[sdiy] How DCOs work

[Richie Burnett]

Thanks for the link Adam,

> At 29:00 he asserts that an inverted sawtooth sounds better in the bass 
> end than a regular sawtooth - I’ve never heard that before.

It seems like a funny statement to make because signals get inverted in many 
places along the signal-chain between an oscillator and the loudspeaker!

However, it could be true if there is something non-linear in the signal 
path that he did the testing with.  Remember that even loudspeakers can be 
quite non-linear, and contribute quite a lot of distortion particularly at 
low frequencies.

When low-frequency sawtooths get passed through AC coupling capacitors 
several times they end up looking more and more like this:

http://i.stack.imgur.com/Ir86Q.png

(The sawtooth waveform out of most synths will look like this if you play it 
low enough.)  It still sounds like a sawtooth, but you can see that the top 
and bottom halves are not symmetrical any more.  Now, if you pass that 
through something that clips one side of the waveform more than the other, 
you will get a different result depending on which way up the waveform is. 
For example, in the linked picture there is a bit of clipping at the bottom. 
If the waveform had been inverted, the curvy part of the "sawtooth" wouldn't 
reach anywhere near low enough to get to this clipping level.

-Richie,



-----Original Message----- 
From: Adam Inglis
Sent: Sunday, October 09, 2016 11:22 PM
To: synth-diy DIY
Subject: [sdiy] How DCOs work

I found this video interesting. It explains how DCOs work and the 
differences between the DCOs found in the Juno 60, 106, Akai AX 80 and the 
Kawaii SX240...
https://www.youtube.com/watch?v=mqY6cVJS9fo

He shows how some DCOs are “more analogue” than others, due to the 
implementation of the master clock.
He then goes through the schematics of said synths highlighting the relevant 
circuits.
At 29:00 he asserts that an inverted sawtooth sounds better in the bass end 
than a regular sawtooth - I’ve never heard that before.


Tom of course has a great page on the Juno DCOs
http://electricdruid.net/roland-juno-dcos/

I guess the most recent application of this technology is the Deep Mind 12

AI


p.s.  he also has a great video on repair/modding an Akai AX 60 - it looks 
simply stunning with red LED faders!





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