powering a mobile rig

Discussion in 'Location Recording' started by rfreez, Mar 1, 2007.

  1. rfreez

    rfreez Active Member

    What are the options for powering a small mobile rig... say an Apogee Ensemble, a laptop and 2 X AEA TRP (outboard preamps) and a headphone distribution unit in a (remote) Church that has no power?

    Sorry, this must be the first thing to know about location recording, but i've never recorded in a place without power before and have no clue...

    How far will the 900W portable generator in the following link get me?


  2. Boswell

    Boswell Moderator Distinguished Member

    If you can put the generator far enough from the church that you really can't hear it, that unit should work for you. As a completely silent alternative for this sort of situation, I've used a UPS (uninterruptable power supply) of the type that you can boost by plugging in 4 external car batteries.
  3. Thomas W. Bethel

    Thomas W. Bethel Well-Known Member

    We have an "on location" rig that consists of a Caravan Case containing a Model 1250 APC UPS and a Topaz Ultra Isolator transformer and we can power our whole rig for a couple of hours. (Laptop, 2 channel firewire interface and headphone amp) Something similar should work for you. If you needed something that would last longer a generator could be added but generators are noisy and just when you need them the most they run out of gas (been there done that) also some generators put out square waves and not sine waves and they are fine for powering hand tools and a job site but not so great for audio equipment. Also a long power cord (if you are thinking for remoting it) could be a problem with voltage drop unless you are using #12 or larger wire and an extention cord that heavy duty would cost a lot and be a bugger to transport. The idea of using a UPS with external batteries is a good one but batteries are heavy and if you don't get sealed ones can be problematic (acid discarge and fumes). If you do use an external battery try and get a DEEP DISCARGE one that is suitable for Marine use. They are more expensive but well worth it.
  4. Zilla

    Zilla Active Member

    My current location rig is completely battery powered. My custom RABBIT mic pre's last about 10hours, the 8-channel converter/interface lasts about 6hrs, but my laptop lasts only ~2.5hrs (so I carry additional batts.) I am really enjoying the independence from venue power quality and accessibility.

    Using a good quality ups should work fine. But if you are a DIYer, battery supplies may be for you. Consider buying additional batteries for you laptop for extended time. It would be easy to build an external SLA battery supply for the TRP without modifing the device itself (voltage is regulated inside the box). I am unfamiliar with that apogee model, so I don't know what would be involved with modifying it.
  5. Simmosonic

    Simmosonic Active Member

    Some nice suggestions here. I'll just throw in my two cents.

    Firstly, I wouldn't even contemplate using a generator if it uses a motor and is going to make noise! Here's what I use:


    I have one of their 32W foldable solar panels along with their 16A/H battery. I take it on my recording expeditions, damn useful thing to have. But there's more to it than that. I also bought an inexpensive 15V DC adaptor (mains to 15V DC) which I can connect in place of the solar panel (or alongside it, in fact) into the charge controller (it has two DC inputs) and keep the battery charged that way. And, I use a 12V DC to 240V AC inverter to step the voltage up again. That is not the most efficient way to do things, of course, but it saves me from having to make all kinds of adaptors and regulators and so on to power all of my AC gear off DC. I use all the existing AC adaptors and chargers, simply plugging them into a powerboard.

    I have been very happy with this system, but before my next expedition I am going to replace the inverter with a pure sine wave model. The one I'm currently using produces what the inverter industry generally calls a 'modified sine wave'. What they really mean is a poorly filtered square wave!!! As Thomas was suggesting, these can feed all kinds of nasty hash into the mains power, and the PSUs on some devices simply can't filter it out. For example, if I power my Dynaudio BM5As off this system, I can hear the continual buzz in the background of the sound.

    Nothing beats DC power for getting rid of those problems, of course. So maybe the inverter is not for you. It is good for me because I use it to power many different things when on location; from external hard drives to soldering irons, camera battery rechargers, iPod rechargers, and electric lights. In fact, right now the whole system is sitting in a remote village in Nepal, providing electric lighting for my fiance's family, primarily so that her brother can study at night. For one day's work and an expense of 1000 Nepalese rupees (about $16 US) I was able to buy and install five low power fluoro lights, with switches, throughout their village home. The solar battery system will stay there until I return in July, by which time the local authorities hope to have hydro installed. They're already running the power poles up the mountain...

    Cool, eh?
  6. Simmosonic

    Simmosonic Active Member

    By the way, if you're contemplating any kind of battery powering system, be sure to check the current requirements of your rig when running off 12V DC. For example, my IBM Thinkpad draws around 7A when running off 12V DC through a 240V AC inverter! That's quite a drain, and means my 16A/H battery is only good for about two hours...

    In fairness, however, I should mention that the Thinkpad is also keeping its two internal batteries charged with that current drain. So, the external battery can power *and charge* the Thinkpad for a couple of hours; after that, the Thinkpad is running off its internal batteries, and that gives me about another three hours at full processing capability (no lower power mode switched in). So about five hours altogether, with no fear of glitching or similar when the external battery runs out because the Thinkpad simply switches to its internal batteries when required...
  7. Cucco

    Cucco Distinguished Member

    This is an interesting topic!

    I'm curious - In the near future, I will be making a mini-recording-truck (either a tow-behind trailor or built into an SUV) in which all of the recording gear is semi-permanently mounted and I merely run line signals into the truck so that I can record inside the truck and not have to be in the venue. The benefits to me are:
    1 - much quicker setup and take down (all I would put into the venue would be the mics, the stands and the preamps - everything else would already be set up.)

    2 - permanent and consistent acoustics - doesn't change with each gig.

    If I do the tow-behind vehicle, I would need to consider some sort of HVAC unit, whereas if I stick with the vehicle itself, no HVAC woes.

    However, I don't think, even with a good DC/AC inverter, I would be able to power everything I need for hours on end (some gigs lasting >8 hours). I've thought about solar as it seems increasingly affordable, or of course a much bigger battery and much bigger alternater.

    Anyone wise on such things?

    (Not meaning to hijack the thread, but it is directly related to the topic...)

    Cheers -

  8. MadMax

    MadMax Well-Known Member

    OK, here's what I did...

    I decided on a trailer... If a truck breaks down, I can ALWAYS get a rental unit to haul the trailer.

    I put a breaker box in the trailer.

    I put 50Amp twist-lock disconnects on several lengths of wire. I can make up almost any length to get from the venue to the trailer... up to 300 ft.

    My cable trunk is a 48x8 Whirlwind 3-way splitter w/300' trunk to match my power.

    I use a power conditioning transformer to kill hum and noise from the line.
  9. Cucco

    Cucco Distinguished Member

    I had a very similar thought.

    If I go into a vehicle though, it would be a brand new Honda Element (amazing amounts of room inside!)

    Very cool! I was thinking 500', but 300' is probably good too. Are you using 12 guage? (HEAVY!!!) What are the approximate lengths of individual cable that you're using?

    Got that part covered.

    That too.

    What do you do about HVAC?

    I've been thinking about one of those little Mitsubishi units.
  10. MadMax

    MadMax Well-Known Member

    I went a bit worse than 12... I went 10-4 SU... ball bustin' heavy!

    2-25's, 1-50, 1-75, 1-125

    I installed a through the wall exhaust fan... no AC. I don't regret the choice, but I'm still thinking about putting one in anyway. The thing I wanted to avoid were the LF issues of the compressor kicking in/out. I figured I could string up a canvas over the top of the rig to provide some shade relief from the heat a LOT cheaper than I could deal with an AC unit.
  11. Thomas W. Bethel

    Thomas W. Bethel Well-Known Member


    A couple of years ago I was going to take some money and invest it in a mobile rig. I did a lot of research on it and came to the following conclusions.

    1. The security for the unit would be a top priority and I don't have a garage. If you have something that is mobile and full of expensive equipment you are just asking to have it stolen. There are many ways to alarm the vehicle and you could even have a GPS unit installed so if it is stolen you could find out where it is. It is also probably NOT a good idea to have your logo on it or in anyway identify it as a mobile recording setup. The less windows it has the better for your and your investment.

    2. You have to have a way of air conditioning it and heating it and it has to be somewhat quiet. When I checked out the AC units for RVs they were noisy and drew a lot of power. Heating would be easier but a lot of our work is on location in Northern Ohio weather and it can be COLD for long periods of time so we do need heat.

    3. The minute one talks to an insurance agent about insurance for the vehicle the insurance agent starts getting dollar signs in their eyeballs and if you tell them it will be used for "commercial audio" work they get big smiles on their faces and start talking about taking south sea vacations and new cars.<GRIN>

    4. I talked to the people that normally do work on my car and they told me that with the amount of equipment I would be hauling that it would be expensive for gas and if the equipment were permanently installed it could be a problem for maintenance since they have to get to places with in the vehicle that might be blocked by the equipment. They were not saying it could not be done but that it might be expensive.

    5. Some of our location work is done a churches and auditoriums and we would need long "shore power" cables for power and long (300 foot) cables for our microphone splitter and those cables and power cord can take up room and are very heavy to load. Also if it is raining or snowing the cables can become very mud covered and you don't want them inside the vehicle.

    6. Sometimes we are supporting a film or TV crew and so we would need to have someway of hooking up our stuff to theirs and most times you don't want to leave the doors or windows open so that means a panel on the outside of the vehicle or a trap door to pass cables back and forth. This also goes for the snake and the power cables and if you are doing things correctly you don't want the AC power cables anywhere near your microphone lines which probably means two trap doors or two panels. When you start cutting and painting body sheet metal it can get expensive very quickly.

    7. You have to have a video camera and intercom system with someone in the hall so you can take care of problems as they arise and be able to see into the venue for cues. Not a real "problem" but it can be problematic.

    8. I worked from a friend's VAN on lots of remotes and so I know a lot of the pitfalls that we encountered and I know that two problems we ran into more than once was mechanical failures in the van and tire problems. If you have a lot of EXTRA pounds in your van it can put very high wear on the tires and the steering and suspension gear and we were probably carrying, with cables and equipment, about 1500 pounds of equipment. Estimates for tire mileage could be cut in half and you may have to go to a higher ply number to be safe.

    9. I also worked out of a complete mobile recording and broadcast van that belonged to the local NPR station and that was a very nice vehicle and had everything built in and very easy to setup and to run. The vehicle developed MAJOR mechanical problems and body problems and they decided to junk it as they could not afford to get it repaired and they were concerned about the cost of the insurance which seem to go up faster than the stock market. Too bad - it was a joy to use.

    10. We have since decided to have all of our stuff in cases and we load and unload our vehicle for every event so most of our stuff is on wheels. It is a pain never the less and the VAN, with all the equipment installed, idea appeals to me every time we have to haul all the equipment back and forth to its storage location and back and forth to the gig but it is also nice not to have to worry the van being stolen loaded with equipment.

    Best of luck on your quest for a mobile recording van....

    The new Sprinter trucks from Dodge http://www.dodge.com/en/sprinter/index.html

    or Freighliner http://www.fl-sprinter.com/index.asp?n=3&p=0&s=3

    seem like the ideal remote van if you can get past the $40,000 price tag.

    The local PBS station decided to go with a standard trailer and had this outfit make it into a TV production setup http://www.gerlinggroup.com/broadcast.htm

    You could also buy this one and do TV at the same time http://cgi.ebay.com/Complete-Television-Production-Remote-Truck_W0QQitemZ270094034111QQihZ017QQcategoryZ3319QQcmdZViewItem
  12. MadMax

    MadMax Well-Known Member

    Thomas speaks volumes about why the trailer option is the way I went.

    Since we're pretty much in the same geographical area, I'd say that our HVAC requirements are going to be approximately the same. The need for cooling is probably the larger concern over heating. Again, I opted for ventilation over cooling... e.g. less power and fewer condensation problems. The main drawback is the sweat factor. I somewhat get around that with a cooler and a bag of towels. I do/did use a 10 foot high pop-up to provide shade over the rig in the heat of summer. (The pop up took a limb last year at a long term session at a residential session... ARRRRGH) ... but they're like $50.

    Rather than running the risk of water leakage from side-wall panel mounts, I opted to cut a trap door in the floor of the trailer. I run my power and signal through that trap door and it locks while traveling/not in use.

    I seriously suggest NOT putting any kind of advertising on your rig... whether you go Van/Truck or trailer.

    As far as insurance... Oooof... tough call. I put everything in castered racks. That way NONE of it is permanently installed... it's easier for thieves, true, but it's also much cheaper to put insurance on the rig. PLUS it does give me the option to take all the gear into a venue if it's better to do a session that way... and take it out when the rig is not on the road. I call it dual purpose, and classify the trailer as equipment transportation purposes only.

    I do transportation the "easy" way... I put E-Track on the walls and strap everything down. When I get to the venue, I pop the straps and start running power and cabling.

    No, it ain't a perfect system... but it's economical and serves me and my purposes quite adequately.

    If you're interested in giving it a try, I'm currently not taking any work due to building the studio... so it's potentailly available for you to do a gig or two to see if this kind of config may be right for your situation. Lemme know if you're interested.
  13. Simmosonic

    Simmosonic Active Member

    Since getting my solar power system, I have become a big convert. It is quite amazing to be powering stuff from the sun! It costs nothing (er, apart the considerable up-front costs) and it makes you realise that whenever you're walking in daylight, you're walking through vast amounts of energy. However...

    Solar is not the be-all and end-all, I'm afraid, unless you can afford lots of panels because more exposed surface area means more current capability. I could go on at length about this, but in my experience the smart application of solar electricity is for opportunistic charging of storage cells, rather than powering things directly and on demand. I say 'opportunistic' because you cannot guarantee when the sun will be shining...

    So, to integrate solar power and batteries into your ‘portable’ application I’d be getting a nice big truck battery (or two, or three, wired in parallel) with a few different ways of charging connected simultaneously. These could include a connection from your vehicle's alternator for charging while driving, solar panels for siphoning energy from the sun whenever it is available, and a mains charging system for whenever you have access to mains power (if you're running cables between yourself and a venue, you may as well see if you can draw from their mains as well).

    I'd have all of these sources going into a charge controller to control the charging of the battery, and I'd also make sure the sources have blocking diodes to prevent them from draining the battery during downtime, or robbing current from each other.

    And then I’d consider powering all of the audio from a pure sine wave inverter connected to the battery. Whenever possible, I would connect to mains from the venue, which would be continually topping up the battery. But if the mains failed, I’d have no problems because the system continues running from the battery; in fact, it sees no change at all.

    The important challenge here is determining the current drain of your system, so you can work out how many ampere/hours of battery storage you’re going to need to do your jobs. And remember that this is at 12V DC, so the required current is much higher than it is at 240V AC to achieve the same power.

    And finally, a laptop, even a Centrino model like mine, draws a surprisingly large amount of current at 12V DC. Add a 3.5 inch hard disk or two and you realise you’re into serious current requirements…
  14. Simmosonic

    Simmosonic Active Member

    We've maybe drifted a bit OT, but I think rfreez will find some of the stuff relevant to his initial question as well.

    One thing I'd like to suggest. Have you seen the upright trolley systems that film sound guys use? Usually, it's like a 19 inch rack mounted on a trolley with two reasonably large pneumatic tyres at the back and handles.

    To move it around, they simply lean it back on its wheels and start pushing. They usually keep the tyres inflated to about 65% or so, so they are never hard or bumpy and provide good shock absorption. The wheels are like those found on a good wheelbarrow or similar, with grippy tread and so on because often these guys are working on dirt or gravel...

    In the bottom of the trolley is usually one or two 12V car batteries, volt metering and related charging equipment. And the rest of the trolley contains their audio equipment - in their case this usually amounts to a recorder, a mixer, some wireless receivers and a drawer or two for all the fiddly little bits and pieces. I have worked with guys using these kinds of rigs on a few occassions, very cool. Everything is wired up and ready to go, so all they have to do is wheel it into location and power up. If there is AC available, they plug into it. If not, they run off the batteries.

    I think that such systems are very cool, and are also good examples of highly-evolved solutions to a particular problem. As usual, I find the film industry has long ago solved problems that are similar to those we face when recording music on location...

    A hose reel containing an appropriate multicore (8 channels or more?) could be built into the bottom of it, solving many of the multicore problems conveniently.

    Such a system for music could be a good compromise between a mobile rig built into a vehicle, and a load of cases being carted into a venue.

    It would be possible to build such a system that housed your laptop, interfaces and drives. It could also have a small pair of studio monitors on arms that folded out from the sides when you wanted them. It has most of the autonomy of a van, without the expense, and can go more places.

    That way, all you'd need was a space to set up. Wheel in, unfold, power up and go for it...
  15. Cucco

    Cucco Distinguished Member

    Hey Greg -
    I've definitely seen what you're talking about.

    My only beef with most portable power solutions is the amount of juice. I don't use a laptop (not because I won't, but because I can't. I need to bring in a lot of channels in many cases and I haven't found a laptop solution that suits me yet.)

    Therefore, my power requirements and physical space requirements are rather large. In addition to powering a PC and 15" LCD, I have to power 2 AD Converters, 1 DA converter, powered monitors, 2-way radio system, and occassionally other gadgets (mixers- nothing huge, small format mixers for camera-dude outputs, etc.)

    That's why the truck is appealing to me. I must admit, I've never had a gig where I couldn't fit a 6x12 trailer.

    The reason I'm considering solar is...
    1 - well, I don't think the sun is going anywhere anytime soon.
    2 - I do like the idea of being ecologically friendly (and not having to burn petrol/gas for power)
    3 - It seems quite robust and time-proven now (if not a little under-utilized.)
    4 - It's actually quite affordable and once it's installed, there's very little continued expense.

    For now though, at least until I can come up with $5K of disposable money, I'll keep hand-trucking everything into the venue and back out. :cry:
  16. rfreez

    rfreez Active Member

    thread hijacking is most welcome... anything to keep the forum active :)

    Solar power seems to have many advantages to it, but some how, i'm not warming to the idea (pun intended :)) I would like the solution to be very portable and non weather Dependant. I will have to do all the lugging around myself :)

    Once again, may i draw your attention to this kipor device
    they claim:

    The quoted noise figure is 60 something dB at 7m... i wonder what would happen if it was stuffed into one of those (guitar cabinet?) isolation boxes... It would still be more efficient than carrying a ups and a bunch of batteries around. Besides, in most cases i expect that there will be some way to keep the generator at a sufficient distance so that noise is not an issue... what do you guys think?

    thanks again, and please feel welcome to discuss any power related issues in this thread... there is always something to learn :)

  17. Cucco

    Cucco Distinguished Member

    This doesn't sound like a hot idea (pun intended there too..)

    First, if it burns fuel, it's going to put off heat and smoke. Neither of which should be confined within a box.

    Additionally, it requires that oxygen be rich (20% in air density) and if it is placed in a confined space, all of the oxygen will burn up and be replaced by CO2, CO, and other nasty, nasty chemicals.

    I think your best bet for using something like this would be to leave it outside of your venue and run cables to it. Of course, if you're at a venue, you probably have the luxury of power.

    One other thing you might consider is a
    Of course, if you're not driving an American-style vehicle (read: BIG car with big battery and healthy alternator), this might not work so well.

    Also keep in mind how much power you're actually drawing. I think that one is rated at 1000W. That can get used up REALLY quickly if you're not careful.
  18. rfreez

    rfreez Active Member

    i am humbled :( its taken me 30 years to learn something as basic as this.

    thanks cucco.
  19. Simmosonic

    Simmosonic Active Member

    I think that depends on your definition of 'efficient'! How much does that portable generator weigh? ;-)

    I am still concerned about the noise of a generator. I expect it may be reasonably quiet in the midrange (the most sensitive bandwidth of human hearing, which is no doubt the area they've focused on silencing), but not so quiet in the low frequencies; the very frequencies that make it through walls and into your microphones with the greatest of ease.

    Such a device shouldn't even be on the list of possibilities, in my opinion. Batteries are the best option. They are silent, and you can charge them up before you head off to the gig (whether by solar or from the mains), and I'd doubt they'd be any heavier than a generator plus extension power lead plus spare can of juice. You can also keep batteries by your side, where you can see them...

    For a little bit of electronic effort, it may be possible to power your entire proposed rig from DC, directly from the batteries, without needing an inverter. More efficient, and no hum or buzz problems to contend with.

    How much stuff do you want to carry with you? I would expect that a "sufficient distance so that the noise is not an issue" is going to require a 100m power lead or similar. Coupled with the weight of the generator and a spare can of juice, it's starting to get heavy.

    And messy...

    What are you trying to do? Record music or mow lawns? :D

    Jeremy made a lot of sense with his comment about not putting the generator in a soundproof box of any kind. It might not be so bad if you can do that while also providing exhaust and air intake vents, but that probably defeats the purpose...
  20. Boswell

    Boswell Moderator Distinguished Member

    I tried the generator route. I hired units, but gave up after two gigs, for most of the reasons others have given, plus living with the smell of petrol for days afterwards.

    As mentioned in my earlier post, I now use a UPS with external 48V booster batteries. It's silent.

    The boosters are 4 sealed 12V batteries in series mounted in a plastic hardshell suitcase. I can switch them in individually for charging using a conventional 12V charger. When I first constructed the suitcase, I thought I would have to make a second one to switch over to for long gigs (the internal UPS battery carrying the load during the switchover). This hasn't proved necessary for my recording rig, and I've refused to do PA work where there's no power. I still use the UPS without the boosters for all other types of gigs, however, ever since I had the unpleasant experience of running off the same mains outlet as a band with a dodgy amp that kept tripping the supply breakers. HD24s don't like having their mains summarily removed - they sulk and won't give you back your recorded data.

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