hello and welcome to the list!
thank you for your valuable info,.you seem to know a
lot about the a100!as for the gate signals in a100,are
you sure that the gate signals are from 0volts to
12volts i thought that they were from 0volts to
+5volts...anyway if you are right,then your theory
explains the problem with the a150/151 and clock
signals...
synthfreak2000
[doepfer_a100]group moderator

--- stinchcombe_t < tstinchcombe@... > wrote:

> Hi everyone. I'm a relative newcomer to the A-100
> scene - bought mine
> last September and its getting bigger with alarming
> rapidity! I was
> going to post this on the Doepfer website forum, but
> (at last) found
> the exact address of this one by accident, and
> decided it would be
> better here. It relates to the compatibility of the
> A111/115/117, as
> discussed in some old messages in the other forum
> ('A117 with A111',
> 'Most hated...'), so apologies in advance if I'm
> going over old ground
> (I've not had chance to spend that much time looking
> back at old stuff
> here...)
>
> In both the 117 and the 115 the input signal is
> merely switched
> through a transistor in order to produce a 'squared
> up' pulse which is
> then fed into the appropriate chip (4006 shift
> register in 117, 4024
> binary counter in 115). The 'rise time' of the
> leading edge of each
> pulse depends on the 'quality' of the input signal,
> and is quite
> critical to the correct operation of the module. The
> recommended rise
> time for the 4000 series family chips is 4 microsec
> at 10V supply down
> to 1 at 15V - we have 12 volt supplies so our
> target is somewhere in
> between. On my 117 if I feed a low frequency sine
> wave in it is quite
> possible not to get any output at all (i.e. similar
> to problem
> reported by 'jim' I guess, with A111, 11/28/01) -
> investigation shows
> that the shift register chip just doesn't run at all
> (it's designed to
> run at frequencies up to about 30MHz, so we're just
> toying with it
> really!). Slowly cranking the frequency of the sine
> wave up has the
> effect of decreasing the rise time, and when it gets
> to about 3 or 4
> microsec, lo and behold, it will burst back into
> life! (To be fair it
> must be said it is obviously much happier with a
> square wave as
> input!) The effect on the 115 seems similar - the
> binary counter seems
> to 'miss a beat' now and again, which you can hear
> as clearly 'a not
> properly divided' signal. The square wave coming off
> the CEM3340 chip
> in my A111 is pretty awful - square is hardly the
> correct word, it is
> well rounded, and becomes more so with increasing
> frequency, so it
> doesn't really drive the 117 particularly well
> either.
>
> Two solutions: there are 2 modules that can help get
> around this - the
> idea with both is the same: stick the signal through
> some nice CMOS
> logic that'll give a lovely 'sharp' pulse out. The
> A150 is probably
> the simplest - square wave into CV input;+5V, -5V
> into the two inputs
> (I use a 129/3 as a simple CV source, plus an
> inverter - a 176 or 174
> would do just as well);then patch output into the
> 117 (or 115). This
> certainly gives the 'playable noise' effect with the
> 117 using the 111
> on my system. Alternatively the divided output from
> the A163 probably
> comes off a chip (I've not checked in detail), but
> that is nice and
> square - just set it to divide by 1.
>
> Overall I'm having great fun with my A100 - learning
> lots about sound,
> music (I'm not a musician) and electronics - I love
> it! I'm expecting
> to get a copy of Chowning's paper on Frequency
> Modulation soon, and
> then I intend to really start exploring the linear
> FM input on the
> A111 (and it will be interesting to see what
> limitations analogue
> places on it, rather than doing it digitally!).
>
> I also have a question of sorts - do people find
> their questions
> eventually get answered through this medium I only
> ask as looking
> back at some old posts here I noticed a query about
> the A-150/A-151
> inability to switch clock pulses. The answer I think
> is in the manual
> - they will only cope with signals less than 8 volts
> (shown in a
> diagram somewhere - this is from memory!), and
> generally clock pulses
> go from ground to supply, i.e. 12 volts, and this
> will upset the
> circuitry somewhat, and it allows some of the signal
> through.
> Depending on where you're trying to send them,
> simply attenuating the
> signal (e.g. A-138 linear mixer) might do the trick.
>
>

=====
synthfreak(parallel worlds)
athens-greece
1 group owner-moderator

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