My ordeal and how I learned to make an audio attenuator

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akalen4u

Wannabie Member
Got fed up, didn't feel like buying something, so I asked a friend to help me figure out what I needed to get to make an attenuator. Went down to radioshack and picked up some resistors. Crossed my fingers as I snipped the mic cord. Did this http://www.electronics-tutorials.ws/att ... attn22.gif [1] and as you can see, it helped a lot.
No attenuator http://youtu.be/q6AuGZOmWKY[2]
wired in attenuator http://youtu.be/JiIRst8oKIA[3]
Now I can finally start. Here is my ordeal so far.
Got a Drift HD 720
Battery DOA
Replacement battery also DOA
Finally get working battery
Replaced the built in mic with a mono mic port
Bought cheap mic
Realized they were stereo
Got an adapter
Connectors stuck out too far
Got an ME-15 mic
Audio clipped out and distorted
Fed up and made an attenuator.
 
Let me explain, this guy bought a Drift HD 720 which doesn't have a MIC port, he modified the camera to add the audio port then the microphone he got, clipped and got bad audio so to solve this he needed an attenuator, that is, a resistive circuit that lowers the output level of the microphone "by hardware" so he ended up with a lower signal level that made the camera happy and didn't clip.
 
Can you show us a pic of the resisters in place?
Is this what I need for my mic? Heres a video with a comparrison between the driftHD and the drift Ghost with the identical mic (ie I swapped cameras on the helmet).
http://youtu.be/UA0D3ZjHqU8
 
Nerb said:
Can you show us a pic of the resisters in place?
Is this what I need for my mic? Heres a video with a comparrison between the driftHD and the drift Ghost with the identical mic (ie I swapped cameras on the helmet).
http://youtu.be/UA0D3ZjHqU8
Click to expand...
Yes, your mic is clipping horribly, ie, it's too sensitive.
For the wind noise, you need to reposition your mic inside your helmet where it doesn't get hit by wind. I got the best audio putting my mic under the right cheekpad. Then I made a video about my helmet setup and moved the mic. Never got it to record as good as it was before moving it. And that's a shame because I don't test if everything is working as expected before each trip and I lost hours of good footage because of bad audio, bad angle, camera is crooked (it's unbelievable how the camera rotated just 3° can ruin the whole video).
Pick some 1k resistors and start playing. The resistor that goes between the two mic pins should be higher in value, 100k or something. Sometimes it isn't even needed.
 
I cant stop the wind noise... Ive put it in the cheek pad, ive put a fluffy think on, ive done everything. Its not a roadbike helmet, so difficult to keep quiet I think.
 
akalen4u said:
Actually I'm a lady.
Click to expand...
I consider that hard to believe.
You got a problem, instead of throwing all away, looked it up, learnt about electronics and hacked a circuit to fix it, put a foot into a Radioshack and better yet, you actually found the solution and you also ride a Ninja 650?
I'm in love.
pls, link your yt channel.
 
Ok, next question.... why an attenuator?
I discovered that because I have 2 mic's, the resistance halved and they became overly sensitive. I added a potentiometer in series and adjusted the final resistance to match a single mic. It seems to have worked?
http://youtu.be/0OtDmJ9bJ2Y
 
Nerb said:
Ok, next question.... why an attenuator?
I discovered that because I have 2 mic's, the resistance halved and they became overly sensitive. I added a potentiometer in series and adjusted the final resistance to match a single mic. It seems to have worked?
http://youtu.be/0OtDmJ9bJ2Y
Click to expand...
A potentiometer is an attenuator, not in the same fashion as the one akalen used but it serves the same purpose.
What kind of mic do you have? One of those "stereo" ones? Why 2 mics?

If you're using an adapter to adapt the 3 contact 3.5 to 2.5 plug, one of the contacts gets completely ignored by the camera (the center one or first ring) so your stereo mic ends up as a single mic.

But again, I don't know what mic/camera combo do you have, you could have a ToyPro and use a 10 pin proprietary port to 3.5mm stereo and that actually works in stereo with the 2 mics.
 
So I've been thinking about making my own attenuator to save space. The one I have is pretty bulky and generates a LOT of extra wiring. Having looked into it, I have 2 questions.

1) How do you know what the impedance is?

2) Does it matter which wire you treat as a ground for a basic mono mic, and if so which one is it?
 
Everyone, try this att circuit, it's about 5db.

7h8r.png



Ignore the plug if you don't have a Drift HD.

Trinith said:
So I've been thinking about making my own attenuator to save space. The one I have is pretty bulky and generates a LOT of extra wiring. Having looked into it, I have 2 questions.

1) How do you know what the impedance is?

2) Does it matter which wire you treat as a ground for a basic mono mic, and if so which one is it?
Click to expand...

1: No way to know that for cheap mics. Assume 1000 to 10000.

2: Any wire, doesn't matter. There isn't even a proper ground level on the mic input, it's floating ground and you cannot short any mic terminal to the camera's ground because of that.

Try the circuit I posted, you can even put the whole circuit between your mic pins if you use SMD resistors.

--- Edit: Resized and optimized PNG file. ---
 
Shirou said:
2: Any wire, doesn't matter. There isn't even a proper ground level on the mic input, it's floating ground and you cannot short any mic terminal to the camera's ground because of that.
Click to expand...
That's pretty much what I expected. It's essentially just a speaker that works in reverse, and speakers don't care which direction the current goes. I just didn't want to find out the hard way that my hunch was incorrect.
 
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