stereo track turns echoy

I recorded an interview on a stereo track using two USB mics (aggregate device). Sound is fine for awhile then everything is echoy.


They warn you that Aggregate Device is not the same as a sound mixer. Aggregate Device combines the two sound bitstreams with zero attention paid as to whether or not they’re in sync. And they won’t be. Do you remember it asking which USB stream you want to use as the “Master?” That’s why. The Master will be in real-time sync and the other will slowly drift over time. If you have a recording studio where one voice will appear on both microphones, then the “leakage” will slowly drift off real time sync. That is almost without question where the “echo” is coming from.

The example is 44100 sample rate. If one microphone is going at 44100.01, and the other exactly on target, they will slowly drift to each other over time. Hollywood goes to very serious, expensive effort to make sure that doesn’t happen when they have to divorce the film camera from the sound recorders.

I don’t know of a fix. Once two voices are burned into one track, that’s full stop.

I would be using analog microphones into a plain sound stereo sound mixer and record that with Host on the Left and Guest on the Right. They will still leak into each other, but they will be in perfect sync and you can apply corrections to one voice with only a tiny leakage into the other.


USB microphones are aggressively non-expandable. One microphone into one computer works OK and you can force two to work on a Mac, but past that, you’re into analog land. Or multiple recorders, and that will still give you an echo problem depending on the recorder or computer.



I went with the USB mics because my AT2020s aren’t working on their own (XLR-to-USB) or through a mixer with USB plug. No sound at all. No fix works. I’m ready to start throwing equipment around my apartment.

If you record a mono track with one USB microphone (no aggregate devices), does that work correctly?