This is one of those sweet little unicorn additions to a kit that changes everything. This post is mostly intended for my long-form recording peers, but I’m sure someone will find some other a creative field recording use for it.
Double your power. Double your time. Double Double Double!
We all know the problem. High capacity storage options available these days and inexpensive, power-sipping recorders have lowered the barrier to capturing lovely, long-term soundscape recordings. If you drive or hike into a location, you’re only limited by what you can carry. Long-term power solutions are the only remaining limitation. This is especially true when traveling by plane to a destination. Your recording time is limited to the combined specs of your microphones, recorder, and power supply. Airline requirements disallow high capacity power banks over 100 WH. You can carry on as many of these as you can lift, but not one can be of a higher capacity. (I’ve pushed this limit. Ask me for gentle tactics to use when passing 55lbs of lithium power banks through security check lines). For most power banks this means a 26800 mAh (roughly 98Wh) cap. A Zoom F6 with four EM272-type microphones (LOM Usi Pro, Oaka Verdi, Sonorous Objects, etc) powered at 24V can record roughly a day on a single 26800 mAh powerbank at 32bit 96k. A Sound Devices MixPre6ii with four MKH8020s will earn you 14 hours. Maybe.
I know. Electronics! Numbers! Specs! Fun!
It’s funny, but not so long ago those were considered INSANELY LONG SESSIONS. These days more and more of us are trying to remove ourselves from the scene by using stashed or remote rigs (drop rigs”). This allows natural ecosystems to recover from our brief intrusion and return to an equilibrium impossible to record if our human bodies remain in the scene. If we’re peeking in from a bush or constantly popping in to replace spent batteries, many sensitive species will curtail their typical behavior or leave altogether. A single day just doesn’t cut it if you desire to record at least one full Dawn Chorus and one full Dusk Chorus along with uninterrupted nighttime tranquility and daytime activity.
If only, we wonder, there was a way to power a recorder from more than one power bank…
Enter the 5V USB-C Dual Supply – Dual Ideal Diodes from 8086 Consultancy in the U.K. http://www.8086.net/products#80860019
This inexpensive little device built for the Arduino and maker scene does exactly that. Plug two USB-C power banks into a single recorder or other device that will use 5V @3A power supplies for nearly double your recording time (for equivalent power banks).
From their copy, “It will draw power from the supply with the highest voltage and if the voltages equalize (due to the current draw) it will share the load on the power supplies connected to both USB-C connectors (droop method).”
I bought a handful of these last Summer and have been battering them repeatedly without fail. They’ve survived in all sorts of conditions, from humid to dry to freezing to high heat without fail. One even sat in a puddle of water at the bottom of a leaky “dry” bag. They’ve been in deserts and tropical rainforests. The only problem I experienced was the poor-quality gaffer tape I used. It lost its stickiness, fell off, and left a gooey residue all over everything.
The dual power supply, though, never had an issue.
Before actually taking them out into the field I thought it wise to give them a go in the controlled environment of my Seattle home. While I tend to be fairly libertine with my equipment, I couldn’t help but hear the whisper of a friend saying he wouldn’t trust his recorder with a $5 part.
I plugged several pairs of power banks into several dual power supplies into several recorders with many mics. Recorders included Sound Devices’ MixPreii-series, Zoom F-series, a Sony A10, and a Roland R-07. Microphones were from LOM, Oaka, Sonorous Objects, Mic Booster, Sennheiser, more Sennheiser, and some more Sennheiser. Power Banks were a mix of Anker, Zendure, and a few oddballs. It was a remedial testing situation. Essentially just recording until the power banks ran down. Then I’d swap microphones and recorders and power banks and go again.
The results varied, as expected, along recorder and microphone power consumption lines. Surprisingly, power bank brands didn’t seem to matter. Zoom F-series and EM-272 mics at 24V are super efficient power sippers. Sound Devices with Sennheiser mics, not so much. Still, recording with a quad set of Sennheiser MKH8020s on a Sound Devices MixPre6ii for more than 30 hours in one shot without changing power banks? That was exciting.
I won’t tell you how long the A10 with PiP-powered Clippies lasted because I don’t know. I gave up waiting after a week of recording without stopping because I wanted to go use the blasted things in the field. 1TB SD cards hold a lot of data, more than a week of pigeons in a window can generate.
It’s dead simple to use, so I won’t even bother explaining. There are two LEDs, one for each UB-C power source. If your bank has power, the corresponding LED lights up. When it runs out, the LED goes out. The Dual Supply smoothly draws from whichever source has more power without any spikes. I worst-case-scenarioed the tests by pulling one bank while recording without any single recorder noticing. The power remained UNinterrupted. I’m not an electrician, so this is essentially magic to me. It was bizarre fun plugging, unplugging, and re-plugging power banks to recorders via the dual supply while remaining in record. Even better, this works with any 5V 3A power supply, including wall chargers and other line power. Replacing power on the fly without interrupting recording will make production work run so much more smoothly. I can almost hear the sounds of excitement from my production sound friends as they realize they can replace power mid-take on set without interrupting production. One less reason to hear someone yell “Hold for sound” is one more step to feeling like a human being on set.
There was a single moment of annoying power interruption, and it had nothing to do with the dual supplies. Some power banks shut off if the power draw falls below a specific current. This can of course happen if you use power banks with unequal charges to start. The dual supply will draw from the higher-charged power bank until both are equalized. Only then will it start to draw from the other or both. In that time there is, of course, the possibility the power bank-in-waiting may just decide to shut off. It’s really important, then, to make sure you either use always-on power banks or banks with a trickle-charge mode.
The only thing I’d like to see is some sort of proper protective sheathing. At $5/ £4/ €4, I’m not complaining. The bare-board style keeps the price down and makes it readily easy for arduino makers to incorporate into their projects. I’m crafty, but not that kind of crafty, so I just slathered mine with hot glue and called it good. The black tape in the photos is there to keep the LED lights dim. They shine like brilliant stars in the dark even when the recorder and supplies are wrapped in a dry bag. Maybe there is a builder out there somewhere with a better idea. It’s up to you to make something a bit prettier than I came up with. If you’re one of those special people who are handy with a 3D printer, you’ve got a perfect subject here.
A little power is lost along the way, so it’s not a perfect doubling of recording time. Your recorder uses power for more than just writing zeroes and ones, of course. In general, it seems to boil down to an increase of 70-95% depending on conditions and gear mix. Regardless, I’ve see some pretty exciting results. An MP6ii with quad MKH8020s recording at 32bit, 96k, ran for a day-and-a-half on two 26800 mAh power banks. An F6 with 4 Sonorous Objects SO.1s records for a touch over three days. An F3 with a pair of Oaka Verdi ran for so long I gave up, just like the A10.
Many of use travel to record and finds ourselves limited by the size of power banks we can carry with us. Airlines will let you carry on as many 100 WH power banks on board with you as you can lift, but those are still single-point limits. Do yourself a favor. Spend the 5 USD/ 4 GBP to give yourself some freedom.
Thanks to Chris from 8086 Consultancy for letting me use a a picture from his site and for creating this little device. If this is the kind of simple kit-improvement that you’re interested in, you can show him a little thanks, too, by purchasing some via one of these fine storefronts. They all come from 8086 Consultancy in the end:
https://www.tindie.com/products/8086net/5v-usb-c-dual-supply-dual-ideal-diodes
https://thepihut.com/products/5v-usb-c-dual-supply-dual-ideal-diodes
https://www.ebay.co.uk/itm/204254803665
https://www.berrybase.de/detail/index/sArticle/10348
All these Costa Rica recordings are from sessions using dual supply. That doesn’t make them better, of course, just an interesting curiosity to know.