ADVICE: Driving headphones from multiple level sources

[sturgjoh]

Hi,

 

Noob here- but been a follower of the forums for a number of years. I have a problem that I hope someone can help me with.

 

Bear with me please....as this may sound slightly bizarre...

 

I run a small PA setup with a small format mixer - Spirit M12. This only has 2 prefade aux sends and we can use upto 4, so my kit of tools now includes two seperate 8 channel line mixers (behringer MX882) to create the Aux 3 and Aux 4 mixes.

All 4 aux mixes (two from the desk and 2 from the line mixers) then go through Behringer FBQ1502 EQ sections before heading off to the multicore, Amps and Monitors.

 

Headphone monitoring from the mix position can now be fun as I can't hear what I send out from Aux 3 or Aux 4 as they are outside the desk (and therefore have no PLF or FL buttons!).

 

 

My ideal solution would be a bigger mixing desk with 4 prefade auxes! but space, and finances prohibit this.

 

 

Other options are as follows but I need to answer some questions first as my technical knowledge fails me.

 

Q1) How can I drive a set of headphones from the output of the FBQ1502 which is already connected to the multicore, and is also a balanced XLR connector?

Q2) If I tap into the balanced line on the GND and Hot in parallel with the feed to the amps will this work?

Q3) Will I need to amplify this signal to drive my headphones?

Q4) how can I switch between sources for my headphones without introducing a pop or crackle down the line to the amps ( my sources are: a) Mixing desk, b) Aux4 FBQ 1502 c) Aux4 FBQ 1502 )

 

I know you can but headphone amplifier boxes, behringer and sampson do a few for not too much money, but can I connect in parallel with the multicore send, and how do I switch between sources?

I was thinking of some sort of high impedance switch box, feeding in to a small headphone amplifier - which I'm happy to build and connect up ( I'm happy wielding a soldering iron! ) but don't know enough about impedance matching! or buffering of signals (especially servo balanced ones!)

 

 

Thanks in advance for any advice - John

[dbuckley]

What you need is a balanced line receiver for each channel (ie four of them) that you connect in parallel with the feed you send you send down your multi, followed by a simple switch and a headphone amplifier of your choice. So its a passive line level transformerless split. For balanced line receiver chips have a look at the range from That Corporation and find a part that suits your preferences.

 

The line receiver will buffer the signal, so nothing you do after the reeiver will affect the signal going to the stage, so you are in effect isolating the stage feeds from your headphone processing.

 

Alternatively, put then entire rackfull of Behringer boxes on eBay, and whilst there, pick up this Gentner PSR1212 which will ao everything both the MX882s will do, and everything useful the FBQs will do, and a bunch more. Ok, you'll need to take your lappie to drive it... I have one of these boxes and they positively rock. Ok, it doesn't have the programability of a SoundWeb, but it has eight DSP processing chains, which is enough for stereo 2 way cross (with stereo or mono subs) and at least four channels of other processing.

[sturgjoh]

Hi David,

 

Sorry I just realised that I'd not replied to you thanking you for your reply. It has got me thinking that I wish I had more time on my hands, and also that I used to love tinkering with electronic circuits and perhaps this is something I will enjoy getting to work sometime in the near future! Thanks for the links.

 

John