opa 549 problem

arvin_ray · 27th April 2005, 08:08 PM

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...

jaudio · 27th April 2005, 09:05 PM

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.

BlackMTX · 28th April 2005, 03:36 PM

check your pcb if there are some shorted ckts.

Hugh M · 29th April 2005, 11:17 AM

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

arvin_ray · 29th April 2005, 04:02 PM

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....

arvin_ray · 29th April 2005, 04:51 PM

here's the pic

jaudio · 29th April 2005, 04:57 PM

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.

BlackMTX · 29th April 2005, 05:39 PM

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.

BlackMTX · 29th April 2005, 05:39 PM

im sorry, it should be 20-0-20V, 4amps

carlosfm · 29th April 2005, 07:06 PM

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?

27th April 2005, 08:08 PM	#1
arvin_ray Banned Join Date: Jan 2005 Location: angeles	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...

29th April 2005, 11:17 AM	#4
Hugh M diyAudio Member Join Date: Sep 2004 Location: Saint John NB	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 __________________ Lots of Fun and Good sound too - Who could ask for more?

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27th April 2005, 09:05 PM	#2
jaudio diyAudio Member Join Date: Oct 2004	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.

28th April 2005, 03:36 PM	#3
BlackMTX diyAudio Member Join Date: Dec 2003 Location: Quezon City	check your pcb if there are some shorted ckts.

29th April 2005, 04:02 PM	#5
arvin_ray Banned Join Date: Jan 2005 Location: angeles	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....

29th April 2005, 04:57 PM	#7
jaudio diyAudio Member Join Date: Oct 2004	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.

29th April 2005, 05:39 PM	#8
BlackMTX diyAudio Member Join Date: Dec 2003 Location: Quezon City	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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