David,

we found the reason for the problem. After all it's logical but it took a
while to find it out.

Technical explanation: when the clock signal appears (positive transition)
it takes a while until the processor outputs the new address to the
multiplexers. During this short time a "wrong" address is applied to the
multiplexer as still the old address is active until the microprocessor
recognizes the new clock and generates the new address. As the clock signal
is used for the trigger length (clock and the active adresses stage are
"and"-wired) very short "wrong" trigger pulses appear at the address
changes. I discussed this problem with Christian Assall who programmed the
A-154 software. But it seems that there is no software solution as it is
already "too late" as soon as the microcontroller recognizes the new clock
signal (correctly the addresses have to be switched simultaneously with the
positive transition of the clock signal). Though the time while the wrong
address is valid is very short (microseconds range) the A-140 responds to
the "wrong" address if very short attack/decay times are chosen and the
range switch is in the center position. The problem is that the A-140 is too
fast ;-) For a pure hardware solution (like the control section of the
A-155) this problem does not occur as there is no microcontroller that has
to respond to the clock signal.

But we found a (hardware) solution. A capacitor (we successfully used a 1nF
capacitor) between the base of the gate transistor Q1 and GND of the A-140
solves the problem. This simple "low pass" filters out such short pulses in
the microseconds range without affecting the other functions of the A-140. I
can send you a photograph that shows the position of the additional
capacitor that is on the bottom of the A-140 board. If you are able to do
this modification we can send you some of these capacitors (via the
representative in your country). Otherwise you have to send in the A-140
module(s) for this modification.

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto: Doepfer_a100@yahoogroups.com ]Im Auftrag von deastman2
> Gesendet: Freitag, 21. April 2006 03:08
> An: Doepfer_a100@yahoogroups.com
> Betreff: 1 Re: A-154/dual A-155 combination false
> triggering problem
>
>
> Dieter,
>
> Thanks for getting back to me. I don't check that email address very
> often. I'll take this offline with you now.
>
> David
>
> --- In Doepfer_a100@yahoogroups.com , "Dieter Doepfer" <hardware@...>
> wrote:
> >
> > David,
> >
> > I have sent you an email on April 18, 2006 (to you directly) with
> this
> > question and got no answer so far:
> >
> > I have problems to understand what you mean with the extra
> triggers. Does
> > this mean that a trigger appears even if the corresponding switch
> is "off"
> > I could not understand this as the switch interrupts the trigger
> line in the
> > "off" state. Please specify when (at which position) the extra
> triggers
> > appear.
> >
> > Best wishes
> > Dieter Doepfer
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: Doepfer_a100@yahoogroups.com
> > > [mailto: Doepfer_a100@yahoogroups.com ]Im Auftrag von deastman2
> > > Gesendet: Donnerstag, 20. April 2006 07:31
> > > An: Doepfer_a100@yahoogroups.com
> > > Betreff: 1 Re: A-154/dual A-155 combination false
> > > triggering problem
> > >
> > >
> > > Dieter,
> > >
> > > Just a gentle reminder ;) I'm still experiencing this problem...
> > >
> > > Thanks,
> > > David
> > >
> > >
> > > --- In Doepfer_a100@yahoogroups.com , "deastman2" <deastman2@>
> > > wrote:
> > > >
> > > > Dieter,
> > > >
> > > > If the A-155's are configured for standalone operation, they
> work
> > > > correctly. Also, if I put the A-154 in manual mode and clock
> the
> > > > first A-155 with an LFO, there is no problem. But if I use an
> LFO
> > > as
> > > > an Ext. Clock source for the A-154, the problem appears, just
> like
> > > > using the internal clock.
> > > >
> > > > --- In Doepfer_a100@yahoogroups.com , "Dieter Doepfer"
> <hardware@>
> > > > wrote:
> > > > >
> > > > > David,
> > > > >
> > > > > before we continue: does this problem occur only with the
> > > > combination of
> > > > > A-155 with A-154 Or does it occur even with a standalone A-
> 155.
> > > > If the
> > > > > A-155's have been modified earlier (for standalone mode) this
> > > > modification
> > > > > has to be cancelled (i.e. undo). Please refer to page 16 of
> the A-
> > > > 154 manual
> > > > > and the attached document.
> > > > >
> > > > > Best regards
> > > > > Dieter Doepfer
> > > > > Doepfer Musikelektronik GmbH
> > > > > Email address: hardware@
> > > > > Web Site: www.doepfer.com
> > > > >
> > > > >
> > > > >
> > > > > > -----Ursprüngliche Nachricht-----
> > > > > > Von: Doepfer_a100@yahoogroups.com
> > > > > > [mailto: Doepfer_a100@yahoogroups.com ]Im Auftrag von
> deastman2
> > > > > > Gesendet: Donnerstag, 6. April 2006 09:54
> > > > > > An: Doepfer_a100@yahoogroups.com
> > > > > > Betreff: 1 A-154/dual A-155 combination false
> > > > triggering
> > > > > > problem
> > > > > >
> > > > > >
> > > > > > I have an A-154 configured to control two A-155's. I've
> > > noticed
> > > > that
> > > > > > for Trigger Rows 1&2 for both A-155's, some steps seem to
> > > generate
> > > > > > one or more extra, erroneous trigger pulses. I looked at
> the
> > > > output
> > > > > > on a scope, and I see the following:
> > > > > >
> > > > > > Steps 1 and 5 show the main trigger pulse, followed by three
> > > very
> > > > low-
> > > > > > level pulses at the spots where steps 2, 3, and 5 would be.
> > > > > >
> > > > > > Steps 3 and 7 show the main trigger pulse, followed by one
> very
> > > > low-
> > > > > > level pulse at the spot where steps 4 and 8 would be.
> > > > > >
> > > > > > Steps 2, 4, 6, and 8 function normally.
> > > > > >
> > > > > > These extra pulses are strong enough to at least partially
> > > > trigger an
> > > > > > envelope generator controlling a VCA with an osc feeding
> into
> > > it.
> > > > > > For example, with all steps/rows on both sequencers in
> the 'off'
> > > > > > position, except for row 1/step 1 on one seq, I get an
> envelope
> > > > > > trigger at step one, followed by a lower-level trigger at
> step
> > > 2
> > > > (and
> > > > > > in theory, it probably triggers again steps 3 and 5, if the
> > > > envelope
> > > > > > was set properly). These extra pulses stay in sync when I
> > > adjust
> > > > the
> > > > > > clock rate.
> > > > > >
> > > > > > I had this same problem when I first got the sequencers
> back in
> > > > > > January, except at that time, row 3 also had the same
> problem.
> > > > With
> > > > > > only one A-155 connected to the A-154, there is no problem.
> > > > Either A-
> > > > > > 155 will function properly with the A-154, but once they are
> > > > chained
> > > > > > together, the problem appears. I sent the A-154 back to
> > > Analogue
> > > > > > Haven for replacement, and the new one they sent me worked
> fine
> > > > for a
> > > > > > couple of months, until yesterday when this malfunction
> > > > resurfaced.
> > > > > >
> > > > > > Other relevant information: The connecting cables were
> replaced
> > > as
> > > > > > well. The sequencers are all powered by a single new PSU2.
> > > Aside
> > > > > > from the A-100, there is nothing else in close proximity
> which
> > > > could
> > > > > > be causing interference.
> > > > > >
> > > > > > I'm hoping there is a simple answer other than shipping back
> > > more
> > > > > > modules...
> > > > > >
> > > > > > Thanks,
> > > > > > David
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > Yahoo! Groups Links
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > > >
> > > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
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