ECM8000 Connection Issue (ground loop?)

[MichiganMan]

I went to take some room readings and noticed that the right channel meter is maxed out with only background noise. If I turn off phantom power to the mic the level dissipates slowly. If I turn power on the meter will quickly max out.

I'm running an ECM8000/XENYX 802 into the Line In right channel of my PC, front right out to my pre/pro, and I'm looping back the front left out to the Line in Left.

Even if I remove the loop back the input is saturated.

Is there something I could have fat fingered on the 802? I did reload my OS and REW recently. Could it be a simple setting I missed in REW?

[brucek]

I'm looping back the front left out to the Line in Left.

Don't use the Left Channel reference method. Use the soundcard calibration file method.

Remove all the cables and put a single loopback on the right channel and create the soundcard file. Save it, then do a measure of the cable to ensure the file is good. The response should be flat. Then remove the loopback cable.

Now use that calibrated channel for your mic and output to the receiver.

brucek

[MichiganMan]

Bruce,

I did as you said, removed the loop back ref and used a sound card cal file. Card cal file looks right?

Well the input still saturates and you can notice a peak at 60Hz. This is the same setup I was using only 3 moths ago without an issue. The picture below should be HTPC fans background noise <30db

I tried two different XLR cables, and plugged the ECM8000 directly into the 802 with the same problem. I setup my old RS meter, RS cal file and everything worked fine.

So I'm thinking something is wrong with the ECM8000 mic or 802 preamp. When I enable line-in to pass through to the pre/pro I get a hum probably 60Hz. If I grab the mic the volume changes as if I was affecting the capacitance some how. Is there a way to rule out one or the other? Or am I missing something?

Anthony

[brucek]

Card cal file looks right?

Yep, fine.

So I'm thinking something is wrong with the ECM8000 mic or 802 preamp.

Looks that way. How about the cable from the 802 to the soundcard? I suppose it's a 1/4"TS to RCA, with an adapter to 3.5mm. Could it be bad?

Probably easier to play around by plugging the 802 directly into your AUX of the receiver for troubleshooting the problem. Then you'll be able to hear the hum (or whatever) and be able to talk into the mic.
Try both channels of the 802.

brucek

[MichiganMan]

Aaah! call me dumb

The problem was the un-balance line from the 802 to the sound card running too close to the PC's coiled AC power cord.

All is well again.