I'm looking to build an amp (preferably a gainclone) with power up in the 400w (4 ohm) range. This will be used to drive my subs (currently 2 10" 300w rms each in a horn loaded 4th order bandpass aka "Wicked One" design by Decware) I've been driving this box for 3 years now with an audiosource amp one/a a 4ohms. I love the box, but the amp just doesn't cut the mustard for my theater room.
I've done searching and found a couple of designs that use Bridge parallel setups but not with the output I'm looking for.
I was wondering about useing 2 banks of either (2) 4780's (4 total) or 4 3886's (8 total) in a push pull. I know it's alot of work, but I'm sure someone here has done it and has a schematic.
I prefer the simpler the better and with as little in the signal path as possible, but beggars can't be choosers
I had seen one site with a BPA300 using 6 3886's, but he had them in inverting configuration because it was easier to adjust individual DC offset. Does someone have a solid design that uses non-inverting configuration but still able to control individual DC offset?
Thanks for all the help, hopefully I can contribute something back in the future.
I've done searching and found a couple of designs that use Bridge parallel setups but not with the output I'm looking for.
I was wondering about useing 2 banks of either (2) 4780's (4 total) or 4 3886's (8 total) in a push pull. I know it's alot of work, but I'm sure someone here has done it and has a schematic.
I prefer the simpler the better and with as little in the signal path as possible, but beggars can't be choosers
I had seen one site with a BPA300 using 6 3886's, but he had them in inverting configuration because it was easier to adjust individual DC offset. Does someone have a solid design that uses non-inverting configuration but still able to control individual DC offset?
Thanks for all the help, hopefully I can contribute something back in the future.
Why do you want to control the offset of each LM? My design, a mixture of BPA200 and Shine7's BPA300 uses 3 LM3886/board, made for easy bridging of two boards, and it uses op-amps as recommended by National to control the dc-offset. Works like a charm.
But as I said it uses only 3 LM/board, bridging would give you somewhat like 325W into 4R, depending on powersupply.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=130386
You could use the schematic and make something own out of it. To hook up another LM3886 to get 4/board is no problem.
But as I said it uses only 3 LM/board, bridging would give you somewhat like 325W into 4R, depending on powersupply.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=130386
You could use the schematic and make something own out of it. To hook up another LM3886 to get 4/board is no problem.
if you want my opinion, maybe you don't, then give up the idea of 400W from a BPA and use one of National's new driver chips.
http://www.diyaudio.com/forums/showthread.php?postid=1562791#post1562791
http://www.diyaudio.com/forums/showthread.php?postid=1562791#post1562791
Shine7's BPA 300:
I thought the only opamp he was used to invert the signal going to one of the pa150's? I understand that since it is push pull the offset can cancell, but it has to be the same (or close) on both sides in the first place doesn't it?
I see you have a noninverted design that does use servo to control offset... interesting, that might be an option.
AndrewT, I always value other people's opinions, thank you very much for chiming in. Are you telling me not to do this style because it is more complex/expensive? The new chips sound very promising, I could definatly manage to do a basic design, but I think I would be better off using one that is already tried tested and true. My current demands are pretty high, I understand the 3886 and the 4780 enough to take someone else's design and add to it to suit my needs. But I don't know much about the newer chips and the output transistors needed to go with them. Also, at about 50ma drive current, I'd have to add a driver, which is more territory i'm unfamiliar with. Does anyone know of any schematics/project logs using these chips for the power range I'm looking at?
I thought the only opamp he was used to invert the signal going to one of the pa150's? I understand that since it is push pull the offset can cancell, but it has to be the same (or close) on both sides in the first place doesn't it?
I see you have a noninverted design that does use servo to control offset... interesting, that might be an option.
AndrewT, I always value other people's opinions, thank you very much for chiming in. Are you telling me not to do this style because it is more complex/expensive? The new chips sound very promising, I could definatly manage to do a basic design, but I think I would be better off using one that is already tried tested and true. My current demands are pretty high, I understand the 3886 and the 4780 enough to take someone else's design and add to it to suit my needs. But I don't know much about the newer chips and the output transistors needed to go with them. Also, at about 50ma drive current, I'd have to add a driver, which is more territory i'm unfamiliar with. Does anyone know of any schematics/project logs using these chips for the power range I'm looking at?
warriorcookie said:
He is using a balanced linedriver, DRV134, to create the inverted signal. That's also what Im doing. The DRV134 is internally made of op-amps and resistors. It can be done by using op-amps but it's more space-saving with DRV134. The disadvantage is that you cant configure it the way you want it as you can with op-amps.
The dc-servo works very good. I can recommend it! When paralleling its important to get the dc-offset equal on every LM3886, or else they will fight each other making one or more chip to oscillate. That will lead to meltdown of the circuit. I have experienced that when using pots and not so well match resistors
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