Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Dec 02, 2012, 07:21 PM
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Lowering osd pro mic input with a resistor?


Hi guys, got a quick one for you all.

I'm using a fpv mic on my ET setup, the problem I'm having is that the audio output of the mic is really loud, the system is set to vol1 for external audio but is still too loud, not massively but just by enough, the voice alerts are half as loud & are at the correct volume, I don't want to turn them up, I'd rather reduce the mic vol.

Can I add a resistor to the mic signal wire Into the osd to lower the volume level of the source rather than adding one on OSD's audio out like suggested in the manual.

Mic I'm using is here:http://www.firstpersonview.co.uk/acc...crophone-1-20v

Thanks for any advice.
Last edited by flyn; Dec 03, 2012 at 01:53 PM.
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Old Dec 03, 2012, 06:49 PM
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Hi Flyn,

That certainly won't hurt anything to try it. you might want to use a small 1K pot temporarily, which would let you determine the actual resistor value to use. You may also need more than 1K.
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Old Dec 03, 2012, 07:39 PM
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Hi Flyn,

That certainly won't hurt anything to try it. you might want to use a small 1K pot temporarily, which would let you determine the actual resistor value to use. You may also need more than 1K.
Hi Billpa,

Thanks for the reply mate, due to the lack of a pot,on the signal wire I soldered inline a low value 3k resistor with no change so I went higher, then a few resistors to make 38K!!

It didnt seem to have any effect, I went to crazy values, 200k & it did nothing. I don't understand why this is....

Thanks
Last edited by flyn; Dec 04, 2012 at 06:48 PM.
Old Dec 06, 2012, 03:05 AM
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Hi Billpa,

Thanks for the reply mate, due to the lack of a pot,on the signal wire I soldered inline a low value 3k resistor with no change so I went higher, then a few resistors to make 38K!!

It didnt seem to have any effect, I went to crazy values, 200k & it did nothing. I don't understand why this is....

Thanks
Maybe because of a very high input impedance. I would try with a logarithm pot, with both extremes at gnd and input, and the middle pin to output. If you want to use just resistors, make a voltage divider with a 10:1 division..
Old Dec 06, 2012, 06:13 AM
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Originally Posted by jcabetas View Post
Maybe because of a very high input impedance. I would try with a logarithm pot, with both extremes at gnd and input, and the middle pin to output. If you want to use just resistors, make a voltage divider with a 10:1 division..
Thanks for the reply mate, appreciate it. It may seem like I know what I'm talking about but in truth I'm a bit of a noob with the ins & outs electronic components - they say a little knowledge is dangerous lol.

You might have to explain a few things, log pots & voltage dividers, thanks man.
Old Dec 08, 2012, 03:34 AM
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You might have to explain a few things, log pots & voltage dividers, thanks man.
When you increase the power of an amplifier 10 times, you perceive it as a double loud sound, making the ear response not linear. To make things easier for sound aplications, there are pots in wich the resistance is logarithmic distributed. You can live with an ordinary pot, but adjustments are more dificult to do.

The ouput of any amplifier or mic is equivalent to a voltage in series with the output impedance. To get a lower voltage level you can put two other resistances in series, connected from the voltage source to ground. The voltage trough the resistance R2 connected to ground is:
Vdivider=Vinput*R2/(Routimpedance+R1+R2)

It is usual to use resistances such that the sum are more or less equal to the output impedance. Then you have to choose R1 and R2 to get the factor you are looking for... Or just use a pot.

Sorry, you ask for an explanation
Old Dec 09, 2012, 02:02 PM
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Haha, I did ask for an explanation didn't I, careful what you wish for I guess!!

Thanks for the reply, electronics, wow different world or what!!

If I were going to use a log pot to lower the volume, bearing in mind that 200k ohms didn't do a whole lot, maybe a slight change but what would you suggest?

Would a voltage change help lower the mic volume? As the mic I'm using is stated to work from 1-20v so I guess it has a regulator onboard, it does have a load of circuitry on it.
Old Dec 09, 2012, 05:07 PM
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Flyn, I don't know how you connected the pot. What I would try is connecting it like this:
Old Dec 10, 2012, 07:25 AM
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Flyn, I don't know how you connected the pot. What I would try is connecting it like this:
Cool mate, not got a pot on at the min, had those resistors inline on the signal wire.

The mic has its own small board packed with components, with x3 wires, black red & signal.

Sorry to be a pain, any idea on a ball-park value on a log pot?

Thanks man
Old Dec 17, 2012, 04:02 AM
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Cool mate, not got a pot on at the min, had those resistors inline on the signal wire.

The mic has its own small board packed with components, with x3 wires, black red & signal.

Sorry to be a pain, any idea on a ball-park value on a log pot?

Thanks man
Try your resistors as above, across the mike instead of in series. Might not need the pot.
That would be from signal to ground.
Old Dec 17, 2012, 08:52 PM
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Cheers mate, will give it a try. Thanks.
Old Aug 29, 2016, 04:05 PM
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Cheers mate, will give it a try. Thanks.
Hi Flyn,
I know this is a very "old" thread, and apologies for "hijacking" it.
I was wondering if you ever got this problem solved? I'm trying to use a mic that looks very much as the one you mentioned on a FPV rig, and also have the sound like supper loud/over exposed.

Did you find out a way os reducing the sensibility of the mic input?

I already tried all the foam tricks, but to no much help.

Thanks for any info you can share, if you still remember something about it.
-


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