Dieter,

Thank you for tracking down the source of this problem. I should be
able to make the modifications myself, but I want to be clear about
what needs correcting. You mentioned adding a capacitor to the A-140
(ADSR) board. Do I really need to modify every module which might
receive a trigger pulse from the A-155 I have seen the same problem
when the A-155s are triggering an A-160/161 , as well as an A-143-1.
Is there any way I can make the modifications to my two A-155 modules
instead

Thanks,
David

--- In Doepfer_a100@yahoogroups.com , "Dieter Doepfer" <hardware@...>
wrote:

>
> 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
> >
> >
> >
> >
> >
> >
> >
>