Building first modular synth - minimum modules required?

Hi All,

Having gone down the rabbithole on the LMNC YouTube channel, I’ve decided to start building a modular synth (I’ve built guitar effects pedals for 10+ years and actually found the channel searching for info on the Valvecaster AKA Safety Valve).

My plan is to first build the simplest modular synth I can (i.e. one each of the modules “essential” for making a usable noise) and then add new modules over time.

Having spent the last couple of months drinking from the internet firehose, I wanted to get someone’s opinion on what this “minimum set of modules” should be. So far I have researched (and ordered the parts for):

A couple of (probably quite “naive”) questions that I’m hoping some people here can help me out with:

  1. What additional (“essential”) modules do I need that I’m missing? An envelope filter? Anything else?
  2. (Probably a stupid question) - what do I plug headphones into that would allow me to listen to the synth? It’s still not completely clear in my head how I actually get sound out of it - do I need an amp? A mixing desk? Something else?
  3. Are there any good DIY solutions to the rails that you screw the modules into when attaching them to your case? The eurorack-style ones I can find online seem expensive, and I’m concerned that using a wooden batten will get chewed up over time.

Any help on this would be appreciated :slight_smile:

Thanks in advance,



A typical/simple synth voice is going to have a VCO and VCF (which you have) and also an envelope generator and a VCA.

Although not required to make noise, you’re also going to want a way to control the pitch on the oscillator (sequencer, stand-alone controller like a beatstep, or even an LFO)

The outputs will be ‘hot’ or line level. No good for headphones but you could plug it into your amp with low gain or make yourself a little headphone output

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Your observations are correct. Aluminum rails are relatively expensive. Wood rails present problems if you want to remove or rearrange modules much.

I think most people in this community (versus almost none in Eurorack, even Eurorack DIY) opt for wooden rails and wood screws. I use aluminum rails, and would not want to put up with wood, but they’re not cheap. (On a per inch basis the cheapest are Vector rails bought in a package of four 60" pieces and cut to length, but that’s a lot of modules’ worth and is a large upfront investment.)

Here is a third option, if you have access to the equipment for it:


As for modules: With a VCO and a filter, you can get sound, and you can vary the quality of the sound, but it’ll be a continuous tone – no separate notes, no variation in loudness. For that you need a VCA to change the loudness (from max to zero), and you need something to tell the VCA what to do — most commonly an envelope generator.

Sam has a simple EG:

and a VCA but it’s kind of odd (tube based! but with no high voltage) and from some messages here it seems some people have had difficulty with it: . You might do better with VCA from Bergman’s site or one of those places. (LMNC has boards and panels for a couple more conventional VCA modules but it sounds like you’re looking for stripboard stuff?)

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I have a stripboard layout for the LM13700 based VCA on MIAW ( search youtube for modular in a week if you haven’t seen it already) they aren’t great - but they’re an easy build and work. (they sometimes leak a bit and the bias is touchy which is why I say they aren’t great.)

Details in my build thread along with the stripboard layout: My first DIY modules - starting a Kosmo format build

A simple LFO is also nice to have when you’re first putting things together. There’s one in my thread but I’m really not happy with it. In fact a better LFO is high on my list of things to build next. I have the LMNC 1145 and it’s amazing…but…it’s kind of too much for a lot of things. Though as others have mentioned a sequencer, MIDI to CV converter or some other controller with CV outputs is also really helpful to have and something you’ll pretty much need at some point.


LFO is nice to have, but if we’re talking “essentials”, I think an envelope generator probably is essential while an LFO isn’t. Unless it’s drones you’re going for, in which case the LFO comes out ahead.

Rene Schmitz has some simple VCAs though you’re on your own if you want stripboard layouts:


An LFO isn’t essential - but I did find it very helpful to have one for quick gratification when building my first modules. It was nice to be able to verify the CV inputs on my first oscilator and filter did something - and having a simple LFO was a quick and easy way to have something I could use as a constantly changing CV source for confirming things were working.

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Yes a LFO can be cool too to test if you have no sequencer for triggering VCA or ENV

so for me : VCO/ VCF / ENVELOPE GEN / VCA / (LFO) / ( and i want to add a sequencer but …)

This is for a “standard” synthesizer voice
but it really depends on what you are looking for.

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If you get a looping envelope generator like the ADSR sam sells, or another VCO tuned way low, you really can get by without an LFO as well.

If we are talkin bare bones, id buy a 2nd OSC before a LFO for this reason since its versatile.


@analogoutput do you have a link for the 4 pack of 60" vector rails you mentioned?

Search for Vector TS600 on Mouser.

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Hmm. The Amazon listing seems to indicate it’s no longer available there.

and “0 in stock” at DigiKey

but 46 available, cheaper! at Mouser

Octopart shows sparse pickings elsewhere

This’d better not be an indication Vector rails are going away.


I knew Mouser had them because I just bought two packs :grinning:


and apparently not the last 2 packs …

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Thanks everyone - seems that I have some research to do on VCAs and Envelope Generators (recommendations welcome - and doesn’t have to be stripboard, happy with just a schematic I can get a PCB fabbed for).

I had been looking at the Safety Valve v2 (AKA “Valve Distorting VCA”) but the build reports in this forum seem a bit mixed so I may need a few more builds under my belt before I tackle it.

As for the euro-rack style rails, I may have to live with chewed up wooden batons for a while and save my funds for PCBs and components :slight_smile:


Although the safety valve is technically a vca it’s more of an effect/distortion module if you ask me

The LMNC envelope is nice, some extra bells and whistles compared to a simple EG. As @Caustic noted you can put it on loop mode and it’s now an LFO. Vca would be a really easy stripboard and you could probably more or less forget about once you get your setup


Wooden rails need care. Use a braddle (how do you spell it) or drill a small pilot hole before screwing and wood filler on old holes.

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there’re a lot of source in this forum, that for me a good VCA


Time to necro… Is there a good place to get nuts for these?

Not many. I get them here.

(No idea why it’s saying Canada, they’re in California.)