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Old 3rd July 2004, 02:37 PM   #1
Stefano is offline Stefano  Italy
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Default Car amp->home amp

I'm going to buy a used Adcom gfa-4304 car amp, it was described as assimetrical class A like aleph amps and i'm curious to know if there is something designed by Nelson.
My intention is to make it an home amp and i can see two ways to do it: to build a 12-14V pwr supply to simulate a car battery or to ignore the "survoltore" (i don't know how to call it in English) and build a much more cheap pwr supply verifying voltages with a meter.
Any opinion or info is welcome!
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Old 3rd July 2004, 04:07 PM   #2
Immo_G is offline Immo_G  Australia
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I haven't seen a real class A car amp, JVC made one which drew about 250ma at 12v while idling (so maybe 40ma idle current per channel), labelled pure class A. Tru Tech makes the A Class, which is 15 watts class A, then about 200 watts AB. Class A in car amps just means their SQ ones, or basically double the price you'd pay for that power

A computer power supply will do about 8-10 amps into 12 volts, which can run a car amp. Alternatively, you should be able to remove the toroid inside the amp, and wire in normal transformer to that point. The only concern i have would be the voltage feedback/monitoring/protection stuff on the 12v side, which would then only get power via a feedback line, might kill the IC. Also it might mute the amp parts.
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Old 3rd July 2004, 04:40 PM   #3
Stefano is offline Stefano  Italy
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Tank you Immo_G for your answer
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Old 3rd July 2004, 04:58 PM   #4
anatech is offline anatech  Canada
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Hi Stefano,
Why don't you just make an AC supply to supply the converted bipolar voltages? This might be more efficient. Just tap into the amp at the filter caps. You don't have to take anything out so you could put it back in the car later.
You will find the amp draws huge peaks from the 12V (actually around 14VDC) supply if you run it that way.
-Chris
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Old 3rd July 2004, 05:15 PM   #5
Stefano is offline Stefano  Italy
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It's exactly what i've in my mind, test the voltage at the PSU-amp node and build an appropriate 220V PSU, it would be more easy since it has minor current necessity
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Old 3rd July 2004, 05:17 PM   #6
Stefano is offline Stefano  Italy
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Anyone could confirm me specifications of the Adcom? It's a 4x30W unit, Nelson do you know something about?
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Old 3rd July 2004, 05:32 PM   #7
anatech is offline anatech  Canada
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Hi Stefano,
Just looked on the Adcom website under "archived products" but the link is down. Try later at www.adcom.com. Someone here may know of the top.
-Chris
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Old 3rd July 2004, 05:43 PM   #8
sss is offline sss  Israel
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first :i dont think that u got a true class A car amp becaause i dont think there is a commercial company stupid enough to make that .

u can use a normal +-25V transformer for most car amps if u will disconnect the switching power supply
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Old 15th July 2004, 01:28 PM   #9
Stefano is offline Stefano  Italy
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No one knows how to find service manual of the adcom? I don't want to mount it in my car and i'm waiting to hear it as soon as possible, Nelson have you really designed those gear? Have you any info?
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Old 18th July 2004, 01:12 AM   #10
bob123 is offline bob123  United Kingdom
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y dont you use a car battery and atach a car battery charger in parallel to allow large currents. this will also give higher quality sound as a battery has no fluxuations in voltage and has unlimited (well nearly) current.
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