Design Goals

I learned a lot of what not to do in the construction of the original OGEE.

• Portable - half a ton instead of a whole ton! {:o)
• Solid construction - so it doesn't fall apart when it is transported!

The original OGEE suffered from broken wires when transported across country in a U-Haul.
• Only "useful" modules.

The original OGEE had a number of modules that sounded neat on paper, but proved to be useless: Switched cap filter, variable slope filter, MUX.
• Pre-configured, overridable patches.

Preconnect modules in a "standard" patch that is the basis of 80% of what I usually do. Connections can be overridden at inputs by plugging in a patch cord.
• Dedicated LFO's and VCA's where appropriate.

VCO's all have dedicated LFO's for PWM. VC Pan, Sample & Hold. VCA on LFO module output tied to midi Mod wheel control. Final VCA on output mixer tied to midi Velocity control.

og3!

Because og2 is not a modular synth, most of the modules have to be completed before I do my backpane PCB's and the front panel. In the meantime, I also have found some other circuits and modules that I wanted to try that would fit in the og2 case. Hence, og3! I picked up a nice rack case and am building a true modular synth. I also wanted to test out my front panel construction techniques before tackling the big one on og2.

Why I still use CEM and SSM chips

Because they're there!

TomG commented on my (old) site once and remarked that they needed to wean me off the CEM and SSM chips. Unfortunately, it looks like I'm still hooked because og2 is full of 'em.

I'm not trying to build a commercial synth here, so I don't have to worry about future supply of parts (well, unless I happen to blow one and need a replacement). Synthesis Technology still carries a number of CEM chips. I wanted to try a couple of the "newer", still available chips, specifically the CEM3374 dual VCO and the CEM3389 VCF/VCA/VCPan. Also, when I decided not to try to resurrect the original OGEE, that meant its parts were available.

I get a significant parts count reduction using integrated synth chips, and I am trying to save space here. I get two full range tri/saw VCO's on one 3"x3" PCB (well, I did add a couple of waveshaper boards too)!

Often the dedicated synth chips produce better modules than what I could build from scratch.