Bpa200 Opa549 Sub Amp

[Gcollier]

Hello Folks!

It's been a while since I posted anything here, a bit busy with other things...like work. In any case, I'm looking for some critique on my BPA sub amp design. It consists of 2 parallel OPA549s bridged with a DRV134. I have used an OPA2134 with a LPF in front of the bridge driver. The total size for all of the boards is 4"x6". I still need to work on the PSU board for the amps, I wan't something nice with a soft start, it will likely be unregulated.

Suggestions are welcone/encouraged

G.

[Gcollier]

Here is the schematic for the bridging board. I would like to incorporate a pot to adjust the LPF, but haven't fir it in yet. Also I may add some sort of offset nulling circuitry.

G.

[swigley]

Gcollier,
I like the design. I'm new at this, so my scrutiny, doesn't mean much. I have just started looking into chipamps to replace the amplifyer in a JBL sub that has died. I was looking at doing something like this design http://www.shine7.com/audio/bpa300.htm, except with four LM3886s instead if six. Like your design, he also uses a DRV134 to bridge two paralelled amps. I was thinking of putting the bridge circuit and the two bridged paralelled amps all on the same board.

I don't know if it's true, but I hear the OPA549 is not very good for higher power amps: http://www.diyaudio.com/forums/showthread/t-40189.html. I'd like to learn more about your design and see a schematic if you have one.

[Gcollier]

Originally posted by swigley
Gcollier,
I don't know if it's true, but I hear the OPA549 is not very good for higher power amps: http://www.diyaudio.com/forums/showthread/t-40189.html. I'd like to learn more about your design and see a schematic if you have one.

I haven't had a chance to build this one yet. I have been busy with other projects. I have build a very similar parallel circut using this chip, and I would say the output is sufficient for my needs. I would agree that the LM chips can get you much higher output. The real issue with the OPA549 is the limited gain bandwith product. For a sub amp high gains are ok, but if you want to use them fullrange you need to keep the gain rather low. The LM3886 does not suffer from this problem. Honestly the simplest solution you might find is to bridge a pair of parallel LM4780's.

I do have another circut I was working on that use the LM3886 similar to what Digi did in the link you posted. Mine is based on that and the Jeff Rowland Concerta design. It is a single board with 3 parallel chips per side. If you are interested I can post it later.

G.

[PierreG]

Originally posted by Gcollier


I do have another circut I was working on that use the LM3886 similar to what Digi did in the link you posted. Mine is based on that and the Jeff Rowland Concerta design. It is a single board with 3 parallel chips per side. If you are interested I can post it later.

G.

I would be interested to see it.

[swigley]

Originally posted by PierreG


I would be interested to see it.

Me too. Thanks for the insight. I'm going to look into the LM4780.

[Alcaid]

Originally posted by swigley
.....
I don't know if it's true, but I hear the OPA549 is not very good for higher power amps: http://www.diyaudio.com/forums/showthread/t-40189.html.
.....

That is not true. It's not suited for high GAIN, it's well suited for high POWER applications. Big difference.
Gain can be taken care of elsewhere in the circuit (preamp, input stage, bridging etc.)
Use a voltage gain of +/- 10 on the OPA549, and they will sing

[jaudio]

I'm using the opa549 in the bridge mode with a gain of 13 each side for a total of 26. The power supply is +/-18.

Sounds very good with Carlos' AD815 preamp.

[Gcollier]

Originally posted by PierreG


I would be interested to see it.

Ok here is my very rough BPA300 design using the LM3886. I have not added the DRV134 on the actual amp board as I was actually looking at using a different balanced line driver for this. I have most everyting routed, I just need to add conections for the incoming power and also the signal input connections. All of the mute pins are connected to a single resistor and capacitor for a soft startup, there are trimpots for each chip to trim the DC offset. The board is 11.75" X 1.75" (yup it's a big one ) I have put this project on the side burner for now as I am too busy with other projects.

G.