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

Main Features 

The two sections of the SFC2 have the same feature set. They sport AES/EBU inputs and outputs on XLR connectors and work at the four standard sampling frequencies of 44.1, 48, 88.2 and 96 kHz. The word-length at the output can be set to 24, 20 or 16 Bits. For proper word-length reduction, dithering must be switched on. Dithering in the SFC2 uses a second order noise-shaping process. The dither noise can be set to be automatically muted in music pauses.






The SFC2 won the “Studio Sound magazine SSAIRA Award” for the year 2000 in the Converters category.





Reviews and user feedback 

Professional Mastering Engineers

“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


“My signal path for 44.1 sources is to up-sample in real-time to 96/24 via the Weiss SFC2, perform outboard eq and dynamics, down-sample to 44.1/24 via the SFC2, then POW-R to 16 Bit for monitoring. By pushing a button on the Weiss I can A/B between up-sampling to 88.2 or 96. The whole chain sounds more open and extended when up-sampled to 96 while monitoring only the final 44.1/16 result.”

Alan Silverman, Arf! Digital, USA

“I heartily recommend the SFC2.”

David Glasser, Airshow Mastering, USA


“At your suggestion, I picked up an SFC2 unit to do my up and down sampling across multiple units. I have been very pleased with the results. A definite improvement. The 48 kHz to 44.1kHz conversion was excellent as well. I even went back and reconverted some files I had already done. Compared to what I had been using, the integrity of the top end was much better and the sound stage stayed in track. Thanks for the suggestion and keep up the good work!”

Bob Boyd, Ambient Digital, USA

Technical Data 

Dimensions (cm)


  • Mains voltage: 115 V or 230 V with voltage selector
  • Fuse rating: 500 mA slow blow
  • Power consumption: 40 VA max



  • Depth: 30 cm
  • Width: 43,3 cm (19")
  • Height: 4,4 cm (1HU)


  • Sampling frequencies: 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz
  • Maximum input word-length: 24 Bits
  • Channel Status Data: Input accepts professional or consumer format
  • Connector: XLR female, 110 Ω


AES/EBU Output

  • Sampling frequencies: 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz
  • Output word-length: 16 Bits, 20 Bits, 24 Bits
  • Connector: XLR male, 110 Ω



Second order noise shaping



The SFC2 is Bit-transparent with a conversion ratio of 1:1

Conversion Spectra

1 kHz Sine 0 dB Converted From 96 kHz
to 44.1 kHz:



1 kHz Sine 0 dB Converted From 44.1 kHz
to 96 kHz:



Because the two sections of the SFC2 can be used completely independent from each other, the applications are manyfold. The sections can be used as a pair of up- and down-samplers (or vice versa), as a simple four channel sampling frequency converter or even just for dithered word-length reduction to 16 or 20 Bits without any sampling frequency conversion.






For Frequently Asked Questions and discussions about this and other products our new Forum will be available soon.


Thank you for your patience.





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