Hi Guys, I just found another transformer that after rectification and with a 56000uF cap I get 40Vdc , I know these (lm3886) can handle the 42Vdc as its limit, would 40V be ok? I have a 2 of these amps bridged(not paralleled) so that I can get 100W output into a 8 ohm load. Datasheet says I should get 50W with +/- 35V. I presume 40v should be ok....what you guys think, would this be ok?
Thank you in advance.
Thank you in advance.
As long as you are going to be using a parralled bridge arangement (using at least four chips for one speaker channel, possibly more) everything should be fine as this voltage is just under the limit for the chip, and it will drop down a bit when you start to load up the transformer.
HI, maybe I wasn't clear, sorry, I will be running it into a 8 Ohm load, not 4...Thank you for the replies
Since you are bridging it, you are effectively halving the load seen by each chip - this is because the current is doubled, so you effectively do have a 4 Ohm load.
As bigparsnip said, you can bridge and parallel 4 chips to split the current in each back to what it would be for an 8 Ohm load, but I would suggest changing the power supply instead - a 2V headroom is little smaller than I would be comfortable with.
There is a good spreadsheet on the National website for this, it should give you a good idea of the limits of the devices (it's called "Overture Design Guide" or something like that).
As bigparsnip said, you can bridge and parallel 4 chips to split the current in each back to what it would be for an 8 Ohm load, but I would suggest changing the power supply instead - a 2V headroom is little smaller than I would be comfortable with.
There is a good spreadsheet on the National website for this, it should give you a good idea of the limits of the devices (it's called "Overture Design Guide" or something like that).
+-40V with a LM3886 gainclone will get you ~200W RMS into 8ohms as long as you can keep the ICs cool enough.
Ive got two 8chan bridged gainclone amps that have been running 40V for a few years now with no problems.
Ive got two 8chan bridged gainclone amps that have been running 40V for a few years now with no problems.
Avenger,
that supply voltage is much too high for a bridged configuration, unless you were to use a 16 ohm load.
Please read the National Semiconductor application note on building high-power amplifiers using it's "Overture" (chip amp) products, which you can download here. They discuss bridged, parallel, and bridged-parallel designs, including how to determine the correct power supply voltage, which is a critical aspect of any amplifier design.
that supply voltage is much too high for a bridged configuration, unless you were to use a 16 ohm load.
Please read the National Semiconductor application note on building high-power amplifiers using it's "Overture" (chip amp) products, which you can download here. They discuss bridged, parallel, and bridged-parallel designs, including how to determine the correct power supply voltage, which is a critical aspect of any amplifier design.
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