Review: Expert Sleepers ES-8 Interface

We’ve talked a lot about Expert Sleepers’ products in recent months. And there’s a good reason – their products seem custom-made for the Max + Modular enthusiast. Gregory has discussed the ES-3 and ES-6 CV interfaces, and Tom has talked a bit about the Disting (and its use for some conversion functions). But recently Os (Andrew Ostler – Expert Sleepers’ mastermind/designer/developer) released the ES-8, which is my perfect interface module.


What exactly do these Expert Sleeper modules do? Well, they take the audio signals generated by your computer (in our case, from your Max patch…) and converts it into voltage values that allow interaction with your modular system. This may seem easy, but there are several details that can snag you with other audio interfaces: you might see that DC voltages are blocked by the interface (meaning that CV control options are limited), or that the levels are simply too low to be useful for modular control. Thus, having a purpose-built interface can solve many problems – and that’s what Expert Sleepers has built its business upon.

This module combines the input and output functions of the ES-3 and ES-8 while also providing USB interface functionality – making it a plug-and-play, 1-cable interface between your modular and Max! So what’s in there, and how well is it working?

What’s in the box

What do you get with the ES-8? It’s simple: it is a 4-in, 8-out audio interface with a USB connection to your computer, and lightpipe connections for expansion. Whoopie, right? Well, there are a few details that make it an excellent addition to my modular/studio combo:

  1. It is properly scaled for Eurorack operation, so everything works in a modular system without much scaling.
  2. It is DC-coupled for both input and output, so it is a great option for both audio and CV routing between your computer and your modular (and especially Max!).
  3. It’s an 8HP Eurorack thing, so it is always there, always part of your modular, and always ready to be brought into your patch!
  4. It’s a tight, smart package that is perfect for the Mac-based Max user (sadly, not yet ready for Windows, because there are no drivers yet available…).

Why is this different?

In fact, having your audio-for-modular interface embedded into the Eurorack system has a few nice benefits, and most of them are related to motivation. I don’t know about you, but whenever I have to start patching a lot of external devices into my modular system, it seems less likely to be a patch that I’ll be willing to keep patched for a long period of time. By having the interface embedded into the modular itself, there is clarity about it being part of the modular ‘system’, and therefore part of the patching environment.

Another key aspect is that the output of Max is tightly tied to the output of the interface, making output scaling much easier to deal with. If you’ve tried using an audio interface as a CV control, you know the frustration of running scaling functions to set the pitch curves, then dealing with the inevitable mismatches of output to scaled value. In the case of the ES-8, there is no separation between the audio value and the CV output, so it is simple to set up well-calibrated pitches. In my case, a simple scale object is all that was needed to get a 10-octave range from computer to modular, and I never once had to calibrate anything.


Of course, depending on the stability of your synth’s power supply and the calibration of your ES-8, your mileage may vary. But I found this the easiest way possible for integrating Max pitched output into my modular rig short of a MIDI-to-CV converter, but the ES-8 provides so much more in terms of flexibility!

Finally, the ES-8 provides some of the most useful indicators possible; the jacks of the module light up in to show the voltage found at that jack!


This means that you can always see what’s happening for each of the inputs and outputs (and you can even see the results if a cable is patched into it…), giving you a lot of feedback on the modular-to-computer linkup without having to have a bunch of metering modules. This is super-helpful when debugging patches, and it just awesome in use.

Interfacing with Max (and MFL)

Interfacing with Max couldn’t be easier. It’s just an audio interface, so you just use a dac~ and adc~ to talk to the interface, make sure the ES-8 is plugged into your computer and selected as the Max audio interface, and start shooting values back and forth. The range of -0.5 through 0.5 within Max will output values from -5 VDC to +5 VDC, which is the typical range I wanted to work with. If you push Max’s whole +/- 1.0 range, you get an output range of +/- 10 VDC, which can be useful for control voltages and triggers (if not pitch).

If Wishes were Kisses…

Expert Sleepers has developed a smart product here, and it checks off most of the boxes that my friends and I are looking for. By being creative with the metering/feedback (using the lit jacks), keeping the width to 8HP and building in flexibility (via ADAT connectors and headers for a ES-5 expansion), users are presented with a ton of capability in a reasonable amount of rack space.

About the only thing that I need are some Windows drivers. I really like using my Lenovo Yoga for live gigs – it works well lid-down, and makes me feel hardware-only even when I’m engaged with Max. But no Windows driver means no Yoga. Boohoo!


Nevertheless, I’m excited about adding the ES-8 as a core tool in my modular. It means that a certain class of modules (loopers/standard effect/ultra-reverbs) don’t need to live in my case – I can use the best-of-class tools I already use with my creative laptop/software rig, and I don’t have to waste case space on duplicates of the things that Max does well (or even better). I also have the whole world of Ableton/Max for Live/standalone hardware that can get integrated into the setup, and the options are expanding. I’m not sure I could recommend any interfacing hardware more highly.

Jan 03 2017 | 10:36 am

Looks fantastic indeed!

I read on the muffwiggler forum that he may add a "standalone mode" at some point, allowing you to use it as you would an ES-6 (i.e. running adat into your sound card, instead of making an aggregate device), which would make this the perfect device for me (instead of an ES-3/ES-6 combo which gobbles more hp).

Jan 04 2017 | 2:07 pm

Yeah, there’s a lot more that could be done with the raw hardware that is in this device. But I have to tell you – just working with this as a standalone interface (meaning that it not only runs audio/CV back-and-forth to the computer, but actually has my audio output as well) is pretty cool! It so greatly simplifies my ‘small modular’ setup, and I already can’t imagine doing without it.

Plus I get to use the Valhalla reverb as my modular verb, so you can imagine how happy I am!


Jan 04 2017 | 2:56 pm

Yeah I can totally see that, and the terminology is definitely confusing (him using "standalone" to mean working *with* another sound card). If I was only planning on controlling a modular that would be idea, but given that I need other I/O, using it in conjunction with another interface would be ideal.

But I agree, in that it seems like the perfect ‘general purpose’ form factor.

Jan 05 2017 | 1:32 pm

now I want : 2x ES-8
I need to figure out how we can use them stacked (lightpipe between them?)
Checking Andrew’s website…

Jan 06 2017 | 10:40 am

You can use two ES-8 as an Aggregate Device in OS X, or you could hook up an ES-3 and ES-6 to an ES-8 to increase the i/o count.

Jan 06 2017 | 1:01 pm

Interesting review.
Is there any information about latency available ? – e.g. what ist the phase shift between a sine signal fed to a ES-8 input fed into a MAX ADC~ that directly outputs to a DAC~ on the ES-8?

Jan 20 2017 | 4:18 am

I don’t have latency, although I plan on doing some investigation shortly.

ES has just announced some new ES-8 news at NAMM, including Windows drivers. Info here:



Feb 04 2017 | 4:38 am

Posted this to the Expert Sleepers forum on MW, but figured I’d put it here in case anyone has had this issue too. I’d love to hear input/thoughts:

Hello Os, sort of a long note and debated email, but figured maybe the conversation would help others.

Here’s the backstory:

I purchased an ES-8 and have been happily working with it for the last few weeks. When I’ve explored audio processing through MAX I’ve noticed digital sounding noise creeping in. I assumed it was a vector size issue. A buddy of mine who is more adept at computer music came over and we were tinkering and I was showing him the module and such. As we were troubleshooting we tried plugging the ES-8 into his computer. All my patches sounded infinitely better with even lower vectors on his computer.

Initially, he thought there may be some quiet software running in the background of my computer that was fucking with the smooth DSP in MAX. He suggested I just update to 10.10.5 (I had been on 10.8.5) as that was his OS. I tried that and the noise was still there. Frustrated I went ahead and did a total wipe/clean install, thinking that I really wanted to just take care of this issue ASAP so I could have a fully functioning MAX/ES-8 setup.

Long story short, after tracking down 10.10 and doing that clean install, the issue is still present. Again, total wipe. The only things I have installed on my computer as of now are Chrome, Pro Tools 11, and Max 7.

Any wisdom? I have a 2012 Macbook Pro and his is probably a bit newer, but am hoping there’s some solution.

I’m reminded why I moved away from computers in music smile

Thanks for your time!

Feb 04 2017 | 8:04 am

Oops, apparently I have a 2010 MBP. 4 gigs of RAM. My buddy has 16 gigs. He is confident 4 is the issue. Upgrading to max out my RAM to 8. I’ll update, but still curious if others are having any issues and if they’ve found RAM to be the factor. (I’m not a computer person!) :)


Feb 05 2017 | 7:28 am

Final update: Maxed out my RAM to 8 gigs. It was still noisy. If you’re encountering noise though, it appears the USB cable could be the issue too. I thought I checked that, but maybe I didn’t? Anyway, happy it’s working and my laptop is set up to last a bit longer :) Here I thought all USB cables were equal.

Feb 06 2017 | 10:39 am


Are you saying that swapping out the USB cable made the noise go away? That’s interesting information!

(And it reminds me of the ancient days, when a cheap SCSI cable would introduce all sorts of noise into recordings…)


Feb 09 2017 | 10:48 am

Hi Darwin, I think that was the issue since even after the OS update and doubling the RAM it was still noisy. What is weird is that the same USB cable was used when we tested my module with my friend’s laptop running my patch. Puzzling…

Feb 09 2017 | 12:06 pm

Beyond setting it up are the any reasons why running it as aggregate device isn’t a good idea? I’m tempted to get one but would want to keep my uad apollo as main soundcard. Would I lose any functionality?


Feb 09 2017 | 12:15 pm

Geoff, I haven’t tinkered with that, but I know I was able to use the ES-8 as my interface with the Max/modular hybrid and then recorded the output of that into my MOTU Ultralite into Pro Tools without any issue. So depending on how you plan to use it, you may not even need to set it up that way.

Feb 10 2017 | 5:33 am


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