CAVE PROJECT! This information is here to support people who have been making MFOS gear since I started posting synth-diy information back in about 2002 or 2003. These projects have ALL been superceded by new and better designs. I do not recommend that you make these since they have been improved over the years. I am not providing any support for these projects beyond publishing this historical information.
This is an intermediate to advanced project and I do not recommend it as a first project if you are just getting started in synths or electronics. Only the circuit and some explanation are shown here. A lot of project building experience and electronics knowledge and equipment ownership (scope, meters, etc.) is taken for granted. If you are interested in building this project please read the entire page before ordering PC boards to ensure that the information provided is thorough enough for you to complete the project successfully.

Ring Modulator Using AD633

This is the simplest circuit to get a really cool ring modulator. The AD633JN does everything for you. It is a low cost (about $5.00 to $6.00 a chip) precision multiplier. I am using it in a really simple configuration that lets you switch from multiplication to modulation. The gain is boosted a bit for multiplication so that in either mode you get approximately the same signal level out (which is completely dependent on the input signal levels). This circuit expects large signals. I am using 10V P to P signals for both the carrier and modulation inputs. If you want to use some lower signal sources I suggest that you amplify them with some op-amps to at least several volts P-P. I just put 3 of these circuits on a Radio Shack bread board and wired it to a panel.

This is perfect for bell tones and many very cool timbres. Have fun...

Analog Devices AD633JN Chip


The Simple Ring Modulator Circuit


Ring Modulator Parts List

Qty. Description Value Designators
1   AD633JN Analog Multiplier   AD633   U1  
1   LF411 Op Amp   LF411   U2  
2   Ceramic Capacitor    .1uF   C2, C4  
2   Ceramic Capacitor    2uF   C3, C1  
1   DPDT Switch   DPDT   S1  
4   Resistor 1/4 Watt 1%(s)   100K   R1, R5, R2, R4  
1   Resistor 1/4 Watt 1%   1K   R3  
1   Resistor 1/4 Watt 1%   43K   R6  
3   1/4" Phone Jack(s)   .   J1, J2, J3