opa 549 problem

[arvin_ray]

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]

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]

check your pcb if there are some shorted ckts.

 

[Hugh M]

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]

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]

my opa 549

here's the pic

 

[jaudio]

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]

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]

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

 

[carlosfm]

Re: my opa 549

here's the pic

Nobody noticed yet that there's something missing on this board?
No PSU caps on the OPA549 chips?

 

[arvin_ray]

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

what is your gain is 22 too high?did u also use 8 opa549??

 

[arvin_ray]

Re: Re: my opa 549

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.

my gain is 22 is it too high?

Nobody noticed yet that there's something missing on this board?
No PSU caps on the OPA549 chips?

my PSU is separated..but for now i have no xformer(24-0-24v 5amps) for it was burn by those OPA's after i load that amp 2 ohms..sorry..

 

[Alcaid]

1. Like Carlos said: Add psu coupling caps as close as possible to the chips.
2. Have you isolated the chips from the heatsink?
3. Those chips can only take +/-30V DC, measure your PSU voltages when not playing music.
4. Gain is too high! I would recommend a gain of 10-12 max.

 

[arvin_ray]

here's a pic of bridge opa 549 2 channel(stereo)

here are the pix of the opa 549 2 channel (bridge)--designed by my friend..

 

[arvin_ray]

bottom view

bottom view

 

[arvin_ray]

top view

top view

 

[BlackMTX]

i use only 4 chips for my subwoofer, 8 chips if you want stereo, used bypass capacitors and zobel network, and to minimize dc offset insert capacitor, you can follow the schematic below if you want, decrease the gain if you want as they say, got this diagram on the thread

 

[BlackMTX]

i thought you connected in bridge-parallel?so u used this circuit?bridge only...