MOTM

hello all,

i just remembered an idea that came to me as an offshoot to that voltage
source module, and my question to the list is:

would a fixed precision voltage source be practical for tuning purposes - ie
derive the reference voltage for A-440Hz, and just put it out on a jack - to
aid calibration of vcos you could even go as far as make up several switch
selectable octaves

any ideas..? or does experience out there find these things impractical /
innaccurate..?

cheers
paul b

Hmmm, I don't think so. The "1V/Oct" standard describes a rate of 
change in pitch, not an absolute voltage per frequency. There's no 
notion of "3.64V = A440". Different VCO designs will oscillate at 
different pitches with zero volts at the CV inputs. You depend on an 
arbitrary setting on the Coarse and Fine tune pots (which themselves 
are just CV sources going to the same CV inputs) to get you to a 
specific pitch.

There were various VCO scaling procedures offered to this list back 
in the archives, around the time the 300 was first released. There 
are sort of 2 camps, the "use a precision multimeter" camp and 
the "use your ear and listen for the beats" camp. One good way to get 
multiple reference octave pitches is to run a VCO into the 120, and 
use the 4 suboctave outputs to tune a second VCO against.

I prefer to use my ear. It's quite a sensitive instrument if you have 
a reference pitch to tune against.

Moe

--- In motm@egroups.com, "sikorsky" <vulture.squadron@s...> wrote:
> hello all,
> 
> i just remembered an idea that came to me as an offshoot to that 
voltage
> source module, and my question to the list is:
> 
> would a fixed precision voltage source be practical for tuning 
purposes - ie
> derive the reference voltage for A-440Hz, and just put it out on a 
jack - to
> aid calibration of vcos you could even go as far as make up several 
switch
> selectable octaves
> 
> any ideas..? or does experience out there find these things 
impractical /

> innaccurate..?
> 
> cheers
> paul b

Dave is right--the 1v/8va is a VCO control and won't help you with tuning
per se.

I've thought about getting a cheapie tuner and mounting it onto an MOTM
panel for tuning. Or even a frequency counter since they build them into
VOMs cheap these days.

Carlos' Moog used to have, I believe, a reference oscillator. Basically a
panel with a jack that put 440 out. I guess you would have a crystal-based
fixed-pitch oscillator in there or something.

From: Dave Bradley <daveb2@...>

> Hmmm, I don't think so. The "1V/Oct" standard describes a rate of
> change in pitch, not an absolute voltage per frequency. There's no
> notion of "3.64V = A440". Different VCO designs will oscillate at
> different pitches with zero volts at the CV inputs. You depend on an
> arbitrary setting on the Coarse and Fine tune pots (which themselves
> are just CV sources going to the same CV inputs) to get you to a
> specific pitch.

ah, i was just thinking (specifically in terms of my #300 vcos) that as my
181 keyboard gives out a specific voltage when you press "A", then i could
duplicate that voltage for convenient tuning
but come to think of it, i think i missed the all important second portion
of the idea which was to also provide a tuning reference, which makes the
whole thing way too complicated and hence useless - damn
which is exactly what i bought a frequency counter for in the first place

cheers
paul b
(off to think up some other stupid idea)

Frequency counters in most sub-$200 VOMs are not very accurate, especially
at audio frequencies.  For $70-$100 you can pick up from ebay an old HP
frequency counter 5314A (labeled "Universal Counter") that has pretty good
accuracy, to 0.1 Hz.  It also has A/B inputs for ratio comparisons, so you
can tune oscillators perfectly to octaves or any other ratio.  It's great
for tuning to perfect ratios, for instance a perfect fifth is 3/2 = 1.5, and
a perfect fourth is 4/3 = 1.33333, etc.

John Loffink
microtonal@...


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

From: "Tkacs, Ken" <ken.tkacs@...>
To: <motm@egroups.com>
Sent: Thursday, January 18, 2001 2:20 PM
Subject: RE: [motm] Re: more voltage sauce again


>
> Dave is right--the 1v/8va is a VCO control and won't help you with tuning
> per se.
>
> I've thought about getting a cheapie tuner and mounting it onto an MOTM
> panel for tuning. Or even a frequency counter since they build them into
> VOMs cheap these days.
>
> Carlos' Moog used to have, I believe, a reference oscillator. Basically a
> panel with a jack that put 440 out. I guess you would have a crystal-based
> fixed-pitch oscillator in there or something.
>
>
>
>
>

I agree, the reference voltage won't do much good for tuning.  Rather than get a
frequency counter, I think the best solution is to spend the $100 or so on a Korg
DTR-2 Rack tuner.  They are worth every penny and look cool too!  I keep a patch
cord plugged between an input on my DTR-1 and an oscillator all the time.  I have
been able to tune multiple oscillators without listening to them and found them to
be dead on when I turned up the volume.

Eric

--- Microtonal <microtonal@...> wrote:
> Frequency counters in most sub-$200 VOMs are not very accurate, especially
> at audio frequencies.  For $70-$100 you can pick up from ebay an old HP
> frequency counter 5314A (labeled "Universal Counter") that has pretty good
> accuracy, to 0.1 Hz.  It also has A/B inputs for ratio comparisons, so you
> can tune oscillators perfectly to octaves or any other ratio.  It's great
> for tuning to perfect ratios, for instance a perfect fifth is 3/2 = 1.5, and
> a perfect fourth is 4/3 = 1.33333, etc.
> 
> John Loffink
> microtonal@...
> 
> 
> ----- Original Message -----
> From: "Tkacs, Ken" <ken.tkacs@...>
> To: <motm@egroups.com>
> Sent: Thursday, January 18, 2001 2:20 PM
> Subject: RE: [motm] Re: more voltage sauce again
> 
> 
> >
> > Dave is right--the 1v/8va is a VCO control and won't help you with tuning
> > per se.
> >
> > I've thought about getting a cheapie tuner and mounting it onto an MOTM
> > panel for tuning. Or even a frequency counter since they build them into
> > VOMs cheap these days.
> >
> > Carlos' Moog used to have, I believe, a reference oscillator. Basically a
> > panel with a jack that put 440 out. I guess you would have a crystal-based
> > fixed-pitch oscillator in there or something.
> >
> >
> >
> >
> >
> 
> 
> 
> 


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In a message dated 1/18/2001 12:45:02 PM, ken.tkacs@... writes:

>I've thought about getting a cheapie tuner and mounting it onto an MOTM
>panel for tuning. Or even a frequency counter since they build them into
>VOMs cheap these days.

A frequency counter would be cool to have, but probably not (as Jon said) 
accurate enough to be helpful. What I have is a mid/cheap priced chromatic 
tuner which is much more accurate than my ARP keyboard. I'm thinking about 
getting one for each synth and just having them in the corner or on an open 
space like there is on the MOTM 900.

John Barlow
(a sheep dreaming of electric androids -- sauce for the gander)

Ive got a Korg CA-20 chromatic tuner mounted on  the front of my 900 PS this
way.  Works for me and 14$! to boot.
Jim

jwbarlow@... wrote:

> In a message dated 1/18/2001 12:45:02 PM, ken.tkacs@... writes:
>
> >I've thought about getting a cheapie tuner and mounting it onto an MOTM
> >panel for tuning. Or even a frequency counter since they build them into
> >VOMs cheap these days.
>
> A frequency counter would be cool to have, but probably not (as Jon said)
> accurate enough to be helpful. What I have is a mid/cheap priced chromatic
> tuner which is much more accurate than my ARP keyboard. I'm thinking about
> getting one for each synth and just having them in the corner or on an open
> space like there is on the MOTM 900.
>
> John Barlow
> (a sheep dreaming of electric androids -- sauce for the gander)