A ring modulator is a great tool in the studio.  It's perfect for making bells, clangs and other odd metallic sounds. You run a signal into the modulator input... something like a hihat pattern or a kick drum works well.  You then place a sustaining tone on the carrier input.  This can be a wave from a VCO, or any sound from your synthesizers or sampler.  When there is no signal input to a ring modulator, the output should be silent. When you put the signal on the modulator input, it combines this signal with the carrier and outputs the result.  Unfortunately, since ring modulators aren't always perfect,  you'll still hear the carrier frequency quietly in the background, even if there's no signal on the modulator input. This article will explain how to calibrate your ring modulator to reduce this bleed through, and how to deal with any residual noise that you may encounter.

The first thing to try is to adjust the trimmers on your ring modulator.  Generally there is an offset adjustment for both the carrier and   signal (modulator) inputs.    To adjust the modulator trim, hook a synthesizer to the modulator input, and leave the carrier input disconnected.  Listen to the output of the ring modulator while adjusting the trimmer, turning it until the bleed  is minimized.  Adjusting the carrier uses the same procedure:  Place a signal on the carrier input, and no signal on the modulator input.  Adjust the trimmer until carrier bleed through is minimized.

Another source of bleed is a DC offset on one of the inputs.  If you're feeding your ring modulator from a module that has both AC and DC outputs, be sure to use the AC output.  Likewise, if you have an adjustable output offset on the source, you can adjust this control to have the minimum amount of bleed.

Finally, if you still have carrier bleed, you can run your signal input through an envelope follower.  Use the envelope follower to gate a VCA on the ring modulator's output.  Essentially if there's no signal input, the VCA is closed and you won't be able to hear the ring modulator... as the signal increase, the VCA opens and allows you to hear the modulator's output