PLAN B analog blog

Bakis,

As always., great to hear from a fellow Greek!

I have noticed this anomaly as well...when my M15s were in mounted
close to my one remiaing Blacet VCO.  Please try this, as it fixed the
problem for me (admittedly a bandaid of sorts):

Move the PWM pot of the module you suspect to be bleeding over to te
M15'a to full CWQ or CCW - enough for that squarewave to be locked out
of oscillation (held full pos or neg).  This takes care of it, atteast
on my system. ,  

As far as what's causing it, is it terrible to say I'm not 100% sure?
 How's that for honest?  One thing I do know, M15's do not cause other
M15's to do this, and I've made special precautions to limit the
amplitude of the square outs well short of the power rail of the op
amps driving them. My suspicions are there are a few square wave
vco/lfo's out there that are not attenuated - that run from rail to
rail. This causes havoc on any power system, much like when LEDs are
not properly current limited and I believe my VCO is especially prone
to picking up on that.  

Most PWM circuits run on the same prinicple as a manual one shot
comparator.  The PWM pot sets the threshold, and the incoming waveform
(non square wave) goes into the other side of the op amp.  This config
allows anything in the incoming wave which is greater in amplitude
than the pot setting to pass to the output as a high.  Problem is, 
unless you design it differently, that high will be at the rail - the
same amplitude as the voltage powering the op amp.  this fluctuation
in current then ricochets through the entire power system.  SOme
istruments are sensitiive to this, some aren't.

The Model 1 power buss I think may take care of this problem.  The
first run of these (50) are arriving in about a week's time form our
PCB vendor.  I'll give you all an update at that time.

When tim allows, I will do some experiements with increasing the value
of the two main bypass caps on the VCO engine bard - currently 10mFs.

- P

hello peter,
since i bought my two model 15 vco's (which sound
great, btw) i noticed that a kind of cross modulation
appears (or maybe linear fm mod?) coming from another
circular changing cv source that is mounted in the
same rack.
at first, i had my model 15's near the dual cyclotron
and the cyclotron lfo's seemed to affect, very
slightly, the pitch of the two model 15 vco's. the
effect was very very slight and did not cause any real
problem.
now i have my two model 15's mounted next to my ZO and
the ZO seems again to affect the two model 15's. it
sounds like the model 15's are cross-moded by the ZO
with a low modulation index. the effect is not
noticable in low and mid frequency pitches, but only
in higher pitches, that some extra harmonics are
introduced and added to the model 15 raw waveforms.
ok, not a real problem, but i was wondering what
causes this cross-mod of the model 15's with the
nearby module.
the rack is ok, as i had changed racks and the PSU
can, for sure, handle the total current draw as it is
a PSU2 and i have estimated the module's current draw.
so, any thoughts?
thank you,
best regards,
Bakis.




Bakis Sirros - Parallel Worlds
[Doepfer_a100] group owner
http://www.parallel-worlds-music.com
http://www.myspace.com/parallelworldsmusic
http://www.shimarecords.co.uk
http://www.rubber.gr
Athens-Greece

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com

i think you can figure that out wrote:
> When tim allows, I will do some experiements with increasing the value
> of the two main bypass caps on the VCO engine bard - currently 10mFs.

Tims and bards, shall I get out the coconuts and english swallows?

;0)

-Brandon

------------------------------------------------------
NOTICE: Due to Presidential Executive Orders, the National Security Agency
may have read this email without warning, warrant, or notice. They may do
this without any judicial or legislative oversight. You have no recourse
nor protection save to call for the impeachment of the current President.

Undoubtedly some sort of subconscious meaning behind that. :-)

Tim J  ->plan b assembler

>
>i think you can figure that out wrote:
> > When tim allows, I will do some experiements with increasing the value
> > of the two main bypass caps on the VCO engine bard - currently 10mFs.
>
>Tims and bards, shall I get out the coconuts and english swallows?
>
>;0)
>
>-Brandon
>
>------------------------------------------------------
>NOTICE: Due to Presidential Executive Orders, the National Security Agency
>may have read this email without warning, warrant, or notice. They may do
>this without any judicial or legislative oversight. You have no recourse
>nor protection save to call for the impeachment of the current President.
>

hello peter,    :-)
yes, you're right! one model 15 does not affect the
other model 15 of mine! only other modules affect the
model 15 pair of mine.
but, anyway, thank you for the info and i'll just set
the PWM knob to 0 or 10 when i am using other waves of
the model 15's.
regarding the pulse/ PWM waves, i will have to stick
with this cross-mod. but it is ok. it reminds me a bit
of my VCS3's that many modules affect other modules in
unknown ways...     :-)
many thanks,
best regards,
Bakis.



--- "(i think you can figure that out)"
<peter@buzzclick-music.com> wrote:

> Bakis,
> 
> As always., great to hear from a fellow Greek!
> 
> I have noticed this anomaly as well...when my M15s
> were in mounted
> close to my one remiaing Blacet VCO.  Please try
> this, as it fixed the
> problem for me (admittedly a bandaid of sorts):
> 
> Move the PWM pot of the module you suspect to be
> bleeding over to te
> M15'a to full CWQ or CCW - enough for that
> squarewave to be locked out
> of oscillation (held full pos or neg).  This takes
> care of it, atteast
> on my system. ,  
> 
> As far as what's causing it, is it terrible to say
> I'm not 100% sure?
>  How's that for honest?  One thing I do know, M15's
> do not cause other
> M15's to do this, and I've made special precautions
> to limit the
> amplitude of the square outs well short of the power
> rail of the op
> amps driving them. My suspicions are there are a few
> square wave
> vco/lfo's out there that are not attenuated - that
> run from rail to
> rail. This causes havoc on any power system, much
> like when LEDs are
> not properly current limited and I believe my VCO is
> especially prone
> to picking up on that.  
> 
> Most PWM circuits run on the same prinicple as a
> manual one shot
> comparator.  The PWM pot sets the threshold, and the
> incoming waveform
> (non square wave) goes into the other side of the op
> amp.  This config
> allows anything in the incoming wave which is
> greater in amplitude
> than the pot setting to pass to the output as a
> high.  Problem is, 
> unless you design it differently, that high will be
> at the rail - the
> same amplitude as the voltage powering the op amp. 
> this fluctuation
> in current then ricochets through the entire power
> system.  SOme
> istruments are sensitiive to this, some aren't.
> 
> The Model 1 power buss I think may take care of this
> problem.  The
> first run of these (50) are arriving in about a
> week's time form our
> PCB vendor.  I'll give you all an update at that
> time.
> 
> When tim allows, I will do some experiements with
> increasing the value
> of the two main bypass caps on the VCO engine bard -
> currently 10mFs.
> 
> - P
> 
> 
> 
> 


Bakis Sirros - Parallel Worlds
[Doepfer_a100] group owner
http://www.parallel-worlds-music.com
http://www.myspace.com/parallelworldsmusic
http://www.shimarecords.co.uk
http://www.rubber.gr
Athens-Greece

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com