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: 1 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
>