RE: ac adapter question

[Edwin Hurwitz <edwin@indra.com>]

>  My understanding is that you have to match the miliamps as well as 
>the voltage. some devices can handle deviations better than others 
>but large variations are to be avoided. Often if one tests actual 
>output with a meter,it's not precisely as marked. Also the polarity 
>of the connector has to match,some have the outer ring positve ,some 
>negative,this is usually marked. I  discovered this when I had one 
>that fit the specs but didn't work ,when I noticeds the  reversed 
>polarity  I cut off the connector, switched it around,and 
>reconnected-worked fine.
>It's easy to find lots of wallwarts at thrift stores for cheap,you 
>can take the device with you to test if they work.



Current (measured in milliamps) doesn't have to match. You want to 
make sure that the adapter supplies more current than the unit needs. 
99% of the time, effects don't draw anywhere near the capability of 
the adapter. My Lexicon LXP 5 is one that needs a full 1500 ma AC. 
Most stomp boxes are in the 50 ma range.


When testing the output of an adapter, often you will find the output 
to be overrated considerably. This means that the output is not 
regulated. While in some cases it may not matter, you really want a 
regulated supply. It will mean that your effects will run a lot 
quieter and more reliably. Some effects will really have a problem 
with an unregulated supply and hum a lot and act  weird. My MXR Micro 
flanger is one of those. Unfortunately it fried after getting hooked 
up accidentally to a reverse polarity adapter. It's unfixable. Good 
news is that the Lexicon G2 has a dead on copy of it.

Anyway, hth.
Edwin
-- 

Edwin Hurwitz
Boulder CO
http://www.indra.com/~edwin
http://www.cafemontalban.com Location Recording Services