My Sine Oscillator Experiment

Over the weekend, I recorded/generated four sine waves of different synthesizer modules and compared the results. Each of the four oscillators are tuned to approximately to 440Hz, close enough to get a sense of each wave shape.

This is a very casual observation of contour and contour only, so please do not read too much into my findings. Here are the results:

Csound Digital Oscillator

This first graph shows a digital sine wave generated within the computer music language Csound. This is what I used as my test reference. Being that this is a purely mathematical construct, I figured this would be the perfect wave to compare against its analog counterparts.

Doepfer A-110 Standard VCO

Upon casual observation, you may notice that the sine isn’t the most accurate in the world. In fact, you might go as far to say this isn’t a sine wave at all. One noticable feature of this oscillator is that little glitch you see at 90º. This is consistent among every cycle at the stated frequency. I have two of these modules, and there were no significant differences when compared to each other.

Now it might sound like I’m completely down on this module. The truth is, I’m actually quite happy with this dirtiness of this unit, as it adds character. It is sometimes the imperfections that make something great.

Plan B Model 15

This unit has the smoothest contour of the three analog examples. Though the shape doesn’t adhere completely to the perfectly generated Csound test reference, it certainly gets close. The peak and the dip seem to be a bit rounder, almost as if they are slightly compressed.

Cwejman D-LFO

Now, I must say that it probably isn’t fair that I’m comparing a device designed specifically for low frequencies. With that being said, the contour fared noticeably better than the Doepfer. You might notice that the peak and the dip are both a little on the sharp side. The D-LFO comes with two oscillators, both of which I tested. I found both to be consistent with one another.

All Examples Compared

For fun, I thought it would be nice to superimpose each example over one another so we can better observe how much variation can exist between sine wave oscillators.

Other Variables in the Equation

Since I recorded the three analog signals, there were at least two extra variables that may have introduced distortion to the resulting wave shapes. The first would be the recording device, an Apogee Ensemble with the soft limit feature set to off. The second is the cable. I used the same cable for all the recordings. I always patched directly from the sine wave outputs to the Ensemble input.

I did go the extra step and recorded the Csound sine wave with the Ensemble and cable. I found there were no significant differences, in terms of contour, between the original generated wave and the recorded version.

My Methods

Last, I want to share the methods I used to collect and present the data. I recorded the three analog signals with the Apogee Ensemble, and with the software Peak. I took screen captures of peak, and then processed them in Photoshop. In Photoshop, I removed the dotted zero line, and replaced it with a solid line. I also resized each image so the waves would have matching periods. Though I compressed the width of each waveform, the contours of the waves were not affected.

And like I said, this experiment is just the casual observations of one guy, and completely non-scientific.

Synth DIY by fonik

close up
flickr photo be fonik2000

My electronics workstation in the garage has been closed for the winter due to extreme cold.  Not that I’ve had the time, anyways.  However, the temperature is on the rise, and I’m looking forward to getting back out there.  The big goal I’ve set for myself is to make some of my very own eurorack modular synth units.

And perhaps by cosmic coincidence, a modular synth enthusiast, who goes by the name of fonik, commented on one of my flickr photos a couple of days ago.  This led me to his photos, which led me to  On his site, he shares in detail his custom modules and schematics.  Having a DIY guide to follow is exactly what I need.

“Rather a musician than an electronics engineer I was always looking for new sounds. This finally(?) let me to modular synth. Once I purchased some Dopefer modules for a modular guitar effect the plan rose to build my own modular synth… this was about 2 years ago and I never held an soldering iron in my hands before.”  – fonik

This is the position I’m in today.  The fact that he has been able to accomplish so much with in such a short period of time gives me hope that I, too, will be able to succeed in my modular synth building endeavors.

The Zeroscillator

Cyndustries Promotional video used at the NAMM Show Anaheim California 2007. This oscillator is amazing!

Video by Cyndustries.

I agree with the video description. The Zeroscillator, by Cyndustries, is amazing! And I really, really want one. I never knew FM synthesis could sound so great. Since the whole process takes place in the analog domain, the Zeroscillator doesn’t have the same issues as digital FM does with aliasing, which allows for timbres not possible with digital FM synthesis.

This unit is my highest priority for when I upgrade my Doepfer sometime in the future.

“From One Single Acoustic Guitar Note”

Tony Miracle, of Venus Hum, explores a technique he used in making the bands new release “The Colors In The Wheel”

Tony takes a simple acoustic guitar note and through manipulation and modulation builds an entire electronic composition in an unrehearsed 15 min improv captured on film.

Gear Used In The Short

G4 Powerbook
Oxygen 8 USB Keyboard
Doepfer Regelwerk Midi Fader / Controlor
Taylor Acoustic Guitar
Ableton Live