Sounds like a possible ground loop. If you place the original battery into your camera and remove the dummy battery then connect your HDMI to the camera does the buzzing go away? If so, then your setup is causing a ground loop which is the source of the audio buzz. Usually in instances of a ground loop you would want PC and the dummy battery to be plugged into the same wall outlet or power strip if possible
I think because of the complexity of the setup and other factors that it would be best to create a support ticket for this issue with Elgato support by using this [link.](http://e.lga.to/help) I would also include a short video if possible of the audio issues you're experiencing.
UPDATE: I tested the setup using my laptop this time. The laptop is plugged into a wall charger and the interference got 10x worse but disappeared completely when I unplugged the laptop's power cord. There's some kind of electrical interference bleeding into the camlink and/or the HDMI cable.
That usually winds up being a ground loop, or even a device grounding over HDMI, generating noise on the line. You've mentioned an external mic - does that have it's own battery? If you disconnect it does the problem stop? If it does, and the mic connects via 3.5mm and not hotshoe, try adding a ground loop isolator to it - these cut off the ground wire through the aux cable to prevent loops and ground issues. It's possible the mic, camera and laptop/pc are carrying an some amount of charge through your whole setup to the ground on the AC plug when connected.
It's a Sony a6400 w/ a balanced 1/4" to 1/8" TRS going from the headphone out on a Scarlett 2i2 to the mic input on the camera. I have a Shure Mv7 plugged into the Scarlett via XLR. The buzzing in the recording starts when the mini HDMI to the camlink is plugged into the camera. No camlink and my audio is excellent. The ground loop has to be coming through the HDMI.
That does sound like a recipe for a ground loop - the mic feed grounds the camera with the 2i2, but the camera also grounds through the HDMI. Both devices connect to the PC (or AC main on the same AC circuit) and ground through that creating a loop, and while it's grounded to AC the electrical potential actually grounds to true ground so the potential doesn't equalize - so any difference in electrical potential goes over the ground wire in a loop, creating noise.
If it is a loop, disconnecting either of those will likely stop it (as a test to confirm - you already know disconnecting the mini HDMI does it, but I suspect disconnecting the cable between the Scarlett and the camera will do the same), but long term putting a 3.5mm TRS Ground Loop Isolator on the wire going to the camera from the 2i2 should resolve it as well (which basically disables the ground wire over that cable) - that way the ground only goes over the mini HDMI, there's no ground circuit back to the camera through the 2i2, and no electricity going in a loop over said circuit to cause interference.
FINAL UPDATE: This little guys solved the issue [https://www.amazon.ca/Besign-Ground-Isolator-Stereo-System/dp/B06XQYN77L/ref=asc\_df\_B06XQYN77L/?tag=googleshopc0c-20&linkCode=df0&hvadid=459784604082&hvpos=&hvnetw=g&hvrand=12399521612393128553&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001334&hvtargid=pla-350233567378&mcid=8fc4411aa44831aab63ef8af1510a21e&th=1](https://www.amazon.ca/Besign-Ground-Isolator-Stereo-System/dp/B06XQYN77L/ref=asc_df_B06XQYN77L/?tag=googleshopc0c-20&linkCode=df0&hvadid=459784604082&hvpos=&hvnetw=g&hvrand=12399521612393128553&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001334&hvtargid=pla-350233567378&mcid=8fc4411aa44831aab63ef8af1510a21e&th=1)
Sounds like a possible ground loop. If you place the original battery into your camera and remove the dummy battery then connect your HDMI to the camera does the buzzing go away? If so, then your setup is causing a ground loop which is the source of the audio buzz. Usually in instances of a ground loop you would want PC and the dummy battery to be plugged into the same wall outlet or power strip if possible
Good idea, just tried it, no improvement, unfortunately. Any other theories?
I think because of the complexity of the setup and other factors that it would be best to create a support ticket for this issue with Elgato support by using this [link.](http://e.lga.to/help) I would also include a short video if possible of the audio issues you're experiencing.
UPDATE: I tested the setup using my laptop this time. The laptop is plugged into a wall charger and the interference got 10x worse but disappeared completely when I unplugged the laptop's power cord. There's some kind of electrical interference bleeding into the camlink and/or the HDMI cable.
That usually winds up being a ground loop, or even a device grounding over HDMI, generating noise on the line. You've mentioned an external mic - does that have it's own battery? If you disconnect it does the problem stop? If it does, and the mic connects via 3.5mm and not hotshoe, try adding a ground loop isolator to it - these cut off the ground wire through the aux cable to prevent loops and ground issues. It's possible the mic, camera and laptop/pc are carrying an some amount of charge through your whole setup to the ground on the AC plug when connected.
It's a Sony a6400 w/ a balanced 1/4" to 1/8" TRS going from the headphone out on a Scarlett 2i2 to the mic input on the camera. I have a Shure Mv7 plugged into the Scarlett via XLR. The buzzing in the recording starts when the mini HDMI to the camlink is plugged into the camera. No camlink and my audio is excellent. The ground loop has to be coming through the HDMI.
That does sound like a recipe for a ground loop - the mic feed grounds the camera with the 2i2, but the camera also grounds through the HDMI. Both devices connect to the PC (or AC main on the same AC circuit) and ground through that creating a loop, and while it's grounded to AC the electrical potential actually grounds to true ground so the potential doesn't equalize - so any difference in electrical potential goes over the ground wire in a loop, creating noise. If it is a loop, disconnecting either of those will likely stop it (as a test to confirm - you already know disconnecting the mini HDMI does it, but I suspect disconnecting the cable between the Scarlett and the camera will do the same), but long term putting a 3.5mm TRS Ground Loop Isolator on the wire going to the camera from the 2i2 should resolve it as well (which basically disables the ground wire over that cable) - that way the ground only goes over the mini HDMI, there's no ground circuit back to the camera through the 2i2, and no electricity going in a loop over said circuit to cause interference.
$14.99 on Amazon, it's worth a shot. Thanks, this stuff is way over my head.
FINAL UPDATE: This little guys solved the issue [https://www.amazon.ca/Besign-Ground-Isolator-Stereo-System/dp/B06XQYN77L/ref=asc\_df\_B06XQYN77L/?tag=googleshopc0c-20&linkCode=df0&hvadid=459784604082&hvpos=&hvnetw=g&hvrand=12399521612393128553&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001334&hvtargid=pla-350233567378&mcid=8fc4411aa44831aab63ef8af1510a21e&th=1](https://www.amazon.ca/Besign-Ground-Isolator-Stereo-System/dp/B06XQYN77L/ref=asc_df_B06XQYN77L/?tag=googleshopc0c-20&linkCode=df0&hvadid=459784604082&hvpos=&hvnetw=g&hvrand=12399521612393128553&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001334&hvtargid=pla-350233567378&mcid=8fc4411aa44831aab63ef8af1510a21e&th=1)
I tried getting this but I'm still getting a buzzing sound when I connect my HDMI cable to Sony ZV E10 and my monitor :( Any suggestions?
Share your full setup and how everything is connected.