The Cyndustries List

Hi there John and other trackers,

John L., we repeated your measurements, but this time we used the
appropriate range setting for low audio which is the MEDIUM range
setting.  You are stretching the LFO range into boy's choir territory.
 For the same frequency range you used, we measured our octave ratios at:

volts   ratio
-1
0     2.009
1     2.003
2     2.007
3     1.996
4     1.999
5     1.989
6     1.981

This shows 6 great octaves and a usable 7th.  Now, why aren't there 10
good octaves?

The topology of the Zeroscillator core is unlike any conventional VCO
sawtooth or triangle core.  The current that runs the core is the
result of arithmetic computations that are all performed in analog --
most critically, a multiplication.  This multiplication (which I have
covered in a previous post) does not exist in conventional VCOs and
because of its very prescence, is a small source of error.  The
multiplier used for this task is the finest one available in the free
world, period.  Additionally, issues of dynamic range loom large in
the design trade-offs that must be made to bring you the absolutely
outrageous amount of modulation this oscillator offers.  Techniques to
maximize accuracy are covered in the Zeroscillator manual.

We have 15V of power supply to work with (Euro versions have 12V). 
Everything has to happen within that space.  Improved accuracy can
always be traded for modulation range.  The HIGH BIAS position
provides 1V of bias and the LOW BIAS position provides about 0.2, if
I'm remembering correctly.  This means in HIGH BIAS we can attain
about 1000% modulation before the multiplier will be taxed for
accuracy (at about 10V).  In LOW BIAS we get about 5000%.  Considering
that 100% is the most you can ever get from a conventional VCO (and
most designs restrict the range to far below that), this is pretty
darn exciting.  The BIAS switch is not there to change frequency
range.  It's there because of accuracy tradeoffs.   To get improved
accuracy you could pump 5V into the LINEAR FM input to give the
multiplier more to work with.  The accuracy will get better at the
expense of the modulation range being reduced to about 200% which may
still be enough for the sound you are looking for.

To answer another question, yes, a precision voltage reference is used
for all critical internal voltages.  The power supply rejection was
tested and found to be superior to the Modcan oscillator.  John Ross
is responsible for adding to the design, the most comprehensive power
supply cleansing I have ever seen on an EM module.  We could have just
regulated down to +/-12V, but that too would have cost us range.

There have been other attempts at thru-zero, analog VCOs in the past.
 None of them turned into products because although they did the FM
thing, none of them tracked well enough to be accepted.  I found the
ZO's tracking to be quite adequate to make any sound I desired along
with a Modcan VCO as a modulator.  Personally, as a user, I have no
complaints with the ZO's performance, and as an engineer, I have held
nothing back about the ZO's operation and design tradeoffs.  We are
doing something in analog that has been traditionally believed to be
the sole property of digital and I believe we have pulled it off well.

In choosing an oscillator, one always compares features and specs, but
comparing the ZO to a traditional oscillator is like comparing apples
and oranges.  They're both fruits, but if you need citrus, an apple
isn't going to cut it.  You can be about the measuring or about the
music.  The Zeroscillator offers sounds that are unobtainable from any
other commercially available analog module in the solar system.  It's
up to each individual musician to decide what is important.  The units
are flying off the shelves and the feedback we are getting from users
ranges from sheer delight to ecstatic euphoria.

--Mark Barton