Ok so I have 300W car amplifier that had burned MOSFETS. Now I repaired the amp and decide to test it in house environment. I set up big 300W toroid transformer that has 12V output. Then I used diodes to convert the AC to DC and on the end I used big capacitors to make it fine.
I turned on the amplifier and it sounds great but when I crank it louder SPECIALLY when the song has strong bass, the protection LED stops and starts the supply as the song goes. So when there is strong bass the amp stops and then continues. It is like the torrid is week?
Can you tell me what could be the problem. Should I test it on car battery? Is it possible that 300W torrid has no enough power?
Thank you.
I turned on the amplifier and it sounds great but when I crank it louder SPECIALLY when the song has strong bass, the protection LED stops and starts the supply as the song goes. So when there is strong bass the amp stops and then continues. It is like the torrid is week?
Can you tell me what could be the problem. Should I test it on car battery? Is it possible that 300W torrid has no enough power?
Thank you.
I used one cap from 6400 uF and I use 8 Ohm 15 inch woofer.
Without this capacitor is much worse because it is turning off even on lower volume. And this always happens on strong bass beats. After the beat it turns back on and the sound is little distorted.
See below
Digisoft, a 10,000UF cap will have about 1Volt of Ripple with a 1Amp load, as you are using only a 6400UF cap this will be worse. A 300W car amp is likely to draw somewhere near 30A so effectively you are going to need at least 100,000UF of capacitance so as to keep ripple voltage below 3V. Of if you like so that the rail voltage doesn't drop below 13V when the capacitor isn't being charged
You don't have anywhere near enough capacitance, simple.
Why not test with a car battery? (A nice big Capacitor!!!!)
If not the one from your car then a second hand one? Get one from a scrap yard maybe, if no good for starting a car it may still have enough 'Ooomph' to test your amp, even if only for a few minutes.
Do make sure you fuse it correctly, even work your way up the fuses untill you are sure all is ok and feel safe enough to fit the 'correct' value.
And do be carefull, it's ''the volts that jolts, but the mills that kills''!!!!!!!
Percy.
If not the one from your car then a second hand one? Get one from a scrap yard maybe, if no good for starting a car it may still have enough 'Ooomph' to test your amp, even if only for a few minutes.
Do make sure you fuse it correctly, even work your way up the fuses untill you are sure all is ok and feel safe enough to fit the 'correct' value.
And do be carefull, it's ''the volts that jolts, but the mills that kills''!!!!!!!
Percy.
Oh thank you. I though the amp is bad.
Anyway I measured the AC voltage at full load it is 12V CONSTANT.
Then I measured the DC voltage and it is dropping from 15V to 14V when there is strong bass beat.
Yes I'll try it tomorrow on my car because it is late now. But I really wanted to hear its sound and when I crank it and I heard of/on sound I was disappointed. Then I put one capacitor from 6400uF and it wss better and I could turn it louder but then again at louder level started turning off. I gues I need more capacitors?
I have one question. I have made Class-D amplifier with TDA and it is 150W. This amp is for home use and it is packed with 300W transformer.. I used one 6400uF capacitor and no matter how loud I turn it doesn't turn off This is puzzling me.
And this amp is somehow hungry for capacitors.
Anyway I measured the AC voltage at full load it is 12V CONSTANT.
Then I measured the DC voltage and it is dropping from 15V to 14V when there is strong bass beat.
Yes I'll try it tomorrow on my car because it is late now. But I really wanted to hear its sound and when I crank it and I heard of/on sound I was disappointed. Then I put one capacitor from 6400uF and it wss better and I could turn it louder but then again at louder level started turning off. I gues I need more capacitors?
I have one question. I have made Class-D amplifier with TDA and it is 150W. This amp is for home use and it is packed with 300W transformer.. I used one 6400uF capacitor and no matter how loud I turn it doesn't turn off
This is puzzling me.And this amp is somehow hungry for capacitors.
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.................I have one question. I have made Class-D amplifier with TDA and it is 150W. This amp is for home use and it is packed with 300W transformer.. I used one 6400uF capacitor and no matter how loud I turn it doesn't turn off
Class D amps require much less current.
Courtesy of Wikipedia:-
''..............The main advantage of a class D amplifier is power efficiency. Because the output pulses have a fixed amplitude, the switching elements (usually MOSFETs, but valves and bipolar transistors were once used) are switched either completely on or completely off, rather than operated in linear mode. A MOSFET operates with the lowest resistance when fully-on and thus has the lowest power dissipation when in that condition, except when fully off. (When operated in a linear mode the MOSFET has variable amounts of resistance that vary linearly with the input voltage and the resistance is something other than the minimum possible, therefore more electrical energy is dissipated as heat.) Compared to class A/B operation, class D's lower losses permit the use of a smaller heat sink for the MOSFETS while also reducing the amount of AC power supply power required. Thus, Class D amplifiers do not need as large or as heavy power supply transformers or heatsinks, so they are smaller and more compact in size than an equivalent Class AB amplifier............''
Right... 12V of AC signal on a 16V supply means that the supply is dropping to about 4V DC when the cap isn't being charged by the trafo & bridge
You have your answer, need a much bigger capacitor
Hey DigiSoft,
your amp is probably quoting power output, not input, so 300w of audio power needs more than that supplied- no amplifiers are 100% efficient.
People regularly bring me amps and tell me 'oh yeah, it puts out so and so', only for me to point out that it doesn't draw that much from the wall.
You could be drawing twice that on peaks, and if you have a digi meter, it may not react quick enough to the transients or filter out what is happening.
I have a friend who put over 1k of audio in his car- the headlights dimmed when it pulled current.
The solution was to fit a one farad capacitor! That is a truly massive value- nearly a hundred and sixty times bigger than what you are using (6400)
BTW- he won a sound off with this system, but without a remote control, no-one could get back in the car to turn it off!
your amp is probably quoting power output, not input, so 300w of audio power needs more than that supplied- no amplifiers are 100% efficient.
People regularly bring me amps and tell me 'oh yeah, it puts out so and so', only for me to point out that it doesn't draw that much from the wall.
You could be drawing twice that on peaks, and if you have a digi meter, it may not react quick enough to the transients or filter out what is happening.
I have a friend who put over 1k of audio in his car- the headlights dimmed when it pulled current.
The solution was to fit a one farad capacitor! That is a truly massive value- nearly a hundred and sixty times bigger than what you are using (6400)
BTW- he won a sound off with this system, but without a remote control, no-one could get back in the car to turn it off!
Wow 1k
I can't feed this beast of 300W and not 1K lol
So there are chances that my headlights may dimm
Well I've asked about this big capacitors but they are really expensive
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Yes I'll try it tomorrow on my car because it is late now. But I really wanted to hear its sound and when I crank it and I heard of/on sound I was disappointed. Then I put one capacitor from 6400uF and it wss better and I could turn it louder but then again at louder level started turning off. I gues I need more capacitors?
I have one question. I have made Class-D amplifier with TDA and it is 150W. This amp is for home use and it is packed with 300W transformer.. I used one 6400uF capacitor and no matter how loud I turn it doesn't turn off
And this amp is somehow hungry for capacitors.
Like someone said - if you're running 12V, you need huge amounts of current. The above mentioned home amp will run at a much higher voltage (30V maybe), so it will require much less current. It's the capacitors that hold up the current until the amp needs it, then the dump their charge, then recharge as soon as they can.
To give you an idea of what's needed, I used 2x 10,000uF caps for my class AB amp, and they aren't enough. I used 5,500uF for my little class D amp (15w/channel).
If you still want to use the amp at home, you can buy high power 12v supplies, such as
POWERCOOL|PC850AUBA|PSU, 850W 80+ DUAL 12V V2.2, POWERCOOL | CPC
This'll probably do. I've never tried them, but they should do for the price you pay. There's lower power ones (down to 350W), so you can choose how much you pay.
Chris
is 300 watts its rms rating or peak? if it is 300 watts rms, that means it will be pulling more than that from the tranny. look at the max wattage rating of the amp and get a torrid that has that rating, or even better get a higher watteg rating
Well I use analog multimeter so I can read fast drops and while the music is running the voltage drops about ~1V DC. But when I crank it louder the voltage start dropping about 1,5-2V DC and then the amp starts shutting down.
How is this possible? This is not very strong amp at all. And my car battery is very fresh.
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