Doepfer

Tim,

thank you for this information. I will try if the additional 1M resistor
will work for the A-111. If this is true we will the resistor for new A-111
and prepare a document how to add this resistor for existing A-111.

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von Tim Stinchcombe
> Gesendet: Sonntag, 7. Mai 2006 10:32
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-113 input sencetivity/tracking problems
>
>
> Hi Dieter & Dirk,
>
> I don't own an A-113, so I cannot see the exact problem first-hand,
> but I did observe the nasty 'mush' on the falling edge of the A-111
> square wave output (when it is below about 300Hz).
>
> I notice that the CEM3340 datasheet says that the falling edge is
> more rounded than the rising one, and that this can be improved by
> placing a 1meg resistor between pins 4 and 5 (pulse out and PWM
> input). This adds some hysteresis to the internal comparator, and
> should 'square up' the output. So I tried it and indeed it _did_
> square up the signal, and also removed all the nasty 'noise' that
> Dieter reported.
>
> Thus this _may_ offer another possible solution, but the datasheet
> warns that adding the resistor might cause the internal comparator to
> oscillate, depending on the board layout etc. It certainly seemed
> well-behaved for the very simply check I made - perhaps Dieter can
> offer a more informed view on how good this might be as a solution
> (e.g. if the VCO is being rapidly switched between different
> frequencies, could this cause any problems?).
>
> Tim
>
> [*Fourth* attempt at posting this, so I really hope multiple copies
> don't suddenly arrive...]
>
>
> --- In Doepfer_a100@yahoogroups.com, "Dieter Doepfer" <hardware@...>
> wrote:
> >
> > Dirk,
> >
> > it took a while but now we found the reason and a solution ...
> >
> > We had problems to understand why the combination of A-110
> (rectangle)/A-113
> > is working perfect but not A-111(rectangle)/A-113 at low
> frequencies.
> > Strangely enough the combination A-111(sawtooth)/A-113 causes no
> problems.
> >
> > The reason is the negative slope of the A-111 rectangle ! Our
> oscilloscope
> > showed in high res mode (1us/div) that the negative slope is not a
> single
> > slope but has some ups and downs (a bit like a down-going triangle).
> > Obviously the waveform converter inside the CEM3340 has this
> behaviour as
> > the rectangle output of the A-111 is nothing but the rectangle
> output of the
> > CEM3340 (only via 1k protection resistor and AC coupling
> capacitor). In
> > normal applications this causes no problems and cannot be heard
> (each VCA or
> > VCF or mixer behind the A-111 smoothes this multiple slopes which
> are in the
> > microsecond range). But the A-113 is very fast and detects these
> multiple
> > slopes at low frequencies. This causes the problems of the A-111/A-
> 113
> > combination you described.
> >
> > There are several solutions for this problem:
> >
> > 1. Do not use the rectangle but e.g. the sawtooth output of the A-
> 111 to
> > trigger the A-113 (the sawtooth has no multiple slopes)
> > 2. Process the rectangle output by any other module (VCA, VCF,
> mixer) before
> > it is used to trigger the A-113.
> > 3. Add a capacitor to the A-113 (in parallel to diode D3). We tried
> 2n2 and
> > then the A-113 tracks perfect from about 10Hz. If you contact me
> directly
> > (hardware@...) I can send you a picture that shows the position of
> D3
> > on the A-113 board. In this case even the rectangle output of the A-
> 111 can
> > be used to trigger the A-113.
> >
> > Best wishes
> > Dieter Doepfer
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: Doepfer_a100@yahoogroups.com
> > > [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von vliesgaard
> > > Gesendet: Donnerstag, 27. April 2006 12:35
> > > An: Doepfer_a100@yahoogroups.com
> > > Betreff: [Doepfer_a100] Re: A-113 input sencetivity/tracking
> problems
> > >
> > >
> > > --- In Doepfer_a100@yahoogroups.com, "Dieter Doepfer" <hardware@>
> > > wrote:
> > > >
> > > > OK, I'll check this with an A-111 and A-113. But it may take a
> few days
> > as
> > > > we are very busy with testing and modifying the BBD modules as
> the
> > customers
> > > > are waiting anxiously for their modules.
> > > >
> > > > Best wishes
> > > > Dieter Doepfer
> > > >
> > >
> > > Don't worry, you get the full 100 points for customer service. If
> only
> > > other company's were that good.
> > >
> > >
> > > One use the A-113 is creating interesting rhythms.
> > > E.g. if you divide the 16th notes of the sequenser, with the A-
> 113, by
> > > 2 3 5 and 7 you get a very complex rhythm patern.
> > > Thats why it should track low frequenty's.
> > >
> > > Greetings Dirk
> >
>
>
>
>
>
>
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