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A simple mini3 question..

post #1 of 4
2/6/10 at 1:05am
Thread Starter 
For Mini3, I've read on AMB that:
"A zener diode protects the amplifier from damage if the battery becomes disconnected while the AC-to-DC adapter is plugged in"
So is it wrong to use it without a battery inside just by AC/DC adapter?
Also;
"A 7812 voltage regulator allows the use of an AC-to-DC adapter ("wallwart") that outputs anywhere between 15V DC to 24V DC (actual voltage) with a minimum current rating of 300mA for battery charging and for running the amplifier"
I guess it is between 15-24V in case you are both listening and charging battery.Am I wrong? So it takes me to the first question again..

Is it OK to power it by adapter as it has no battery inside and if it is, what should be the voltage?

I feel like I am missing something and asking a stupid question

Thanks..
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post #2 of 4
2/6/10 at 7:27am
Nothing wrong with using it without a battery and any wallwart that fits those requirements will be fine for it.
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post #3 of 4
2/6/10 at 7:40am
Thread Starter 
Thank you
I still find it confusing though why it says 15-24V since it can run by a 9V battery.
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post #4 of 4
2/6/10 at 7:53am
A 15-24V wallwart can be used because there is a voltage regulator (U2) to drop the voltage down to 12V. 15V minimum is needed to ensure that there is enough voltage headroom to fully charge the battery. There has to be sufficient voltage to overcome the dropout voltage across U1, plus some more to be a little higher than a fully-charged 9V battery (which would exceed 10V).

If you run the amp without a battery installed, be sure that the zener diode (D4) is installed and working properly, or the amp might be damaged by allowing overvoltage to get around the voltage regulator. See the schematic and circuit description at the Mini³ website to figure out why this might happen.
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