SFC2 sampling frequency converter

The SFC2 is a versatile sampling frequency converter with two completely independent stereo converters in a single 19 inch (1HU) unit. A SFC basically consists of a high order, linear phase, digital low pass filter. With the proper design of that low pass filter the quality of the SFC process can be made “arbitrarily” good – independent of the conversion ratio. Like what we achieved in the SFC2.
Standard sampling frequency converter chips continuously measure the input frequency and then generate the output frequency and the filter specifications accordingly. This results in coefficient “jitter” because the input signal sampling frequency jitter modulates the cutoff frequency of the digital filter. The SFC2 uses a fixed-ratio scheme where the output is directly derived from the input sampling frequency – therefore no coefficient “jitter”, no filter modulation, more transparency.

The main application of the SFC2 is integrating playback or outboard equipment into an environment that either runs at double- or standard-sampling frequency. To allow this equipment to be positioned anywhere in the processing chain, the SFC2 features two completely independent two-channel sampling frequency converters to simultaneously down- and up-sample a signal. Alternatively, it can also be used to convert the sampling frequency and reduce the word-length of any two stereo audio signals at the same time.

“The Weiss SFC2 is an excellent SRC, maybe the best one-step SRC in the world. One up-down-up or down-up-down pass through that is nearly transparent, and even when not transparent very acceptable to the ear.”
– Bob Katz, Digital Domain, USA