nunosga, post: 450895, member: 50630 wrote: Can I simple use a Y cable with 2 mono jacks on one end , and a stereo jack on the other to connect these two?

no.

is that a Behringer 802?

Don't try to use both outputs (L and R) of the mixer to feed the monitor. Simply use the L output. If the mixer has pan controls, pan all the channels hard left.

If the mixer output is unbalanced, use a TS lead; if it's balanced,use a TRS lead.

My big worry is your tapping off the mic level signals to go into your mixer. You must use a transformer-isolated splitter to avoid the PA's phantom power damaging the mixer inputs.

Boswell, post: 450907, member: 29034 wrote: My big worry is your tapping off the mic level signals to go into your mixer. You must use a transformer-isolated splitter to avoid the PA's phantom power damaging the mixer inputs.

If it's actually a DI box then the line to the mini mixer is likely an unbalanced "through" rather than a split of the XLR output.

Thanks for your interest guys!

quote: "If it's actually a DI box then the line to the mini mixer is likely an unbalanced "through" rather than a split of the XLR output."

Indeed, I believe that the feed to the mixer is just a bypass in the DI. It will be just like the dry signal from the guitar or mic.
And being a sort of bypass in the DI (a Behringer DI4000) i hope there will be no bleed of power from the PS phantom. ...Right?

Anyway, I'm still trying to figure if I can feed both left and right into the balanced input of the monitor. So, if I try to mono the signal by shorting left and right, what can go wrong?
In the monitor side I guess it will be ok; It's just an unbalanced signal...but on the mixer side I'm not so sure.

By the way its's a 502 USB behringer mixer.

nunosga, post: 450911, member: 50630 wrote: 'm still trying to figure if I can feed both left and right into the balanced input of the monitor

no. you can't do that. why would you want to do that anyhow? Boswell gave you good direction.

nunosga, post: 450911, member: 50630 wrote: I'm still trying to figure if I can feed both left and right into the balanced input of the monitor.

It's a single speaker. What possible benefit would you get from feeding it a stereo signal? (hint: none)

Boswell's advice is rock-solid, as are his concerns about exactly how you're splitting those signals.

Are you using the 1/4" passthrough jacks to route the guitars to the 502, and the XLR output to the FOH console? If so, that shouldn't be an issue.
The question is, how exactly are you splitting that mic signal?

nunosga, post: 450895, member: 50630 wrote: Can I simple use a Y cable with 2 mono jacks on one end , and a stereo jack on the other to connect these two?

That's not how things are done..
Most mixers have aux output which is ideal to send to monitors. They are usually balanced output and should go to xlr input on the monitor.
If you want a close representation to what is sent to the PA (FOH) it can be done if the Aux send is post fader by putting them all to unity.

Other ways of doing it would be to use Tape out (if present). Or use main insert send, if present on the mixer...

With the model of the mixer, I'll be able to be more specific of how better it could be done

nunosga , you asked why you shouldn't use that Y cable, here's why.

Using a Y cable like you described, with 1x "stereo" TRS to 2x "mono" TS connectors to feed a single balanced TRS input is going to cause total cancellation of any signal common in both left and right channels. (You have to get away from the mono / stereo terminology - at least as far as this kind of cable goes).

The Tip of one unbalanced TS is wired to the Tip of the balanced TRS. The Tip of the other TS is wired to the Ring of the balanced TRS. When that gets to the balanced input on the speaker, the Tip will go to the positive-phase half of the balancing amp - no problem. Meanwhile, the signal on the Ring will be coming in to the negative-phase of the balancing circuitry. When the inverted signal from that side of the amp gets summed with the positive signal the equal-and-opposite signals cancel each other out. The result is anything panned to the center on the mixer is completely cancelled out. Any source(s) partially panned left / right will probably still be audible, but suffer from serious phase issues. Any sources panned hard left / right should be fully audible although one channel (whichever is connected via the Ring) will be completely out of phase.