Audio modulation circuit

[SGiard]

I have been looking to find a simple circuit that could do amplitude modulaion of an audio wave by another and can't find anything on google. Does anybody know a circuit or have a link to such a circuit?

Thanx...

 

[MikeMl]

Its called a four-quadrant multiplier. Analog Devices makes several.

 

[audioguru]

I used the MC1496 balanced modulator IC to make audio scrambling for a wireless microphone teleconference system. The audio was completely scrambled on an ordinary radio but the decoded sounds were perfect.
It used a single-sideband method.

 

[SGiard]

Thanks for the replies... I would have (naively) thought that there would exist a simple circuit you could make with discrete components to achieve this. AM has been done at radio frequencies for, what, almost a century now. Is modulating audio so much harder than modulating at radio frequencies?

 

[Nigel Goodwin]

No, it's easy to do, although you've not really been very explicit what you're trying to do - but tremelo effects are amplitude modulation.

 

[SGiard]

You are right I hadn't thought of that and will look into it. I am just a hobbyist so I am playing with op amps these days and came across the summing amplifier and built one and fed different waveforms into it to look at the result on the scope. I had read somewhere that modulation is similar to multiplying a waveform by another so I was expecting to find some kind of circuit about as simple as a summing amplifier that would do that but all I found were references to ICs doing the job like one of the replies I got. I am starting to think this has to do with the fact that in multiplication you have to care about the sign of the different input and sign the output accordingly. Is that part of the problem?