I drew this up from an old issue of The Mix years back... I presume it'll be reproducable, it's not that unique a design 
Costs something like a fiver to build and all the parts should be readily available. Germanium diodes are better, but they never arrived from place I ordered from on eBay, and they've gone quiet now. 
Silicon diodes need a much higher voltage to conduct than germanium ones. That will work okay but you might find you need to drive it with quite a strong carrier to get it to work well.
It works like this - when the carrier signal is positive, the middle of the output transformer is positive, so the diodes pointing left conduct. When the carrier is negative, the diodes pointing right conduct, but you'll see that they are crossed over. This inverts the signal.
If you find that carrier breakthrough is a problem, stick a 10k pot across the output transformer with the wiper connected to the carrier input. If that doesn't do it, wire the wiper to ground. Trim the pot for least carrier breakthrough.
If you were doing it properly you'd have a third transformer wired between the centre-taps of the two existing transformer, and send the carrier into that.
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Topic: How do I make my own effect pedal / Passive Ring Modulator (Read 41843 times)