I have a Behringer Xenyx 502 mixer.

My problem is the microphone levels are always much hotter than the phone line. Boosting the phone line isn't the problem as much as not overdriving the microphone into the red. But that seems to be the only way people on the phone can hear me.

When my microphone levels look normal, they say they can't hear me. I don't know mixers very well, but I must not have the adjustments right. If I can't make this work, do I need an even simpler, cheapie Radio Shack mixer?

See image below to see how I have it wired to my PC...

enter image description here

  • Are you sure the problem isn't with the device sending the output to the phone? If you are sending good signal, then an impedance mismatch or perhaps a level problem on the device sending it to the phone is the problem.
    – AJ Henderson
    Commented May 24, 2013 at 3:17

1 Answer 1


Your set-up seems quite weird to me. Channel 1 is panned to the right, while channel 2/3 is also to the right. Shouldn't it be panned to the left, so that you can record each signal in a different track?

Also, you seem to connect both Left and Right output channels to the AutoHybrid input. This way, the person you are talking to would also hear his own voice. This could be troublesome if a considerable delay existed.

Although this might not be an immediate solution for your problem, I would connect it as follows:

enter image description here

You could also try to set a lower trim in channel 1, and turn up a bit the master output. This could make the mic overdrive a little less (but don't expect a miracle. I just think it would be helpful to avoid forcing the preamp).

In what concerns to the signal levels, the AutoHybrid seems to be receiving a weak signal from the mixer. This is actually unlikely to happen (I guess the PC gets a pretty strong signal). The AutoHybrid manual states the following:

Null Adjust

The Null Adjust is a 15 turn pot used to determine how much of your Send audio is delivered to the Caller output jack. Use a small flatblade screwdriver to make adjustments to this control. To find the absolute nu.. for any telephone line, follow this procedure:

  1. Place a call to a quiet location.
  2. Send a signal into the AutoHybrid Send jack at a moderate level. A test signal or tone works best.
  3. Connect the Caller output jack to a meter or scope, or listen to this signal through your external audio equipment.
  4. Try to remember the position of the adjustment screwdriver blade and the number of turns you are making as your first adjust clockwise, then back to the original position, then counter clockwise. When the level of this signal is at a minimum, you have achieved the maximum null for the phone line. The maximum null you can achieve is approximately 20 dB.

This makes me think that this pot isn't properly adjusted, so the device is actually attenuating its input. Messing around with it should work in case the previous didn't.

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