Doepfer

I can't duplicate the folded triangle waveforms shown in the A-137 
manual (chapter 2). The shown waveforms consist of straight lines, but 
I get rounded waveforms.

Here is an example oscilloscope view:
http://www.esnips.com/doc/278f44e2-ce2a-4ff1-8f17-1f7ef5d795d7/A-
137_weirdness_1
(I hope the link isn't too long for Yahoo.)
The settings are:
- All CV inputs at full counter clockwise and unplugged
- Input level at 12'o clock
- Multiples at 9'o clock
- Folding level at 12'o clock
- Symmetry at 12'o clock
- Harmonics at full counter clockwise

Questions:
- Is this the expected output on these settings
- Why does a triangle input get rounded?
- What settings should give the straight line waveforms shown in the 
manual?


Best regards and thank you for your time
Jari Jokinen

Hi Jari,

At roughly the same settings as you give, my A-137 gives a very 
similar trace to yours. Because of the 4 stages acting one after the 
other, it is quite hard to see the effect of each stage and/or 
controls in isolation. I suspect the diagrams in the manual are 
rather diagrammatic of what is going on, rather than the literal 
truth, but I'll study the circuit a little, and see if I can answer 
some of your other questions.

Tim

--- In Doepfer_a100@yahoogroups.com, "jalmari3" <jari.jokinen@...> 
wrote:
>
> I can't duplicate the folded triangle waveforms shown in the A-137 
> manual (chapter 2). The shown waveforms consist of straight lines, 
but 
> I get rounded waveforms.
> 
> Here is an example oscilloscope view:
> http://www.esnips.com/doc/278f44e2-ce2a-4ff1-8f17-1f7ef5d795d7/A-
> 137_weirdness_1
> (I hope the link isn't too long for Yahoo.)
> The settings are:
> - All CV inputs at full counter clockwise and unplugged
> - Input level at 12'o clock
> - Multiples at 9'o clock
> - Folding level at 12'o clock
> - Symmetry at 12'o clock
> - Harmonics at full counter clockwise
> 
> Questions:
> - Is this the expected output on these settings
> - Why does a triangle input get rounded?
> - What settings should give the straight line waveforms shown in 
the 

> manual?
> 
> 
> Best regards and thank you for your time
> Jari Jokinen
>

On the A-137 page there are some green/black figures demonstrating 
control setting effects. They seem to be real oscilloscope captures, 
as I was able to reproduce them with reasonable accuracy. So, my A-
137 seems to work normally.

Some observations (and some might think nit-picking):

- Of the above mentioned figures "Changing the Symmetry" 
and "Changing the Harmonics" pictures are swapped.

- The above mentioned figures are said to demonstrate: "changing a 
control from low (left picture) to high (right picture)". This 
doesn't necessarily translate to from full counter clockwise to full 
clockwise - at least in my unit.   

- It is best to start experimenting with Harmonics at 9'o clock or 
more. First I assumed, that full counter clockwise was somewhat 
neutral setting.

- The Harmonics control works "a little bit like the resonance 
control of a filter". It doesn't sound at all like a filter though.

- The diagrams in the manual showing some triangle wave folding are 
indeed diagrammatic. I can't reproduce them.

Best regards
Jari Jokinen   

--- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe" <timothy@...> 
wrote:
>
> Hi Jari,
> 
> At roughly the same settings as you give, my A-137 gives a very 
> similar trace to yours. Because of the 4 stages acting one after 
the 
> other, it is quite hard to see the effect of each stage and/or 
> controls in isolation. I suspect the diagrams in the manual are 
> rather diagrammatic of what is going on, rather than the literal 
> truth, but I'll study the circuit a little, and see if I can answer 
> some of your other questions.
> 
> Tim
> 
> --- In Doepfer_a100@yahoogroups.com, "jalmari3" <jari.jokinen@> 
> wrote:
> >
> > I can't duplicate the folded triangle waveforms shown in the A-
137 
> > manual (chapter 2). The shown waveforms consist of straight 
lines, 

> but 
> > I get rounded waveforms.
> > 
> > Here is an example oscilloscope view:
> > http://www.esnips.com/doc/278f44e2-ce2a-4ff1-8f17-1f7ef5d795d7/A-
> > 137_weirdness_1
> > (I hope the link isn't too long for Yahoo.)
> > The settings are:
> > - All CV inputs at full counter clockwise and unplugged
> > - Input level at 12'o clock
> > - Multiples at 9'o clock
> > - Folding level at 12'o clock
> > - Symmetry at 12'o clock
> > - Harmonics at full counter clockwise
> > 
> > Questions:
> > - Is this the expected output on these settings
> > - Why does a triangle input get rounded?
> > - What settings should give the straight line waveforms shown in 
> the 
> > manual?
> > 
> > 
> > Best regards and thank you for your time
> > Jari Jokinen
> >
>

Thank you. I posted earlier some comments. I think I understand the 
parameters now.

Best regards
Jari Jokinen

--- In Doepfer_a100@yahoogroups.com, <hardware@...> wrote:
>
> The waveform pictures in the A-137 user's manual are idealized 
graphs and
> used only to explain the basic function of the module. In reality 
the
> clipping and folding is not hard (as shown in the pictures) but 
soft.
> Finally the audible result is important but not the scope picture. 
You will
> find more idealized graphs in other manuals too. Showing the "real"
> waveforms, frequency response curves or other parameters would 
complicate
> the explanations.
> 
> In the A-137 the combination of the four parameters (multiples, 
folding
> level, symmetry and harmonics) define the output waveform. You 
should obtain
> a triangle output (with A-110 triangle as input) with these 
approximate
> settings:
> 
> audio input level ~ 2
> multiples = 0
> folding level = 0
> symmetry ~ 3 (between 9 and 12 o'clock)
> harmonics ~ 2 (~ 9 o'clock)
> 
> Starting from this setting you should be able to see the functions 
of the
> four parameters very good at the scope.
> 
> Your settings are far away from generating a triangle at the output 
(with
> input level at 12'o clock and multiples at 9'o clock you have 
already some
> multiplications).
> 
> Best wishes
> Dieter Doepfer
> 
> 
> > -----Ursprüngliche Nachricht-----
> > Von: Doepfer_a100@yahoogroups.com
> > [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von jalmari3
> > Gesendet: Mittwoch, 15. August 2007 19:49
> > An: Doepfer_a100@yahoogroups.com
> > Betreff: [Doepfer_a100] Is my A-137 faulty?
> >
> >
> > I can't duplicate the folded triangle waveforms shown in the A-137
> > manual (chapter 2). The shown waveforms consist of straight 
lines, but
> > I get rounded waveforms.
> >
> > Here is an example oscilloscope view:
> > http://www.esnips.com/doc/278f44e2-ce2a-4ff1-8f17-1f7ef5d795d7/A-
> > 137_weirdness_1
> > (I hope the link isn't too long for Yahoo.)
> > The settings are:
> > - All CV inputs at full counter clockwise and unplugged
> > - Input level at 12'o clock
> > - Multiples at 9'o clock
> > - Folding level at 12'o clock
> > - Symmetry at 12'o clock
> > - Harmonics at full counter clockwise
> >
> > Questions:
> > - Is this the expected output on these settings
> > - Why does a triangle input get rounded?
> > - What settings should give the straight line waveforms shown in 
the

> > manual?
> >
> > Best regards and thank you for your time
> > Jari Jokinen
>

The waveform pictures in the A-137 user's manual are idealized graphs and
used only to explain the basic function of the module. In reality the
clipping and folding is not hard (as shown in the pictures) but soft.
Finally the audible result is important but not the scope picture. You will
find more idealized graphs in other manuals too. Showing the "real"
waveforms, frequency response curves or other parameters would complicate
the explanations.

In the A-137 the combination of the four parameters (multiples, folding
level, symmetry and harmonics) define the output waveform. You should obtain
a triangle output (with A-110 triangle as input) with these approximate
settings:

audio input level ~ 2
multiples = 0
folding level = 0
symmetry ~ 3 (between 9 and 12 o'clock)
harmonics ~ 2 (~ 9 o'clock)

Starting from this setting you should be able to see the functions of the
four parameters very good at the scope.

Your settings are far away from generating a triangle at the output (with
input level at 12'o clock and multiples at 9'o clock you have already some
multiplications).

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von jalmari3
> Gesendet: Mittwoch, 15. August 2007 19:49
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Is my A-137 faulty?
>
>
> I can't duplicate the folded triangle waveforms shown in the A-137
> manual (chapter 2). The shown waveforms consist of straight lines, but
> I get rounded waveforms.
>
> Here is an example oscilloscope view:
> http://www.esnips.com/doc/278f44e2-ce2a-4ff1-8f17-1f7ef5d795d7/A-
> 137_weirdness_1
> (I hope the link isn't too long for Yahoo.)
> The settings are:
> - All CV inputs at full counter clockwise and unplugged
> - Input level at 12'o clock
> - Multiples at 9'o clock
> - Folding level at 12'o clock
> - Symmetry at 12'o clock
> - Harmonics at full counter clockwise
>
> Questions:
> - Is this the expected output on these settings
> - Why does a triangle input get rounded?
> - What settings should give the straight line waveforms shown in the
> manual?
>
> Best regards and thank you for your time
> Jari Jokinen

--- In Doepfer_a100@yahoogroups.com, "jalmari3" <jari.jokinen@...> 
wrote:
>
> I think I understand the parameters now.

Perhaps not quite yet: I didn't expect, that harmonics control would 
respond to negative values (negative CV applied). Resulting waveforms 
are interesting and apparently can't be done with knobs only.

Best regards
Jari Jokinen