Discussion about the Korg PolySix synthesizer

Hi,

Im having problems to calibrate the filter section on the KLM366 board.
I followed the procedure from the servicemanual, and everything went well until:
Page 19
(3) VCF RESONANCE adjustment.

I followed instructions,
CN05-7 is at 0,02V
CN05-11 is at 8,00V.

Next the manual says:
1) Connect the oscilloscope and freqcounter with TP1
2) Play any single key and try to adjust VR6 so that the VCF waveform amplitude is 300mVp-p +/- 20mV

And here is the point I don't get it.
When I measure with my scope on TP1, the signal differs from every voice and key.
I can turn VR6, but I found out that when changing VR8, they interact with eachother.
So what is the starting situation?

Maybe I missing something completely, but I hope someone can put me in the right direction.

At 22:12 Uhr +0000 08.02.2012, sigma.draconis wrote:

> And here is the point I don't get it.
> When I measure with my scope on TP1, the signal differs from every voice and
> key.

Hold it right there. It's normal that the voices differ (especially before
calibration). However if the keys also affect the frequency you may have
not set the KBD TRACK control to zero. This is important.

> I can turn VR6, but I found out that when changing VR8, they interact with
> eachother.
> So what is the starting situation?

There is some (slight) interaction. I believe when the frequency (as set
with VR8) is way off you may get a somewhat different result for the
amplitude. But as long as the frequencies are roughly in the ballpark you
shouldn't get too much of a difference.
I take it you noticed that the RESONANCE control needs to be set to "full"
for the VR8 calibration?

Thanks for replay.

--- In PolySix@yahoogroups.com, Malte Rogacki <gacki@...> wrote:
> > When I measure with my scope on TP1, the signal differs from every voice and key.
> Hold it right there. It's normal that the voices differ (especially before
> calibration). However if the keys also affect the frequency you may have
> not set the KBD TRACK control to zero. This is important.

Indeed, the KBD TRACK is pointed at zero, and everything else is set to "standard".
Except WAVE-FORM at PW and PW/PWM to 10.
And offcourse the CUTOFF and RES to the settings needeed for adjustment.

> > I can turn VR6, but I found out that when changing VR8, they interact with eachother.
> > So what is the starting situation?
> There is some (slight) interaction. I believe when the frequency (as set
> with VR8) is way off you may get a somewhat different result for the
> amplitude. But as long as the frequencies are roughly in the ballpark you
> shouldn't get too much of a difference.
> I take it you noticed that the RESONANCE control needs to be set to "full"
> for the VR8 calibration?

In this case the VR8 were way off indeed.
(Ik know that for calibrating them, RES has to be set at 10 )

For some reason I don't get, for me, expected results.
What should the waveform look like?
I can get with turning the pots to something looking like triangels pointing to the right.
(Starting long side left and getting shorter to the right, until zero)

Or, when turning VR8 completely turned to the left, some kind of triangle waveform.
Many shapes between, are not trigerable.

At 14:10 Uhr +0000 09.02.2012, sigma.draconis wrote:

> For some reason I don't get, for me, expected results.
> What should the waveform look like?

Pretty much like a sine wave, regardless of the frequency.

> I can get with turning the pots to something looking like triangels pointing
> to the right.
> (Starting long side left and getting shorter to the right, until zero)

So it looks more like a sawtooth? This definitely should not happen.

Does the Polysix work otherwise? Basically this is just the filter
calibration we're talking about; so do the unfiltered sounds (for example
sawtooth or square) sound ok?

--- In PolySix@yahoogroups.com, Malte Rogacki <gacki@...> wrote:

>
> At 14:10 Uhr +0000 09.02.2012, sigma.draconis wrote:
> > For some reason I don't get, for me, expected results.
> > What should the waveform look like?
>
> Pretty much like a sine wave, regardless of the frequency.

Yes, that makes sence to me to.
I just fixed a Juno-106 (my other hobby project) with broken voice and the calibrating of the filters was just as you describe.
Sine waves within accepteble parameters.

That's why I thinking, I'm doing something completely wrong...

> > I can get with turning the pots to something looking like triangels pointing
> > to the right.
> > (Starting long side left and getting shorter to the right, until zero)
> So it looks more like a sawtooth? This definitely should not happen.

Yes, maybe you're right, but then a modulated sawtooth.
A bitt difficult to discribe.

> Does the Polysix work otherwise? Basically this is just the filter
> calibration we're talking about; so do the unfiltered sounds (for example
> sawtooth or square) sound ok?

Yes, without the filters it sound nice, and also in tune.

When I got this PolySix, it was a completely disaster.
The battery was leaked in almost the worst possibillity, and coroded 2 PCB's, also everything was way out off tune.
I cleaned everything. fixed the PCB's changed a few parts, and did all the tuning, except the filter tuning, for some reason, I didn't get it, or understand it.
Every other function works OK, but you can hear the filters are not correct tuned.

I'm not in a hurry, it's just a hobby, but it would be nice, if I can fix it :)

1. Is it the same wioth all six voices that you cannot adjust for the
requested value?
2. Can you post a picture of the oscilloscope screen?
3. I would not worry too much about minor, very well audible,
differences. This is the filter and not on oscillator...

Johannes


sigma.draconis wrote:

> Hi,
>
> Im having problems to calibrate the filter section on the KLM366 board.
> I followed the procedure from the servicemanual, and everything went well until:
> Page 19
> (3) VCF RESONANCE adjustment.
>
> I followed instructions,
> CN05-7 is at 0,02V
> CN05-11 is at 8,00V.
>
> Next the manual says:
> 1) Connect the oscilloscope and freqcounter with TP1
> 2) Play any single key and try to adjust VR6 so that the VCF waveform amplitude is 300mVp-p +/- 20mV
>
> And here is the point I don't get it.
> When I measure with my scope on TP1, the signal differs from every voice and key.
> I can turn VR6, but I found out that when changing VR8, they interact with eachother.
> So what is the starting situation?
>
> Maybe I missing something completely, but I hope someone can put me in the right direction.
>
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>

When I want to make a photo off the waveform, I found out that some parts aren't working correct anymore.

So indeed the "clean" waveforms are not as they used to be.
PW/PWM doesn't work correct and the SUB-OSC isn't doing anyhing.
TRI isn't stable to.

Because it worked before I didn't payed attention to it, and was focused on the filters.

Have to dive in this first before I can continue.
Hope I have time for it this week.

Thanks for helping so far :-)

--- In PolySix@yahoogroups.com, Johannes Hausensteiner <johau@...> wrote:
>
> 1. Is it the same wioth all six voices that you cannot adjust for the
> requested value?
> 2. Can you post a picture of the oscilloscope screen?
> 3. I would not worry too much about minor, very well audible,
> differences. This is the filter and not on oscillator...
>
> Johannes
>
>
> sigma.draconis wrote:
> > Hi,
> >
> > Im having problems to calibrate the filter section on the KLM366 board.
> > I followed the procedure from the servicemanual, and everything went well until:
> > Page 19
> > (3) VCF RESONANCE adjustment.
> >
> > I followed instructions,
> > CN05-7 is at 0,02V
> > CN05-11 is at 8,00V.
> >
> > Next the manual says:
> > 1) Connect the oscilloscope and freqcounter with TP1
> > 2) Play any single key and try to adjust VR6 so that the VCF waveform amplitude is 300mVp-p +/- 20mV
> >
> > And here is the point I don't get it.
> > When I measure with my scope on TP1, the signal differs from every voice and key.
> > I can turn VR6, but I found out that when changing VR8, they interact with eachother.
> > So what is the starting situation?
> >
> > Maybe I missing something completely, but I hope someone can put me in the right direction.
> >
> >
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>

Finaly got time to dive in this problem again.
After concluding that the basic waveforms also are not correct, I found out that there was, shame on me, en loosy(?) connector.

After reconnecting it, everything works the way it has to be, and I could finalize the calibration process.
No strange things yet :-)

Thanks for all help!

--- In PolySix@yahoogroups.com, "sigma.draconis" <mreuvekamp@...> wrote:
>
> When I want to make a photo off the waveform, I found out that some parts aren't working correct anymore.
>
> So indeed the "clean" waveforms are not as they used to be.
> PW/PWM doesn't work correct and the SUB-OSC isn't doing anyhing.
> TRI isn't stable to.
>
> Because it worked before I didn't payed attention to it, and was focused on the filters.
>
> Have to dive in this first before I can continue.
> Hope I have time for it this week.
>
> Thanks for helping so far :-)
>
> --- In PolySix@yahoogroups.com, Johannes Hausensteiner <johau@> wrote:
> >
> > 1. Is it the same wioth all six voices that you cannot adjust for the
> > requested value?
> > 2. Can you post a picture of the oscilloscope screen?
> > 3. I would not worry too much about minor, very well audible,
> > differences. This is the filter and not on oscillator...
> >
> > Johannes
> >
> >
> > sigma.draconis wrote:
> > > Hi,
> > >
> > > Im having problems to calibrate the filter section on the KLM366 board.
> > > I followed the procedure from the servicemanual, and everything went well until:
> > > Page 19
> > > (3) VCF RESONANCE adjustment.
> > >
> > > I followed instructions,
> > > CN05-7 is at 0,02V
> > > CN05-11 is at 8,00V.
> > >
> > > Next the manual says:
> > > 1) Connect the oscilloscope and freqcounter with TP1
> > > 2) Play any single key and try to adjust VR6 so that the VCF waveform amplitude is 300mVp-p +/- 20mV
> > >
> > > And here is the point I don't get it.
> > > When I measure with my scope on TP1, the signal differs from every voice and key.
> > > I can turn VR6, but I found out that when changing VR8, they interact with eachother.
> > > So what is the starting situation?
> > >
> > > Maybe I missing something completely, but I hope someone can put me in the right direction.
> > >
> > >
> > >
> > >
> > >
> > > ------------------------------------
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> >
>