I want to build a voice changer that takes its input from a line out?

I want to build an "in-line" voice changer. There are loads of kits and devices to build one that takes input from a microphone but I cannot find an inline one at a sensible price.
I bought a Vellman kit - but this too has an on board mini microphone.


I was considering just replacing the mic with a line-in socket.
I will also attach a line out socket to the speaker output pins.

I have done some reading and it appears as if:
The mic output will be a few millivolts.
The line input will be 1-1.5v
So looks like something will go phut.
Can I just put a resistor in line with the line-in socket - and if so what size?

Any other thoughts on how I can do this with hardware (not software).

Many thanks

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What you need is called impedance matching.
But that can be quite tricky in modern days when an elecrete microphone is used instead of an old school magnetic type.
Modern mics provide a change like an adjustable capacitor, old ones produce an actual voltage signal.
IMHO the best way would be to check where the mic signal goes and is amplified.
At the point where it turns into a real signal you can use a matching connection to your line input.
In case that is too much you can check this website for a more direct approch using just resistors.


Just too lazy to paste all the stuff here ;)

Thanks for this.
2 resistors and bit of wire.... ;-)

Keep in mind that just because it looks it easy does not mean it is ;)
Best to check the levels with an oscilloscope before soldering it all together.
And as always: Start with the lowest volume to prevent damage.

And the input is AC coupled.

SteveM290 (author)  steveastrouk9 days ago
Whatever that means! :-)

It means don't connect the line in directly to the pin after your resistance network, keep the capacitor shown in the circuit

SteveM290 (author)  Downunder35m9 days ago
I'll use the largest resistor sizes and keep volume down to start.
I don't have a scope and wouldn't know what to do with it.
I have multimeter - a decent one.

iceng SteveM42110 days ago

If you are skilled the resistor end wire will do it easily :)

Unless you are using SMT devices..