MixPre 3 in-camera sound problem

[EphraimP]

I'm getting a strange, fluttering distortion sound when I plug the 3.5 mm out from my MixPre 3 II into my X-T3 Mic jack. It fluctuates around -20db and makes using the in-camera track impossible. The sound recorded to the MixPre's card is fine. I've checked settings (mic out, not line) and used tone generation to make sure the sound level coming in is where it should be. When I turn all the inputs off and just send tone, the fluctuation disappears.

This has happened with two different 3.5 mm cables, one of which works fine when I use my DXA preamp with the camera. 

While I've been fine using the recorder's card and syncing in post for interviews, I'd like to be able to use the MixPre as an audio interface for live streaming and route it through the camera to avoid sound/picture sync issues. Anyone had this problem and figured the solution out?

I'm hoping a certain beardly antipodean audio pro might weigh in here.

[Grimor]

There's a menu in advanced mode that is "Phase" where you can invert to avoid electrical interference/hums. Don't know if it makes changes to the 3,5mm output, but you can try anyway

[BrunoCH]

On 5/9/2020 at 5:53 AM, EphraimP said:

I'm getting a strange, fluttering distortion sound when I plug the 3.5 mm out from my MixPre 3 II into my X-T3 Mic jack. It fluctuates around -20db and makes using the in-camera track impossible. The sound recorded to the MixPre's card is fine. I've checked settings (mic out, not line) and used tone generation to make sure the sound level coming in is where it should be. When I turn all the inputs off and just send tone, the fluctuation disappears.

This has happened with two different 3.5 mm cables, one of which works fine when I use my DXA preamp with the camera. 

While I've been fine using the recorder's card and syncing in post for interviews, I'd like to be able to use the MixPre as an audio interface for live streaming and route it through the camera to avoid sound/picture sync issues. Anyone had this problem and figured the solution out?

I'm hoping a certain beardly antipodean audio pro might weigh in here.

What are your settings?
XT3: external mic level adjustment?
MixPre3: stereo out gain?
and the tone level  you used?

[IronFilm]

Can you post a sample please?

[EphraimP]

I figured it out, sort of. It has to do with the power source. I've got my X-T3 rigged up to run off a Fotga V-Mount battery plate powered by a cheap Juicebox 95 wh battery. So, naturally when I've tried to use the MixPre with the camera I've plugged it into the usb out from the battery, because the recorder eats batteries like nobody's business. I recently picked up a Powerextra NP-F960 style battery with DC and USB outlets. I plugged its usb into the MixPre to look at my settings and jacked it into the camera. No distortion. I checked with the V-Mount setup, distortion. I then checked with 4 AA batteries and with the MixPre's included USB C charger. No distortion. 

So, clearly the V-Mount setup is the culprit. I don't understand why, as I used the same USB cable for the NP-F and V-Mount setups. I no f-all about electricity though, so hopefully someone better informed has an idea.