[sdiy] New Oakley Flanger/Chorus module

[Oakley Sound]

 > …but *seven* trims? Are all those really necessary?

In my opinion, yes. Although, if you set them all to their mid-points 
the module would still work well enough for a lot of folk.

So the seven trimmers...

Two for each of the BBDs - input bias/offset voltage (essential for 
minimising distortion if you want as large a dynamic range as possible 
especially across the three makes of 3207 out there) & output balancing 
(probably could have dropped this one)

Two for the 1V/octave VCO - scale and tune.

One for feedback adjustment - partly to allow users to decide whether 
their module self-oscillates and partly because different 3207s do seem 
to have differing insertion losses.

It takes about five minutes to do. It's pretty easy really so long as 
you have a scope with a frequency counter.

Going back to input bias voltage - I found that the V3207, BL3207 and 
MN3207 all required different offsets to get the best out of them. 
Although the differences were not that great at lower clock frequencies 
the differences between the Coolaudio ones and the others were more 
pronounced at clock frequencies over 400kHz.

I did have a more complex system by which the clock CV altered the input 
bias voltage - shifting the bias voltage as the delay time was changed. 
This worked quite well. However, the additional increase in headroom was 
pretty minimal and I decided the extra complexity (and trimmer) wasn't 
worth it.

Tony

www.oakleysound.com