Off-Ramp 4 User Manual Empirical Audio Rev. 1.
Off-Ramp 4 User Manual Empirical Audio Rev. 1.0 1. Function/Technology The Off-Ramp 4 is a versatile hi-res compatible USB interface. The function of the OffRamp 4 is to convert USB signaling into S/PDIF, AES and I2S so that a DAC can be driven with a computer audio data stream. The Off-Ramp 4 reduces jitter in the digital data stream by re-clocking using local oscillators.
with DACs. The Off-Ramp 4 is a re-clocker, meaning that the timing of the data flow into the device is retimed using internal clocks. This has nothing to do with the timing or tempo of the music. Because it utilizes an asynchronous USB interface, the master or system clock for your audio system is located in the Off-Ramp 4. This clock provides the timing for the dataflow from the computer source. This is the optimum way to achieve low jitter.
2. Front-Panel: 2.1.1. Power LED Green indicator indicates DC power is applied to the DC input on back-panel. 2.1.2. Data Error Yellow indicator indicates that data stream is corrupted or not PCM. 2.1.3. USB Fault Red indicator indicates that USB cable is not connected or the USB port at the computer is not active.
3. Back-Panel 3.1. 12VDC Input This is the power input for the Off-Ramp 4. The power from this input goes directly to the voltage regulators, and any installed 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 Off-Ramp 4 supplies 2.5 Amps @ 12VDC.
3.3. S/PDIF Coax Output The S/PDIF coax output (optionally AES/EBU output) is the primary output that will connect to most DACs. The output impedance is 75 ohms. The cable that connects from this connector to your DAC should preferably be of highest quality and match the 75 ohm impedance. The S/PDIF output is transformer-coupled and isolated from earth ground. The RCA jack is made of high-quality direct-gold plated copper with Teflon insulator, so it is better than most BNC connectors.
4. Software Software drivers must be loaded to support the USB interface for both PC and Mac before connecting the USB cable. For operation on a PC, Kernel Streaming is recommended to bypass Kmixer on XP machines and WASAPI on Vista and Win7 machines. 4.1. USB Drivers Drivers are located on the included CDROM disk. Load the appropriate driver for your machine and OS and execute it on the computer before powering the Off-Ramp 4 or connecting the USB cable to the computer for the first time. 4.2.
• Play a track or playlist using your player application 6. Specifications Inputs 1. USB – async 24/192 max sample-rate Outputs 1. S/PDIF coax 2. AES/EBU 3. I2S on RJ-45, Empirical Audio standard (3.3V or optional 5V) Jitter specs (cycle to cycle, standard clock): S/PDIF coax output - <500psec total P-P jitter I2S Clock outputs - <250psec total P-P jitter 7. Compatibility The Off-Ramp 4 is designed to work with all DACs and SS receivers/processors.
