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Automatic Input Selection


Gareth Owen

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In the orchestra pit I have a number of musicians, several of which double up on multiple mic'd instruments.

 

Lets take Reed One as an example :

 

Reed One plays Saxophone and Flute. I have two mics rigged to cover Reed One, in this case a Neuman KM140 positioned for the Saxophone and a Shure KM81 overhead for the Flute.

 

How can I automatically switch between inputs depending on which instrument is being played? I'm not looking to reduce channels here - I'm trying to ensure only one desk channel is unmuted at any given time.

 

Bare in mind that the Flute is much quieter than the Sax so gating is out of the question. The musician herself insists that her score is far to complicated to have time to press a button between instruments, and although the show in question is heavily programmed, there are too many instrument changes to allow the sound operator to swap either manually or through programming.

 

This particular is on a Digidesign Venue, but I'm actually looking for a generic anwser which could be applyed to any console or show.

 

So, any ideas?

 

Please note that I'm not looking for suggestions as to which is the best mic for either application - I beleive this has been covered in more than enough detail in previous threads.

 

Thanks in advance for your responses! :(

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I think maybe the instrument stand is the key here.

 

Some form of pressure sensitive (or whatever works) device that breaks the signal chain (in as clean a way as possible) to the mic when the instrument is put in its stand.

 

This wouldn't work with a simple switch, too noisy, especially with +48v supplied. So some form of resistance altering device would be required to effectively turn down the channel. It might not necessarily need to be to -inf.

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I think maybe the instrument stand is the key here.

 

Some form of pressure sensitive (or whatever works) device that breaks the signal chain (in as clean a way as possible) to the mic when the instrument is put in its stand

 

Just connect the switch between pins 2 and 3 of the XLR to mute the microphone.

 

This will work irrespective of whether the phantom power is on or off.

 

David

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Just connect the switch between pins 2 and 3 of the XLR to mute the microphone.

This will work irrespective of whether the phantom power is on or off.

David

So shorting out the circuit, shorting out the +48v, and sending a click / pop / other noise through the system?

 

Not often I dissagree with Rob, but............

 

I'm sure I've made switches that are wired like that before & had no problems.

 

Cirtainly the phantom isn't an issue, as you're only shorting one +48V to another, leaving the 0V on pin one untouched.

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I'm sure I've made switches that are wired like that before & had no problems.

Cirtainly the phantom isn't an issue, as you're only shorting one +48V to another, leaving the 0V on pin one untouched.

 

This does in fact work, and if you are feeling really paranoid, you can wire a 100uF cap in series with the switch with a 10K resistor across the switch contacts.

The effect is that the cap blocks any dc offset, and the resistor ensures the cap is charged to the appropriate level when the switch closes.

 

I would investigate the possibility of an instrument stand, a microswitch and some epoxy resin.

 

Regards, Dan.

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But the mics are in roughly the same place, so the sax will always be loud enough to open the flute channels gate...

 

Change the flute mic to a clip-on and the relative levels in each mic will be enough to only trigger its own gate. I also think the assumption that a musician will always put an instrument back on a stand is a bit flawed.

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