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Old 18th January 2005, 07:45 AM   #1
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Default need good but simple amp

heloo i have two opa541 and two opa549. so can u guys tell me some good but simple schematics that i can use these in. i am an amateur havent built many circuits yet.

i also have a 20-0-20v 5amp transformer.

basically i need it to power a subwoofer. its ok if the schematic doesnt have a low pass filter. just need an amp that can pass frequencies down to 30 hz atleast
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Old 19th January 2005, 12:13 AM   #2
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start with the chip's data sheet and then use the search button
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Old 19th January 2005, 01:49 AM   #3
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Do you need PCB layout too?

Becayuse I've built a bridged OPA549 amp (about 150-200W into 8ohm), and have a working PCB file.

The schematic is from National's AN-1192, the BP100 schematic.

If you are interested let me know. I'll put it up on my website.
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Old 19th January 2005, 03:18 AM   #4
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hi there nerd,
i really would appriciate if u put it up on ur website.i am kinda new to this stuff.

and also can u tell me wut is a eagle file and which software do i need to open it?

and the amplifier u r talk abt , can it power a subwoofer of 12ohms?

and do u know anything 4 the opa541.

(and please put up the schematic and also the pcb layout)

and if its not too much trouble could u teach me how to print a pcb. u can put it on ur website if u want.

cuz i print boards with the toner transfer method(lazer print the layout on a butter paper and the iron it and transfer it on the copper board and the etch it in fecl3). but 4 that u need a jpg or acrobat file of the layout which is scaled and should be black and white.
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Old 19th January 2005, 05:04 PM   #5
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First, I'll get it up on my site soon.

Second, an eagle file is a file that opens in Eagle Layout Editor. You can use the free version (the one I use) to open it. It can be downloaded at www.cadsoft.de

Third, 12 ohms is no problem. In fact, it will run cooler because each chip sees a load of 6 ohm instead of 4 ohm. You willl get slightly less power, but not much.

Fourth, I don't like the OPA541. Every attempt I have made using one has started on fire, because it can't drive 4 ohm speakers as well as the 549 can. It may drive your 12 ohm speaker, but if the impedence drops down during use, you run the risk of the same thing happening. You should be fine with 4 ohm though using your supply, but the OPA549 can supply more current to the speaker.

Finally, you can use the toner transfer method. Using eagle, just disable all layers except bottom and pads (I'm using my new computer to type this and it doesn't have it installed yet. When I install it I will tell you how to get to this menu). Then, put the paper in your laser printer and go to file then print. You don't need to mirror the image, but do choose black and white option and click OK.

After the page comes out you can iron it onto the board and etch.

I have been planning on putting a guide to toner tranfer on my site, so I'll do that too.
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Old 19th January 2005, 05:35 PM   #6
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I have had a OPA541 down to 2 ohm with no problem and this at max volume, felt like the room was filled with water. All needed it proper cooling.
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Old 19th January 2005, 06:30 PM   #7
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Well mine was from a cold start, not the slightest bit warm on a large heatsink. The voltage was +/-36 which is within the limit of +/-40.
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Old 20th January 2005, 01:09 AM   #8
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hey i have that eagle software installed.
thing is can u send a link to ur site plz.

i have a 20-0-20v 5amp transformer will that work?

i already have a schematic have a look

ipossible can someone send me the eagle file 4 this schematic. i am not good at pcb designing
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Old 20th January 2005, 01:23 AM   #9
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there is a link to my site in my signature.

you should go for bridge if you want higher power, but if you dont then single chip is fine.
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Old 20th January 2005, 04:26 AM   #10
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where can i find a bridge circuit?

and can u send me a eagle file for the above circuit plzzzz.

i cant seem to find a good circuit for opa549.

wut do u think is the above circuit good enough or do u have any other sugestions?
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