How do I bridge a OPA549?

Status
Not open for further replies.
Jump to Latest
#9
have you searched?

this one is nice if you already have a balanced signal 😉
 

Attachments

  • brgc_circ.jpg
    brgc_circ.jpg
    90.1 KB · Views: 667
#10
For my subwoofer project I got a few OPA 549S chips, and some DRV 134 burr-Brown Line balanced drivers, nice if you only have a single-ended input and want to drive a bridged amp.

There is also a method of using a single resistor to bridge amps, Which I have found degrades sound in some cases and improves it on others. You may want to try this.

In addition if you have a buffer amp capable of driving low impedance ~100 ohms, you could drive one amp from its + input and other through the - input. I do not see any major advantage of doing this over the method explained in the much-quoted AN1192, but it is an alternative anyway.
 
#12
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?🙁
 
#14
JojoD818 said:
sangram,

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

JojoD
Click to expand...

🙁 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 🙁
 
#15
thomashek said:
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?🙁
Click to expand...

Do you really need all that gain? Try it with 100K resistors and the pot.
 
#20
Is it bridged or single ended? What is the gain you are using?
Click to expand...

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! :xeye:

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

Very amazed,
JojoD
 
Status
Not open for further replies.
Top Bottom