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Old 27th April 2005, 08:08 PM   #1
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Unhappy opa 549 problem

i have built an 8pcs opa 549 (bridge paralleled using drv134) using 24v-0-24v xformer and ive heard a hissing sound while playing music,its some kind of osscilation or EMI i guess???where does this came from cn somebody help me...





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Old 27th April 2005, 09:05 PM   #2
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Check all ground connections(including signal input ground).

Check the connections from the drv134 to opa549. If the drv134 is not well connected,you will get hiss

What is your gain? It might be too high.

OPA549 has the max voltage list at +/-30,your supply voltage might be too high.
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Old 28th April 2005, 03:36 PM   #3
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check your pcb if there are some shorted ckts.
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Old 29th April 2005, 11:17 AM   #4
Hugh M is offline Hugh M  Canada
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If you are using a PCB, make sure to scrub off any flux with alcohol.
I've run into this issue on several occasions. I guess you could call it "Flux Coupling"
Hugh
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Old 29th April 2005, 04:02 PM   #5
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tnx..i have fix it already i change the value of the resistor and it works well but because of a little heatsink i have u cnt even touch it because its too hot!!!..and its killing my xformer coz i only got 4700uf caps 50v...and whenever i use my large caps 120000uf 40v it kills the opa..but before the opa crashes u can hear a noisy sound it isnt a hum but its a loud sound like osscilation then my opa burns can u help me with this tnx a lot....
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Old 29th April 2005, 04:51 PM   #6
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Default my opa 549

here's the pic
Attached Images
File Type: jpg dscf0017.jpg (79.9 KB, 380 views)
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Old 29th April 2005, 04:57 PM   #7
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If you are not using the all metal(can)opa549 then the voltage from you transformer is too high(24*1.414=33.936). It is triggering shutdown.
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Old 29th April 2005, 05:39 PM   #8
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i used the same heatsink as yours, single sided,10 inches, but no problem at all, the heatsink is warm but not hot, i used 24-0-24V,4amp, the sound is good,it really kicks my subwoofer.
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Old 29th April 2005, 05:39 PM   #9
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im sorry, it should be 20-0-20V, 4amps
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Old 29th April 2005, 07:06 PM   #10
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Default Re: my opa 549

Quote:
Originally posted by arvin_ray
here's the pic
Nobody noticed yet that there's something missing on this board?
No PSU caps on the OPA549 chips?
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