Inside the Korg Polysix. Analog synths with Storage

[kr61ab67]

Congratulations to the designer(s) of this beautiful and great sounding machine, and thanks Doc for posting this video !

[TheReasonWhyGuy]

I love to just look at hardware...

[synthpro]

The polysix is built almost like the Akai AX-80. It is also a 80's poly synth. I am taking electronics at college and hope to learn a little more about this kind of stuff. Great video and thanks for posting!

[sounddoctorin]

Welllll not quite 'almost' :-). It was assumed on some websites that the AX80 had VCO's. However it's very similar I believe (though I still haven't seen a diagram) to the JUNO's and other DCO synths of the day which use an op amp integrator that is digitally controlled to generate the saw waves. Otherwise the signal path thereafter is analog though all controls for envelopes are digital also. Whereas the polysix is completely analog on all those things. I have been inside the AX80..

[synthpro]

That is neat to know! So just to make sure I am correct, a DCO still uses a viberating chip to produce the sound, but it is digitally controlled insted of voltage controlled. Is that right?

[sounddoctorin]

There are various things labelled "DCO". The first things were apparently the Crumar DS-1 and the JEN Sx-1000 I believe someone told me also around the same time. At least the DS-1 used multivibrator chips that actually had a preset R/C with analog CV mixed in from the bender etc. So I guess it was really a VCDO. :-) Then the polysynths were at first using DCAO's like ax80. Curiously Akai went the other way and most of the rest of their synths used the CEM3394 VCO/VCF/VCA chip!

[sounddoctorin]

Continuing, then synths like the Korg DW's, DSS-1, Ensoniq Mirage and ESQ-1/SQ80, SCI Prophet VS / 2000, and Kawai K3 came along that had still analog filters but used entirely digital processing to generate the waveforms right out of a DAC. This of course allowed the flexibility to do some more interesting timbres since the data could be read right from a ROM chip or in the case of the samplers, sampling RAM. So these were DCDO's I suppose. The siel DK600 Is unique. VCDGAO's :-)

[synthpro]

Very Interesting! I enjoy learning about things like this. Thanks for the information!

[sounddoctorin]

PS and on my sounddoctorin website in the global synth section under production synths you'll find akai and the ax80. I archived the document akai used to have up about the ax80. That's the only 'official' info I've been able to locate on it to date.

[geox19801]

i noticed on mine that it makes a lot of background noise without playng any keys.

anyone have the same problem??

cheers

[synthpro]

@geox19801 well, I have never been under the hood of a Korg polysix yet but based on other synths I have worked on, you may have some bad filtering capacitors in some of the audio circuits. I have had rare cases where dust created noise as well.

Hope this helps somewhat.

[5Ttruck]

Vids like this are the ones that should have 2 million+ views. Great information, nicely narrated - I get really pissed off watching all these vids where people spend 2 minutes saying "umm" and "sorry hang on a sec while I get this working"

[helicoptered]

Youtube Junkies.. ?

[aceyage]

Amazing, amazing, amazing...

Thanks a lot for your insight!

Subscribed!

[cedrimske]

hello nice video

do you can help me

i have a problem with my polysix

the led in the program part stay activated the led 2 and b

and the vca vco vcf slector dont work he stay on vco on all position

and the sub osc selector dont work too

isome time all the fonction work i dont know why but now he dont work

if you can help me

sorry for my bad english i am french

thanks

[lesingemonotone]

Nice little walkthru the Polysix, Bob!

I'm sure this movie will come in handy as an introduction for all those DIY getting into restoring their busted Polysixes.

Good work and keep em coming! :)

/Le Singe Monotone