and USB in. This can be changed on the fly to select various sources. 2.1.2. Power LED Illuminated when there is DC power to the Pace-Car USB. 2.1.3. FIFO Overrun indicator Illuminated when the internal memory has overflowed. For this to occur, the data input rate must be higher than the data output rate. Check rear-panel SampleRate switch for correct position in Modes 1,2 and 3.
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.
3.3. Toslink Input The Toslink input (optical) is for use in Modes 1,2 or 3. It should be connected to the source device Toslink output. This 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 Toslink has a door on it that flips up inside when you insert the optical cable end. Some cable ends are too large and can damage the door, so if it is difficult to insert, don’t force it.
3.8. Word-Clock output Word-Clock is output on a SMA connector with 5V logic levels and 50 ohms output impedance. Other configurations are optional, including low-impedance, 75 ohms impedance or 3.3V logic levels. Provides a clock signal equal in frequency to the sample-rate of the incoming data-stream to a source device, such as 44.1kHz. Turns off if there is no incoming signal on the selected input. Consult with Empirical Audio to be sure you have the right configuration for your source device.
5. Specifications Inputs 1. USB 2. S/PDIF coax 3. Toslink 4. 12VDC AC adapter Outputs 1. S/PDIF coax or AES/EBU 2. I2S on RJ-45, Empirical Audio standard (3.3V or optional 5V) 3. Word-Clock output 4. Master Clock output for 44.1 5. Master Clock output for 96 Controls 1. Front Panel input select switch for USB, S/PDIF or Toslink 2. Rear-panel select switch for 44.1/88.2/176.
Compatibility The Pace-Car 2 is designed to work with all DACs and SS receivers/processors. The I2S output can be converted to 5V optionally for DACs such as Stello or Northstar. Sample-rates supported by USB/Modes 1 and 2: 44.1kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz Sample-rates supported in Mode 3: 44.1kHz, 88.2kHz, 96kHz Included 1. Pace-Car USB with 2 standard clocks (except with upgraded clocks) 2. 12VDC AC adapter 3. 5m USB cable 4. CDROM with drivers and other software 5.
