Friday, 23 April 2010

Patch Tips #9 - A-119 as Frequency Doubler



The A-119 External Input module can be used to double the frequency of an LFO when used for clocking purposes. Here's the how and why:

Patch a square wave LFO to the A-119's asymmetrical input, set the input gain so that no clipping occurs and then adjust the threshold level to attain a 'clean' signal from the gate out.

Here's an example featuring the original and doubled clock:



Because the A-119 features a full wave rectifier to accomplish its envelope following duties, the negative half, or 'off' period, of the square wave is flipped into positive territory, in effect doubling the frequency.

There is a slight delay to the doubled clock, but this is understandable due to the speed of the A-119 and the threshold necessary to avoid a standing, permanent gate.

In the second example, I've also taken the sine output of the LFO and fed to a wave multiplier to get a third, syncopated clock:



Feeding the wave multiplier with a triangle wave will yield different clocks. For more wave-folded beats, see this post.

4 comments:

Josh Kay said...

Wow, my 119 was already getting tons of use as an envelope follower / filter shaper but now, well... I'm just going to have to get another one. Thanks for sharing!

Navs said...

No probs, Josh. I love these sorts of discoveries!

matthew said...

thanks for the inspiring and educational blog! can i ask what you use for the oscilloscope images? is it computer based?

Navs said...

Thanks Matthew. Glad you like the blog.
The scope shots are from the discontinued, but free OSX-only AudioXplorer. SignalScope is better but costs €80.