Best practices - AC power for small cart

[Dave Pullmer]

Hi! Had a simple question about best practices for powering a small cart set up. I’ll be powering a 833 bag on my mini cart with a PSC triple play as my bds - I messaged Ron at PSC a while back asking if he recommended running the triple play AC adaptor into a power conditioner or a power bar for additional surge protection. 
 

His response was that the power supply provided operates over a wide AC voltage range and there’s no real reason to use a surge protector.

 

I feel like from what I’ve seen from fellow sound mixers, a lot of people like to go into an additional power bar or conditioner for surge protection. Curious as to what best practices other mixers have been doing.

[The Documentary Sound Guy]

That's a big topic.  My take is that unless you are willing to spend big, it's probably not worth it.  And, if you are willing to spend big, it's worth doing a real risk assessment for what you are hoping to protect against.  In most cases, you'll never know if you are getting value for your money, and it's hard to put a price on the insurance it offers.

 

Most cheap surge protectors offer limited protection that burns out over time.  But there's no way of testing whether a surge protector is still good, so you never really know whether your are protected or not.  In addition, the most common type of surge that can *really* damage your equipment is a lightning strike, and that is almost certainly beyond the capacity of a cheap surge protector.  It's possible to spend more (much more) on better, more reliable surge protection, but you are then looking at a much higher price tag.

For small surges — the kind that you are likely to experience in everyday usage powering from a generator, or from significant power swings on mains power — I would trust PSC / Ron's advice.  Based on how you've quoted him, the triple play AC adapter sounds like an auto-ranging, switching power supply, and he's right, it will tolerate a wide range of voltages (probably in the range of 90-240V), which covers all the voltage ranges you are likely to encounter in everyday use.  It is also almost certainly fused (I doubt they'd get FCC approval without it), so if your input voltage does somehow end up out of spec, the fuse / power supply might fail, but your equipment should be fine.

An aside:  A power conditioner is definitely unnecessary here.  A power conditioner just smooths out the voltage and offers tighter voltage regulation compared to an unknown power source.  Given the auto-ranging nature of the PSC power supply, it simply doesn't need power conditioning.  There are other power characteristics (mainly, ripple), which *might* matter to audio quality if you happen to be plugging poor quality analogue gear directly into the power supply, but regulating the AC input probably doesn't matter for the majority of the equipment we use in the field.  There are several layers of electronic regulation between the AC source and your audio, so if you don't hear a problem, you don't need to fix it.

That covers the "cheap" end of the spectrum.  It doesn't cover catastrophic situations like lightning strikes, or a truly awful grid failure, where the input voltage may spike to thousands or millions of volts, which in turn could induce circuit-melting current, even for very brief moments.  You live in Vancouver like I do, so you can consider the odds of a lightning surge to be miniscule.  We very rarely get truly serious lightning storms (I recall one in my lifetime), and if we do, our topography makes it extremely unlikely a strike will get into the mains.  That goes double given that most of the time you'll be plugged into a generator that isn't connected to the mains at all.  The likeliest source of a lightning surge is a light gets left out in a storm in the open, and that attracts a lightning strike that takes out the whole film set.  If a light is left out in those circumstances, the gaffer isn't doing their job ... but it's fair to argue that you might want to protect against gaffer incompetence.  Of course, you could also just choose to disconnect and run off battery if you think you are in such circumstances.

 

Beyond that, the other possibilities where surge protection could help are various types of catastrophic failure, either of genny, or something in the mains.  None of these are impossible, but they are probably equal in likelihood to a component in the PSC power supply or in your equipment itself failing.  Which is to say, the odds are very, very small.  Given an expensive enough surge protector, it's possible you could reduce those very, very small odds of failure to very, very, very small.  But it's very hard to calculate or guess those odds.  So, for me, it comes down to how much am I willing to pay to prevent those very, very small odds?  Given the value of my equipment that is actually at risk, (mainly, my recorder, and a few lower value items), I'm not really willing to pay $500+ (5%) to protect $10,000 of equipment against such a vanishingly small possibility.  $500 may feel small for peace of mind, but it doesn't feel like good value to me.  Maybe I just like to live dangerously.

On the other hand, if i were to identify a specific risk that I might need to protect against (plugging into boat power, perhaps?), that calculus could change for me, and I might be willing to pay to insure against that specific risk.  But I have yet to encounter such a risk, and I'm truly having trouble coming up with examples of what that risk could be.  Maybe other, more paranoid people can enlighten me.

Anyway, that's my $0.02.  My words are cheaper than even the cheapest surge suppression.

[Derek H]

I’d use a basic power strip with some level of surge protection from a reputable brand like Tripplite or APC. Couldn’t hurt and a power strip is useful on a cart for more than just surge protection. Many of the “cheap” surge protectors that use consumable protective circuits do have lights on them to let you know that protection is still functioning. 

[Fred Salles]

 I wonder why would you want to power your cart from AC? Especially if it is a mini cart with 833 in a bag. There are many choices of reliable batteries nowadays. 
Asking Just out of curiosity as we have such diversity of practices. 
I have used AC on a cart only once when I rented a Mentor station ( power station and distribution from DCAudiovisuel here in France) as it also allows to charge any type of battery and I was short of battery pack. It is surge protected so i did not need to think about that. Nowadays my cart runs on 2-3 vlock batteries for a full day. 4max if over 10 hours. I do not find the need to charge during the day. 

[The Documentary Sound Guy]

I'm in the process of building a cart.  I could power everything except the monitor bank off batteries for a full day or more.  The lowest power consumption I could find on a two-screen monitor bank was about 25W.  That was more that the rest of my equipment put together, with the exception of my battery charging station.  My battery station requires 160W.

As long as my cart includes monitors, I'm going to need AC power for at least part of the day, or I'm going to have to change batteries during the day (est. every 5 hours), which means the *charger* has to be plugged in somewhere.  Since *something* has to be plugged in, it might as well be the cart, which can then power everything else, including the montiors and charging station.

[Conor]

Personally I would only invest in power surge protection and conditioning if I knew I was going to be operating on shoots where power is supplied by fueled generators. If they're not properly set up or used, s**t happens.

[Dave Pullmer]

Interesting, thanks for chiming in everyone. For sure the cart doesn’t technically need to be on AC power, but like Devon mentioned with the video monitors - that is the one item I have always been hooking up to AC. And with a more power hungry bag in the 8 series, if I’m already booking something up to AC why not the rest of my gear.

 

Sounds like I may just get a power strip from Tripplite and hook my PSC triple play and video monitor into it.

 

I remember from assisting for different mixers people would have AC to DC cart power like the Meon Life - am I missing something here by not incorporating a AC to DC strip on a sound cart?