About
Often used by famous filmaker/composer John Carpenter, Ensoniq SQ-80 is one of the most unique synths ever produced: 8 bit digital PCM waves, oscillator-sync, AM (ring modulator), Prophet filters, 4 analog envelopes, 3 LFOs, lot of modulation and endless programming possibilities. Model SQ-80 is basically ESQ-1 with added new waveforms (75 total) and a floppy drive.
Ensoniq SQ-80
With its large display, SQ-80 is a synthesizer with one of the most easiest programming interface. No hidden menus and multi multibuttons here! Select any part of the tone (OSC1, DCA1...) and everything is shown on the display. Then you simply press the soft button below the parameter and move data slider to change the value. As a result SQ-80 (ESQ-1) is the one of the fastest synths to program. No one needs PC editor for this synth - too slow.
OSC1 settings
Filter settings
Tone parameter buttons
Amplitude Modulation (ring modulation)
In case of SQ-80 oscillator 1 is defining the amplitude of oscillator 2. For example, you take the square wave at OSC1 and high pitched sine wave at OSC2. You will get a clear example of what amplitude modulation does, and it should sound something like this.
In such process, OSC1 is called the modulating signal, while OSC2 is called the carrier. As you can hear, the OSC1 (square wave) with its shape ''cut out'' our sine wave, which was at about 930 Hz. I took a very low frequency of the square wave, so that you can get the picture. However, more interesting things happen when you increase the frequency of the modulating signal (for such low frequencies you will use LFO anyway).
To avoid any equations, let's just say that amplitude modulation is a process in which two signals go into modulator that mathematically multiplies them. Looking at the frequency domain, this modulator gives their sum and difference at the output (actually this is really over-simplified explanation but I'm forced to do so since every equation has a tendency to halve the number of readers). For example: lets take two sine waves, one at 100 Hz and other at 1000 Hz. At the output of AM modulator we will have 1000+100 and 1000-100, which means one signal will be at 1100 Hz and the other one at 900 Hz.
Unfortunately SQ-80 is letting OSC2 signal go through amplitude modulator, which reminds of non-balanced amplitude modulators. Those are the kind of modulators used in AM radio transmitters. They are specific for one feature - they let the carrier go through it. I think in SQ-80 they were using balanced modulator, but for some reason they decided to let OSC2 signal go trough it. That means, with AM in SQ-80 you won't get pure amplitude modulation (sum and difference of oscillator frequencies) but also the OSC2. This can be seen on the image below.
Image above shows us output from the amplitude modulator, after it multiplied two input waves. OSC2 (carrier) was set at about 1500 Hz (rounded value), and modulating signal was at about 500 Hz, both sine waves to make the picture as clean as possible. As you can see, there are two signals at the output marked as ''sidebands'' right where they should be (1500+500=2000Hz and 1500-500=1000Hz), but there is also a carrier at 1500 Hz, which shouldn't be there. As a result of this, it is not the same if you put one pitch to OSC1, some other to OSC2 and decide to swap their pitches or waves. It we would swap OSC pitches in this example, sidebands would remain the same, but the carrier would move from 1500 to 500 Hz. This might be good or bad, depending on what kind of AM you prefer. Note that some harmonics can be seen too, but more on that later.
With amplitude modulation, you can create a lot of bells and metallic sounds, some digital pianos and endless amount of strange sfx sounds. Don't forget to use LFO's and ENV's to vary the frequency of one or both oscillators, and don't just stick to sine waves.
Distortion
Actually there is one thing that adds a little bit of distortion in SQ-80 and those are DCA's 1-3 (note: DCA 4 has nothing with this case, so let's ignore it and assume it is set to standard value of 63). It appears that the optimum value of DCA 1-3 level is about 50. Increasing it to full value of 63 will introduce a little bit of distortion. This can be good if you like a touch of gentle distortion. But if you prefer 'clean' sound, keep DCA1, DCA2 and DCA3 levels at 50. Of course, that doesn't mean you should make all the sounds that way! Don't forget that you bought SQ-80 because of it's cool 8 bit harsh samples. This slight distortion can pump it up for some original sounds that no other synth can match (except it's older brother ESQ-1).
Left image shows spectrum of a sine wave at DCA1 level 50, right image shows at DCA1 level 63. I played a note on the frequency of 440 Hz. Thin green line shows tolerated value of about 45 dB from the peak of the tone, which ensures your ear won't hear other harmonics. Anything above that will be spotted (unless you are totally deaf). Measuring showed that increasing DCA level from 50 to 63 adds 8dB to first (fundamental) harmonic, but 21dB to 3rd harmonic. This is a clear evidence of a distortion! If there was no distortion, both harmonics should go up for the same amount - that is 8dB. Please keep in mind that this is really a slight distortion, and in many cases you won't notice it when you put level to 63.
Note: Probably because of 8bit resolution, a sine wave is not pure, but contains some harmonics. This can clearly be seen on the left image above as well in the amplitude modulation example.
Ok, let's get into real business. Here are the .mp3 sound examples of Ensoniq SQ-80 which will demonstrate it's synthesis capabilities. Lets start with some presets, then we will move to few i programmed (marked with*). All sounds are 100% dry with no effects.
island.mp3 (285kB) - As you can hear the SQ-80 is stereo. The trick is that you can assign a controller (velocity, keyboard, lfo...) to pan parameter that is located on the last amplifier DCA4. As a result, tone will sound ''stereo''. However, most of the sounds on SQ-80 are mono.
Deep Synthesis: Home
11. 04. 2005
Don Solaris
