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Old 5th February 2011, 07:05 AM   #11
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Hi Robilo
Have you looked at the current rating of the fuse in your car amplifier????
Mad Mark
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Old 5th February 2011, 03:06 PM   #12
roblio is offline roblio  Dubai
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Originally Posted by madtecchy View Post
Hi Robilo
Have you looked at the current rating of the fuse in your car amplifier????
Mad Mark
hi yah its has two 25A fuse. can i used my 13vac 5a?is it safe?
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Old 7th February 2011, 12:21 PM   #13
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No, it's not safe. I wouldn't even recommend using the 12V transformer you hooked up, since 12Vac * SQRT(2) = 16.9Vdc, which exceeds the maximum input voltage of your amp. Realistically, it will only provide something like 12Vac * 1.3 = 15.6Vdc under load, but then you're still pushing the envelope. What's probably saving your amp right now is the fact that your little 36VA transformer is probably struggling to cope with the power demands of the amplifier, causing the voltage to drop. Possibly the transformer runs hot as well, especially if you play the amp.

Pay heed to the advise others have given already in this thread. You'll need more power even if those 600W printed on the amp is a gross exaggeration; if it is capable of doing about 75W rms as Martin suggested, you'd still need a transformer that's about 6-10 times the size of the transformer you're using now. And any transformer that supplies more than about 11Vac (>15.5Vdc rectified; maybe about 14.3Vdc effectively under load) is a no-go, as you risk blowing up the amp with a too high input voltage.
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Old 7th February 2011, 01:45 PM   #14
roblio is offline roblio  Dubai
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Originally Posted by mastodon View Post
No, it's not safe. I wouldn't even recommend using the 12V transformer you hooked up, since 12Vac * SQRT(2) = 16.9Vdc, which exceeds the maximum input voltage of your amp. Realistically, it will only provide something like 12Vac * 1.3 = 15.6Vdc under load, but then you're still pushing the envelope. What's probably saving your amp right now is the fact that your little 36VA transformer is probably struggling to cope with the power demands of the amplifier, causing the voltage to drop. Possibly the transformer runs hot as well, especially if you play the amp.

Pay heed to the advise others have given already in this thread. You'll need more power even if those 600W printed on the amp is a gross exaggeration; if it is capable of doing about 75W rms as Martin suggested, you'd still need a transformer that's about 6-10 times the size of the transformer you're using now. And any transformer that supplies more than about 11Vac (>15.5Vdc rectified; maybe about 14.3Vdc effectively under load) is a no-go, as you risk blowing up the amp with a too high input voltage.
thanks mastodon i better change my transformer if thats so. what would you recommend (transformer Vac and amp)if i want to use those 75W rms full power?
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Old 7th February 2011, 02:00 PM   #15
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also, which is better full wave rectifier or half wave?
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Old 7th February 2011, 02:00 PM   #16
AndrewT is offline AndrewT  Scotland
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sell the car amp to someone who wants to use it in a car.

Buy or build a mains powered amplifier for use in a mains powered home.
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Old 7th February 2011, 02:55 PM   #17
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You could try to find a transformer that will output about 10 Vac @ 20A minimum (200VA) for 75Wrms per channel and a bridge rectifier that will stand such currents (so including an adequate heat sink). And it might be a good idea to filter the power as well, so you'll need some big elcos. Mind you, we're working at this hypothetical 75W per channel, but it's possible that this amp is capable of much more. That would require an even beefier power supply though, so you're venturing into the realms of really expensive and infeasible parts.

Or you could do as Andrew says and just build something else. Because this car amplifier just isn't going to be a very practical solution, all considered.
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Old 10th February 2011, 07:37 AM   #18
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if i buy a power amplifier what would be the best?in terms of brand and watts?what i want is to put up 4 12" subwoofer. also i need a low-pass x-over. can i buy it as one just like the car amplifier?
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Old 10th February 2011, 09:18 AM   #19
AndrewT is offline AndrewT  Scotland
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if i buy a power amplifier what would be the best?in terms of brand and watts?what i want is to put up 4 12" subwoofer. also i need a low-pass x-over. can i buy it as one just like the car amplifier?
buy 8ohm drivers.
Parallel them into two pairs to give two 4ohm loads.
Buy a 2channel 4ohm capable amplifier. That amplifier, if 4ohm capable, should easily drive 2r0.
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