[sdiy] Midi oscillator!! (ot)

[Sean Ellis]

Did you just call Tom a troll? His webpage is an incredible treasure trove 
of synth diy stuff. With the recent thread about midi synced oscillators it 
might be good for you to read his section detailing the exact workings of 
the Juno series DCOs.
http://www.electricdruid.com/index.php?page=info.junodcos

Cheers,
Sean

----- Original Message ----- 
From: "cheater cheater" <cheater00 at gmail.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, July 15, 2008 11:09 PM
Subject: Re: [sdiy] Midi oscillator!!


> Successful troll is successful
>
> On 7/15/08, Tom Wiltshire <tom at electricdruid.net> wrote:
>>
>>  On 15 Jul 2008, at 20:05, Samppa Tolvanen wrote:
>>
>>
>> > I know midi is 31.25k Bauds a second, but You can divide all the 
>> > important
>> > frequencies from that, right?
>> >
>>
>>  No, not really. The Juno 106 uses what is basically a divider-based
>> oscillator for its DCO, but it clocks it at 1MHz in the worst case, and 
>> at
>> 4MHz in the higher range. A shade over 31KHz isn't even close.
>>
>>  You won't have anything like enough frequency accuracy as you go up the
>> range. Think about the number of steps in each octave:
>>
>>  Octave 1:  31250 / 1000 = 31.25Hz
>>  Octave 2:  31250 / 500 = 62.5Hz
>>  Octave 3:  31250 / 250 = 125Hz
>>  Octave 4:  31250 / 125 = 250Hz
>>  Octave 5:  31250 / 62 = 504Hz
>>  Octave 6:  31250 / 31 = 1008Hz
>>
>>  As you can see, there are 500 hundred different frequencies I can 
>> generate
>> in Octave 1, but only 250 in octave 2. This gets worse as I go up, until 
>> I
>> only have 31 frequencies in octave 5. It'd be nice if these lined up with
>> quarter tones, but they won't. On top of that, errors in the division 
>> creep
>> in by octave 5, where the true value should be 62.5, but I have to divide 
>> by
>> 62.
>>
>>
>> > I'm not looking at making any existing solution obsolite
>> >
>>
>>  No, you're not!
>>
>>  Regards,
>>  Tom
>>
>>
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