How do I bridge a OPA549?

[JojoD818]

sangram,

Hi, could you please post a schematic of the OPA549 amp setup you used in your sub? Thanks!

JojoD

[Thomas Giz]

Hi MAD_K

I used your scheme with two opa549 for balanced signal input to built indeed nice sounding amp. However I implemented 220K feedback resistors instead of 100K ones. I also put two stereo 100K steeped attenuators to control signal input. Everything is working fine but one thing. There is a kind of white noise at the output of the amp. No hum at all only that noise. It did appear after attenuators were connected so I think that's the reason or maybe there is something else.
I figured out that when I turn the pot to level where attenuation is at level of about 50K the noise is minimal. Is 100K too much for pot. Any other clue?

[hitsware]

Originally posted by JojoD818
mike,

Alright! Thanks a lot! At least I know what I'm getting into. If you have any other ideas please let me know.

Cheers,
JojoD

http://home.comcast.net/~jhyamamoto/bridgeamp.gif

[sangram]

Originally posted by JojoD818
sangram,

Hi, could you please post a schematic of the OPA549 amp setup you used in your sub? Thanks!

JojoD

Sorry man I've just relocated and my stuff is going to get here only in 1 month, so I don't have access to the schematics till then.

Nothing too complex however I used the schematics off of the datasheet as the application is not particularly demanding. The OPA 549 are configured as non-inverting amplifiers and the two speaker terminals are connected to the outputs of the two amps. The single-ended input is fed into an unity-gain configured DRV134, which has a balanced output. Each of the outputs is connected to a opa 549 input.

I still have to construct the sub, phase control and the MFB section, it will take ~6 months (I don't get much free time).
Sorry I couldn't help you with a schematic

[Mad_K]

Originally posted by thomashek
Hi MAD_K

I used your scheme with two opa549 for balanced signal input to built indeed nice sounding amp. However I implemented 220K feedback resistors instead of 100K ones. I also put two stereo 100K steeped attenuators to control signal input. Everything is working fine but one thing. There is a kind of white noise at the output of the amp. No hum at all only that noise. It did appear after attenuators were connected so I think that's the reason or maybe there is something else.
I figured out that when I turn the pot to level where attenuation is at level of about 50K the noise is minimal. Is 100K too much for pot. Any other clue?

Do you really need all that gain? Try it with 100K resistors and the pot.

[Tony]

In the TI datasheet for the 549, I can only find a parallel setup. This is not the same as bridge right?

you can use the ns techniques for bridging the power op amps, just pay attention to the pinouts as they may not be the same, but the priciples for bridging are the same...

we have a local site devoted to gainclones....
http://www.pinoydvd.com/start.htm

[JojoD818]

Tony,

Nice link! Thanks! I have not owned a DVD myself, now I can learn before I buy! Planning to buy a NextBase DVD Player.

JojoD

[JojoD818]

Hi everyone,

I was so amazed with the 549! I used it on a 12 inch dual voice coil sub using only one of the coils and it rocks! I keep on catching stuff that falls around my workbench!

I can't believe a small chip can drive such a huge speaker! Good things do come in small packages .

JojoD

[miguel2]

Is it bridged or single ended? What is the gain you are using?

Miguel

[JojoD818]

Is it bridged or single ended? What is the gain you are using?

It is single ended, single amp driving a dual 4 ohm voice coil sub. I tried connecting only one voice coil and it became very loud. I series the coils for an 8 ohm connection and it was also good.

I built 2 channels of the OPA541 and connected each amp to each of the coils and was very amazed how well it sounded. Tomorrow I will try it loud since it is already 10:32PM here, neighbors might get mad!

Then I will build another channel of the OPA549 and test it with the same setup as the OPA541.

Very amazed,
JojoD