With the Maths, you have some possibilities to modulate the envelope. However the Math only has a rise and fall... so basically attack and decay. The Neutron has four stages per envelope. So if you're looking to replicate the Neutron's envelope generators, that might be hard with The Maths module. It will sound different.
To get closer, I would try something like a TipTop Z4000NS. You get CV control over all four stages, plus the "deviator" offset. The Z4000 is a little trickier to use as the deviator and attenuator always come into play. But that's the module I'd pick. The Maths is a good pick, don't get me wrong. But I can see you having an awesome patch on the Neutron then trying to swap out EGs and not being able to replicate the Neutron's envelope with the Maths.
-- Ronin1973
The Z4000NS looks like what i would want from an ADSR env, plus its 8hp and not expensive at all. I might throw it in the rack, but keep Maths as well.
For the output module, why not looking at a mixer+out+headphones out ?
In fine, you might end up with several voices when you'll get another vco
I started with a 4ms listen four and i replaced it by a XOH (with a XPAN before to increase the XOH limited mixer capabilities and save space)
The Quad VCA before the Out will do the job in the first time but as your rack will grow out, the needs of VCAs as well
However listen to the pro, I am still a beginner
-- anglr
When I'll add another VCO i'll need a lot of other modules including more VCAs, a filter or a LPG, maybe envelope generators etc. But that won't happen very soon. I'll be looking at a dedicated mixer then and at the end of the routing i'll always just need some "modular level to line out". I'm also looking at Lifeforms Outs as a cheaper alternative to Intellijel Outs, i have no idea about the sound quality on both modules tho.