Hello everyone!
I am a bit curious as to how to get high power out of some LM3886 or TDA chips. I am looking into buying a 1600 watt 8 ohm sub woofer and was wondering how i can put around 1000 watts into this. I was looking at using a lot of LM3886 chips/kits. I ran across the BPA200 schematic and was wondering if something like this would work. Bascially 2 x 4 LM3886's in parallel and then bridged. Would 2 x 8 LM3886's in parallel then bridged add more power? Or would that just split up the load?
Thanks in advance!
I am a bit curious as to how to get high power out of some LM3886 or TDA chips. I am looking into buying a 1600 watt 8 ohm sub woofer and was wondering how i can put around 1000 watts into this. I was looking at using a lot of LM3886 chips/kits. I ran across the BPA200 schematic and was wondering if something like this would work. Bascially 2 x 4 LM3886's in parallel and then bridged. Would 2 x 8 LM3886's in parallel then bridged add more power? Or would that just split up the load?
Thanks in advance!
There are some basic power equations that impose some limits.
Power to a load R will be P = V²/R which is equivalent to P = I²R.
Those expressions are valid for DC and for RMS AC.
We can also solve them for voltage and current:
V = √(P R) and I = √(P/R)
So, for 1000 Watts into 8 Ohms, V = 89.44 Volts RMS
V peak = (√2)(V rms) = 126.5 Volts peak
That's more voltage than the chipamps can handle.
The only way to get that much power with a lower voltage would be to lower the R value.
Power to a load R will be P = V²/R which is equivalent to P = I²R.
Those expressions are valid for DC and for RMS AC.
We can also solve them for voltage and current:
V = √(P R) and I = √(P/R)
So, for 1000 Watts into 8 Ohms, V = 89.44 Volts RMS
V peak = (√2)(V rms) = 126.5 Volts peak
That's more voltage than the chipamps can handle.
The only way to get that much power with a lower voltage would be to lower the R value.
Wow thanks for the great information! I guess it looks like im either gonna have to find a 4 ohm sub or wire two of these in parallel. I can't even think of a chip amp that's capable of putting out 100 volts. I know the lm3886 is capable of about 40 volts... but does anyone know how many volts bridged? I guess I would only be able to achieve 500 or so watts at around 40 or 50 volts with the lm3886. Anyone have any other amp suggestions?
Thanks!
Bridging the 50W LM3886 may develop about 200W in Bridge Mode.
I posted an article at http://www.diyaudio.com/forums/subwoofers/211687-maplin-sub-woofer-project.html which explains the maths behind bridging amplifier modules.
You'll need to drill down to Post #4
I posted an article at http://www.diyaudio.com/forums/subwoofers/211687-maplin-sub-woofer-project.html which explains the maths behind bridging amplifier modules.
You'll need to drill down to Post #4
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Bridging allows one pair of amplifiers to deliver double the power into double the load impedance.
If you start with a pair of 68W chipamps and bridge them, the maximum you can get is 2*68W into your new load. Note that two 68W chipamps can deliver 68W+68W into two loads. That is exactly the same maximum power output as for the bridged arrangement.
If you parallel chipamps, you can drive a load to twice the current. This allows one to halve the load impedance for approximately double the power. But that doubling of power cannot actually be achieved. The lower the load impedance, the worse that loss from theoretical becomes.
Let's take a 68W 3886 running at near maximum supply voltage.
It will deliver 68 into 8r0.
Bridge a pair of them and you get 136W into 16r0.
Now take 4chips and parallel & bridge them.
You can now drive half that 16ohm impedance, i.e. 8r0 and get nearly double that 136W. 250W might be achievable. 4 chips in BPA200 arrangement to get a maximum of 250W into 8r0. These cannot be used to drive a 4r0 load any higher than than that same 250W maximum !!!
That 4chip could be increased to 8chip in a BPA400 arrangement and could drive a 4r0 load from near maximum supply rails. Expect 450W into 4r0 as a sensible maximum power capability
Far simpler to pick up an lme49811 and use that to run on +-90V supply rails for big power delivery.
If you start with a pair of 68W chipamps and bridge them, the maximum you can get is 2*68W into your new load. Note that two 68W chipamps can deliver 68W+68W into two loads. That is exactly the same maximum power output as for the bridged arrangement.
If you parallel chipamps, you can drive a load to twice the current. This allows one to halve the load impedance for approximately double the power. But that doubling of power cannot actually be achieved. The lower the load impedance, the worse that loss from theoretical becomes.
Let's take a 68W 3886 running at near maximum supply voltage.
It will deliver 68 into 8r0.
Bridge a pair of them and you get 136W into 16r0.
Now take 4chips and parallel & bridge them.
You can now drive half that 16ohm impedance, i.e. 8r0 and get nearly double that 136W. 250W might be achievable. 4 chips in BPA200 arrangement to get a maximum of 250W into 8r0. These cannot be used to drive a 4r0 load any higher than than that same 250W maximum !!!
That 4chip could be increased to 8chip in a BPA400 arrangement and could drive a 4r0 load from near maximum supply rails. Expect 450W into 4r0 as a sensible maximum power capability
Far simpler to pick up an lme49811 and use that to run on +-90V supply rails for big power delivery.
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No, max is ~68W
No, I explained the options by referring to the BPAx00 arrangements.
The 200 and 300 in the National titles are what they recommend and expect in Watts from each of these arrangements. National don't show the 400, as far as I have seen. They only show the 200 and 300 arrangements. Both are relatively complex to get working properly and often cannot be debugged by inexperienced builders, i.e. they blow up.
lme49810 and lme49830
lme49810 and lme49830
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Try search for this , IRAUDAMP9
Or IRAUDAMP7 Full Bridge.
For such high power woofers, its better to go for Class-D
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