Thursday 5 March 2020

Synthesizer Build part-22: RING MODULATOR (Yusynth design).

An excellent ring-modulator to serve as an extra source of weird sounds. This one is simple to build and works very well.

Next to the filter and the FM and Sync capabilities of a VCO, I think the ringmodulator is one of the most important ingredients for sound shaping in any synthesizer and an often overlooked one. No synth should be without one. The ring-modulator was something I always wanted to include in my DIY synthesizer and I was thinking of doing it the old fashioned way with audio transformers but they are very expensive. So I went looking for designs that used semiconductors and came across the Yusynth design. I ordered some MC1496N IC's from a shop near where I live because I didn't want to wait for components from China, what with the Corona virus going on etc. and I wanted to be sure I got real MC1496's and not fakes, which is so often the case with IC's from China. The MC1496 is a chip you will find in many vintage synthesizers and also in the Macbeth studio systems Dual Oscillators for Eurorack (a favourite of Colin Benders). They have a built in ringmodulator that uses this chip. Anyway, I got the chips the next day and I set out to make a stripboard layout.
A ringmodulator takes two signals and multiplies them. If you input just one signal you won't get anything out because if you multiply by nothing (zero) the outcome is nothing. So both inputs need a signal going in for this to work. (That's why you can use Ring-modulators as crude VCA's when switched to DC mode) One is called the Carrier wave and the other is called the Modulator wave. You can modulate the amplitude of the carrier and so get AM modulation. You can get the most beautiful results from this circuit. It can produce very cool bell like sounds or very gnarly AM modulated sounds. You can spend hours experimenting with it. I myself usually combine the output from the ringmodulator with the output from one of the VCO's going straight into a mixer so I can add both signals up and then send that through a filter and/or the lowpass gate and boy do you get phat sounds like that!

Click here to go to the original Yusynth article.  

Schematic for single ringmodulator:

Here is the (verified) stripboard layout I made from it. The original schematic is for a double ring modulator but I only built one. But it's just the same circuit repeated. I used this layout for my build so it is tried and tested. Note that the electrolytic capacitor on the AC output jacks has it's polarity reversed from those on the AC inputs.

Stripboard only:

Bill of Materials:
There different types of 1496 chips for sale, like MC or LM, but the letters in front of the numbers don't matter. They just indicate which firm produced the chip. They will all work fine in this circuit as long as they're 1496's.


You can find the tuning procedure on the Yusynth website. I'll describe the procedure here:

There are two trimmers to adjust: A1 and A2. These trimmers are used for cancelling the input signals. The settings are quite simple, you will need a signal generator that delivers a sinewave signal with a 10V peak to peak (+/-5V) output amplitude. You can also use a VCO in your synthesizer to do this. 
The Yusynth website talks about audio amplifiers but it's easier to use a VCO with sinewave and a VCA from your synthesizer to do this and make sure you connect an oscilloscope to the output signal with a frequency counter enabled so you can set your VCO to 1kHz.
Here is how to proceed :
  1. Set your audio generator (or VCO) to 1kHz and set the output level of the generator to 10Vpp.
  2. Connect the output AxB of the module to an audio amplifier or your VCA. Be sure to set the input potentiometer of the amplifier to a low value: the output level of the module is 10Vpp and most of the audio amplifiers expect an input level that doesn't exceed 1Vpp. If you use a VCA it'll be okay.
  3. Connect the signal generator to the input A with a capacitor (AC-INPUT). There, you must hear the 1kHz signal at the output AxB.
  4. Adjust the trimmer A2 so that the 1kHz signal can no longer be heard at the output.
  5. Disconnect the signal generator or VCO from input A and then connect the signal generator to the input B  with a capacitor (AC-INPUT). There, you must hear the 1kHz signal at the output AxB. Adjust the trimmer A1 so that the 1kHz signal can no longer be heard at the output.
Now the module is ready to operate. A last check can be done by connecting the 1kHz signal to both inputs A and B (AC inputs): there you must hear a signal which is twice as high in frequency (2kHz).
It will be a bit of a balancing act to get these signals on the zero volt line on your oscilloscope. Turning one potmeter might create an slight offset voltage that you can trim away with the other trimpot. If all is well you should easily be able to tune the ringmodulator in a few minutes.
If only one input is used there should be no output (because something times zero = zero) and if there's a signal on both inputs you'll get the two signals multiplied out of the output. That's why a ringmodulator can also be used as a crude VCA.
When I first tested my ringmodulator I kept measuring a negative offset of -9V on the output if I stuck a signal into input B. It turned out that my TL072 was faulty. I stuck a new one in and all was well.

Ring modulation is a very interesting way of combining two frequencies and can get very complex very quickly if you use waves that have a lot of harmonic content like squarewaves. More on the theory involved is here on this Wikipedia page about ring modulation.

I didn't think I could fit any more modules in, but this one was just small enough to go into the wood panel above the modules, next to my Sample and Hold module. Here's a look at the finished panel and how I fit the stripboard behind it with a little copper L-Bracket I made myself and soldered onto the stripboard.

Ignore the sawdust specks in the bottom picture, LOL. I took it just after putting the module in and the synth was covered in fine dust.
Okay that's another one done. This is getting to be quite a big and powerful "sound design machine." It's about time I made a new case that I can put on top of this synthesizer so I can keep building ^___^

If you have any questions please leave them in the comments below!

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  1. hi eddy, do you have a video or sound demo of this? also (again), does it work on 12v? cheers

    1. No I'm sorry I have no demo of this. I actually used it just a moment ago. You can get weird sound combinations with is and if you feed it 2 sinewaves, one lower than the other, it produces sort of bell like sounds. It's really cool. Should work fine on dual 12V. I might make a demo of it later.

    2. sounds good. what do you feed into which input on this module?
      do you reckon there is a difference between 1496N and 1496P?


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