passive ring modulator

[JAMESveeder]

Okay, so I've made a passive ring mod using the following schematic.

It works and all, but I have a 555 timer chip ring modulating a normal synthesizer, and the 555 osc bleeds through heavily. Is there any way that I can prevent this from happening?

Edit: i'm assuming i'm going to need some kind of resistance on the input of the 555 oscillator and it's just way too loud, i was experimenting and used another synth with volume control and it allows for the carrier to amplify the modulator

Edit 2: i've replaced the 1N4148 diodes with germanium diodes and now the modulator bleeds through even when using another, quieter signal, but the modulation sounds much cleaner

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[v-un-v]

[blue hell]

Using a sine oscillator instead of a square would get rid of some of the bleed through.

Remaining bleed would then caused by transformer dual winding not being perfectly equal and diode tolerances

[JAMESveeder]

o.O

i have NO idea what i've done, but i've gotten it to start taking ANY two different pitches and it ring modulates them after I soldered this together.

for example, if i use a synth and I'm using two oscillators and I change the frequency of one, it RMs both oscillators together, even if it's coming in from one input... very interesting sounds coming out of this...

would anyone know why this is happening?

here's the video of what happens: http://www.youtube.com/watch?v=aI5BbLznuD8[/url]

[emdot_ambient]

According to the CGS info for their Real Ring Modulator you can limit bleed through by using diodes that are matched for voltage drop. It won't eliminate the issue, but limit it to some degree.

It also says, "a compressor-expander could help if better suppression is required." But I'm not really sure exactly how one would implement that.

Essentially what you described in the OP is normal for this circuit, and is probably the biggest reason this type of circuit has largely been abandoned in favor of four quadrant multipliers, which are still called Ring Modulators, albeit erroneously.

[TheAncientOne]

The lower the forward voltage of the diodes, the less signal distortion you will get. Most ring modulators tend to use Germanium diodes. My favourites were the Mullard 0A5 gold-bonded diodes, (for that added mojo). Any Germanium signal diode will do. For a more modern touch, I been meaning to try some schottky diodes.

I've got loads of Schottky's if you want to send me an address I'll post a couple of sets in return for the postage.

||\/||ike

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I've built this type of ring modulator and minimized bleedthrough by having a volume control on the inputs. I turn it down low enough that I don't hear any bleedthrough of the carrier, but still hear ring modulated sound on the output. With both volume controls set correctly, I have little or no bleedthrough.

I used silicon diodes when I built it, but have actually been meaning to replace them with some geraniums, which I now have.