Hello, I have a PCIe card with AES/EBU 110 Ohm output that I want to connect to the AES/EBU 110 Ohm input of my DAC through a cable.
I would like to add galvanic isolation to this connection using the 1:1 transformer LL1572 by Lundahl.
Which schematics do you suggest, among the solutions A-B-C below? Thank you in advance.
Solution A:
Solution B:
Solution C:
I would like to add galvanic isolation to this connection using the 1:1 transformer LL1572 by Lundahl.
Which schematics do you suggest, among the solutions A-B-C below? Thank you in advance.
Solution A:
Solution B:
Solution C:
None of the above. IEC60958 say to have the transformer in the signal and connecting the grounds with the shield of the cable. So your transformer should go between pins 2 and 3 and pin 1 should connect to the shield of the cable. For normal distances in house you could leave pin 1 unconnected.
As for a transformer, a miniciruits T1-1T is also usable.
As for a transformer, a miniciruits T1-1T is also usable.
It's solution A with pin 1 in the source connected to the cable shield (and pin 1 floating in the destination), right? Thank you 🙂
Are you actually seeing problems with "background noise over pin 1" from your PC? If so, what has led you to your conclusion that ground issues (since we're talking about pin 1) are the real cause?
Might you have a pin 1 problem?
I detached pin 1 from the drain/destination, and the S/N ratio improved. PC is notably a high frequency source of noise, which finds a bridge through the shielding. As far as I know, the pin 1 problem is in analog audio, not in digital audio. Anyway, both PCIe and DAC are robust and modern pro audio devices, it's the PC the source of noise.
That's it.
But I'm worried that you would have issues in a digital link. Like you say, pin 1 issues should not occur in digital connections. Those devices are not pro-audio or they would not have that problem in the first place. Transformer isolation in AES is more or less standard in pro audio. Cards like a Pulsar do have that. And if the noise on the digital ground finds its way into the analog side then there is something wrong in the pcb design. I have used several DA convertors with pc's and this never was an issue (RME, Fostex, Crystal Semiconductor) or with integrated audio interfaces like a Roland FA-66 (ok, Firewire but that is a digital connection to the laptop). I even never noticed something like that in the digital switchbox I made years ago.
Thank you Havoc,
I actually have a RME AES PCIe and it works very well. No issues.
I made pin 1 floating on the drain (DAC side) of the AES/EBU XLR connector
of the cable, and it works even better. Please try yourself. ***
The CPU voltage is not really constant over time, and it acts
as a high frequency antenna. Even with the best PCIe card in the world,
this noise goes trough pin 1 / shielding as it is the chassis ground. Maybe
I am naive and there are other approaches. I am not an electrical engineer 🙂
-R
*** This does not make any sense with analog audio, instead, and it is better to have
both pins 1 connected to the chassis for analog, according to the RANE documentation).
I actually have a RME AES PCIe and it works very well. No issues.
I made pin 1 floating on the drain (DAC side) of the AES/EBU XLR connector
of the cable, and it works even better. Please try yourself. ***
The CPU voltage is not really constant over time, and it acts
as a high frequency antenna. Even with the best PCIe card in the world,
this noise goes trough pin 1 / shielding as it is the chassis ground. Maybe
I am naive and there are other approaches. I am not an electrical engineer 🙂
-R
*** This does not make any sense with analog audio, instead, and it is better to have
both pins 1 connected to the chassis for analog, according to the RANE documentation).
Of course a ground wire can carry ground conducted EMI/RFI. Once that's inside a dac it can intermodulate with the audio in forward biased semiconductor junctions and or cause other noise problems in the audio band. Nothing new here. This all well known stuff.
There are some app notes about this for op amps and some commentary in the forum:
https://www.diyaudio.com/community/...ormance-cmos-audio-op-amp.335416/post-6640167
https://www.st.com/resource/en/appl...etic-interferences-emi-stmicroelectronics.pdf
https://www.ti.com/lit/an/sboa128a/...99142&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.ti.com/lit/an/sbot003/s...16705&ref_url=https%3A%2F%2Fwww.google.com%2F
There are some app notes about this for op amps and some commentary in the forum:
https://www.diyaudio.com/community/...ormance-cmos-audio-op-amp.335416/post-6640167
https://www.st.com/resource/en/appl...etic-interferences-emi-stmicroelectronics.pdf
https://www.ti.com/lit/an/sboa128a/...99142&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.ti.com/lit/an/sbot003/s...16705&ref_url=https%3A%2F%2Fwww.google.com%2F
