MOTM

Today I was watching the LED on my MOTM-101 Noise/S&H module blink merrily
away. It crossed my mind that it would be handy if that clock signal could
be used to drive other things. Sure, you can use an LFO to drive the S&H and
other things, but if you could drive everything from the 101's clock, you'd
free up an LFO for more interesting tasks. So then I noticed that there's
even room for another jack in the lower row of the 101's panel, whereupon my
interest was sufficiently piqued to pull out the schematic.

It looks like tapping the output of the 555 timer would be easy enough. It
even looks like there is an unused section of a TL072 wired as a unity-gain
buffer which could be used to buffer the 555's output, although you'd have
to cut a PCB trace to free the grounded input, which is kind of scary.

Has anyone tried this? Any reason why it's not a good idea? I realize that
the 555-based clock probably isn't as stable as the MOTM oscillator core
found in the 320 LFO, but in many instances it is probably good enough.

--Adam

-- 
Adam Schabtach
adam@...
http://www.studionebula.com     * *  CD now available!  * *

Adam,

You must be reading my mind! :)  I was twiddling around with the 101 S&H
today, sampling a saw wave, and was thinking about how nice it would be to
have a clock out signal to drive an EG for amplitude enveloping, although I
had not yet pursued a plan of action.  It sounds like you are on the right
track.  This modification could certainly be of use to everyone who owns a
101.  It would be greatly appreciated if, once you have a solution, you
would make it available to the list.

Cheers,
George
----- Original Message -----
From: Adam Schabtach <adam@...>
To: MOTM listserv <motm@yahoogroups.com>
Sent: Sunday, November 10, 2002 4:24 PM
Subject: [motm] Adding CLK OUT to MOTM-101?


> Today I was watching the LED on my MOTM-101 Noise/S&H module blink merrily
> away. It crossed my mind that it would be handy if that clock signal could
> be used to drive other things. Sure, you can use an LFO to drive the S&H
and
> other things, but if you could drive everything from the 101's clock,
you'd
> free up an LFO for more interesting tasks. So then I noticed that there's
> even room for another jack in the lower row of the 101's panel, whereupon
my
> interest was sufficiently piqued to pull out the schematic.
>
> It looks like tapping the output of the 555 timer would be easy enough. It
> even looks like there is an unused section of a TL072 wired as a
unity-gain

> buffer which could be used to buffer the 555's output, although you'd have
> to cut a PCB trace to free the grounded input, which is kind of scary.
>
> Has anyone tried this? Any reason why it's not a good idea? I realize that
> the 555-based clock probably isn't as stable as the MOTM oscillator core
> found in the 320 LFO, but in many instances it is probably good enough.
>
> --Adam

It's an easy mod, and I think Dave Bradley at www.hotrodmotm.com has already done it.

Paul S.

----- Original Message ----- 

From: "Adam Schabtach" <adam@...>
To: "MOTM listserv" <motm@yahoogroups.com>
Sent: Sunday, November 10, 2002 3:24 PM
Subject: [motm] Adding CLK OUT to MOTM-101?


> Today I was watching the LED on my MOTM-101 Noise/S&H module blink merrily
> away. It crossed my mind that it would be handy if that clock signal could
> be used to drive other things. Sure, you can use an LFO to drive the S&H and
> other things, but if you could drive everything from the 101's clock, you'd
> free up an LFO for more interesting tasks. So then I noticed that there's
> even room for another jack in the lower row of the 101's panel, whereupon my
> interest was sufficiently piqued to pull out the schematic.
> 
> It looks like tapping the output of the 555 timer would be easy enough. It
> even looks like there is an unused section of a TL072 wired as a unity-gain
> buffer which could be used to buffer the 555's output, although you'd have
> to cut a PCB trace to free the grounded input, which is kind of scary.
> 
> Has anyone tried this? Any reason why it's not a good idea? I realize that
> the 555-based clock probably isn't as stable as the MOTM oscillator core
> found in the 320 LFO, but in many instances it is probably good enough.
> 
> --Adam
> 
> -- 
> Adam Schabtach
> adam@...
> http://www.studionebula.com     * *  CD now available!  * *
> 
> 
> 
> 
> 
> 
>  
> 
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
> 
>

> This modification could certainly be of use to everyone who owns a
> 101.  It would be greatly appreciated if, once you have a solution, you
> would make it available to the list.

I think I'll take a stab at it, particularly now that Paul has described it
as "easy". Once I get around to doing it, I'll take photos as I go and put a
description on my website, and an announcement here.

--Adam

-- 
Adam Schabtach
adam@...
http://www.studionebula.com

The available space for another jack was too tempting, so I planned out this
modification before initial assembly of my MOTM-101.  You have a couple of
options for the clock out signal.  It could just be a buffered INTCLK
signal, which would make the 555 clock available as a separate output.  But
I chose to bring out the signal originating at pin 7 of U7B, which is the
comparator that generates the clock from the external input (normalled from
the INTCLK).  That way the clock out is integrated with the module.  It
yields the signal that is currently triggering the S&H, whatever the source.
Of course if you are not using the S&H output, you can still use the clock
out.

I bent pin 5 of U3 (U3B) upwards before soldering in the chip and wired the
pin later to buffer the output of U7B.  (You also have U8B as a candidate
for the buffer.)   You can select the voltage level of this output.  I made
a voltage divider with a 39K resistor between U7B-7 and U3B-5 and a 15K from
U3B-5 to ground.  That yielded a signal of approximately +/- 4V (a bit
smaller than I had expected, but I didn't redo it).  A 1K resistor connects
U3-7 to the new clock out jack.

This mod requires no trace cutting.  If you do this on an assembled
MOTM-101, you can probably cut pin 5 on U7B close to the PCB and carefully
bend up what's left.  You'd have to solder two resistors to it, if you chose
my approach.

Richard Brewster

----- Original Message -----
From: "Adam Schabtach" <adam@...>
To: "MOTM listserv" <motm@yahoogroups.com>
Sent: Sunday, November 10, 2002 4:24 PM
Subject: [motm] Adding CLK OUT to MOTM-101?


> Today I was watching the LED on my MOTM-101 Noise/S&H module blink merrily
> away. It crossed my mind that it would be handy if that clock signal could
> be used to drive other things. Sure, you can use an LFO to drive the S&H
and
> other things, but if you could drive everything from the 101's clock,
you'd
> free up an LFO for more interesting tasks. So then I noticed that there's
> even room for another jack in the lower row of the 101's panel, whereupon
my
> interest was sufficiently piqued to pull out the schematic.
>
> It looks like tapping the output of the 555 timer would be easy enough. It
> even looks like there is an unused section of a TL072 wired as a
unity-gain

> buffer which could be used to buffer the 555's output, although you'd have
> to cut a PCB trace to free the grounded input, which is kind of scary.
>
> Has anyone tried this? Any reason why it's not a good idea? I realize that
> the 555-based clock probably isn't as stable as the MOTM oscillator core
> found in the 320 LFO, but in many instances it is probably good enough.
>
> --Adam
>
> --
> Adam Schabtach
> adam@...
> http://www.studionebula.com     * *  CD now available!  * *
>
>

I was also just thinking the same thing!!  That space for a jack at the end
of the bottom row is like a rotating neon sign that says "mod me" :)

Anyway, I was also wondering, what is the difference between the 100 and
the 101??  I would look through the archives, if it weren't for all the ads.

At 2:24 PM -0700 11/10/02, Adam Schabtach wrote

>
>but if you could drive everything from the 101's clock, you'd
>free up an LFO for more interesting tasks. So then I noticed that there's
>even room for another jack in the lower row of the 101's panel

>But I chose to bring out the signal originating at pin 7 of U7B,
>which is the comparator that generates the clock from the
>external input (normalled from the INTCLK).  That way the clock out is
>>integrated with the module.  It yields the signal that is currently
>>triggering the S&H, whatever the source. Of course if you are not using
>the >S&H output, you can still use the clock out.

If you are using the external input, wouldn't you already have the clock??

If the internal clock is normalled to the external clock input (which I
pressume you mean by a switched jack), couldn't you simply tap either
signal off the jack??

If I do this mod, I'd have it so the clock out is always the internal clock.

> >But I chose to bring out the signal originating at pin 7 of U7B,
> >which is the comparator that generates the clock from the
> >external input (normalled from the INTCLK).  That way the clock out is
> >>integrated with the module.  It yields the signal that is currently
> >>triggering the S&H, whatever the source. Of course if you are not using
> >the >S&H output, you can still use the clock out.
>
> If you are using the external input, wouldn't you already have the clock??

Not necessarily.  An internal comparator, U7B, processes the external input,
which could be any shape waveform, and turns it into a pulse.  My clock out
mod provides access to that processed input, which is the same timing signal
the S&H gets internally.  If the external input were a pulse waveshape to
begin with, yes, the clock out would be the same waveshape as the external
input.

Another benefit to bringing out the comparator-processed external input is
that you don't need a multiple to drive something else from the external
clock.

>
> If the internal clock is normalled to the external clock input (which I
> pressume you mean by a switched jack), couldn't you simply tap either
> signal off the jack??
>
Yes, but you would not obtain the processing afforded by the comparator.

> If I do this mod, I'd have it so the clock out is always the internal
clock.
>
That's a valid option.  I preferred the comparator output, both for the
processing and for integration with the S&H.  The nice thing about a mod is
that you can do it your own way!

-Richard Brewster

Both are valid options.  There's room for an Int/Ext switch... :)

George
----- Original Message -----
From: Richard Brewster <pugix@...>
To: <motm@yahoogroups.com>; <media.nai@...>
Sent: Tuesday, November 12, 2002 7:03 PM
Subject: Re: [motm] Adding CLK OUT to MOTM-101?


> > >But I chose to bring out the signal originating at pin 7 of U7B,
> > >which is the comparator that generates the clock from the
> > >external input (normalled from the INTCLK).  That way the clock out is
> > >>integrated with the module.  It yields the signal that is currently
> > >>triggering the S&H, whatever the source. Of course if you are not
using
> > >the >S&H output, you can still use the clock out.
> >
> > If you are using the external input, wouldn't you already have the
clock??
>
> Not necessarily.  An internal comparator, U7B, processes the external
input,
> which could be any shape waveform, and turns it into a pulse.  My clock
out
> mod provides access to that processed input, which is the same timing
signal
> the S&H gets internally.  If the external input were a pulse waveshape to
> begin with, yes, the clock out would be the same waveshape as the external
> input.
>
> Another benefit to bringing out the comparator-processed external input is
> that you don't need a multiple to drive something else from the external
> clock.
>
> >
> > If the internal clock is normalled to the external clock input (which I
> > pressume you mean by a switched jack), couldn't you simply tap either
> > signal off the jack??
> >
> Yes, but you would not obtain the processing afforded by the comparator.
>
> > If I do this mod, I'd have it so the clock out is always the internal
> clock.
> >
> That's a valid option.  I preferred the comparator output, both for the
> processing and for integration with the S&H.  The nice thing about a mod
is

> that you can do it your own way!
>
> -Richard Brewster

> Anyway, I was also wondering, what is the difference between the 100 and
> the 101??  I would look through the archives, if it weren't for all the ads.

I was just thinking yesterday about how a mailing list I subscribe to, which
is hosted by www.topica.com, has no advertisements in its email. I don't
know about searching the archives, though.

--Adam

Richard--

Thanks a bunch for describing your clock-output mod. I may well end up doing
the mod your way, instead of tapping the 555 as per my original idea. I
suppose one advantage of using the internal clock signal is that you can
trigger the S&H externally *and* still use the internal clock for something
else. I'm not sure whether or not that outweighs the benefit of using the
comparator-based signal as you describe.

As for cutting a PCB trace vs. cutting and lifting an IC pin, I'm not sure
which I'd rather do. I suppose the advantage of cutting and lifting the IC
pin is that if I really blow it, I can just replace the chip altogether. :-)

--Adam