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required voltage/amperage


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y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: February 28, 2009 at 11:21 PM / IP Logged  
Ok so I have a spare car amplifier running around, and I also can get a power converter from AC to 12V DC with 0-29A.  I was wondering if this power converter would be "strong" enough to run an amplifier.  I figured with the extra amp lying aroud I could wire it up to my tv, and use a "homemade" surround sound system with the extra junk lying around.  I'm not sure how many amps an amplifier requires - too me thats it's purpose increase amperage right?
haemphyst 
Platinum - Posts: 5,054
Platinum spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: March 01, 2009 at 1:53 AM / IP Logged  
How many watts is it? Generally, figure this:
Output power * 1.5 = Input power
Input power / 12 = Input current
To go the other way around...
You have 29A. 29A * 12V = 348W
348W * .6 (60% efficiency) = 208W
208W / 2 = 104 WPC RMS
That 29A power supply will power *up to* a 100 WPC amplifier comfortably.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: March 01, 2009 at 9:57 AM / IP Logged  

Im assuming 208W/2 = 104 WPC is you assuming its a 2 channel amplifier correct?  If its a 4 channel amp then it would be 52WPC etc....

So assuming a 2 channel amp, and the 104WPC limitation - I wouldnt want to set the amp to put out a constant 100W - because of the fluctuations right?  That would be like the max output, so I would want to set it somewhere around 80W RMS?

haemphyst 
Platinum - Posts: 5,054
Platinum spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: March 01, 2009 at 1:09 PM / IP Logged  
Already figured into the calculations. Peak power comes from within the amplifer, generally, and I am still going to stick with the 100 WPC safe range. 20 watts per channel will make zero audible difference anyway.
Unless you are running sine wave power, (but who listens to sine waves, anyway?) there will be no WAY for you to "set the amp to put out a constant 100W". Music doesn't behave like that.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: March 01, 2009 at 1:20 PM / IP Logged  

Sorry, I used the wrong wording there - I didnt mean a constant 100W.  What I mean is adjusting the gain to make it louder etc.  Wouldnt the amplifier start clipping earlier than it would normally? 

Although I guess it doesnt really matter; in the end all I have to do is just adjust the gain like I normally would...


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