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Fine tuning the Synthacon(TO KEN or anyone else that can help!)

Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-07 by earthtodylan2000

Hello,

My Synthacon is working but seems a bit too hot and the
Frequency knob control is a bit too wide.

Trying the John Loffink mods...

"...Output "level" jumper/resistor: I put 180K in the level position,
in addition to the 47K already in the op amp feedback path, or
just put 220K total in the 47K position."

"...First, decreasing the size of the input divider resistor on the CV
input section, 1K in Ken's circuit, increases the range of the
frequency control. I put 2.2K in parallel with the 1K resistors, or
you can swap the 1K with a 680 ohm resistor."


Where are those on the circut board?


And the resonance pot seems to jump the resonance around.
It goes up as you turn it, then down, stops, then goes up again.
What's that about?

Thanks so much!

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-07 by sasami@hotkey.net.au

>"...First, decreasing the size of the input divider resistor on the CV
>input section, 1K in Ken's circuit, increases the range of the
>frequency control. I put 2.2K in parallel with the 1K resistors, or
>you can swap the 1K with a 680 ohm resistor."
>
>Where are those on the circut board?

The 1k is the one neares to the power connector end of the board, running
width-ways, and right next to the 220k input resistors.

> And the resonance pot seems to jump the resonance around.
>It goes up as you turn it, then down, stops, then goes up again.
>What's that about?

Overdrive. A lot of us love that. You are sending the filter into a chaotic
mode. If you don't like it, put a 1k trimmer in line with the pot, then
adjust it for the desired maximum with the pain pot all the way up.

Kem
_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-10 by earthtodylan2000

Ken,
Thanks for the info. I like the overdrive I just don't like that the
resonance goes up and down then up again as I turn the pot CW
and CCW.

1. Question:

The 1k trimmer is a pot(?) that goes from the wire on the board,
to the middle terminal on the pot(1k)? Right? Then to either the
left or right terminal on the pot?

2. Question:

In the mod section it says:

" I also added 220K of series resistance to the FREQ knob."

Do I just put a 220k resistor from wire from the board to the
middle terminal of the FREQ pot?


Thanks,
Dave
Show quoted textHide quoted text
> Overdrive. A lot of us love that. You are sending the filter into a
chaotic
> mode. If you don't like it, put a 1k trimmer in line with the pot,
then
> adjust it for the desired maximum with the pain pot all the way
up.
>
> Kem
>
__________________________________________________
_____________________
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-10 by sasami@hotkey.net.au

>1. Question:
>
> The 1k trimmer is a pot(?)
(a small dedicated trim-pot)

cut the wire going from the middle of the resonance pot, and solder the two
sides of the cut wire to the trim pot - one to the middle terminal, and the
other to one of the outside terminals (which outside terminal doesn't matter
- it just affects the rotation of the trimmer).

>2. Question:
>
>In the mod section it says:
>
>" I also added 220K of series resistance to the FREQ knob."
>
> Do I just put a 220k resistor from wire from the board to the
>middle terminal of the FREQ pot?

Best ask the person who did the mod :). Possibly between the +ve connection
and the top of the pot to limit the range.

Ken
_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-10 by earthtodylan2000

Ken,
My 2nd question is from your Synthacon mod webpage under...

"Notes from John Loffink"

Again it's...

" I also added 220K of series resistance to the FREQ knob."

Do I just put a 220k resistor from wire from the board to the
middle terminal of the FREQ pot?

I'd just like to understand how to do this.

Thanks

Dave
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
>
> >1. Question:
> >
> > The 1k trimmer is a pot(?)
> (a small dedicated trim-pot)
>
> cut the wire going from the middle of the resonance pot, and
solder the two
> sides of the cut wire to the trim pot - one to the middle terminal,
and the
> other to one of the outside terminals (which outside terminal
doesn't matter
> - it just affects the rotation of the trimmer).
>
> >2. Question:
> >
> >In the mod section it says:
> >
> >" I also added 220K of series resistance to the FREQ knob."
> >
> > Do I just put a 220k resistor from wire from the board to the
> >middle terminal of the FREQ pot?
>
> Best ask the person who did the mod :). Possibly between the
+ve connection
> and the top of the pot to limit the range.
>
> Ken
>
__________________________________________________
_____________________
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-11 by sasami@hotkey.net.au

Dave,

> My 2nd question is from your Synthacon mod webpage under...
>
>"Notes from John Loffink"
>
>Again it's...
>
>" I also added 220K of series resistance to the FREQ knob."
>
> Do I just put a 220k resistor from wire from the board to the
>middle terminal of the FREQ pot?
>
>I'd just like to understand how to do this.

My answer is still the same :)

>> Best ask the person who did the mod :). Possibly between the
>> +ve connection and the top of the pot to limit the range.

As you have described it may work as well. I've NEVER done this mod myself.

Ken
_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-11 by earthtodylan2000

Thanks...but do you mean putting the resistor(220K) between the
2 teminals on the pot? The ones with the +ve and, the center
one that you connect to the board with a wire?

Dave
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
>
> Dave,
>
> > My 2nd question is from your Synthacon mod webpage
under...
> >
> >"Notes from John Loffink"
> >
> >Again it's...
> >
> >" I also added 220K of series resistance to the FREQ knob."
> >
> > Do I just put a 220k resistor from wire from the board to the
> >middle terminal of the FREQ pot?
> >
> >I'd just like to understand how to do this.
>
> My answer is still the same :)
>
> >> Best ask the person who did the mod :). Possibly between
the
> >> +ve connection and the top of the pot to limit the range.
>
> As you have described it may work as well. I've NEVER done
this mod myself.
>
> Ken
>
__________________________________________________
_____________________
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-11 by sasami@hotkey.net.au

>Thanks...but do you mean putting the resistor(220K) between the
>2 teminals on the pot? The ones with the +ve and, the center
>one that you connect to the board with a wire?
>
>Dave

Nope. I mean putting it inline with the positive wire, so disconnect the
positive wire from the pot and put the resistor in-between.
_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-11 by John Loffink

Yes, just put the 220K resistor from where the wire on the board is
connected and wire it to the middle terminal on the freq pot.

What I try to emphasize is that the Steiner VCF circuit is sensitive to the
gain of the transistors, which is a highly variable parameter. You may or
may not require the modifications depending on your transistors. I can say
that several people had similar results to mine before the modifications,
with the frequency range knob only useful to the 11 or 12 o'clock position,
while other people on this list apparently had a fuller control range and
didn't need the modifications. The values I ended up with did correspond
fairly closely to values I found on a Japanese version of the schematic.

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
Show quoted textHide quoted text
> -----Original Message-----
> From: earthtodylan2000 [mailto:earthtodylan2000@...]
>
> Ken,
> My 2nd question is from your Synthacon mod webpage under...
>
> "Notes from John Loffink"
>
> Again it's...
>
> " I also added 220K of series resistance to the FREQ knob."
>
> Do I just put a 220k resistor from wire from the board to the
> middle terminal of the FREQ pot?
>
> I'd just like to understand how to do this.
>
> Thanks
>
> Dave
>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-11 by Richard Brewster

I'm interested to see if John Loffink will comment. I interpreted this
to mean to add 220K in series with the 220K resistor on the schematic.
So I put a 430K resistor on the PC board. The range doesn't seem quite
right.

-Richard Brewster

sasami@... wrote:
Show quoted textHide quoted text
>>Thanks...but do you mean putting the resistor(220K) between the
>>2 teminals on the pot? The ones with the +ve and, the center
>>one that you connect to the board with a wire?
>>
>>Dave
>>
>>
>
>Nope. I mean putting it inline with the positive wire, so disconnect the
>positive wire from the pot and put the resistor in-between.
>_______________________________________________________________________
>Ken Stone sasami@... or sasami@...
>Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
>Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>
>
>
>
>

Re: Fine tuning the Synthacon(TO KEN or anyone else that can help!)

2004-06-11 by earthtodylan2000

Hey John...

Thanks for the comments.

My FREQ knob does max out at the halfway point as you turn the
pot. I'm hoping that this mod will help.

I'm going to use the Synthacon with a Moog Voyager and a small
Blacet system(binary zone, dark star chaos, time machine,
miniwave, etc...) Do you have any advise or experience with
these? Anything I can do with the Synthacon VCF.

And by the way... The Synthacon does sound pretty cool at this
point. I know that when I get this one working it will be in use all
the time. I would just bit more control over the FREQ and
Resonance.

Thank you



Show quoted textHide quoted text

--- In cgs_synth@yahoogroups.com, "John Loffink"
<jloffink@a...> wrote:
> Yes, just put the 220K resistor from where the wire on the
board is
> connected and wire it to the middle terminal on the freq pot.
>
> What I try to emphasize is that the Steiner VCF circuit is
sensitive to the
> gain of the transistors, which is a highly variable parameter.
You may or
> may not require the modifications depending on your
transistors. I can say
> that several people had similar results to mine before the
modifications,
> with the frequency range knob only useful to the 11 or 12
o'clock position,
> while other people on this list apparently had a fuller control
range and
> didn't need the modifications. The values I ended up with did
correspond
> fairly closely to values I found on a Japanese version of the
schematic.
>
> John Loffink
> The Microtonal Synthesis Web Site
> http://www.microtonal-synthesis.com
> The Wavemakers Synthesizer Web Site
> http://www.wavemakers-synth.com
>
>
> > -----Original Message-----
> > From: earthtodylan2000 [mailto:earthtodylan2000@y...]
> >
> > Ken,
> > My 2nd question is from your Synthacon mod webpage
under...
> >
> > "Notes from John Loffink"
> >
> > Again it's...
> >
> > " I also added 220K of series resistance to the FREQ knob."
> >
> > Do I just put a 220k resistor from wire from the board to the
> > middle terminal of the FREQ pot?
> >
> > I'd just like to understand how to do this.
> >
> > Thanks
> >
> > Dave
> >

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