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Contact microphone

howdoi

Apr 26, 2014
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Apr 26, 2014
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I need to set up a contact microphone system to record through a wall continuously for a little while. Most of the wall microphones sold online are battery powered. I recently purchased the following two models:

Nikkei Acoustics
http://nikkei-acoustics.com/
_S8J7478.jpg


Unbranded F-999B
http://www.micronic.co.uk/store/ite...ugh-wall-ceiling-contact-probe-microphone-set
timthumb.php


It is unbranded, but seems to be a rough copy of this one from Sun Mechatronics: http://www.sun-mechatronics.co.jp/EN/wall-contact-box/f-555.htm

The Nikkei Acoustics model originally ran on a standard replaceable 9V battery. I don’t have a photo, but the battery setup was similar to this:
fl330_amp02.jpg


At my request, its eBay reseller was able to solder a DC connector onto it for me, enabling it to run off an AC-DC mains adapter instead. Its internals are shown below:

The case disassembles easily with a hex key.
Ignore the battery taped on top.
IMG_1239.jpg

IMG_1240.jpg


The circuit board then slides out manually from the case (it is held by friction).
IMG_1245.jpg


The DC connector is shown here. Its cable is fed through the circuit board to the other side, and held in place with a dab of hot glue.
IMG_1250.jpg

IMG_1266.jpg


Here is the other side of the circuit board, showing the actual soldered connections of the DC connector’s cable.
IMG_1272.jpg

UBJprM3f6T6vMDm_7Ftnc7DGd2EcmaXEb8q5tG4TpA=w366-h488-no


I want to know if it is possible to fit a similar DC connector to the F-999B model. Unlike the Nikkei model, which ran on a standard replaceable 9V battery before the modification, the F-999B model runs on a fixed rechargeable internal lithium ion battery. Its internals are shown below:
IMG_1212.jpg

7GMaaqiMy56R1PuN5rDXMUMGxr4Po7ktTKD-fP2maw=w366-h488-no

TwUFwEq1W6I046DmmsXR07vFfA2KR-5LW7mE9AQ5OQ=w600-h450-no

IMG_1216.jpg


The F999-B has better sound quality, because the preamp is better (although the actual microphone of the Nikkei is better). If the DC connector modification can be made to it, I want to use the F999-B instead. It did actually come with an AC-DC adapter plug, which the seller told me could be used for continuous mains operation. After reading the manual, it became clear that this was inaccurate. The supplied adapter is only for charging the internal lithium battery, and the manual says the unit must be turned off during recharging. Hence, I need to remove the lithium battery completely, and replace it with a soldered DC connector like on the modification shown above. Unfortuantely, I don’t know what DC voltage to apply once it is complete. The lithium battery is specified as 3.7V, but (if I understand correctly) this can correspond to higher voltages in normal DC batteries.

I don’t know how to solder myself, so I need to know:

  1. If the modification is possible
  2. Who could do it (Electronics shop? Hobby shop? etc). I’m based in London but could post the unit out for the job and then pay for return if the shop is far away.
  3. What voltage I should send to the unit after the modification is complete.

If it is performed successfully, I will need another 3 or 4 done.

Thanks for your time...
...and apologies for my cluelessness.
 

(*steve*)

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