We’ve had a variety of different forms of a similar question lately. How does one connect a line level signal to something that only has a mic input? This seems to come up a lot when working with consumer electronics gear such as video cameras or inexpensive computer sound cards.
Just to make sure we are all on the same page here, microphones generally put out a very low voltage signal, sometimes called “mic level” in our line of work. Mic levels are much lower than (typical) line level signals so any equipment designed to work only with microphones as an input may be overloaded when you hit it with a line level signal. The likelihood of this varies widely so it’s always best to try it first and see what your results are.
If you do find distortion, and there is no way to change the input characteristics of the device, then your only alternative is to lower the output of the sending device. Of course there are a couple of ways to accomplish this:
- If possible, simply turn down the output of the sending device until the receiving device stops distorting. This has the advantage of being extremely easy (and free), but can also compromise the signal to noise ratio of the sending device (and thus your signal).
- If option #1 is no good then plan B is to buy or build a pad to put in the signal path to lower the voltage of the signal coming in. Such devices can be purchased or it is possible to build your own. The main advantage to building your own (besides cost) is you can customize the amount of gain reduction and connectors to your specific set up. Unfortunately the methodology involved in designing and building pads is beyond the scope of this inSync (though we may eventually cover it in the future). This is one of those jobs best left to a qualified technician unless you are skilled at soldering. Information on how to design them can be found in any number of electronic textbooks.