class D amp diy

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Hello,

I want to realize a Car Audio amplifier for a JBL GT4-12 sub :
http://tsfarsenic.chez.tiscali.fr/jbl1.jpg
http://tsfarsenic.chez.tiscali.fr/jbl2.jpg

but i don't know what enclosure and what amp class I have to use

so , I want to know what box and amp class you reommanded to me and for the amp please with a schematic and if it's possible, little explications

I have others little questions :

- for the alimentation : direct on the battery or i have to make regulation ? to use trafo ?

- what type of protection i have to use ? (for amp & speakers)

- defore the amp I want to do a n active low-pass cross-over adjustable to 50Hz at 200Hz, it's a good choice for you ??

PS: I'm sorry if mmy questions had already asked but I'm French and I have lot of difficulty for understand (and speak ...) English so please don't give me url of english or american web site and if it's possible use simple English for answer to my questions, it will be more easy for me for understanding

Thanks a lot
Jeremy
 

ocool_15

Member
2004-11-26 3:15 am
sk
Interesting link, Ill be looking into that magazine for sure. Here is a common power supply DIY schematicRod E link
for a car audio amp the hardest part by far is the power supply. Active Crossover are covered in winisd program(normally box building). I might suggest building the appropriate amplifier first then the preamp/active crossover and then the power supply.
The LM4780 chip amp would give you 120W at 4ohms. Might be a place to start.
 
thanks to you for your answers

so ocool if it's possible to use class B amp , I d'ont know what fonction i have to use in plus for protection , alimentation, adjustable cross-over adjustable gain and for the remote

have you some schematics and the arithmetics for found the components value ?

i don't found interested things on french web sites, i hope you can give me informations that I need
 
I've found this I think it's a good thing :

http://users.swing.be/edwinpaij/ampli_mosfet.htm

and the same a little most powerful

http://users.swing.be/edwinpaij/ampli_mosfet_360_w.htm

but +70V / -70V power .....

there is a means for do 70V with 14V of car battery ?

there is too DC protection module for speakers and short circuit protection module for the amp in the same web site :

http://users.swing.be/edwinpaij/module_de_protection_cc_pour_hp.htm

http://users.swing.be/edwinpaij/short_circuit_protection.htm
 

ocool_15

Member
2004-11-26 3:15 am
sk
As I was saying the power supply will probably be the most difficult part. The best way to do it is with a PWM(pulse width modulator) supply. There are a TL499a is a common starting integrated circut. Basically for you to up the voltage and have enough current still you need to convert the car DC to AC and then run the AC through a transformer to get the required output voltage. for the amp I would recommend building a gainclone(look up in google based normally on LM3875 integrated circut) or try one on a lm4780 as these chips will have your protection circutry built in and reduces complexity for you to make alot.

For the variable active crossover I'm not sure of a good site or link but I could probably draw out a mono variable op amp based one at some point.
 

ocool_15

Member
2004-11-26 3:15 am
sk
ok here is what I put together as I need basically the same thing as you do but not right now. 12dB/octave lowpass
Basically used these 2 resources:
http://www.colomar.com/Shavano/intro_opamp2.html
Linear team win isd
R1=R2 and you would you a 2 gang potientometer to give you the variable crossover point.
gain is set intitially at 1 but by decreasing R4 you will increase gain so you would use a single gang potientometer there. I am not a professional engineer or anything so if there are any changes that should be made anyone let me know.
 

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kpero

Member
2005-04-21 10:37 pm
Croatia
That is cross over with aktive system for bas control. With that you can
drive your speaker lower than it will be normal in small box.
If you don't know in smaller box you can't produce lower bas so well.

With this EAS you boost lover frequency and atenuate higher frequency.

It's something like Linkwin transformer but ,this staff has low pass filter.
 
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