Wall microphone

[howdoi]

Hi

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
<MOD EDIT: Personal commercial link removed>


Unbranded F-999B
**broken link removed**

It is unbranded, but seems to be a rough copy of this one from Sun Mechatronics: **broken link removed**

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:
**broken link removed**

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.

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

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.

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

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:

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.

 

[cowboybob]

...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. ...

Welcome to ETO, howdoi!

1. Yes, it is possible.
2. It's a simple enough modification, but I have no way of knowing who to select. Can you find any Amateur Radio Operators (Hams)? They ought to be able to do the change.
3. 3.7 VDC means 3.7VDC mains power supply for your amplifier. That isn't a standard "wall-wart" value. If you have access to a Radio Shack, check with them for a solution. (for a circuit board modifying type person as well). I should note the 3 AAs (or AAAs) in series will provide 3.6VDC, which is close enough for your purpose.

We can provide solutions as well, but since your experience is as you say, I wouldn't want to suggest anything that you can do for yourself. At least not just yet.

 

[asterix1]

Hi,
I want to talk about the wall microphone F-999. Does it realy do his job?
Let me explain; I live in the Netherlands and my neighbour, i'm prety sure, does produce synthetic drugs upstairs his livingroom. He always works on the night when we are asleep. Police can't do anything if they not seen or smell something strange and can not force the house in the middle of the night. First the sounds of the machines, water, was good to hear but when he was arrested for something else they have isolate it a little.
Butt still I hear the sounds of the machines/ vacuum pump, so I want to recode it and let it hear to the police so they know its pretty sure and come to my home to listen often.
The walls are 20 cm (it are old houses) but does the F-999 a good job. Is it not a cheap copy from the sk-300 or F-555 but are a lot more expensive.
https://www.megaspyshop.nl/kopen/afluisteren/wandmicrofoons/
What is your experience with the F-999, to hear through a wall to get sounds and voices?

regards Gerard

 

[audioguru]

Is it legal to snoop on somebody?
I think a contact mic fastened to a wall or ceiling makes horribly muffled sounds (boom, boom) with some resonant peaks (shrieks) thrown in.
Professional snoopers use a spy radio transmitter with its mic in the room being snooped.

 

[asterix1]

Professional snoopers use a spy radio transmitter with its mic in the room being snooped.

But not always you can get in that room

 

[audioguru]

But not always you can get in that room

A laser beam (or invisible IR) can enter the room through a window and sounds can vibrate a reflective object (glass covering a photo on a wall?). Its modulated reflection can be received by a receiver outside the room.
The window itself can be vibrated by sounds in the room and reflect modulated light or IR to a receiver.

 

[Misterbenn]

Its not a big job, I could do it if you cant find anyone.