Vintage Synth Repair

Normally I calibrate a synth using my Boss TU-12H tuner which works
over a wide range and is very portable.  However, this weekend I
was calibrating a Jupiter-8 and discovered something.  After going through
it with the tuner, I powered it up and started playing some widely spaced
chords to hear the oscillator interaction.  The beating was very unpleasant.

I decided to use my scope and tune by the Lissijous (sp?) method.  I
created a 220, 440, 880, and 1760 sine waves in Cool Edit and ran the
output into one scope trace and the synth output into the other. 

The end result was that I tuned the synth faster and it sounded better
using that method.  Since the JP-8 is not necessarily the most precise
instrument across all the octaves, there was still some beating, but it
was more 'musical' sounding.  Unless I started replacing components, I
don't think I can eliminate all beating across 16 VCOs across 8 octaves.

What do you guys use for tuning?  Anyone using a strobe tuner?  How does
that compare for 'real world' sound and speed?
-- 

_______________________________________________________________________
Tom Moravansky                                    tom@...

Isn't it a known fact that to get a musically useful tuning you cannot
go by a perfect mathmatical tuning?  Seems to me I remember that if you
tune "by the numbers" on a freq counter you will get odd harmonics and
beating.  But if you tune "by ear" you will find that the numbers aren't
exact on the freq counter, but it will be far more musically useful.

If anyone knows of a web page where this is documented fully, let us
know.  I'd be interested in seeing the math.

Rob

>>> tom@... 03/18/02 07:13 AM >>>
Normally I calibrate a synth using my Boss TU-12H tuner which works
over a wide range and is very portable.  However, this weekend I
was calibrating a Jupiter-8 and discovered something.  After going
through
it with the tuner, I powered it up and started playing some widely
spaced
chords to hear the oscillator interaction.  The beating was very
unpleasant.

I decided to use my scope and tune by the Lissijous (sp?) method.  I
created a 220, 440, 880, and 1760 sine waves in Cool Edit and ran the
output into one scope trace and the synth output into the other. 

The end result was that I tuned the synth faster and it sounded better
using that method.  Since the JP-8 is not necessarily the most precise
instrument across all the octaves, there was still some beating, but it
was more 'musical' sounding.  Unless I started replacing components, I
don't think I can eliminate all beating across 16 VCOs across 8 octaves.

What do you guys use for tuning?  Anyone using a strobe tuner?  How does
that compare for 'real world' sound and speed?
-- 

_______________________________________________________________________
Tom Moravansky                                    tom@...


To unsubscribe from this group, send an email to:
vintagesynthrepair-unsubscribe@egroups.com

 

Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

> Isn't it a known fact that to get a musically useful tuning you cannot
> go by a perfect mathmatical tuning?  Seems to me I remember that if you
> tune "by the numbers" on a freq counter you will get odd harmonics and
> beating.  But if you tune "by ear" you will find that the numbers aren't
> exact on the freq counter, but it will be far more musically useful.
> 
> If anyone knows of a web page where this is documented fully, let us
> know.  I'd be interested in seeing the math.

It is a fact that the human ear isn't quite linear in this respect - the
perception of octaves gets closer together as you get higher. But this
only really starts to get noticeable really quite high up! You will find
that people like violinists just do this naturally when pitching very high
notes. I am not sure whether pianos and such get tuned like this or not.

As far as beat frequencies go, they're down to pure mathematical
relationship, just like Lissajous, they are also what make nice intervals
sound nice, simple ratios like 2:1, 3:2 and so on. The less simple the
ratio is, the more dissonant the interval, in general. Tuning by ear will
produce nasty beat frequencies the higher up you go, as you are deviating
from the clean ratios. So, I think the problem here lies in the accuracy
of the electronic tuner rather than the human ear effect.

Apologies if I'm teaching grandma to suck eggs here ;-)

Regards,
Matt Nolan.

--- Matt Nolan <matt@...> wrote:
> It is a fact that the human ear isn't quite linear
> in this respect - the
> perception of octaves gets closer together as you
> get higher. But this
> only really starts to get noticeable really quite
> high up! You will find
> that people like violinists just do this naturally
> when pitching very high
> notes. I am not sure whether pianos and such get
> tuned like this or not.

With regard to pianos, yes, it's called "stretch
tuning".  I remember once reading Donald Fagen of
Steely Dan bemoaning the fact that you can't stretch
tune a synthesizer...

BaM

=====
This message has been brought to you by the little ASCII art duck who never stopped complaining: o< THIS SUCKS

__________________________________________________
Do You Yahoo!?
Yahoo! Sports - live college hoops coverage
http://sports.yahoo.com/