PLAN B analog blog

Peter-

I have two of the Model 15 oscillators, both of which have pots that behave a bit oddly -- the 
"morph" pot seems to jump from pure sine wave to the secondary waveform pretty instantly 
(not a smooth transition at all).

Also on one of them the pulse width knob only ranges from around 4 to 6; it's silent if you 
turn it further in either direction. The pulse width on the other kicks in at around 2-3 and 
runs fine all the way to totally clockwise.

I know that the oscillators are all a bit different but is this behavior normal?

Thanks -- Michael

Michael,


Have a look through the archives of this yahoo group - there are 
various comments/explanations about this.

feel free to contact me offline if you have further quesitons.

- P




--- In PLAN_B_analog_blog@yahoogroups.com, "michaeltritter" 
<mtritter@...> wrote:
>
> 
> Peter-
> 
> I have two of the Model 15 oscillators, both of which have pots 
that behave a bit oddly -- the 
> "morph" pot seems to jump from pure sine wave to the 
secondary waveform pretty instantly 
> (not a smooth transition at all).
> 
> Also on one of them the pulse width knob only ranges from 
around 4 to 6; it's silent if you 
> turn it further in either direction. The pulse width on the other 
kicks in at around 2-3 and 
> runs fine all the way to totally clockwise.
> 
> I know that the oscillators are all a bit different but is this 
behavior normal?

> 
> Thanks -- Michael
>

Hello!

I find this: "My PWM does the same thing only works between the 10-3 
positions, but I think you need to have an wave inputted above the 
PMW dial?" How do the PWM knob behave then? Is a dummy plug enough? 
Is there more?

Best regards
Jari Jokinen  

--- In PLAN_B_analog_blog@yahoogroups.com, "(i think you can figure 
that out)" <peter@...> wrote:

>
> Michael,
> 
> 
> Have a look through the archives of this yahoo group - there are 
> various comments/explanations about this.
> 
> feel free to contact me offline if you have further quesitons.
> 
> - P
> 
> 
> 
> 
> --- In PLAN_B_analog_blog@yahoogroups.com, "michaeltritter" 
> <mtritter@> wrote:
> >
> > 
> > Peter-
> > 
> > I have two of the Model 15 oscillators, both of which have pots 
> that behave a bit oddly -- the 
> > "morph" pot seems to jump from pure sine wave to the 
> secondary waveform pretty instantly 
> > (not a smooth transition at all).
> > 
> > Also on one of them the pulse width knob only ranges from 
> around 4 to 6; it's silent if you 
> > turn it further in either direction. The pulse width on the other 
> kicks in at around 2-3 and 
> > runs fine all the way to totally clockwise.
> > 
> > I know that the oscillators are all a bit different but is this 
> behavior normal?
> > 
> > Thanks -- Michael

As with alot of VC inputs which control a function that also has a
maual control such as a pot, once a VC iis inserted, the pot acts like
an offset to that external control.

Pots can generate either a voltage or current based on how they are
configured.  If the specific function requires a voltage pot, then a
VC can be added with the simple addition of a jack and a resistor.
It's too easy to pass up, therefore it's done quite alot.  For
instance, all VCOs with Frequency pots (name one that doesn't have one
of these!) and a VC frequency input is handled this way.  Inside,
these two are configured as a summer...think of it as a mixer, with
the voltage-producing pot hardwired into one channel, and an external
VC input into the other side. This is how the Morph, Frequency and PWM
circuits operate on the M15.  The pot is a voltage divider hardwired
into one side of two input voltage mixer, the external  VC input is
the other.  Since the pot produces a constant voltage (the specific
level your wiper position dials up), that voltage serves as an offset
to the VC input, which can if you want it ot be, be alternating - in
motion.  

I scaled the pots on the M15 as I did purposely because the offset it
produces with a VC input allows that input to have more control over
the pulse width than if the pot wasn't configured that way.  All the
things you can do with the PWM input for instance when the pot is set
outside the normal audible range would be unavailable.  I found it to
be unique and this was appealing to me.

The problem lies not in the funtion of the pot, but the fact that I've
not got off my ass and composed manuals for these instruments, which
is criminal.  I really need to do that.

best,

- P