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Subject: Re: [korgpolyex] New Voice Chips?

From: Michael Hawkins <korgpolyex800@...>
Date: 2014-05-30


I'll need to see the PIC stuff first before I can make comment. I may try and get a basic functional diagram going so that we can nail down the precise way in which we can plug this into the existing Poly main board and start comparing techniques and component choices.

If the PIC VCO is producing a digital output then we shall need a D2A but they can be constructed with some low tolerance resistor ladders = cheap. I have to also check the levels on the Poly to see if the existing TG is producing 0-5 or -5 - +5 volt signals. Either way, we can easily deal with that too. The challenge is to make this CHEAP.

I have also looked at using a 28C256 chip and using sampled waveforms much like the DW-8000 DWGS but I think the PIC path is a better one with the potential to produce a unique sound, possibly updatable/downloadable code. Possibly a selection of waveforms. If we can use a PIC for each voice that's in the 2-3 buck range then supporting components and PCB should all come somewhere in the 50-100 range total kit cost. I would definitely pay 100 bucks to upgrade the tone generator in the Poly to be true independent clocks along with independent detune, modulation etc plus better actual waveforms themselves. PWM, square, saw, triangle. Apart from the complete lack of MIDI (which was fixed by the HAWK), the waveform generation on the Poly is the worse thing about the sythn. It's one of the reasons it gets a lot of criticism and is often considered a toy.

Mike


On Thursday, May 29, 2014 9:14 PM, "John David Duncan john.david.duncan@... [korgpolyex]" <korgpolyex@yahoogroups.com> wrote:


This all sounds great.

I guess there's also D/A converters.
And then combining the new audio signal with the old signal before the input to the filter (without overloading the filter input and clipping).
Am I right about that or am I misunderstanding something?

JD





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> And lastly, we need a digital interface that allows selecting note frequency across the same range as the existing TG.
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> On Thursday, May 29, 2014 6:12 PM, "Michael Hawkins korgpolyex800@... [korgpolyex]" <korgpolyex@yahoogroups.com> wrote:
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> Yes, I am in general agreement regarding using 8 PIC chips, one for each DCO. And hopefully, each can take a voltage control signal for envelope generator VCA control. Because we already have those available in the existing circuitry. Then we also need another voltage control input for frequency control. So that MG and joystick pitch bend can control each PIC oscillator. Finally, we also need detuning (which can be digital control.
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> Mike
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> On Wednesday, May 28, 2014 8:28 PM, "bperkins211@... [korgpolyex]" <korgpolyex@yahoogroups.com> wrote:
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> Maybe the topic got buried in the other thread, but there was mention of trying to build a new voice for the HAWK.
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> I was suggesting perhaps we try to use a simple 8bit PIC with a small wavetable set, one PIC for each voice.  So maybe a 6 or 8 chip voice board?  Imagine the combo's you could come up with since each voice could be a different wavesample.
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> I put a line out to the guy who wrote the code for the Electric Druid's VC DCO pic chip.  He might give some pointers on how to mod his wavetable PIC code to work with a digital uC instead of all VC.
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> I did post questions to Mike about some of the features he was after.. I think my post got covered over and lost before he saw it??
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> ~Blaine

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