I was looking for a budget semi modular and after a lot of search, I ended up with Behringer Neutron, one of the best budget choices to experiment with modular synthesis.
Neutron is equipped with 3340 VCO, the clone of the legendary CEM3340 found in analogue classics of the late ’70s and early ’80s. Lot's of other stuff you'd expect from a semi-modular synth are included. Sine, triangle, sawtooth and square with independent width control, an additional tone mod setting allows further tweaking. Furthermore, oscillator sync, white noise generator plus the ability to freely mix between the two sound sources and an external audio source to the oscillator mix, located in the rear panel; Neutron delivers, with sound-wise, amazing results and functionality! On top of that, the quite big patch bay, perfectly located. Connectivity with other modular synths is of course available, that renders Neutron an absolute component in bigger modular setups (connecting cable provided). Also, it can be mounted on a Behringer modular synth rack. Having said that, Neutron can be used as a standalone unit or connected with a keyboard/sequencer controller. But even without a controller, it can do amazing things.
Neutron has a con however, an annoying problem that I sincerely hope will/can be fixed in future firmware updates. It has to do with the onboard delay unit that kills some frequencies, making the sound duller when applied! In my case that is not an actual problem as I'm using an external delay, but nevertheless, it is a problem.
I'm a harsh noise artist, so I wanted something... harsh and believe me, Neutron can be quite harsh in a very positive way! That vitriolic little beast loves industrial music, loves noise, loves harsh stuff. Neutron can give you some scorching sonic annihilation, even without external pedals/effects but in the same, a full arsenal of quiter/softer sounds with endless tweaking possibilities. Of course, no save preset function is available, something expected from a modular synth. But fear not, huge databases with settings can be found online, making your experimentation horizon endless.
The overall sound of Neutron is spectacular, it delivers in any way possible and remember, it is a budget synth. There isn't something more you'd want in that money.
Last but not least, the design/color, which I personally love but has gotten some harsh criticism. But that is not a problem after all as you can buy an aftermarket faceplate of your choice.
Final words: a highly recommended piece of gear for the beginning of your modular synth experiments, if you are after a synth with a more modern sound.