OPA549 psu at 31.1v will it be stable? - Page 3 - diyAudio
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Old 1st September 2012, 04:43 PM   #21
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Originally Posted by AndrewT View Post
<snip>
Do you/we design the amplifier heatsink and the cap multiplier heatsink for maximum power testing on a continuous duty?
I don't !!!!
I never design for 'that should be OK' because there are always exceptions that will go beyond your assumptions. Always assume idiots are using the gear. You'll rarely be disappointed.

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Old 3rd September 2012, 05:51 PM   #22
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I would like to know the possibility of using OPA549 in bridged mode but driving even 4 ohms speakers? Since this chip itself is capable of giving a continuous current output 8 ARms so instead of paralleling I would like to bridge it. What should be the Transformers secondary ratings for this configuration. Right now im using 18-0-18 as my sec output from the trafo. Any recommendation for Bridged mode... driving 4 ohms speakers as well...
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Old 3rd September 2012, 06:23 PM   #23
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Originally Posted by rhythmsandy View Post
I would like to know the possibility of using OPA549 in bridged mode but driving even 4 ohms speakers? Since this chip itself is capable of giving a continuous current output 8 ARms so instead of paralleling I would like to bridge it. What should be the Transformers secondary ratings for this configuration. Right now im using 18-0-18 as my sec output from the trafo. Any recommendation for Bridged mode... driving 4 ohms speakers as well...
Nope. Chips are not rated RMS. They are rated at maximum Voltage and current. A 4 Ohm resistive load on a bridged OPA549 with a split 25 Volt supply will draw 12 Amps at signal peaks. Your device is rated for 8 continuous, 10 peak. Bridged into 8 Ohms will make it with a resistive load but a reactive is more difficult. Find a different chip or go discrete.

G
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Old 4th September 2012, 12:02 PM   #24
AndrewT is offline AndrewT  Scotland
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If your PSU is ~+-25Vdc then expect the maximum output from the chipamp to be ~20Vpk.
Into a 4r0 test load the current demand will be ~5Apk. And only 2.5Apk into 8r0.

With a 8ohms speaker, the maximum current demand can be around three times the equivalent resistor load. Expect the current demand to be 7 to 8Apk. This takes most chipamps to near their current limit.

Into 4ohms speakers, that same +-25Vdc supply will take all chipamp beyond their peak current demand. i.e. no chipamp I know of can meet a 15Apk current demand for a 4ohms speaker.
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Old 5th September 2012, 03:11 AM   #25
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He was talking bridging which you know will double the currents. Also the subject line mentions split 31s so who know what he'll really do?

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Old 5th September 2012, 06:43 AM   #26
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hi andrew why cant we use parallel chips? it will use 7.5 amps from each...
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Old 5th September 2012, 09:32 AM   #27
AndrewT is offline AndrewT  Scotland
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because it takes skill to get them to not blow up !!!!
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