SP – Ring Modulator

Buy the PCB:

Steiner Ring Modulator
Steiner Ring Modulator
Available Qty: 25
Price: $35.00







This module multiplies a signal to modulate either with itself or a carrier signal. Ideally, the output is only made of of two signals, one shifted up by the carrier signal frequency and one shifted down by the carrier frequency.

From the Synthasystem manual:

The Ring modulator is a sound modifier. its use involves a signal to be modified and a carrier signal which is usually a since wave from on of the VCOs.

The RM is equipped with a knob to mix the input signal with the modified output signal. With this knob all the way counter clockwise, the signal passes through the RM unaltered in any way. with the knob all the way clockwise, the output signal is completely the Ring Modulated signal.

The input and carrier signals are both canceled. What appears in the output is all of the signal frequencies shifted up and down by the frequency of the carried signal. hence, twice as many frequencies appear in the RM output as are fed into the signal input.

For example. A major Triad is fed into the RM signal input with a 100 Hz sine wave fed into the carrier input.

Input Frequencies    Carrier      Output Frequencies
440.0 Hz                  100 Hz       340.0 & 540.0 Hz
554.4 Hz                  100 Hz       454.4 & 654.4 Hz
650.3 Hz                  100 Hz       550.3 & 750.3 Hz

Thus the RM produces an effect on musical sounds that seemingly changes all of its key and timbre (timbral) characteristics.

As in all RMs, the carrier must be carefully nulled for proper operation. A front panel adjustment marked Car. Null is provided for this purpose. Turn all input signals except carrier signal from oscillator al the way down and the mix pot all the way clockwise. The applied carrier will be heard in the output. Adjust the front panel trimmer until a null or minimum carrier is heard in the output. RM is then ready to be used with the input signals. Now the inputs and mix pot can be adjusted as desired.

The MULT/SQUARE switch when in the MULTIPLY position causes the RM to operate as described above. When in the SQUARE position, the carrier input is internally disconnected and the input signal is used as both input and carrier signal. the effect on sinetones is to double the frequency, but on audio and other complex signals, the effect is markedly more pronounced–voices and audio signal are seemingly “scrambled” when the mix knob is all the way up.



This module has two inputs. First a signal to modulate. Second, the carrier signal.


This module has one knob and a trimmer. The knob is a Dry/Wet fader. You could also just use a switch here if you want. The trimmer is for the carrier null. This is on the front panel because any carrier can be obnoxious and you can use this to minimize the carrier bleed through into the output.


There is one switch which either connect the carrier signal to the carrier input, normal operation, or it connects the input signal to both so it effectively multiplies the signal by itself.


Hooking it up is pretty simple. Connect a signal to modulate to the signal input and if you want, a carrier to the carrier input. The output can go to your amplifier, a filter, phase shifter, or anywhere else an audio signal can be used.



This module was originally built with carbon core, 5% resistors with one or two 1% metal film resistors. So, you have a wide range of options here. I recommend using 1% tolerance, metal film resistors everywhere.


There are probably a billion different ceramic capacitors at a place like Mouser. Pick a capacitor that can fit the hole easily, typically 0.1 inch on centers. I can’t find a 0.2 uF ceramic. Use 0.18 or 0.22. It blocks DC, so maybe bigger is the better choice if you have one.

Pick good quality electrolytics where designated.


MC1495. Get the On Semiconductor ones from ArcadeChips.com. Mark is great to work with, the parts came fast, they are a good price, and they work. Mark has a lot of these.

I purchased some Motorola ones from another source and they were all bad.


The original used 2N5172 NPN transistors. These are still available at Mouser. Get the Central Semi 2N5172s. I don’t know another source right now. You can always substitute a generic small signal NPN if you want to.


Your choice for your panel. If you use the panel I laid out, the holes and spacing will work for the Alpha 12 and 16mm pots. You can probably use nicer BTI, Bourns, etc. 9mm pots with “pot chiclets”


Use good trimmers, please. A good Bourns multi-turn trimmer like Bourns 3296Y series will fit the pad layout and work well.

For the panel mount trimmer, I made a little PCB chiclet to make this easier. I suggest using a Bourns adapter, p/n H-83P. It has plastic 5/16 inch threads, so the hole is 0.3125 inches in diameter. It seems to work with any standard 3.4 inch multi-turn trimmer. Insert the trimmer and push it til it snaps into place.

Another option is a Vishay part p/n 006-1-0 or 006-1-1, or 006-1-2, or 006-1-3. It depends on what type of shaft you want to have. These have a smaller, metal bushing. A 0.22 inch hole works fine. They are a bit smaller than the Bourns and about 3 times as expensive. $5.00 compared to about $1.50. If you use this one, I’d also recommend getting the Vishay trimmer adjustment tool. It’s made to fit down the hole if you don’t buy the adapter with a shaft. No Vishay part number. Mouser p/n 594-8T000.

The Bourns trimmers which work are the 3006 series. Easy to find.

The Vishay trimmers which work are the model 43P 3/4″ 20 turn series. Easy to find.


For the panel I laid out, a good 3.5mm or 1/8 inch jack will work. I use the Switchcraft 42A Tini-Jax true 1/8 inch jack. These are switched jacks and they work with 1/8 inch plugs and 3.5 mm plugs.


A good SPDT switch here. See General Component Notes.



I assume you know the basics of soldering. I like to insert the low lying parts first, like resistors, diodes, etc. After these, I install the IC sockets. Next capacitors, transistors, connectors. Use a good solder, either an organic flux, which you should wash regularly, or a no-wash flux.

Take a break every so often, wash off the flux if you are using a flux which required cleaning. Double and triple check orientations, pins, and solder joints.

Power Supply Regulation/Filtering:

Some additional comments here. This module is unique in that it is the only Steiner module I’ve seen which is designed for +/- 12, not +12/-10 volts.

The power/regulation section has 2 voltage regulators on it which can be set to +/-12 volts or simply omitted depending on your needs. If you are coming from +/-15 volts, you need both regulators.

If you are coming from +/-12 volts, you don’t need the regulators. The LEDs are not strictly needed. They are there to establish a base current draw so the regulators will work, but you can install them if you like to have visual feedback for power.

Important… if you don’t install the regulators, you have to install a jumper between pins 2 and 3 as shown on the Power/Regulation PCB or you won’t get power.



This PCB has four holes to allow flexible mounting configurations.

Panel Notes:

There is nothing too special. I suggest using connectors on the PCB and jacks on the flying wires. The spacing and holes are setup for Alpha 16 mm or 12 mm pots. The jack holes are 0.25 inch in diameter.