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Sunday, July 18, 2010

More on the trimmers

I thought I'd better clarify a bit on the trim pots. The VCO proper has 10 trim pots. Here is the Prototype PCB layout:

Min pulse width
Max pulse width
Phase sync trim
DC offset for the sine output
Sine shape
Sine shape bias
Triangle shape
Volt/octave trim
DC offset for the saw output
DC offset for the triangle output

More than other VCOs I've ever seen or built, but reasonably straight forward to set. The single turn trimmers visible in the photo on the edge of the PCB are simply surrogates for the panel pots. I used these because I thought it would simply be easier to deal with than a bunch of big pots with flying wires.

The next step for the VCO is to verify I can actually set the V/Oct trimmer and get it to track. I would like to verify the sync input, too.

Before I post the schematics, I need to add a provision for an onboard LED to provide a minimum load for the regulators if needed. Then as soon as I verify and triple check the component values, I'll order what I hope to be the last prototype and then this one should be ready to go.

There are only two more modules which are more complicated. The other ones, even the filter, are really pretty straight forward and I think they will turn around fast. The sequencer and the frequency divider will take more time. The sequencer just because of quantity, the divider because of complexity.

I think there is real reason to get the sequencer done soon if not next on the list. Nyle is very interested in having the sequencer well documented and he is excited to get it done, more than enough reason for me to put some effort into it. After that, I think the EGs, VCA, and VCF definitely need to be done as they are the core of any modular. The others are pretty simple and will come later.

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