living sounds
Well-known member
I've got an old Protools interface from which I've salvaged the pulse transformers for my new multichannel converter.
Attached to the transformer primaries of the AES/EBU inputs are 100pf capacitors to (chassis) ground. I couldn't find a similar arrangement in any papers or datasheets.
I've looked at the input (primaries) of my converter with a scope with and without capacitors attached in an identical manner and could see the expected change in the waveform (less overshoot but slower rise time). It's hard to say which one is better, though, since the waveform doesn't looks like a clean squarewave either way on my 50MHz scope (at 44.1k).
The signal path has a proper shield connection to chassis, so the balanced connection shouldn't be picking up much RF. The trafos secondaries are terminated by a 110 ohm resistor.
Beyond RF, could there be a reason in the pulse transformer's makeup that mandates the caps? All I could measure was a primary inductance in the ballpark of similar transformers intended for AES/EBU connections.
Attached to the transformer primaries of the AES/EBU inputs are 100pf capacitors to (chassis) ground. I couldn't find a similar arrangement in any papers or datasheets.
I've looked at the input (primaries) of my converter with a scope with and without capacitors attached in an identical manner and could see the expected change in the waveform (less overshoot but slower rise time). It's hard to say which one is better, though, since the waveform doesn't looks like a clean squarewave either way on my 50MHz scope (at 44.1k).
The signal path has a proper shield connection to chassis, so the balanced connection shouldn't be picking up much RF. The trafos secondaries are terminated by a 110 ohm resistor.
Beyond RF, could there be a reason in the pulse transformer's makeup that mandates the caps? All I could measure was a primary inductance in the ballpark of similar transformers intended for AES/EBU connections.