How to determine polarity for a device?
April 23, 2006 2:00 PM   Subscribe

How can I tell what polarity a device is? I have a Sonic Impact T-Amp and I want to use a universal adapter for it -- all I know is it's 12v and can be powered by 8 AA batteries.
posted by mattholomew to Technology (8 answers total)
 
You can try using an ohm meter between each input and a metal part of the chasis, sometimes the negative is tied to ground.
posted by StickyCarpet at 2:11 PM on April 23, 2006


You're familiar with the standard symbol for polarity for adapters, right, and are asking because you can't find one?
posted by TheOnlyCoolTim at 2:14 PM on April 23, 2006


TheOnlyCoolTim -- Yes, good question -- there is no marking indicating polarity on the device.
posted by mattholomew at 2:17 PM on April 23, 2006


The center pin is positive (under the 'some advice' section) - this page was the first one listed when googling for Sonic Impact T-Amp.
posted by bemis at 2:18 PM on April 23, 2006


You're familiar with the standard symbol for polarity for adapters, right, and are asking because you can't find one?

I have a number of devices with no polarity indicators on the body. Normally the supplied adaptor has the polarity indicated, but if you lose the adaptor you're hosed. Although normally I just try both settings and so far I haven't had anything blow up.
posted by delmoi at 3:23 PM on April 23, 2006


Look under DC adaptors in the McMaster Carr catalog at www.mcmaster.com for instructions on reading the polarity symbol
posted by Raybun at 3:36 PM on April 23, 2006


Sorry to derail but I have to know: is it really as good an amplifier?
posted by jouke at 10:29 AM on April 24, 2006


I got a T-Amp for Christmas and bought a Radio Shack universal AC/DC converter for it. The converter came with a choice of adapters and I carefully matched one to my amp, then plugged the adapter in backwards and reversed the polarity. Good news is that I didn't damage the amp -- it simply wouldn't operate. When I put the adapter on right, everything worked.

jouke, the amp is amazing for $30. You will have to match it with high-efficiency speakers (on the order of 85 db) to get reasonable sound. (Your opinion of "reasonable" will almost certainly vary from mine.) If someone criticizes the quality of the output, they're missing the point.
posted by forrest at 2:44 PM on April 24, 2006


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