The Cyndustries List

Thanks, Cynthia.  I found the trimpot easily.

I ended up with a setting close to the original factory setting. But I 
was not able to fix a problem of the ZO tracking sharp in the lower 
octaves of the high range. I started down this calibration road because 
I noticed that the ZO and the MOTM-300 being used as the FM source in 
the starter ZO patch were not tracking each other well.  The beats were 
quite noticable.  I spent a couple of hours taking measurements, after 
setting the 1V/oct trimpot.  Here's what I found.

I measured with a digital voltmeter and a digital frequency counter.  
For comparison I performed the same tests on the MOTM-300 VCO.  The 
results were all obtained by the same method and instruments, using the 
same power supply.  I created a 1V source by a mixer with bias (my own 
mixer-comparator) and measured for 1V at the 1V/oct input jack.  For 
each reading I dialed up a frequency, applied 1 volt and recorded the 
new frequency, which ideally is double for the next octave.  For the ZO 
I did this in all four combinations of High/Low Bias and High/Mid 
range.  I only measured what I could dial up that started in the audio 
range. Each number pair below represents the HZ value before and after, 
so 30/60 means 30HZ/60HZ.

Low Bias/Mid Range
30/60 - right on
60/119.8

Low Bias/High Range
30/66
60/123.2
120/241.5
240/480 - right on
480/957

High Bias/Low Range
30/60.2
60/120 - right on
120/239.7
240/478.4

High Bias/High Range
30/66
60/124
120/243
240/482
480/960 - right on
960/1916
1920/3825

MOTM-300
30/60 - right on
60/120 - right on
120/240 - right on
240/480 - right on
480/960 - right on
960/1918
1920/3834

The ZO tracking isn't bad, but it isn't great either.  The ZO starts out 
on the low end tracking more than one octave per volt (sharp), passes 
the sweet spot and starts going flat gradually.  By contrast the 
MOTM-300 tracks perfectly over about six octaves and then also start 
going a little flat.  Now this flatness on the high end may be by 
design, due to psycho-acoustic effects, I seem to recall. I'm not a 
music VCO expert. But sharpness on the low end isn't good.

For my ZO the tracking is accurate over at best about three octaves.  
The lower octaves track better in the low range and the higher octaves 
track better in the high range.  This was a useful finding.  Of course I 
tested only my own ZO, so I can't say whether this is the general 
character of a ZO or not.  Still, I would be interested to hear from 
other ZO owners whether they are able to replicate my findings.

-Richard Brewster

http://www.pugix.com







Cynthia Webster wrote:

>Hi Richard!
>
>First, please be quite certain that it is the ZO and not rather
>that another oscillator (or keyboard) in your system being slightly off...
>
>The Zeroscillator 1volt/octave trimmer is located on the top
>board where the power plugs in.   If you locate the logo
>saying Cynthia CYN109-C and rotate the ZO so that this logo is
>reading right side up, then the trimmer is the first one to the left,
>(right after the Tempco).  It is a multi-turm trimmer laying flat.
>
>The other two trimmers next to it are for shaping the sine wave.
>
>We also have a precision Volt to the Octave Calibration Gadget
>in the works as a new product which should help tune-up all of
>the oscillators and keyboards in any system.
>
>We're planning a revision to the manual soon to include more
>infoon the power connector, and the trimmers etc, but we've been
>way busy building Zeroscillators night & day instead! 
>
>Best Wishes!
>
>
>Cynthia
>
>http://www.cyndustries.com/
>
>
>Richard Brewster wrote:
>
>  
>
>>I've discovered my ZO is a little bit off on the 1V/Oct tracking.  It is
>>more apparent at lower frequencies.  It would be handy if the manual
>>pointed out the location of the 1V/Oct trimpot.  I haven't tried looking
>>for it yet, but I will.
>>
>>-Richard Brewster
>>
>>http://www.pugix.com
>>
>>    
>>