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Old 21st May 2004, 01:46 AM   #1
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Default car audio amp, which way should i go?

i want to build my own amp for my car sub. i'm just starting to collect the parts for it. i dont want to spend all that money on an amp, so i figured i'd just build one.

whats the best way to go?? bridge 2 opa541 chips which can run off of 12V (how much power would that deliver???) or (try and) build a SMPS to turn 12VDC into +/-60 or so??

would the bridged 541 produce good sound, loud volume yet low distortion??

the speaker is a 8-ohm 8" speaker.
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Old 21st May 2004, 04:44 AM   #2
Immo_G is offline Immo_G  Australia
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running bridged off 12 volts into an 8 ohm speaker would give about 10 watts rms off memory. Not really worth the effort, i doubt you'd get over road noise before you clipped it.

I intend to build a smps (getting there, slowly) basically like Rods design (sg3525 based), and then probably P3A amps off it, running around +/-35v . However, for 8 ohm i can see where the higher voltage would come into play.
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Old 21st May 2004, 11:43 AM   #3
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since that chip can run off of a single power supply, is there any kind of linear power boosting circuit i can build to boost the 12V to something higher?? I dont want switching since they are more complicated to build.
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Old 21st May 2004, 03:37 PM   #4
E007 is offline E007  China
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Default here are another idea for you,

you can find the other woofers, which impedance are 4 Ohms or 2 Ohms better, eight inchs. But the cost will increase.

In fact that is very difficulty for the DC-DC convertor build if you are an amateur, you need the coil, MOSFET for switching, and filter, you also need the PCB layout(that is very important)......
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Old 23rd May 2004, 11:44 AM   #5
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i found this schematic while searching.

I have a source for all the parts, except what type of a torrid is needed, and does it even have to be a torrid?

Also, there is a connection labeled Remote. why do i need a remote on it? Since i dont want it, how many other parts connecting to it can i get rid of?

Also, there are +/- 30V feedback connections. what are those for? Can i get rid of them?

Finally, do i need the three 100uh inductors?

EDIT: Do i need that fan also? if not, how many parts connecting to it can i get rid of?

EDIT: Also, how much amperage should this circuit produce?
Attached Files
File Type: zip smps schematic.zip (70.6 KB, 343 views)
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Old 23rd May 2004, 01:42 PM   #6
Immo_G is offline Immo_G  Australia
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I don't think it has to be a toroid, i'm not a transformer expert though (not a fan of that class in my course .

Remote is car use, turns the amp on and off when the headunit/cd player is turned on and off, so the amp isn't idling overnight draining ya battery.

the Feedback means the IC will control switching pattern and length (pwm) to maintain 30 volt rails (ratio dependant). Without this, it basically goes to max with no load, and comes down under load.

Someone said inductors were purely for the feedback circuit, to make the pulse work better, i guess it might get rid of high freq transients or something, a lot don't have them.

Fan depends entirely on your heatsinking, most amps don't have a fan. Allows an easy connection though.

I think Rod said the circuit will do enough for 6 gainclones, its very toroid dependant.

http://sound.westhost.com/project89.htm is best source of info for this circuit.
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Old 29th May 2004, 02:53 AM   #7
dangus is offline dangus  Canada
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Saving money is not a good reason to build an amp. Saving money is why you walk through pawn shops, swap meets, and yard sales looking for a good deal on a used amp.
It'll cost at least as much in parts to build an amp as to buy one, because you can't get parts as cheap as they do in Taiwan, and you'll have to buy whole rolls of copper wire when you only need 6", and pay UPS to deliver the toroid core, etc etc.
How about calling around at the local car audio stores and see if they have any broken amps you can have cheap? Then maybe you can fix it, or at least salvage the case and transformer. Maybe if the amp portion is dead, you can still use the power supply section.
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Old 29th May 2004, 03:03 AM   #8
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just buy an amp.... even a 30watt rms Avalanche amp would be cheaper to buy than making a 30watt amp.. $70... sure, its only 30watts, but to get 30watts you need to step the voltage up.. so... yeah.. lol
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Old 29th May 2004, 02:30 PM   #9
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well all the parts for the PS i can get free samples of or already have (i probably also have a torrid that would work).

The amp would be a lm4651/4652 170W amp.

i guess i shouldnt have said it that way, i want to build it for the fun also.
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Old 31st May 2004, 02:17 PM   #10
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what about using a diode voltage tripler or quadrupler rather than a torrid?
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