Multi!Wav Digital PRO Series Technical Notes

Some Technical Questions Answered

Do the signals that go through the AES/EBU connectors remain balanced throughout the card, or does it become unbalanced at any point and then just split into a balanced signal?

The AES/EBU signals remain fully balanced, for both transmission and reception. Both reception and transmission used shielded transformers as well, which greatly improves the CMRR (common mode rejection ratio). The receiver is a balanced differential receiver, and the transmitter is also a balanced differential transmitter. Note that the signals do NOT become unbalanced, either in the receiver or transmitter.

Does the card have its own internal clock for determining the sampling rate, and how accurate is this clock? What are the jitter ratings of the card? To what extent does electrical noise from other computer components affect the digital signals leaving the card?

The card can sync to a variety of sources, as well as from crystal sources. The crystals oscillators are specified with a jitter of 50pS. The card uses four-layer construction with controlled impedance traces. All critical clock signals are critically damped on PCB traces that are long enough to consider transmission line effects. The word clock PLL is separately powered from a filtered regulated power source. The digital audio source PLL is filtered with a 2 pole passive filter (since the digital audio source has a reference frequency roughly 256 times higher than the word clock, the passive filter exceeds the recommendations of the digital audio receiver), and provides excellent jitter reduction. Finally, in addition, the 24-bit delta-sigma DAC provides excellent jitter reduction.

The clock accuracy of the internal clock oscillators is specified as 100ppm over temperature. For professional audio applications the card is normally synchronized to the studio clock, whether it be the external word clock or digital audio clock. Note, however, that the card can be operated as a master, and it can generate word clock, so that it can be also be used as a master studio clock.

There have never been any reports of adjacent card pickup interference. Critical circuitry is carefully laid out. The analog section uses shielded internal layers for critical traces, and also uses the bottom layer as a shield.

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