Considering a Fully Portable Modular

So I have a bunch of hardware that I have rigged up together. I can run a guitar, bass, drum interface, synth keyboard, two guitar pedals and an iPad. I currently use an Apogee Jam as my audio interface but I am thinking about the old lunchbox ES-8 setup.

Here’s the thing though. Power supply.

I created a thread on Audiobus where I was basically talking to myself trying to figure out how to have all my gear be portable and solar powered. I am happy with where I got to on this, but I want some kind of battery solution integrated into the eurorack lunchbox.

I was reading this thread on wiffmuggler and it is just want I don’t want…carrying around a big battery and a modular.

Any thoughts?

As usual, I am clicking on the links and getting totally lost in the videos and discussions therein. :relaxed:

On the topic of portable modulars, I have been in a fairly similar boat. I have yet to see the battery pack that doesn’t at least double the encumbrance of lugging it around. Eventually I just kind of gave up. Now I will either try to work with just my iPad and the nanoKEY Studio or I plug into a public outlet. Many public parks will have electrical outlets for public events, so I just keep an eye out for them when I am riding my bike and have found a few spots that work well.

But more often than not, if I want to sketch in musical form while out and about the iPad is my only tool.

I wonder if there is some way to make something like a Rumburack and install a battery pack which would could be accessed from the side or something. It could be an interesting design project.

This really is the answer if you don’t want to carry a big battery. Modulars can draw a lot of current depending on what you put in them, which means you need a decent sized battery or a small battery with a large, expensive lightweight solar panel (but then what happens on cloudy days?).

Out of curiosity I thought I’d do some quick back of the envelope calculations. It seems to me that the simplest approach would be to use a single DC supply voltage. I found a MicroZeus Power Supply that takes 15V at a maximum of 2000mA and provides +12V/1000mA, -12V/500mA ,+5V/170mA.

Assuming for the moment that this would be sufficient, you would need appropriate batteries. I chose NiMH AA batteries because they are relatively cheap, widely available, and easy to find chargers for. I assumed 2000 mAH batteries although you can find them anywhere from 800 to about 2500 mAH. At 1.2 volts it would take 12 to 14 batteries to provide a nominal 15 volts for the MicroZeus. Each battery weighs about an ounce, so by the time you add some kind of case you would be looking at about a pound. Battery costs would be somewhere in the $60 to $80 range depending on capacity. In theory, at full draw from the supply, you would probably get somewhat less than an hour although I doubt that you could actually draw anywhere near 2 amps from the batteries due to internal resistance. Of course the run time would be dependent on the load. I have a battery powered Roland Cube bass amp that runs on 8 AA batteries and it seems to run forever. It works great with the UltraNova and Audulus on the iPad. I don’t think powering the rig directly from solar would be practical but you could certainly add a solar charger if needed. A 12 volt gel-cell would also be a possibility but you would probably have to find a different supply. I don’t know if the MicroZeus would run at 12v in.

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Yeah there are some solar power battery hybrids out there now that are roughly the size of the small Zissou case - I believe they can charge when they’re running so you can basically get a longer lasting battery.

That can be done although it does complicate the electronics somewhat. You would need a pretty good size panel to provide a couple of amps at 15 volts but something smaller could still extend the run time.

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What about this V88 model from Voltaic?

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I don’t live in a city. I am more interested in being completely self sufficient – no grid boys, no grid.

As far as cloudy days go, you can run off the battery for a while, plus you still get some energy from the panel. Makes me wonder about optimized modules that are engineered not to draw power needlessly.

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Truly you are a future aztec!

Just curious, is this part of a creative isolation strategy?

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I have a hard time with people. :expressionless:

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Generally speaking I prefer the company of dogs myself. :dog2:


The battery looks perfect for this application. At 16v it would easily drive a microZeus or similar and it has plenty of capacity. Lithium chemistry has a much higher power density than NMh so your power to weight is much better. I didn’t consider Li batteries because of the need for a fairly complex charge circuit, but this has the electronics built in. Also looks like it would interface with a solar panel fairly easily. The price is comparable to what you would spend for a DIY solution so this looks like a better way to go.

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I had a look at the site for the LBZ54 Lunchbox case that @biminiroad mentioned in his article on the ES8 setup he runs. They list a number of options that work well with the case. Is there any advantages/downsides to using a uZeus and the Voltaic V88 inside the Lunchbox instead of what Pulp Logic lists on their site?

On another note, a couple of things come to mind. One is that the iPad doesn’t allow for multiple audio interfaces. So if I use the ES-8, I will have to not use my Apogee Jam as a guitar input. However, in this video the fellow mentions that you can plug another audio interface into the ES-8. I assume that he has missed the point that iOS can only deal with one interface at a time.

So, then how to I get a good clean boosted (with pre’s) guitar signal in?

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I’m not sure about the voltages and current draw, I’d rely on @stschoen to give his 2 cents on that, but the main advantage of putting the power supply on the back of the Lunchbox is that it doesn’t use any HP and you have more room for modules.

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Nice looking case. I don’t see any advantage to using the uZeus over the power supply they offer, in fact the two power supply options they list look like they are more flexible regarding input voltage than the uZeus and you’re not using any rack space for a supply. Whether you would need the 450 mA or 1000 mA supply would depend on the modules you have installed. At 24000 mAh the Voltaic V88 has 4 times the capacity of the 6000 mAh Talentcell option, but I expect it’s also more expensive and probably larger. Mounting the battery inside would obviously improve the portability, but might make recharging more difficult and of course it might not leave much room for modules. Personally I would probably leave the V88 outside.


A lot of times it’s already like origami behind the panels with the cables, finding room for a battery is probably impossible.


Thanks for the input @robertsyrett and @stschoen. I am wondering how @biminiroad deals with the guitar input question I raised above. Both my instruments are acoustic with acoustic pickups. I am always trying to drive the signal harder without generating too much background noise.

As far as what I would want to put into the box I am really drawn to a complex sequencer.

Even though the Nerd Seq is probably old news by now, it still interests me. However, I am very picky about workflow. I don’t mind a quirky simple arranger, but I like when something strikes the right balance b/w simplicity and flexibility. Yeah, the more I think about it, it is the sequencer modules that seem to draw my attention. I feel like it could be a central brain, but I would like something that can save my work. Then, maybe, I can free up the processing power of the iPad by not relying too heavily on Beatmaker 3 or Cubasis 2 or whatever.

At the same time I really have no idea at this point what would make the most sense. I would have to get a sense of how Audulus integrates with an ES-8 and what sort of Euro modules are best to have as hardware. I don’t want to go from having something in software that works well to hardware, just for the sake of it. Delays and Reverbs seem to eat CPU. What’s it like using a module as a send?

I mean, maybe the sequencer is just a kitchy and cumbersome way to do something that you can do much better with a DAW or by just setting up a sequencer in Audulus. I suppose that getting to thinking about this now is good because I clearly need to spend a while considering my options.


That nerd seq seems pretty legit! I find that I use my digitakt in the capacity that you are describing along with yarns to be the central hub of sequencing and I will just send a clock into Audulus. That would take up nearly all the lunchbox so your lunchboc would mostly be the nerdseq and not much room left to put in stuff to sequence, especially if you also plan to get an ES-8.

edit: this might all change though when midi out lands. I am definitely looking forward to trying out sequencing the digitakt with Audulus :exploding_head:

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You can plug your guitars directly into the ES-8 and amplify it digitally in Audulus. The noisefloor of the ES-8 is pretty low so you probably won’t notice it, especially when the guitar is in the mix.

I would suggest anchoring it somehow with some slack in case you plan to be moving around a lot - don’t want to be breaking a jack while playing.

The video of me doing the ES-8 analog delay I just have my electric guitar plugged straight in. An acoustic guitar with a pickup will probably have a louder signal to start with and have better fidelity anyway.

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Are you using as preamp with the acoustic pickups? I have a Fishman acoustic undersaddle with a Prefix Pro preamp on one of my mountain dulcimers and there’s more than enough level to drive an ES-8. Besides the gain, the pre provides quite a bit of tone shaping.

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