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| Author | Topic: digital I/O |
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JohnCowan Member |
posted 25 September 2000 00:48
 
What exactly does changing digital I/O format do in regards to the Capybara 320. Does this just change the status bits as it does with some other equipment I have? I have run SPDIF digital signals into and out of the Capybara when it was set to AES/EBU and there seems to be no problem. I am aware that the electric properties of the AES signal are 2-7v into 75 ohm load while the spdif are 0.5v into 110 ohms. I am curious if the Capy circuits are adaptive somehow to the type of signal it receives so that the exact voltage and impedance matching is not critical within reasonable limits, of course. A number of SPDIF devices can easily handle a higher voltage than 0.5v input. Also, a simple resistor network can help match AES going into SPDIF. My concern is more with sending SPDIF into the Capy set for AES. This is a concern because the two digital I/Os cannot be set differently. Thanks for any enlightenment. John Cowan IP: Logged |
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SSC Administrator |
posted 25 September 2000 11:07
Switching between AES/EBU and S/PDIF causes the digital i/o transmitter and receiver chips to use different settings for the status bits in the digital audio stream. The Capybara-320 receivers will more-or-less ignore the status bits, so that you could properly receive a S/PDIF stream when the Capybara is set to AES/EBU. When developing the digital i/o, we looked into all of the options for switching between the two formats: changing impedance and voltage levels, etc. After carefully looking over the chip specs and consulting with Crystal semiconductor, we arrived at an impedance mid-way between the 110 ohms for AES/EBU and the 75 ohms for S/PDIF. We also transmit at the AES/EBU recommended level (which is the larger of the two voltages). This should not cause any problems for S/PDIF receivers, since the specs says that they should be able to handle this level without malfunctioning. On the receiver side, the Crystal digital receiver chips are sufficiently sensitive to properly receive even very attenuated S/PDIF signals. IP: Logged |
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