March 20, 2018
Analog Synthesizers / Desktop / From £500-£1000 / Keyboard / Siel / Vintage

Siel DK600

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The Siel DK600 analog polyphonic keyboard is a real hidden gem of a synth, it’s also boasts a thickness of sound due to no less than six dual oscillators that’s twelve in total!! Other well-known synths that were similar during the same era were the Juno 106 for example but can sound less beefy in comparison, but this is up for debate I am sure, it has six notes of polyphony as does the DK600.

The oscillators are stable due to them being DCO’s, that said like most synths released at this time are no stranger to issues, for example one of the most common faults with this model comes from a soldered battery on the main board, once it leaks it will likely eat its way through the tracks on the PCB’s and probably destroy most of the surrounding chips and components close by. I have one that needs such attention the repairs will be documented in the future, I already clipped of the offending battery while it awaits attention.

Getting back to the synth itself, most of the controls are on the surface, pitch bend, mod wheel, 3 FLO’s filter cutoff, resonance, AMP (ADSR attack, decay, sustain, release and so on…

There is a midi implementation onboard and a tape function can be used to restore the factory defaults. Everything is well protected in side with a mainly metal case, and a convenient lift keybed/keyboard for those all-important repairs / servicing that the unit may need in the future.

It should be noted that there was an expander module model EX-600 produced too which had the same synth engine as the keyboard version, it’s a desktop model so no rack mounting as standard, that can only be edited by an external midi controller or patch editor.



A rare synthesiser with a beefy sound and great sounding filters if you can find on that broken or working buy it, I know from experience what these synths are all about. This website is a great resource for repairs of this model while you wait for my own repair guides:






Year Produced


Keyboard/Number of keys

61 note keyboard with full size keys and velocity.

Sound Generation

Analog synthesis

Maximum Polyphony

6 voices


Can store up to 95 different patches


Two DCO’s for each of the six voices totalling twelve!


Cutoff, Resonance, SSM filter chips


Three LFO’s


ADSR (Attack, Decay, Sustain, Release


None onboard



Common Faults

Check battery fault, or battery leakage


Controllable by MIDI, with velocity






Showing a repair of the DK600 after battery damage



Download Siel DK-600 User Manual pdf

Download Siel DK600 Schematics pdf


66Khz studios.



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