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Loud Speaker?

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ChrisGreece52:

--- Quote from: madires on June 01, 2013, 02:51:31 pm ---
--- Quote from: ChrisGreece52 on June 01, 2013, 10:30:56 am ---
--- Quote from: SeanB on May 31, 2013, 03:16:46 pm ---Distortion is easy, LM386 run till it clips.............

Or 2 back to back diodes and a low value series resistor with about 2Vpp of signal works as well.

--- End quote ---
yeah but lm386 is a crappy amp so i need something with more power.

--- End quote ---

I think he meant that you could use the LM386 as a preamp stage just to generate the distortion.

--- End quote ---
oohhh ok ... but why should i use lm386 as a preamp for distortion while i can just change the value resistors i can use to change the gain (that is what i mean by distortion it may be wrong.)

ChrisGreece52:
So finally after all i learned i want to go with something outputs 30 volts (15 +/- )watts thats the best state ( distortion wise) but i can not find a transformer suitable for the application)
At 24 watts my goal (output power )
the chip will dissipate 14 watts of heat
so i need something that outputs (24+14 =38) 38 watts
from the formula that i saw in an answer we have P = V I so I = P/V => I = 38/30 = 1.266 Amps (pretty good  and achievable)
I posted this so i make sure that i wont screw the calculations up
Thank you
 Datasheet :
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXyuqt.pdf

mariush:
Yes, sounds about right.

A 24v transformer will have a peak DC voltage of 1.414 x 24v = 34v. With the drop in rectifiers, that's about 31v.

So +/- 15v is doable with a 24v center tap transformer and big capacitors on the output (let's say 2x3300-4700uF 25v on each side, negative and positive, so 4 capacitors in total ), or if you make the design in the datasheet that's with single power supply, about 8200-10000 uF 50v (in whatever capacitor combination you want, you can put capacitors in parallel to increase size)

A transformer rated for 24v AC rms 40-50VA would do.

See below for some examples

mariush:
And don't forget about the heatsink.

At low volumes, it won't waste that much power, but if you get it going at high output, it will waste 10-15w of power.
Tiny heatsinks don't work, like the datasheet says you need a relatively big heatsink (compared to what you may be used to) with low thermal resistance.

Either screw it on a CPU heatsink with the cpu fan running at low speed, or get a large heatsink like the one in this picture:

http://www.ebay.com/itm/100x55x10mm-Aluminum-Heatsink-for-Electronics-Computer-Electric-equipment-H104-/171015086436?pt=LH_DefaultDomain_0&hash=item27d14b2164
http://www.ebay.com/itm/100x55x10mm-Aluminum-Heatsink-for-Electronics-Computer-Electric-equipment-H104-/200801981466?pt=LH_DefaultDomain_0&hash=item2ec0bb141a
http://www.ebay.com/itm/100-45-10mm-Aluminum-Heat-Sink-TO-220-w-o-stand-for-LED-Power-IC-Transistor-/260865037352?pt=LH_DefaultDomain_0&hash=item3cbcc49428
http://www.ebay.com/itm/100x35x10mm-High-Quality-Aluminum-Heat-Sink-For-Computer-Electronic-H62-/181110957180?pt=LH_DefaultDomain_0&hash=item2a2b0de47c
http://www.ebay.com/itm/100x35x10mm-High-Quality-Aluminum-Heat-Sink-For-Computer-Electronic-H62-/190808608538?pt=LH_DefaultDomain_0&hash=item2c6d144f1a


If you get something like the above, you must screw the chip somewhere close to the middle of the heatsink, not on the side.  Don't forget to use some cpu thermal paste between heatsink and the chip.

ChrisGreece52:

--- Quote from: mariush on June 02, 2013, 01:47:12 am ---And don't forget about the heatsink.

At low volumes, it won't waste that much power, but if you get it going at high output, it will waste 10-15w of power.
Tiny heatsinks don't work, like the datasheet says you need a relatively big heatsink (compared to what you may be used to) with low thermal resistance.

If you get something like the above, you must screw the chip somewhere close to the middle of the heatsink, not on the side.  Don't forget to use some cpu thermal paste between heatsink and the chip.

--- End quote ---
I will get something from the above ones i was thinking about the first one.
And of course middle.
But shall i use thermal paste?? (like in a CPU for better heat transmision)

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