convert extension jack to line audio out help

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dj56
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convert extension jack to line audio out help

Post by dj56 »

Hi.

Looking to see if anyone has any suggestions to convert a cb radio extension speaker jack to a low level line out audio?

Just needs to be 1 channel as the ext jack is.

I need this for recording purposes as the regular audio is over powering and does not sound good so was hoping to try line audio level to see if that would help.

thanks
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ch25
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Re: convert extension jack to line audio out help

Post by ch25 »

Take audio from audio amp IC input.
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Re: convert extension jack to line audio out help

Post by ChubbyChops »

How about an inline attenuator?
dj56
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Re: convert extension jack to line audio out help

Post by dj56 »

ch25 wrote: 23 Jun 2022, 18:16 Take audio from audio amp IC input.
this has to work on different radios so doing the audio at the amp chip is a no.

thanks
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Re: convert extension jack to line audio out help

Post by dj56 »

ChubbyChops wrote: 23 Jun 2022, 18:31 How about an inline attenuator?
been trying to find a good small circuit on the web im sure ill find one
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Re: convert extension jack to line audio out help

Post by lbcomms »

Either an attenuator from the output IC or taking the signal from the input of the IC will have one big limitation, the volume control will change the level, not ideal for recording. This one IC add-on (easily built on a bit of perfboard) has output is independent of the volume control (standard 2V line level):

https://lbcomms.weebly.com/

Then click on "Documents" - Universal "Line out" adapter for recording receiver audio

File is "lineout_universal_adaptor.pdf" (weebly direct linking is broken so can't directly link to it)
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ch25
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Re: convert extension jack to line audio out help

Post by ch25 »

Ext speaker socket is always vol knob position dependent, so inline att won't work as it should.
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Re: convert extension jack to line audio out help

Post by paulears »

You've got a low impedance source so all you really need is a couple of resistors - that's it. In fact, the really simplest way to get the levels sorted is to find a pot - any value really, and pop in a box - 1K to even 100K will work for this purpose. Ground to one of the three connections, the speaker audio to the one on the opposite side. Then the ground also goes to the recorder and the wiper contact in the middle takes the audio to the audio input of the recorder. It's an impedance mismatch, but the pot will handle the voltage conversion and one setting will be a perfect match. without some more components, the only real suck it and see feature is that the most suitable setting will be close to one end or the other. A small preset pot would work, where you adjust it with a screwdriver. The principle is very simple. The wiper at any point splits the resistance. if it's split equally, then 1V in produces half a volt at that middle position. If you turn the knob nearly all the way, then the output might be a tenth of a volt. That's a big over simplification, but attenuators like this are the basis of loads of devices. You can do it with speaker audio and RF if you wish. 2 25 Ohm resistors would produce half the input at the output, and would be an attenuator too. Ideally you choose values that match the output impedance - but in practice little passive mixers with 10K input impedance will match headphones and low volume speakers quite well. If you built it from two very small resistors, they'd even fit into the jack plug!
dj56
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Re: convert extension jack to line audio out help

Post by dj56 »

lbcomms wrote: 23 Jun 2022, 19:54 Either an attenuator from the output IC or taking the signal from the input of the IC will have one big limitation, the volume control will change the level, not ideal for recording. This one IC add-on (easily built on a bit of perfboard) has output is independent of the volume control (standard 2V line level):

https://lbcomms.weebly.com/

Then click on "Documents" - Universal "Line out" adapter for recording receiver audio

File is "lineout_universal_adaptor.pdf" (weebly direct linking is broken so can't directly link to it)
Thanks for the info. Do you know if this is sold on the net/ebay of some place?

thanks
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Re: convert extension jack to line audio out help

Post by lbcomms »

dj56 wrote: 25 Jun 2022, 01:26 Do you know if this is sold on the net/ebay of some place?
No, sorry, it's a home made circuit that any decent tech / electronics hobbyist should be able to knock together and install in an hour or two.
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