Hello. I have quite a bit of experience with "old school" modular synths (ARP, Moog), but this is my first foray into the world of eurorack.
My current design: 
It's a pretty straight-foward synth at the moment, which is fine with me. After I get this built, I would anticipate adding more modules in a 2nd cabinet (that's not a problem is it?)
Any comments or suggestions would be very much appreciated.
Thank you in advance,
Greg
I note the absence of VCAs here...even with designs that replicate the old-school East Coast architecture, you're gonna want a few of those. My suggestion would be to yank the Chatterbox and panners, then put in a stereo VCA mixer that has the panning functions on CV, and use whatever space is left for a couple of linear, DC-coupled VCAs for CV amplitudes. Also, you might consider a bit of a nod to the West Coast (and adding some killer functionality) by pulling the A-145 and 146 and replacing them with Doepfer's A-171-2s. They're basically a rework of the Serge VCS via Ken Stone's redesign. I'm supposing you're planning on using in-line mults. Lastly, have a look at Expert Sleepers' FH-2 as a substitute for the Doepfer A-190-3...much more flexible, and expandable to boot.
And as for the second cab...what? You're considering stopping at TWO?
Lugia - thank you very much for this. I mistakenly believed the 2 VC panners were also VCA's. Will update, and definitely research your other recommendations - thanks again. Much appreciated.
Technically, they are VCAs...sort of. They're implemented in such a way that they have (as a rule) two VCAs with an inverter in the control line of one. Each VCA gets an equal input signal feed, and the control signal works so that if one VCA is opening, the other is closing. In that arrangement, though, they're a pain to use for amplitude control. Plus, panners tend to use linear VCAs which, because our hearing reacts to sound pressure as loudness in an exponential manner, don't really work well for controlling the amplitude in audio lines. Exponential VCAs work best for that, although you can use linear VCAs if you're controlling them with an exponentially-weighted control signal, like an exponential envelope.
Plus, consider going with a VCA arrangement upstream from your final mixer that allows you to CV manipulate individual VCO outputs. With that Quad VCO, you could pair up an Intellijel Quad VCA which also functions as a 4-1 mono CV mixer, and with the right VCA control inputs (maybe using Doepfer's A-144 Morph Controller?) and VCO tunings, you can do things like swept additive harmonics over fundamental-type combinations from the other VCOs. Or a lot of other things besides!
This is really great information. Thanks for all these ideas. Lots to consider.
So, I've gone in and made some changes based on your recommendations. One additional question - would you think that the Toppobrillo 4-chan vc stereo mixer (lower right) would be suitable for use as a VCA? I like the VC panning function.
Again, many thanks for your insightful advice.
Yep, that's an excellent choice! Not only does that give you VCA audio level control, you also get the panning under CV and CV on your AUX send as well. With that 2hp Verb, that's perfect...just patch the AUX send on the Toppobrillo to the Verb's Left input, and you get one-point stereo out. Patch that to your AUX returns, and you've got full CV over the reverb! Note also that the CUE send can work here, too...for example, patch that to the frequency shifter, and return that via a strip on the mixer, and you can drop signals in a similar manual AUX path from your cue sends. Just be careful to NOT activate the cue on that one strip for the frequency shifter, or bad feedback happens (unless you think that might be fun! as in...cue out to delay, delay to frequency shifter, FS to strip one with cue on, and manually control the feedback of that loop to get stairstepping pitch-shifted echoes of your other thru-cue signals! nuts!).
The other changes are primo, too! I see you went with the VCA control over the Quad VCO trick...that'll be loads of fun. Plus the VCSs. Yeah, this is shaping up to be a killer rig...
Lugia - thanks again for all the great advice and information. Very much appreciated.
