| JayV |
I plan to build two 4 channel lm3886 amps, to drive linkwitz orion with...
I have several 2*38V/1500VA toroids, so i put one in each amp! How much output should i expect in 8 ohm? I belive the rails will be somwhere inbetween 45 and 50V...
How much heatsinking will i need per amp?
How much capacitance per psu (shared on 4 ch)? |
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| bigparsnip |
The maximium allowable input voltage for the chips you want to use is only +/- 42 volts, so I think theat your current transformers will provide too high a supply voltage as they are.
As you only need to drop down the voltage a little from the supply you could try wiring another four or five rectifier dioeds in when you build the supply, but I doub't that this configuration would sound too good. |
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| JayV |
| i have read its 80v or something |
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| Paulr |
84v is the maximum voltage with an input signal, but this is the maximum difference between the two supply rails i.e. -42v & +42v.
Maximum voltage with no signal is 94v i.e. -47v & +47v.
At the voltage you're suggesting you will not be able to connect any source without being completely out of the devices operating area.
This info is on page two of the data sheet under the "Absolute Maximum Ratings" section
Also a 1500VA transformer will give you about 40Amps @ 38Vac, so about (guys pls check my calculation here) 22Amps @ 52Vdc before filters & other reductions. The 3886 has a peak output of 7Amps (at +-20v supply) so even ignoring the voltage they may be a bit on the overkill side unless youre planning a bridged parallel amp per transformer
cheers
Paul |
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| JayV |
| what about opa549? With single supply? (using just one of the secondaries?) |
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| ray_jay |
I'm using 25 - 0 - 25 800Va trans , this gives _+ 33V at no load and is sufficient in my medium sized room to give 95-100Db,
cheers
Ray |
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| ray_jay |
Ok,
I should have noted that I am using 8 * lm3886 on the orions,
why are you using 4 ?, another amp on the woofers ?,
cheers
Ray |
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| JayV |
| as i wrote in the first post i'm building a pair of 4 channel amps, one for each channel, less heat and my transformators is pretty big :D i will also build a 2 channel bridged amp to drive the thors.... |
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| acliao |
| How do you adjust the DC offset on all 4 (or 8) LM3886 outputs to make sure they don't "fight" with each other? |
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| JayV |
| is that a problem when they just share the transformator? |
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