Analog Renaissance Tests Out the New Sound Semiconductor SSI2164

You might recall Sound Semiconductor announced the availability of the SSI2164 QUAD VCA chip back in March of 2018 (data sheet here). The SSI2154 is technically an updated design of the classic SSM2164 found in the Octave Voyetra Eight, Siel DK 600, Opera 6 & Kiwi, and the full blown Waldorf Wave. Analog Renaissance was commissioned by Sound Semiconductor to write an application note on the chip in practical use. The following are some of his findings including a couple of demos and a cool oscilloscope synth cat. :)

via Analog Renaissance:

"Sound Semiconductor (basically SSM risen from its ashes) hired me a few months back to write an application note AN701: 'Designing Voltage Controlled Filters for Synthesizers with the SSI2164' for them.

This job quickly escalated because while analyzing this IC's design, it became apparent that it is far more capable, due to its advanced design over its predecessor the SSM2164 (and its cheap knockoffs), than what I expected from reading the datasheet.

Its exceptional THD and noise specs allow building ultra clean filters that are virtually distortion and noise free, its excellent channel tracking means that it is very suitable for multi-mode filters which rely on precision and inherent in its design is the same type of asymmetric distortion responsible for the legendary SSM2040’s sound and more.

The 32-page manuscript is now being reviewed and edited to match their house-style, and should be made public soon. Imho it's quite extensive and covers next to SSI2164 specific content quite a bit of VCF design in general, circuit history and some novel stuff.

As there are already more than enough datasheets, application notes and books filled with non-working (read: tested in spice) nonsense, I accepted this job on one condition: build, test and since it's about synthesizers, hear everything before writing about it.

The small building blocks were breadboarded, but as this type of construction quickly becomes impractical for larger designs, certainly when they need multiple sources and control voltages, and impossible to do meaningful measurements on beyond a certain level, due to coupling and EMC issues, I built 3 filters in eurorack format, which also allows for quick connection to other synth and audio equipment.


SSI2164 - 2040 VCF Published on May 5, 2019 dnaab136

The first one, on the left, is an ultra-clean 4-pole VCF with a SNR better than 107dB (A-weighted) and THD is less than 0.0066%. Both these numbers are the limit of my current test equipment.

The second one, in the middle, is a VCF that employs the SSI2164's SSM2040-like non-linearities and for the first time since the early 80's done monolithically.

The 3rd one, on the right, expresses my contempt for what can and can't be done by ignoring a few mathematical constraints and is a self-oscillating 6dB/oct (1-pole slope) VCF.


SSI2164 - Mathematically impossible self-oscillating 6dB/oct VCF Published on May 6, 2019 dnaab136

Math wasn't happy with this, so it sounds a bit angry and, one of its main features is its capability of transforming sine waves into cats.
one of its main features is its capability of transforming sine waves into cats.

All 3 modules borrow 2 things from power electronics: A FET-bridge that allows plugging in the power cable in any orientation, without the voltage drop associated with diode bridges, and an S-Curve dimmer, originally intended for incandescent lamps but here used for a reversing attenuator with a dead zone in the middle.

The first 2 are multi-mode and have next to the standard 4-pole output a few extra outputs: 2 & 4-pole band-pass and a 2-pole low-pass. All outputs have the exact same phase response and can be mixed to obtain variable slope filters.

I'll bring these to Superbooth in one of these waldorf KB37 keyboards, with some basic VCO, LFO, ADSR and mixer modules for you to play with along with a printout of my manuscript and what is already edited (about 2/3rd) for publication."

SIEL DK 70 - 80's Italian Polysynth

video upload by The Free Radikal

"Similar to a Korg Poly 800 but accepts midi CC's for most parameters and midi velocity"

KIWI by Siel: 15 sounds (Ex Opera 6/DK-600)

video upload by Valmont

"I made one demo here but I could just go on more, it sounds too great!
The KIWI, more often branded Opera 6, or DK-600, is a super rare super great italian synth.
Sometimes reminds me of the Jupiter 8 and the Oberheim OB-8, if we put appart the abscence of crossmod. The EG are hella tight, the DCOs are damn bright and full, the filter so mellow...... The epitome of the analog polysynth, far away from the cliché of italian synths.
Also an expensive instrument in the 80's as it cost 50% more than a Korg Poly 61, a Juno 60, a SX-210 or Yamaha DX9... Nowadays it would be about 4.400€ if we adjust the inflation, so definitely not an amateur synth! It was just about the level of a Prophet 600, which funny thing is that they are absolutely opposite in sound characters (and in components, 100% CEM for P600, 100% SSM for KIWI), but they go so well together! They are probably my 2 fav synths in my room :)

Thinking about installing the voicepanning on this one too tho :D

0:00 - mild minds
0:19 - dahlias
0:34 - rbmk
0:59 - 42
1:16 - kujenga
1:29 - gris
1:50 - forbidden
1:56 - model
2:14 - jupiteresque
2:35 - windy beacon
3:01 - deluxe cream
3:25 - hermes
3:42 - sputnikzer
3:53 - blue weekend
4:12 - humble"

Siel DK70

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via this auction

As for the DK70, an interesting side note according to the description is that it was released in Brazil as the Giannini GS 7010 polyphonic synthesizer. You can find demos of it in the archives here.

"It is very similar to a Korg Poly-800, in that it operates like an analog synth, but its oscillators, LFO and envelope generators are all digital. Like the Poly-800, the DK-70 has eight oscillators/voices, but all the voices are mixed together through a single "monophonic" analog lowpass filter which was shared for all voices. Like a monophonic synthesizer, the filter was switchable between single or multiple modes. In single mode, the first key pressed triggers the filter envelope, and unless all keys are released, the filter does not re-trigger. In multi mode, each key pressed in turn triggers the filter envelope, even if other keys are still pressed down.

The oscillators are called "DCOs", and the envelope generated called a DEG (for Digital Envelope Generator). Digital components were much cheaper at the time and this allowed the DK70 to approximate the sound of an analog synth, but have 8 note polyphony without being cost prohibitive to the average user.

An unusual feature of the DK70 is that, while it appears to have the form factor of a standard synth, it has guitar strap pegs and can be used as a keytar. (The Poly-800 also had this feature.) An accessory called the "Stage Set" can be attached to the left side to provide a grip (similar to that of the SH-101), where the player may manipulate a ribbon-style pitch bender, as well as have access to buttons that change patches, change octaves and engage the LFO modulation.

It stores 50 patches, 10 of which are user assignable. A cartridge port accepted a cartridge which could store an additional 50 patches. All programming is done via pushbuttons, somewhat limiting its "tweakability" for live performances.

It also has an onboard two-track sequencer, which can be programmed by setting the tempo and recording a performance (unlike a step sequencer, where notes were entered in sequential order and played back at fixed durations). The performance would then loop when played back.

The synth engine was also available as a keyboardless, rack-mount or table top version called the Expander-80, similar to the Korg EX-800. Released in Brazil as Giannini GS 7010 polyphonic synthesizer"