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View Full Version : Gear Head Question - AC Inverter



Ukuleleblues
03-02-2012, 10:32 AM
I want to hook up my amp to a 12 volt battery. I found an 12-110v inverter real cheap and I bought it for a Teardrop trailer I am building. I hooked it up to a couple of PA's and Amps and I get a HUM. I started reading and determined I hade a modified sine wave inverter and they can make electronics hum. Supposedly a Pure Sine Wave inverter is what I need. Has anyone hooked up a pure sine wave inverter to their PA/AMP with the result being no hum?

1931jim
03-02-2012, 12:07 PM
Last summer at the campground I was talking guitars and amps with a bunch I jam with and one of the guys finally settled on an amp without the inverter because of the hum. It was a very small little one input device. I think it was called a piglet or pignose or something with pig in the name. I will be talking to them again probably over the weekend.

OldePhart
03-02-2012, 12:18 PM
Pure sine wave inverters are quite expensive. Most of the inverters you see are modified sine or even just a filtered square wave because they are much cheaper to make and run much cooler.

One option is simply to run off the 12volt battery with no inverter, then charge the battery when the amp is off. Most small amps will run for at least 2 or 3 hours off of a large motorcycle battery and much longer off an automotive or marine battery. If you need more time, you can just swap the batteries. (I don't generally recommend putting lead-acid batteries (sealed gel or liquid) in parallel because each is capable of delivering enough current to melt down the wiring if a cell shorts in the other battery.)

I actually converted a Danelectro "nifty-fifty" to run off a pair of gel-cell batteries (wired for +/- 13v) and converted the internal power supply of the amp to recharge the batteries. It will run for hours off a single charge.

John

ricdoug
03-02-2012, 01:43 PM
I have a long 25' cigarette lighter cord for my Carvin S400D, Jimmy. I don't know if you still have yours, but the cord is http://www.carvinguitars.com/products/single.php?product=C25 . Ric

Ukuleleblues
03-02-2012, 04:35 PM
I was thinking about trying this inverter.

http://www.theinverterstore.com/the-inverter-store-product.php?model=pwri30012s

ricdoug
03-02-2012, 05:30 PM
It will be interesting to hear how that works. I have a modified sine wave converter in the garage that I've used with a laptop and also to charge some NiMH batteries. If I have some spare time I'll give it a whirl with a PW50. Ric

OldePhart
03-03-2012, 10:06 AM
One option is simply to run off the 12volt battery with no inverter, then charge the battery when the amp is off...

Doh! Boy I must've been tired when I wrote that reply! It completely blazed past me that you were talking about running non DC amps off of batteries. :embarassed:

What I said about inverters still stands - sine wave inverters are 'spensive. One thing you might try is a good Furman power conditioner between the inverter and amp. Of course, by the time you do that you're looking at spending as much as a better inverter (or a battery-powered amp) would cost. I have a small non-rack-mount Furman that I use at church because our power is so nasty with all kinds of noise running on it. The unit was designed for high-end home theater installations. If I remember right it was about $100. It cleans up our power pretty nicely. Really all it is is a large filter but it takes the noise from the light dimmers and such right out of the line so I bet it would clean up the output of an inverter, too.

John