MOTM

It's true that a meter should just meet your needs, otherwise you are 
throwing away good module money.  I suppose if you don't know your needs in 
advance (and are rich) you can buy a very accurate meter.  Maybe Paul will 
say what accuracy is needed for the MOTM module tuning.

Some tuning procedures, like the 1V/oct calibrations, require not only an 
accurate frequency counter but also a calibrated 1 volt source.   So you 
first have to calibrate your voltage source.  Then you check for 1V/oct 
response in multiple octaves.  If you are twisting a multi-turn trimpot, 
you have to go back and forth over the best spot several times to get the 
closest setting.  I guess my point is that meter accuracy buys you only so 
much and the rest is careful procedure.  If your meter or your procedure 
(or maybe your ear) is off, the result will be off.  It all comes down to 
what sounds right to the ear.  I calibrate sine wave shapers by ear, even 
though I also use a scope to view the waveform.

Why not get a "cheap" meter to start with and if you really notice that the 
accuracy is not sufficient for your needs, then buy a better one.  It never 
hurts to have two meters, either.  Meters that cost $30 today are as good 
or better than what we paid $200 for twenty years ago.  I've been happy 
with my $30 Craftsman Model 82139.

-Richard Brewster

At 05:51 PM 8/29/03 -0500, John Loffink wrote:
>A new Extech 5/6 digit handheld multimeter is only $229 at
>Future-Active.  It has the highest frequency resolution I've seen at
>that price.  Do you need this for building MOTM modules - well, probably
>not.  Your ear is a fine tuned instrument when it comes to frequency
>deltas.  For tuning VCOs you use a calibrated source such as MIDI-CV
>converter, and then tune to octaves by ear.
>
>Now if you're using the meter to tune notes, such as VCOs driven from
>analog sequencer stages, the meter becomes more critical.  More
>inexpensive meters have lower accuracy than your MOTM VCO, typically 1
>Hz or 0.1 Hz resolution and 1% or 0.1% accuracy.  Paul published some
>tracking numbers showing at 800 Hz the MOTM-300 was within .03 Hertz of
>perfect tracking.  You can translate this to say your meter would need
>better than .03 Hertz resolution and better than .03/800 x 100% =
>.00375% accuracy to measure this.  Now even my Extech isn't that
>accurate, but it's close. To put it another way, a 0.1% accurate meter
>is only guaranteed to measure from 799.2 to 800.8 Hz for that perfect
>800 Hz signal.
>
>Bottom line is, decide whether you need this accuracy in a meter and
>then check the specks of any potential purchases.  For tuning a cheap
>instrument tuner might serve you better.
>
>John Loffink
>The Microtonal Synthesis Web Site
>http://www.microtonal-synthesis.com
>The Wavemakers Synthesizer Web Site
>http://www.wavemakers-synth.com