User manual WEISS ADC2

[. . . ] · · · AES/EBU on XLR in one or two wire format S/PDIF on RCA Firewire (to be implemented). DSP · POW-R dithering to 16 bits, settable to three different algorithms according to the POW-R standard. Two segment compressor / peak limiter Double-precision processing 40bit floating-point · · · · · · · Daniel Weiss Engineering Ltd. , Florastr. ch Page 2 of 2 weiss@weiss. ch OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER OPERATION OPERATION ADC2 Block Diagram Fig. 1 ADC2 Block Diagram Schematic Input Control Panel This section describes how to use the input control panel (see Fig. [. . . ] This gain can be used for optimal gain adjustment and to drive the peak limiter (see below). The gain ranges from - (off) to +18. 0 dB, the resolution is optimized for fine control around 0. 0 dB while still allowing complete fade-out. A special algorithm is used for click-free gain transissions (no "zipper" noise). To clear the peak hold value, double-click the "peak hold" key!Double-click resets both input and output peak hold. Daniel Weiss Engineering Ltd. , Florastr. ch Page 4 of 4 weiss@weiss. ch OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER OPERATION Threshold If "threshold" is lit, the rotary knobs control the threshold of the compressor section. If "peak hold" is active, the output peak value is displayed. The threshold can only be adjusted for the compressor section, which has a fixed ratio of 2:1. The limiter has a fixed ratio of :1 with a fixed threshold of 0. 0 dBFS. Because the signal before the output gain never exceeds 0. 0dBFS, the limiter is inactive if the output gain is £ 0. 0dB. If the threshold is set to 0. 0 and the output gain is below 0. 0 the dynamics section is inactive. 5 Compressor with -6. 0dB Threshold 0. 0 -6. 0 0. 0 -12. 0 -12. 0 -6. 0 -6. 0 0. 0 +6. 0 The overall gain reduction applied by the compressor / limiter is shown in the yellow bargraph. Note that the compressor uses auto gain makeup: depending on the threshold, a gain is added after the compressor to ensure that 0. 0 dBFS input results in 0. 0 dBFS output (graphically speaking, auto gain make-up "fixes" the transfer curve at the (0. 0, 0. 0) point). -12. 0 -12. 0 -6. 0 0. 0 +6. 0 Fig. 3 Compressor with 0. 0dB Threshold To activate the limiter, set the output gain to a positive value. The gain reduction applied by the limiter is visible on the yellow bargraphs. To soften the transmission from linear to limiter segment, the compressor can be activated by adjusting the threshold parameter. ch Page 5 of 5 weiss@weiss. ch OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER OPERATION Sync and Dither Control Panel If none of these two keys are lit, the ADC2 uses internal sync. POW-r Dither To requantize the input signal from 24bit to 16bit format, a special technique is used to avoid distortion, called dithering. Many dithering schemes are available today, both professional and homebrewed. The ADC2 uses the POW-r scheme, which is widely regarded as one of the best, if not the best2, and is used in a variety of digital equipment. The POW-r scheme offers three different presets which can be selected with the dither keys "pow-r 1", "pow-r 2" and "pow-r 3". The choice should be based on listening tests and preference of the recording engineer. Fig. 6 ADC2 Sync and Dither Control Panel Output Frequency If the analogue inputs are selected ("digital in" is not lit), the A/D sampling frequency can be set in the sync source block: Sampling quency Fre- 44. 1 / 48 kHz key 44. 1 kHz 48 kHz 44. 1 kHz 48 kHz 44. 1 kHz 48 kHz fs x 2 / fs x 4 key none none sf x 2 sf x 2 sf x 4 sf x 4 44. 1 kHz 48. 0 kHz 88. 2 kHz 96. 0 kHz 176. 4 kHz 192. 0 kHz Dithering is in "auto black"3 mode: if digital zero is detected at the ouput, dithering is switched off. [. . . ] ch Page 11 of 11 weiss@weiss. ch OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER TECHNICAL DATA Low cut frequency response: 1st order highpass, 3dB point at 40Hz Frequency Response: @ fs = 44. 1kHz: 20Hz . . . > 40kHz +- 0. 3dB THD+N @ 1kHz: less than -103 dBFS @ -3 dBFs output level, unweighted SNR @ -40dBFS input: > 110dB unweighted Linearity: t. b. d. Crosstalk: < -120dB, 0. . 20kHz CMRR: > 90dB @ 1kHz > 80dB @ 20kHz > 60dB @ 20Hz Interchannel phase tracking: Better than +- 0. 3°, 20Hz to 20kHz All measurements taken at the least sensitive setting of the input attenuators, i. e. (= sensitivity for 0dBFS output level). Daniel Weiss Engineering Ltd. , Florastr. ch Page 12 of 12 weiss@weiss. ch OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER TECHNICAL DATA Parameter Tables Analogue Gain Line Input [dB]: -26. 0, -25. 0, -24. 0, -23. 0, etc. [. . . ]