I want to investigate the possibility of using a differential SPDIF line driver on the output of a device to:
- eliminate the need for a SPDIF output transformer as these require all sorts of contortion to get them right & I don't have the equipment or time or knowledge to do so.
- provide a purely resistive 75ohm load to the DIT for better impedance matching rather than the inductive/reactive load that a SPDIF transformer presents.
I'm using a DIT4196 Digital transmitter which has differential output line drivers. I'm not talking about AES, 110ohm balanced, I still want to use existing SPDIF 75 ohm cabling & the DAC will have standard SPDIF input circuitry - transformer receiver, etc. Would I lose out on the common mode noise rejection if not having twisted pair? How much of a drawback would this be?
Firstly, why isn't this done more often? Am I missing something? I know probably grounding issues would be a problem if not using a balanced driver but in this case are there other gotchas?
I know there are T-pad calculators for working out the resistive network needed to apply some attenuation & keep it 75ohm but they apply to single ended output - how do I adjust for balanced output?
Would a resistive divider be too much load for the DIT4196 line drivers? The datasheet specifies their characteristics as being able to output from min 2.6V to max 3.3V at 30mA when powered from 3.3V
- eliminate the need for a SPDIF output transformer as these require all sorts of contortion to get them right & I don't have the equipment or time or knowledge to do so.
- provide a purely resistive 75ohm load to the DIT for better impedance matching rather than the inductive/reactive load that a SPDIF transformer presents.
I'm using a DIT4196 Digital transmitter which has differential output line drivers. I'm not talking about AES, 110ohm balanced, I still want to use existing SPDIF 75 ohm cabling & the DAC will have standard SPDIF input circuitry - transformer receiver, etc. Would I lose out on the common mode noise rejection if not having twisted pair? How much of a drawback would this be?
Firstly, why isn't this done more often? Am I missing something? I know probably grounding issues would be a problem if not using a balanced driver but in this case are there other gotchas?
I know there are T-pad calculators for working out the resistive network needed to apply some attenuation & keep it 75ohm but they apply to single ended output - how do I adjust for balanced output?
Would a resistive divider be too much load for the DIT4196 line drivers? The datasheet specifies their characteristics as being able to output from min 2.6V to max 3.3V at 30mA when powered from 3.3V
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