Bridge OPA549

soundNERD · 23rd November 2004, 12:56 PM

I built a subamp using 2 OPA549 bridged into a Rockford Fosgate car sub I picked up for 20 bucks at best buy (can't afford an expensive speaker right now).

First, the sound. It's got a ton of power, but, like every audio thing best buy sells, the speaker is thuddy and hits way too hard. It could also be because I have no x-over yet. (just listening through a portable cd player).

Second, the question. On the schematic national has in their AN-1192, it says use a 47k and a 51k. Thats not enough, so I moved the decimal place over one, so a 470K and a 511K. Since I have nothing close to 511k, I used 470K on both. Is this effecting anything? I would think it would affect power output because one amp clips before the other is even at it's full volume level. Right?

Should I change it to a 511k or something close to it?

pics coming soon...

soundNERD · 24th November 2004, 02:12 PM

Anybody?

Alll I need to know is if I should change the feedback resistor on the one amp, if it would make a big enough difference to matter.

GregGC · 24th November 2004, 04:07 PM

I don't think it would make a difference. Going to 470k from 47k would increase the noise level a little bit, but for a car sub that would be insignificant. Why do you need such a high gain, though?

/Greg

soundNERD · 24th November 2004, 06:59 PM

No, I mean going from 470k on the inverting amp to 511k, and leaving 470k on the non-inverting amp.

I do not know why it needs to be that high, but the output of any of my audio sources produces almost no volume with 47k and 51k, but the perfect amount with 470k.

23rd November 2004, 12:56 PM	#1
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Bridge OPA549 I built a subamp using 2 OPA549 bridged into a Rockford Fosgate car sub I picked up for 20 bucks at best buy (can't afford an expensive speaker right now). First, the sound. It's got a ton of power, but, like every audio thing best buy sells, the speaker is thuddy and hits way too hard. It could also be because I have no x-over yet. (just listening through a portable cd player). Second, the question. On the schematic national has in their AN-1192, it says use a 47k and a 51k. Thats not enough, so I moved the decimal place over one, so a 470K and a 511K. Since I have nothing close to 511k, I used 470K on both. Is this effecting anything? I would think it would affect power output because one amp clips before the other is even at it's full volume level. Right? Should I change it to a 511k or something close to it? pics coming soon...

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24th November 2004, 02:12 PM	#2
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Anybody? Alll I need to know is if I should change the feedback resistor on the one amp, if it would make a big enough difference to matter.

24th November 2004, 04:07 PM	#3
GregGC diyAudio Member Join Date: Oct 2003 Location: Toronto	I don't think it would make a difference. Going to 470k from 47k would increase the noise level a little bit, but for a car sub that would be insignificant. Why do you need such a high gain, though? /Greg

24th November 2004, 06:59 PM	#4
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	No, I mean going from 470k on the inverting amp to 511k, and leaving 470k on the non-inverting amp. I do not know why it needs to be that high, but the output of any of my audio sources produces almost no volume with 47k and 51k, but the perfect amount with 470k.