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Old 9th April 2006, 04:14 AM   #1
methar is offline methar  Thailand
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Join Date: May 2005
Location: BKK
Default Question on OPA549 / OPA541

I searched old threads but still cannot exactly find the answers to the question belows.

1). As the max continous current of an OPA549 is 10A, do we really need 10A transformer for each of them? If not, what is recommended Amphere the transfer should be (for mono)?

2). For one 18-0-18V (300VA) for stereo at gain x10 gainclone, which one of OPA549 or OPA541 should be used?

3). How much Watts will we get from OPA549 with +/-25Vdc ?

4). For subwoofer (gain x22), should we go for OPA549 (+/- 25Vdc), or OPA541 "AP" (+/-34Vdc) ?

5). For subwoofer, how the parallel two of LM3875 (+/-35V) goes compare with OPA541/549 as I already have LM chips on hand?

Million thanks!
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Old 3rd July 2006, 08:51 PM   #2
DACMan1 is offline DACMan1  South Africa
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Join Date: Jun 2006
1) No. These chips will anyway only do about 4 amp continuous and they really start doing funny stuff when you ask them do dissipate more than 40W, regardless of hetsink temp. For mono, about 80VA transformer would be mor than enough.

2) These are not as powerful as TI clams!! So go for the 549.

3. If you're optimistic, these will drop about 3V off your rail, so thats 25-3=22. 22^2/(2*8)=30Wrms into 8 ohm.

4) Maybe puttin about 5 of the 541 in parallel could be acceptable.

5) If you already have LM3875 amplifiers, don't waste time on these burrbrown op-amps! I've used them quite a bit, their always a let down.
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Old 4th July 2006, 04:21 PM   #3
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Join Date: Mar 2003
Location: Windsor
I agree completely with DACMan1, although the TI chips can sound good, they just don't have the output of the LM series. I would equate the OPA549 to an LM1875. I had some very nice boards I threw together with 4 OPA549 in bridge parallel, that I was planning on using as a sub the end it just didn't have the output I needed.

If you take something apart and put it back together again enough times, eventually you will have two of them.
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