# Using an underpowered DC power supply: not smart? **URL:** \ **Category:** Factual Questions\ **Created:** [November 5, 2003, 2:53am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470 "2003-11-05T02:53:12Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Hoops](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hoops/32/6408_2.png) [@Hoops](https://boards.straightdope.com/u/Hoops)\ **Post date:** [November 5, 2003, 2:53am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/1 "2003-11-05T02:53:12Z")
Howdy all. I have a synth module–a Roland JV-1010 to be exact–that uses a wall-wart-style DC power transformer, bulky in the unfortunate manner of its ilk. I have a smaller power supply that will allow me to squeeze an extra space out of my power strip. But the synth wants to see 12VDC 400 mA, and this one is only 300 mA. I have, perhaps foolishly, tested it and it seems to work fine. But if I use it regularly, will I be shortening the instrument’s life span? ---
**Author:** ![LordVor](https://avatars.discourse-cdn.com/v4/letter/l/90ced4/32.png) [@LordVor](https://boards.straightdope.com/u/LordVor)\ **Post date:** [November 5, 2003, 5:00am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/2 "2003-11-05T05:00:02Z")
Not likely that it’ll be shortened from not having enough power. More likely that it’ll be shortened when your underpowered power supply is pushed to its upper limits, overheats, and starts on fire. Seriously, though, that 400 mA is the synth’s peak draw. That’s with the volume turned all the way up, and a fudge factor added in. If you don’t crank it, and the 300 mA supply is a good quality, you should be fine. But that’s still “should”, and power strips are, what, $5 at Home Depot? -lv ---
**Author:** ![MaryEFoo](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MaryEFoo](https://boards.straightdope.com/u/MaryEFoo)\ **Post date:** [November 5, 2003, 5:07am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/3 "2003-11-05T05:07:12Z")
Guess #1: it would shorten the power-supply’s life span more Guess #2: risk would be higher, the greater the volume being emitted ---
**Author:** ![MaryEFoo](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MaryEFoo](https://boards.straightdope.com/u/MaryEFoo)\ **Post date:** [November 5, 2003, 5:08am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/4 "2003-11-05T05:08:21Z")
Wups, double post. ---
**Author:** ![vasyachkin](https://avatars.discourse-cdn.com/v4/letter/v/c5a1d2/32.png) [@vasyachkin](https://boards.straightdope.com/u/vasyachkin)\ **Post date:** [November 5, 2003, 5:16am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/5 "2003-11-05T05:16:50Z")
i agree with everything said above. and i want to congratulate you too, you have got to be the first person i communicate with who is as cheap as my father. he would rig up some point-to-point wiring for sure and not waste $3 on the power strip from home depot. you could also buy an extention cord at the 99C store, but that CRAP is just as likely to start a fire by itself ( uses shit contacts that give sparks and plastic that melts very easily ) so i don’t recommend you go that route. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 5, 2003, 5:40am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/6 "2003-11-05T05:40:48Z")
I think it’s not such a good idea. Here’s why: The typical Class 2 AC/DC adapter is not at all well voltage regulated. A “12V” adapter might actually provide 16V without a load. The voltage drops down to 12V when matched with the load it is intended to feed. A lower wattage adapter is more likely to drop _under_ 12V on your load. You device will try to compensate by drawing more current, etc. Death spiral awaits. Doesn’t seem worth the issue of size. If you want to be careful about this, actually measure the voltage coming out of the adapter while you are using it and compare to the original. More than say a half volt difference would probably be bad. ---
**Author:** ![Hoops](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hoops/32/6408_2.png) [@Hoops](https://boards.straightdope.com/u/Hoops)\ **Post date:** [November 5, 2003, 9:26am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/7 "2003-11-05T09:26:33Z")
Well, the issue is not really one of price but space. This is for my six-space rack that I use in live performance and cart around regularly. There’s really barely enough room for one strip, and mounting them securely to the ABS molded plastic is a pain. Also a heavier power supply tends to fall out of the strip during transport. But if the general consensus here is that there is a danger of fire via overheating then I will try to find room to mount another strip (or resign myself to taking the extra 30 seconds before and after each gig to connect and disconnect the original power supply and just keep it in my gig bag). Thanks for everyone’s insight. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [November 5, 2003, 2:49pm UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/8 "2003-11-05T14:49:23Z")
If the power supply is regulated, and if it’s rated for a maximum current of 400 mA at 12 VDC, then I would bet the farm the synth module uses less than 400 mA under any condition. When selecting a regulated power supply, the designers very likely measured the module’s maximum continuous current draw at 12 VDC, and then selected a power supply that has the capability to produce _more_ than this current by 25% to 50%. So will a 300 mA supply work? Maybe. Maybe not. If you use a 300 mA supply and the module requires _more_ than 300 mA, the voltage will decrease. Strange things could happen if this occurs. My advice: Stick with the 400 mA supply, and figure out a way to fit it into your system. ---
**Author:** ![LordVor](https://avatars.discourse-cdn.com/v4/letter/l/90ced4/32.png) [@LordVor](https://boards.straightdope.com/u/LordVor)\ **Post date:** [November 5, 2003, 3:05pm UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/9 "2003-11-05T15:05:38Z")
Another option, get a 1 foot extension cord like [this](http://www.cablesamerica.com/product.asp?cat%5Fid=702&sku=03137) , plug it into your strip, and plug the real power supply into that. -lv ---
**Author:** ![vasyachkin](https://avatars.discourse-cdn.com/v4/letter/v/c5a1d2/32.png) [@vasyachkin](https://boards.straightdope.com/u/vasyachkin)\ **Post date:** [November 8, 2003, 5:36am UTC](https://boards.straightdope.com/t/using-an-underpowered-dc-power-supply-not-smart/211470/10 "2003-11-08T05:36:01Z")
> [@](#): > > \*Originally posted by Hoops \* > **Well, the issue is not really one of price but space.** aaight then, i take it back 🙂