HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 02, 2012, 07:21 PM
Registered User
flyn's Avatar
United Kingdom, England, Cambs
Joined Jun 2009
101 Posts
Discussion
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.
flyn is offline Find More Posts by flyn
Last edited by flyn; Dec 03, 2012 at 01:53 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 03, 2012, 06:49 PM
billpa's Avatar
Joined Nov 2003
4,936 Posts
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.
billpa is offline Find More Posts by billpa
Site Sponsor
Reply With Quote
Old Dec 03, 2012, 07:39 PM
Registered User
flyn's Avatar
United Kingdom, England, Cambs
Joined Jun 2009
101 Posts
Quote:
Originally Posted by billpa View Post
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
flyn is offline Find More Posts by flyn
Last edited by flyn; Dec 04, 2012 at 06:48 PM.
Reply With Quote
Old Dec 06, 2012, 03:05 AM
Registered User
Joined Oct 2012
26 Posts
Quote:
Originally Posted by flyn View Post
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..
jcabetas is offline Find More Posts by jcabetas
Reply With Quote
Old Dec 06, 2012, 06:13 AM
Registered User
flyn's Avatar
United Kingdom, England, Cambs
Joined Jun 2009
101 Posts
Quote:
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.
flyn is offline Find More Posts by flyn
Reply With Quote
Old Dec 08, 2012, 03:34 AM
Registered User
Joined Oct 2012
26 Posts
Quote:
Originally Posted by flyn View Post
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
jcabetas is offline Find More Posts by jcabetas
Reply With Quote
Old Dec 09, 2012, 02:02 PM
Registered User
flyn's Avatar
United Kingdom, England, Cambs
Joined Jun 2009
101 Posts
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.
flyn is offline Find More Posts by flyn
Reply With Quote
Old Dec 09, 2012, 05:07 PM
Registered User
Joined Oct 2012
26 Posts
Flyn, I don't know how you connected the pot. What I would try is connecting it like this:
jcabetas is offline Find More Posts by jcabetas
Reply With Quote
Old Dec 10, 2012, 07:25 AM
Registered User
flyn's Avatar
United Kingdom, England, Cambs
Joined Jun 2009
101 Posts
Quote:
Originally Posted by jcabetas View Post
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
flyn is offline Find More Posts by flyn
Reply With Quote
Old Dec 17, 2012, 04:02 AM
Registered User
France, Bourgogne, Nevers
Joined Feb 2012
557 Posts
Quote:
Originally Posted by flyn View Post
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.
wazoo22 is offline Find More Posts by wazoo22
Reply With Quote
Old Dec 17, 2012, 08:52 PM
Registered User
flyn's Avatar
United Kingdom, England, Cambs
Joined Jun 2009
101 Posts
Cheers mate, will give it a try. Thanks.
flyn is offline Find More Posts by flyn
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion OSD not level - any ideas? Efliernz Hoverfly Technologies 9 Nov 30, 2012 02:10 AM
Question OSD level indicator tilted randomly Stacky Hoverfly Technologies 9 Sep 06, 2012 08:32 PM
Question OSD Pro, eLogger V3, GPS V4 problems updating firmware in OSD Pro jbfoamy Eagle Tree Systems 23 Jun 02, 2012 03:59 PM
Discussion Eagle Eyes Ground Station with other OSD than OSD Pro ? BillyJo FPV Talk 3 May 26, 2012 10:56 AM
Sold Eagle Tree OSD Pro Complete Setup (eLogger, OSD Pro, GPS Expander) picassolsus FPV Equipment (FS/W) 4 May 11, 2012 12:59 PM