I've finally decided to get into eurorack modular, because it looks fun and I really like the idea of building your own personal synth... I've been making music for a while now, mostly with a DAW (Reason) but recently purchased some synths. It just feels more real and I spend enough time on the computer already!

My equipement :
- Beatstep Pro
- Microbrute
- Erebus
- Blofeld (desktop)
- Digitakt
- 2 effects pedals (Zoom MS-70 CDR & Boss RV-6).

I'm mostly into ambient, IDM, but also techno and dub techno... Some glitchy stuffs too...

Questions / remarks :
- The case : the TipTop Audio Mantis looks nice and not too expensive. I like the look of the Eowave 104HP studio case too. Any reasons why I should choose one over the other? (besides a stronger and internal power supply for the Mantis, or a cheaper price for the Eowave one).
- I'd like to interface my current setup with the modules, hence the Pico INPUT to get the sounds of my synths eventually. Any opinions on this module? Will it keep the signal clean?
- My audio interface is a Focusrite Scarlett 18i8 that should be able to handle modular levels. Do you advice nevertheless some kind of attenuator / mixer before plugging the outputs of the modular? If yes, why? :-)
- I plan first to get to the "basics" (VCO-VCF-VCA-Envelope...) with the Black Wavetable VCO and the Polivoks VCF, the Z4000 and the Veils. Any opinions on this? Should I start with another combination first?
- The Clouds might be replaced by its successor as I heard it will be out soon.
- Any good suggestions to fill the gaps are heartily welcomed :-) Still looking for some nice effects modules that could also be used with my actual synths.

Thank you for your time and your good advices!

ModularGrid Rack

Hokay...let's get into this. Thus far, the equipment you have on hand makes sense, although using it in tandem with Reason where timing issues are critical might reveal some limitations. I've heard from a lot of professional types that Reason can have problems with timing and sync when dealing with external clocking. My best guess is that Reason varies its latency, so if you start with a fixed latency value and Reason opts to alter this on the fly without warning, your timings between in the box and outside of the box can slip and get a bit sloppy. I've also heard that FL can have issues of the same sort, but not to the magnitude of Reason. And yes, I've used Reason (quite some time back) along with several other DAWs over many years, and I eventually opted to stick with Ableton Live out of experience...which has largely been very positive. So if you notice timing 'slop' starting to ease into your work, suspect Reason first.

  • The case : the TipTop Audio Mantis looks nice and not too expensive. I like the look of the Eowave 104HP studio case too. Any reasons why I should choose one over the other?

OK...with powered cases, you need to take several things into consideration. The most obvious is amperage...a sufficient supply should actually supply more than you need, because some modules can load-spike a bit on power-up, with some being worse than others. You want a lot of margin between your total module draw and the supply's rating...and not only because of this point, but also because letting the power supply 'loaf' will mean less component wear, and that spells better stability and reliability over the long-term. I personally like to overspec power supplies by 1/3rd, but that's an old habit from amateur radio work where amperage draws can sometimes fluctuate sizably and abruptly. +20%, however, is good enough.

Also, check what sort of supply you're dealing with. There's two kinds; in Eurorack, we almost always deal with switching-type supplies. These actually use high-frequency methods of regulating and rectifying incoming AC...and because of this, some of them can be noisy at the DC rail outputs. So if the case in question has a switching supply, you're going to want filtered power busboards...these not only knock down the HF crud from lesser-quality switchers, they also help to remove backplane crosstalk resulting from modules sending crud back down their DC supply lines and dirtying up the power rails. The other kind is linear supplies...the 'gold standard', really. Very clean and stable DC outputs, and usually beefy components are used in these that don't tend to fail from simply being a little touchy. Drawbacks: they're heavier, and they're more expensive. But those are really the only drawbacks; performance-wise, they're a big step up from switchers, and in big 5U systems, you tend to see them much more than switching supplies. Honestly, these days I've been looking a bit more seriously at Erica's powered 126 hp x 2 cabs; sure, they're 200 EUR more than the Eowave, but those Latvians build those things for serious work, with 2.5A on each 12V rail via an internal linear supply. And also, this is a good example of getting what you pay for...with hefty linear-supplied DC being well worth the price!

  • I'd like to interface my current setup with the modules, hence the Pico INPUT to get the sounds of my synths eventually. Any opinions on this module? Will it keep the signal clean?

As noted above, Erica builds serious stuff. The sole flaw I see with the INPUT, though, is that it lacks either an envelope follower (to derive CV from the incoming signal's dynamics...very useful, actually) or a gate/trigger comparator (to send one of those when the incoming audio's dynamics cross a certain amplitude level...again, quite useful as a control source). But if the idea is to just send audio in without deriving any control functions, it'll work well for that.

  • My audio interface is a Focusrite Scarlett 18i8 that should be able to handle modular levels. Do you advice nevertheless some kind of attenuator / mixer before plugging the outputs of the modular? If yes, why? :-)

Here's why: first of all, modular synths can be a bit touchy and unpredictable with signal levels...these can jump around a LOT, from very low, barely audible to (potentially without warning!) 10V RMS or more! If you want to be 100% certain that you can protect the Focusrite (which is a fairly low-end device, not something particularly rugged) from input overvoltage, you WILL need something to step the synth levels down to normal line-levels.

Second: the Focusrite probably has balanced inputs. The patchpoints within a modular are 99.999% UNbalanced (there's a couple of exceptions). These have different impedances, and depending on how touchy the Focusrite is about incoming impedance, it might not like something other than a 600 Ohm balanced incoming signal, resulting in several sorts of irritating outcomes like weird frequency responses, distortion, or even potentially component harm.

Third: ground loops. These are frickin' annoying hums and noises that creep into audio when a signal source is on one ground, but the device it's connected to is on another, and the ground plane tries to establish itself via your audio line. Avoiding this is done in two ways: ground lifts at the connected device (potentially less effective) and balanced and isolated outputs at the source (the 'correct' way). Now, you might argue that if the synth is connected via a DC line from a 'brick' supply, this won't be a problem; if so, you may be in for some annoying surprises, because the ground plane will ALSO try to establish itself via the DC rails under certain conditions, which will destabilize the synth altogether due to AC 'ripple' on the DC supply.

Last: DC offset. You DO NOT want this coming out of your outputs! DC, when fed to amplifiers and speakers in sufficiently high voltages, can cause everything from the infamous 'DC thump' (best known from the ARP 2600, which had DC-coupled outputs) when a signal is present to, under extreme cases, actual electronic damage to amplifiers and PHYSICAL damage to speakers. I've seen this, btw...it's a definite 'oh shit!!!' moment that you don't want to experience!

The solution to all of this is to have an output module that offers some sort of audio isolation, certainly DC isolation, and preferably balanced TRS or XLR output jacks. Best of all are isolator/outputs that offer transformer isolation, as having a little 'iron' in your signal creates very small euphonic harmonic emphases due to transformers' having hysteresis...which is a complex thing I'm not going to explain here (I don't have the time, space, or desire for carpal tunnel syndrome!), but which slightly emphasizes even harmonics in a way that 'warms' the audio and tightens it up without imposing apparent distortion. This, plus attenuation to get the synth-level signals under control, is 100% necessary at a modular synth's output. If you're serious about how your instrument can and should sound, something of this sort is absolutely essential!

  • I plan first to get to the "basics" (VCO-VCF-VCA-Envelope...) with the Black Wavetable VCO and the Polivoks VCF, the Z4000 and the Veils. Any opinions on this?

See https://www.modulargrid.net/e/forum/posts/index/3015 I don't write these things for lulz, after all.

  • Any good suggestions to fill the gaps are heartily welcomed :-) Still looking for some nice effects modules that could also be used with my actual synths.

Well, yeah...but it seems like you need to get to a more concrete stage in build development first. You're missing the Clouds yet assuming Mutable's replacement will be the same form factor (which wasn't the case with the Plaits, which replaced the Braids), and that's not the best way to proceed. Remember: this isn't a race...you're not trying to crash-build something for a gig this coming weekend. Consider carefully...and do some research. Look at others' racks and look at classic modulars to see why they were built the way they were, and with what. Back up first and build several 'sketches'...if one or two look promising, hone in on what makes them promising. And don't be afraid to screw up, because MG has a 'delete' function whereas physical devices and the costs associated with them definitely don't. Good luck!

Thank you Lugia for your detailled answer, really appreciated!

About Reason : as said, I just want to focus on the hardware, so I'm seldom using Reason anymore. Anyway, during the rare times I was using it with the synths, I never noticed any timing issues yet.

The case : the Mantis case has 3A on the +12V distributed over 3 zones (1A each). So I guess there should be enough margin there.

Great tip on the input, I'll have a look at the other options to have more functions, could be useful indeed :-)

For the output : I've read so many different opinions on this, so couldn't get to a decent conclusion. Yours is the most motivated one I found ;-) So an attenuator like the Intellijel triatt followed by an output module (stereo) should do? I've updated the rack with it. There's so many options but I'd like to keep the prices not too high if possible.

Your essay was an interesting read. I plan on using the BSP to send the signals and already have 2 LFOs from my synths so it should get me started... slowly. I just want to build it progressively by starting from the basics. Along the way I might switch to other modules than the ones projected here, I don't know. I'm in no hurry at all as you tend to imply. The Clouds is here for now, we'll see if I like its replacement or not once it comes out, that can wait. This rack is not my first draft and I hit the 'del' button often! I was just to a point where I was satisfied with it and couldn't go any further without asking for opinions first. I'm using VCV rack to get used to the whole modular "concept" and see if it works for me. And Youtube has been a very good friend to discover new modules or check the ones I'd like to have.

Again, thanks for your answer. Cheers!

My advice- unless you have limitless pockets and wads of cash to burn is to RUN AWAY NOW! Just kidding :-)

Eurorack is super expensive. I priced out a basic 10 module system with case and power and it was 4-5k!
I can only imagine a serious 9Ux200HP system costing 20k or more.

Oooh...be careful about how you're reading that Mantis power spec! Tiptop's site says it has 3 x 1A on the +12 rail only; the -12 rail is limited to 1100 mA, and if that's exceeded there'll be problems.

Eurorack power uses bipolar DC supplies for the 12V rails. One side is positive, the other negative, and the 'common' acts more like a 'neutral' line for the bipolar supply purposes. While the +12 rail handles the largest loads as a rule, the -12V rail can add up pretty quickly as well, and BOTH amperage criteria have to be watched to prevent overloading each of the 12V busses. My suggestion is to find powered case solutions where you have suitably large amperage potential on all rails to avoid overtaxing any parts of the power supply setup.

As for the output/mixer issue...if you're going to mix down to mono (which would be what the TriATT would allow), just get a mono output module. Stereo mixers would be better, though, because you're going to want to step up to a spatialized output signal eventually, so my suggestion would be to look into a small performance mixer that allows CV control over audio levels (via exponential VCAs in the mixer), panning, an AUX send/return for paralleling a global effect, and mutes to drop parts of a global patch out to immediately vary the sound. Qu-bit's Mixology is probably the best value in these at present...four channels, stereo, AUX send and return, and so forth, all under voltage control for $399 which is actually pretty cheap when you consider what's built into it. And if you already have a Clouds, running the Mixology output into it, then on from the Clouds (using the Clouds as a post-mix 'playable' processor) to a stereo output would be the way I'd go.

Input-wise, I've found that Doepfer's A-119 is probably the best feature-to-value module of that sort.

Also...when speccing modules, try this trick: divide the module's price by the hp width. The lower you can get the resulting number, the cheaper the overall space utilization becomes. One of Eurorack's little secrets is that when you have room to spread out and use larger-width modules, the price-per-hp tends to go DOWN, so staying in tightly-confined cabs can actually be more spendy with respect to space used than going with something where you can use bigger modules.

Yes I am aware of the different amperage on the +12 and -12, I just mentionned the +12 here because as you said it has the biggest load. For now I have 377mA on the -12V so there's still room too. I'll keep an eye on both for sure, and even on the +5V part!

For the mixer, I was looking at the Black Stereo Mixer from Erica Synths. Less features than the Mixology, but still seems to do the job at mixing stereo and the 4th mono input can provide some panning action.

The Doepfer A-119 looks great, thanks for the tip. I was looking at the Entry Point from Pulplogic but it's more than twice the price.

Yep...the price discrepancy on the Entry Point for the same functions (pretty much) as the A-119 just doesn't make sense, plus you lose 2 extra hp of space to it. Granted, it has that square-wave 'extractor', but if you're not inputting something that has a very pure waveform in the first place, or which has numerous pitches, that's not likely to function properly. Not quite the same thing as a proper P-V converter, which tends to be a bit pricier.

And if we're talking Erica mixers, have you had a look at their Black Output Module? Pricier, but you get a stereo mixer with CV over panning, 3 mono channels and one stereo, a master gain, balanced outputs + a headphone amp, and it only takes up four more hp. That thing is pretty serious, takes care of the output + stereo mix thing, gives you a proper stereo in for the Clouds. $150 more, but I think you get your money's worth on that, given that the Black Stereo Mixer is roughly $150 and a stereo output will run another $75-100 for something decent. Plus the panel width used should be the same.

(Later): OK, I banged on it a little...several modules went away, and the goal here was to jack the functionality up as much as I could in a small space. 6 EGs (two AHDSR, two ADSR w/ inverters, two AD), 6 VCA (Intellijel Quad ($10 cheaper than Mutable's) and two linears), 6-channel mixer for sources, added a Maths, condensed the effects while breaking them out a little for some separate processing. Kept the Clouds, added the Black Output v2, plus also crammed in a ring mod and waveshaper, and cleaned up the signal flow. Here 'tis:
ModularGrid Rack

Thanks for your proposition! I'll have a closer look at it.

Maths was on my list, but couldn't manage to fit it in. I'm hesitating a lot between the Pico DSP and the Black Hole DSP which comes with more controls and effects.

What I like about the Dual ADSR are the extra options (EOD, cycle), but Maths seems to have similar options.

I don't know where you live, but here everywhere I look the Veils is 20 to 40€ cheaper than the Intellijel Quad!! :-P

USA...makes sense, since Mutable's in the EU and Intellijel is Canadian and subject to NAFTA tariff relaxations. Same difference, though...they're pretty much interchangeable.

Right...in fact, Maths is more complex, because you also have CV over 'rise' and 'fall' rates, allowing you to CV-shape the resulting output curves on the fly as part of your patch. Basically, it's a module that's derived from the classic Serge Dual Universal Slope Generator...and as such, you can use it as an envelope, complex function gen, LFO, or even an actual VCO at a pinch!

As for the 3hp Erica DSP...think carefully here: most of your signal paths tend to be mono, but the DSP has a mono in and stereo outs, meaning that not only is it an effects processor, it's also where you can generate a stereo signal to feed both channels of the Clouds. I jammed that in like that so that you could take a mono signal, stereoize it for the Clouds, then pass the Clouds on to the stereo channel of the Erica mixer. Thinking in signal chains like that is a real key to getting maximum function out of a build!

I have changed the setup I'm aiming for quite a lot :
ModularGrid Rack

I already have the mantis case and the following modules :
Doepfer A-119 to input other synths. This will eventually be removed once I have some sound sources in the rack.
Erica Synths Black Hole DSP & Pico RND.
MI Veils.
Intellijel Triatt.

Any advice / opinions on this version? The hardware I have so far (cf first post) still holds.

Thank you you expert knob twiddlers!

That's a damn fine build there! All the bases are getting hit with this, and there's even a few quirks that just make SO much sense, like the CV switch (awesome tool for generative work!), plenty of VCAs, lots of break-out-able mixer/attens, little hidden function bits, and so forth. It's a really rich sandbox, usable for most anything, and a great example of what you can jam into a smaller cab with some diligent MG work!

Thanks for your feedback Lugia!

This comforts me in my planning. Aside from buying modules new, it's important to have a good build so I can plan ahead and be able to react quickly if a module comes up on second hand!