Discussion about the Korg PolySix synthesizer

Hi,
I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:

"5.) Now start to tune UNIT0. Take the adjustment procedure as a hint
of what will happen when you turn certain potis"

I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.

Thanks for any guidance or offers of help!

Jesse Olley

How do you come along?
Here is what happens (should happen):
1) set the front panel Tune knob to center position
2) on KLM-366: set sliding switch to "normal" position (away from CN12)
Be sure to have selected POLY Key assign mode
3) set potis VR10 (Tune Low) and VR11 (Tune High) of UNIT0
to center position
4) tune UNIT0 (you can recognise which voice (or UNIT as they call it)
is active by the small LED on KLM-366) in low, mid, and high range by
poti VR2 (high), VR3 (low), VR15 (mid), and VR14 ("D# ADJ"). VR14
does have very little impact. When tuning low notes switch the
OCTAVE setting on the front panel to 16', when tuning high note set
it to 4'. Use a chromatic tuner.
5) once you are satisfied with UNIT0 (it will NOT be 100%!) proceed to
UNIT 1. Dont touch the common potis VR2, VR3, VR14, and VR15; just
VR10 and VR11 of each UNIT. Do not use the tuner for that but rather
tune it to UNIT0, observing the effect of tone beating. You have to
play UNIT0 and the UNIT you want to tune.
6) If you are through with all 6 UNITs set up a "chord" of six equal
notes using the HOLD mode and press CHORD MEMORY. Now play notes
over the whole range (low 16' .. high 4') and listen. All 6 voices
sound simultaneously. But in contrast to UNISON mode the voices are
not detuned but "equal". Still they will not be equal 100% over the
whole range. It is 6 independent oscillators with true analog
circuitry, which will not be 100% perfect.
If you are satisfied with the precision set SW1 to the "Stretch
Tuning" position (towards CN12). Now the tuning is set intentionally
off a few cent over the whole range, you can check this with the
tuner. This adds richness to the sound as the 6 voices start (even
more) beating.

I hope this helps.

Johannes


blindcatfishwillie wrote:

> Hi,
> I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:
>
> "5.) Now start to tune UNIT0. Take the adjustment procedure as a hint
> of what will happen when you turn certain potis"
>
> I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.
>
> Thanks for any guidance or offers of help!
>
> Jesse Olley
>
>
>
> ------------------------------------
>
> PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links
>
>
>

What about a polysix that takes... 5 mins for just a SINGLE voice to be in tune (the other 5 are in tune as soon as you switch it on)? Obviously it's IN tune as it ends up in tune, but the fact it's only ONE voice (always the same one!) that has a delay 'warming up' does it hint a fault with one of it's chips or caps? if so I'd like to fix it.

thanks

To: PolySix@yahoogroups.com
From: johau@gmx.net
Date: Tue, 22 Sep 2009 21:43:41 +0200
Subject: Re: [PolySix] out of tune?





















How do you come along?

Here is what happens (should happen):

1) set the front panel Tune knob to center position

2) on KLM-366: set sliding switch to "normal" position (away from CN12)

Be sure to have selected POLY Key assign mode

3) set potis VR10 (Tune Low) and VR11 (Tune High) of UNIT0

to center position

4) tune UNIT0 (you can recognise which voice (or UNIT as they call it)

is active by the small LED on KLM-366) in low, mid, and high range by

poti VR2 (high), VR3 (low), VR15 (mid), and VR14 ("D# ADJ"). VR14

does have very little impact. When tuning low notes switch the

OCTAVE setting on the front panel to 16', when tuning high note set

it to 4'. Use a chromatic tuner.

5) once you are satisfied with UNIT0 (it will NOT be 100%!) proceed to

UNIT 1. Dont touch the common potis VR2, VR3, VR14, and VR15; just

VR10 and VR11 of each UNIT. Do not use the tuner for that but rather

tune it to UNIT0, observing the effect of tone beating. You have to

play UNIT0 and the UNIT you want to tune.

6) If you are through with all 6 UNITs set up a "chord" of six equal

notes using the HOLD mode and press CHORD MEMORY. Now play notes

over the whole range (low 16' .. high 4') and listen. All 6 voices

sound simultaneously. But in contrast to UNISON mode the voices are

not detuned but "equal". Still they will not be equal 100% over the

whole range. It is 6 independent oscillators with true analog

circuitry, which will not be 100% perfect.

If you are satisfied with the precision set SW1 to the "Stretch

Tuning" position (towards CN12). Now the tuning is set intentionally

off a few cent over the whole range, you can check this with the

tuner. This adds richness to the sound as the 6 voices start (even

more) beating.



I hope this helps.



Johannes



blindcatfishwillie wrote:

> Hi,

> I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:

>

> "5.) Now start to tune UNIT0. Take the adjustment procedure as a hint

> of what will happen when you turn certain potis"

>

> I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.

>

> Thanks for any guidance or offers of help!

>

> Jesse Olley

>

>

>

> ------------------------------------

>

> PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links

>

>

>

_________________________________________________________________
With Windows Live, you can organise, edit, and share your photos.
http://clk.atdmt.com/UKM/go/134665338/direct/01/

[Non-text portions of this message have been removed]

I remember years ago, that I had the same problem, had to plug the unit in while setting up the rest, in order to be able to play it correctly later. I remember (vaguely) opening it up and going to component on someone's advise and carefully adjusting a turn-screw to get the voice more in tune. THat back fired because once it stablized, it was out of tune the 'other' way. Eventually it would stay in tune an I used it that way for 3-4 years, until it fried itself....:{

--- In PolySix@yahoogroups.com, Paul T <sharpfish@...> wrote:
>
>
> What about a polysix that takes... 5 mins for just a SINGLE voice to be in tune (the other 5 are in tune as soon as you switch it on)? Obviously it's IN tune as it ends up in tune, but the fact it's only ONE voice (always the same one!) that has a delay 'warming up' does it hint a fault with one of it's chips or caps? if so I'd like to fix it.
>
> thanks
>
> To: PolySix@yahoogroups.com
> From: johau@...
> Date: Tue, 22 Sep 2009 21:43:41 +0200
> Subject: Re: [PolySix] out of tune?
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> How do you come along?
>
> Here is what happens (should happen):
>
> 1) set the front panel Tune knob to center position
>
> 2) on KLM-366: set sliding switch to "normal" position (away from CN12)
>
> Be sure to have selected POLY Key assign mode
>
> 3) set potis VR10 (Tune Low) and VR11 (Tune High) of UNIT0
>
> to center position
>
> 4) tune UNIT0 (you can recognise which voice (or UNIT as they call it)
>
> is active by the small LED on KLM-366) in low, mid, and high range by
>
> poti VR2 (high), VR3 (low), VR15 (mid), and VR14 ("D# ADJ"). VR14
>
> does have very little impact. When tuning low notes switch the
>
> OCTAVE setting on the front panel to 16', when tuning high note set
>
> it to 4'. Use a chromatic tuner.
>
> 5) once you are satisfied with UNIT0 (it will NOT be 100%!) proceed to
>
> UNIT 1. Dont touch the common potis VR2, VR3, VR14, and VR15; just
>
> VR10 and VR11 of each UNIT. Do not use the tuner for that but rather
>
> tune it to UNIT0, observing the effect of tone beating. You have to
>
> play UNIT0 and the UNIT you want to tune.
>
> 6) If you are through with all 6 UNITs set up a "chord" of six equal
>
> notes using the HOLD mode and press CHORD MEMORY. Now play notes
>
> over the whole range (low 16' .. high 4') and listen. All 6 voices
>
> sound simultaneously. But in contrast to UNISON mode the voices are
>
> not detuned but "equal". Still they will not be equal 100% over the
>
> whole range. It is 6 independent oscillators with true analog
>
> circuitry, which will not be 100% perfect.
>
> If you are satisfied with the precision set SW1 to the "Stretch
>
> Tuning" position (towards CN12). Now the tuning is set intentionally
>
> off a few cent over the whole range, you can check this with the
>
> tuner. This adds richness to the sound as the 6 voices start (even
>
> more) beating.
>
>
>
> I hope this helps.
>
>
>
> Johannes
>
>
>
> blindcatfishwillie wrote:
>
> > Hi,
>
> > I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:
>
> >
>
> > "5.) Now start to tune UNIT0. Take the adjustment procedure as a hint
>
> > of what will happen when you turn certain potis"
>
> >
>
> > I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.
>
> >
>
> > Thanks for any guidance or offers of help!
>
> >
>
> > Jesse Olley
>
> >
>
> >
>
> >
>
> > ------------------------------------
>
> >
>
> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links
>
> >
>
> >
>
> >
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> _________________________________________________________________
> With Windows Live, you can organise, edit, and share your photos.
> http://clk.atdmt.com/UKM/go/134665338/direct/01/
>
> [Non-text portions of this message have been removed]
>

well 5 of the 6 are 'perfect' this one voice (unit) has now drifted even higher and the tuning pots don't provide enough range to bring it into tune with the others.. so if I am to assume the chip is dying can't understand as I swapped the 2056 between units and the chips didn't make a difference (the voice was still voice 4 out of tune even with chip swap) now if it's chip 2044 (the famous ones!) then I've not tried a swap yet... I'll pick one up if that does it..

thanks

To: PolySix@yahoogroups.com
From: jpirard_1999@yahoo.com
Date: Fri, 25 Sep 2009 16:00:05 +0000
Subject: [PolySix] Re: out of tune?





















I remember years ago, that I had the same problem, had to plug the unit in while setting up the rest, in order to be able to play it correctly later. I remember (vaguely) opening it up and going to component on someone's advise and carefully adjusting a turn-screw to get the voice more in tune. THat back fired because once it stablized, it was out of tune the 'other' way. Eventually it would stay in tune an I used it that way for 3-4 years, until it fried itself....:{

--- In PolySix@yahoogroups.com, Paul T <sharpfish@...> wrote:

>

>

> What about a polysix that takes... 5 mins for just a SINGLE voice to be in tune (the other 5 are in tune as soon as you switch it on)? Obviously it's IN tune as it ends up in tune, but the fact it's only ONE voice (always the same one!) that has a delay 'warming up' does it hint a fault with one of it's chips or caps? if so I'd like to fix it.

>

> thanks

>

> To: PolySix@yahoogroups.com

> From: johau@...

> Date: Tue, 22 Sep 2009 21:43:41 +0200

> Subject: Re: [PolySix] out of tune?

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

> How do you come along?

>

> Here is what happens (should happen):

>

> 1) set the front panel Tune knob to center position

>

> 2) on KLM-366: set sliding switch to "normal" position (away from CN12)

>

> Be sure to have selected POLY Key assign mode

>

> 3) set potis VR10 (Tune Low) and VR11 (Tune High) of UNIT0

>

> to center position

>

> 4) tune UNIT0 (you can recognise which voice (or UNIT as they call it)

>

> is active by the small LED on KLM-366) in low, mid, and high range by

>

> poti VR2 (high), VR3 (low), VR15 (mid), and VR14 ("D# ADJ"). VR14

>

> does have very little impact. When tuning low notes switch the

>

> OCTAVE setting on the front panel to 16', when tuning high note set

>

> it to 4'. Use a chromatic tuner.

>

> 5) once you are satisfied with UNIT0 (it will NOT be 100%!) proceed to

>

> UNIT 1. Dont touch the common potis VR2, VR3, VR14, and VR15; just

>

> VR10 and VR11 of each UNIT. Do not use the tuner for that but rather

>

> tune it to UNIT0, observing the effect of tone beating. You have to

>

> play UNIT0 and the UNIT you want to tune.

>

> 6) If you are through with all 6 UNITs set up a "chord" of six equal

>

> notes using the HOLD mode and press CHORD MEMORY. Now play notes

>

> over the whole range (low 16' .. high 4') and listen. All 6 voices

>

> sound simultaneously. But in contrast to UNISON mode the voices are

>

> not detuned but "equal". Still they will not be equal 100% over the

>

> whole range. It is 6 independent oscillators with true analog

>

> circuitry, which will not be 100% perfect.

>

> If you are satisfied with the precision set SW1 to the "Stretch

>

> Tuning" position (towards CN12). Now the tuning is set intentionally

>

> off a few cent over the whole range, you can check this with the

>

> tuner. This adds richness to the sound as the 6 voices start (even

>

> more) beating.

>

>

>

> I hope this helps.

>

>

>

> Johannes

>

>

>

> blindcatfishwillie wrote:

>

> > Hi,

>

> > I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:

>

> >

>

> > "5.) Now start to tune UNIT0. Take the adjustment procedure as a hint

>

> > of what will happen when you turn certain potis"

>

> >

>

> > I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.

>

> >

>

> > Thanks for any guidance or offers of help!

>

> >

>

> > Jesse Olley

>

> >

>

> >

>

> >

>

> > ------------------------------------

>

> >

>

> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links

>

> >

>

> >

>

> >

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

> __________________________________________________________

> With Windows Live, you can organise, edit, and share your photos.

> http://clk.atdmt.com/UKM/go/134665338/direct/01/

>

> [Non-text portions of this message have been removed]

>






















_________________________________________________________________

MSN straight to your mobile - news, entertainment, videos and more.

http://clk.atdmt.com/UKM/go/147991039/direct/01/

[Non-text portions of this message have been removed]

So the 2044 and 2056 are checked as ok (just swapped them to other units and it's still voice 4 playing up). So could this be bad caps? resistors or something else? maybe a bad non socketed IC?

hmmm

To: polysix@yahoogroups.com
From: sharpfish@hotmail.com
Date: Mon, 28 Sep 2009 16:17:20 +0000
Subject: RE: [PolySix] Re: out of tune?

























well 5 of the 6 are 'perfect' this one voice (unit) has now drifted even higher and the tuning pots don't provide enough range to bring it into tune with the others.. so if I am to assume the chip is dying can't understand as I swapped the 2056 between units and the chips didn't make a difference (the voice was still voice 4 out of tune even with chip swap) now if it's chip 2044 (the famous ones!) then I've not tried a swap yet... I'll pick one up if that does it..



thanks



To: PolySix@yahoogroups.com

From: jpirard_1999@yahoo.com

Date: Fri, 25 Sep 2009 16:00:05 +0000

Subject: [PolySix] Re: out of tune?



I remember years ago, that I had the same problem, had to plug the unit in while setting up the rest, in order to be able to play it correctly later. I remember (vaguely) opening it up and going to component on someone's advise and carefully adjusting a turn-screw to get the voice more in tune. THat back fired because once it stablized, it was out of tune the 'other' way. Eventually it would stay in tune an I used it that way for 3-4 years, until it fried itself....:{

--- In PolySix@yahoogroups.com, Paul T <sharpfish@...> wrote:



>



>



> What about a polysix that takes... 5 mins for just a SINGLE voice to be in tune (the other 5 are in tune as soon as you switch it on)? Obviously it's IN tune as it ends up in tune, but the fact it's only ONE voice (always the same one!) that has a delay 'warming up' does it hint a fault with one of it's chips or caps? if so I'd like to fix it.



>



> thanks



>



> To: PolySix@yahoogroups.com



> From: johau@...



> Date: Tue, 22 Sep 2009 21:43:41 +0200



> Subject: Re: [PolySix] out of tune?



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



> How do you come along?



>



> Here is what happens (should happen):



>



> 1) set the front panel Tune knob to center position



>



> 2) on KLM-366: set sliding switch to "normal" position (away from CN12)



>



> Be sure to have selected POLY Key assign mode



>



> 3) set potis VR10 (Tune Low) and VR11 (Tune High) of UNIT0



>



> to center position



>



> 4) tune UNIT0 (you can recognise which voice (or UNIT as they call it)



>



> is active by the small LED on KLM-366) in low, mid, and high range by



>



> poti VR2 (high), VR3 (low), VR15 (mid), and VR14 ("D# ADJ"). VR14



>



> does have very little impact. When tuning low notes switch the



>



> OCTAVE setting on the front panel to 16', when tuning high note set



>



> it to 4'. Use a chromatic tuner.



>



> 5) once you are satisfied with UNIT0 (it will NOT be 100%!) proceed to



>



> UNIT 1. Dont touch the common potis VR2, VR3, VR14, and VR15; just



>



> VR10 and VR11 of each UNIT. Do not use the tuner for that but rather



>



> tune it to UNIT0, observing the effect of tone beating. You have to



>



> play UNIT0 and the UNIT you want to tune.



>



> 6) If you are through with all 6 UNITs set up a "chord" of six equal



>



> notes using the HOLD mode and press CHORD MEMORY. Now play notes



>



> over the whole range (low 16' .. high 4') and listen. All 6 voices



>



> sound simultaneously. But in contrast to UNISON mode the voices are



>



> not detuned but "equal". Still they will not be equal 100% over the



>



> whole range. It is 6 independent oscillators with true analog



>



> circuitry, which will not be 100% perfect.



>



> If you are satisfied with the precision set SW1 to the "Stretch



>



> Tuning" position (towards CN12). Now the tuning is set intentionally



>



> off a few cent over the whole range, you can check this with the



>



> tuner. This adds richness to the sound as the 6 voices start (even



>



> more) beating.



>



>



>



> I hope this helps.



>



>



>



> Johannes



>



>



>



> blindcatfishwillie wrote:



>



> > Hi,



>



> > I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:



>



> >



>



> > "5.) Now start to tune UNIT0. Take the adjustment procedure as a hint



>



> > of what will happen when you turn certain potis"



>



> >



>



> > I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.



>



> >



>



> > Thanks for any guidance or offers of help!



>



> >



>



> > Jesse Olley



>



> >



>



> >



>



> >



>



> > ------------------------------------



>



> >



>



> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links



>



> >



>



> >



>



> >



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



>



> __________________________________________________________



> With Windows Live, you can organise, edit, and share your photos.



> http://clk.atdmt.com/UKM/go/134665338/direct/01/



>



> [Non-text portions of this message have been removed]



>





















__________________________________________________________



MSN straight to your mobile - news, entertainment, videos and more.



http://clk.atdmt.com/UKM/go/147991039/direct/01/



[Non-text portions of this message have been removed]






















_________________________________________________________________
Get the best of MSN on your mobile
http://clk.atdmt.com/UKM/go/147991039/direct/01/

[Non-text portions of this message have been removed]

>>> From Johannes

If you are satisfied with the precision set SW1 to the "Stretch
Tuning" position (towards CN12). Now the tuning is set intentionally
off a few cent over the whole range, you can check this with the
tuner. This adds richness to the sound as the 6 voices start (even
more) beating.

>>>

This is so illuminating! I was always confused by the part of the tuning procedure involving SW1 because (a) I couldn't figure out what the switch was doing, (b) I didn't know what the manual meant by "stretch tuning", and (c) the manual tells you to move SW1 "away from VR1" which is not possible since VR1 is to the *left* of this up-and-down switch. So confusing!

Luckily, Johannes saves me from my ignorance. Again. Thank you!

Chip

--- In PolySix@yahoogroups.com, Johannes Hausensteiner <johau@...> wrote:
>
> How do you come along?
> Here is what happens (should happen):
> 1) set the front panel Tune knob to center position
> 2) on KLM-366: set sliding switch to "normal" position (away from CN12)
> Be sure to have selected POLY Key assign mode
> 3) set potis VR10 (Tune Low) and VR11 (Tune High) of UNIT0
> to center position
> 4) tune UNIT0 (you can recognise which voice (or UNIT as they call it)
> is active by the small LED on KLM-366) in low, mid, and high range by
> poti VR2 (high), VR3 (low), VR15 (mid), and VR14 ("D# ADJ"). VR14
> does have very little impact. When tuning low notes switch the
> OCTAVE setting on the front panel to 16', when tuning high note set
> it to 4'. Use a chromatic tuner.
> 5) once you are satisfied with UNIT0 (it will NOT be 100%!) proceed to
> UNIT 1. Dont touch the common potis VR2, VR3, VR14, and VR15; just
> VR10 and VR11 of each UNIT. Do not use the tuner for that but rather
> tune it to UNIT0, observing the effect of tone beating. You have to
> play UNIT0 and the UNIT you want to tune.
> 6) If you are through with all 6 UNITs set up a "chord" of six equal
> notes using the HOLD mode and press CHORD MEMORY. Now play notes
> over the whole range (low 16' .. high 4') and listen. All 6 voices
> sound simultaneously. But in contrast to UNISON mode the voices are
> not detuned but "equal". Still they will not be equal 100% over the
> whole range. It is 6 independent oscillators with true analog
> circuitry, which will not be 100% perfect.
> If you are satisfied with the precision set SW1 to the "Stretch
> Tuning" position (towards CN12). Now the tuning is set intentionally
> off a few cent over the whole range, you can check this with the
> tuner. This adds richness to the sound as the 6 voices start (even
> more) beating.
>
> I hope this helps.
>
> Johannes
>
>
> blindcatfishwillie wrote:
> > Hi,
> > I've searched all I can on this great forum but I still can't figure out how to get by polysix back in tune. Andrew did a spectacular job restoring the CPU board but now I need to give attention to the tuning board. I have the service document but can't make much sense of it. It seems too many things are out of spec to make it work. There is a post from Johannes stating:
> >
> > "5.) Now start to tune UNIT0. Take the adjustment procedure as a hint
> > of what will happen when you turn certain potis"
> >
> > I just can't figure out what pots to turn to make what happen. The problem (and I should have stated this earlier) is that an octave in sound stretches more than an octave worth of keys.
> >
> > Thanks for any guidance or offers of help!
> >
> > Jesse Olley
> >
> >
> >
> > ------------------------------------
> >
> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links
> >
> >
> >
>

I'm still studying this...

On the schematic for KLM-366 in the Service Manual, I'm assuming that "SW1" is the switch shown near IC18 that, when closed, jumps around R26. My question is, which position of the switch corresponds to what state?

If the switch is up ("normal" tuning?), does that mean that the switch is open or closed? Conversely, if the switch is down ("stretched" tuning?) is it open or closed?

Then, analyzing the circuit a little bit, I'm not quite sure how this switch affects the tuning of the instrument. Sure, if the switch shorts across R25, it'll change the DC voltage at the "+" input of IC18 a tiny bit...it'll be -6.9880V when shorted and -7.0012V when open...which is a difference of ~0.042 volts, which at 0.5 V/octave, is about 32 cents. But this isn't a CV for pitch. This is something else.

This signal (after differencing with the -7.0V highest "C" coming out of x6 of IC31) is fed to transistor Q3, which controls the current in octocoupler PC1, which affects (somehow) the exponential converter embodied by Q12 that converts the volt/octave scaling to Hz/volt scaling that is ultimately used by each voice.

Does anyone understand what is happening here? Clearly, this is not only implementing the stretch tuning, but must also be tied up with the pitch correction feedback to improve pitch stability. Can anyone explain how this works?

Thanks!

Chip

--- In PolySix@yahoogroups.com, "chipaudette" <chipaudette@...> wrote:
>
> >>> From Johannes
> If you are satisfied with the precision set SW1 to the "Stretch
> Tuning" position (towards CN12). Now the tuning is set intentionally
> off a few cent over the whole range, you can check this with the
> tuner. This adds richness to the sound as the 6 voices start (even
> more) beating.
> >>>
>
> This is so illuminating! I was always confused by the part of the tuning procedure involving SW1 because (a) I couldn't figure out what the switch was doing, (b) I didn't know what the manual meant by "stretch tuning", and (c) the manual tells you to move SW1 "away from VR1" which is not possible since VR1 is to the *left* of this up-and-down switch. So confusing!
>
> Luckily, Johannes saves me from my ignorance. Again. Thank you!
>
> Chip
>

Correcting my own post a bit...

> This signal (after differencing with the -7.0V highest "C" coming out of x6 of IC31)

This part is probably not true. I sometimes forget that IC31 is *after* the exponential converter. So, while I do think that it is true that x6 holds the voltage for the highest "C" produced by the Polysix, I don't know what the voltage is here.

Even if it was before the expo converter, I think that the voltage of highest C (by the time it gets to KLM-366) would be +3.5V, not -7.0V, so I was talking crazy anyway.

Sorry for any confusion.

My original question still stands, though...what the heck is happening in this part of the circuit? How does it cause the "stretched tuning" to be effected?

Thanks!

Chip