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Old 18th December 2008, 06:29 PM   #1
Sponkii is offline Sponkii  Denmark
diyAudio Member
Join Date: Dec 2008
Question My first diy D subwoofer amp

Hello everybody..

I'm new in this forum .. but hope that don't matter ..

I know a bit about electronics, and i would like to know a lot more (still under education)..

but right now I have set my mind on a diy Class D amplifier, just to make it "easy" I'm going for a sub woofer amp..
the goal of watt??.. hmm around 150-200watts..

there is some things that i would like you to help me with:

1. my switching freq on my test board is 50-100khz and the sound is actually okay considering my audio source is a cheap FM-radio.

the oscillator and "comparator" is two LM833.
what i used for my triwave is this:

so here it go:
1: at how high freq do you think that i can go to with my LM833 ?

2: why is there a lot of noise in the audio when i plug my speaker to the mosfet driver (i haven tried to make a push-pull stage with mosfets yet), when there is no noticeable noise when i drive my speaker direct from the output of my LM833..

the speaker is a 10watt 8ohm..

hope you can help me ..
- any questions, ill do my best to answer..
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Old 20th December 2008, 07:01 PM   #2
Sponkii is offline Sponkii  Denmark
diyAudio Member
Join Date: Dec 2008
Default ??

any one got some info ..
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Old 8th January 2009, 10:31 PM   #3
diyAudio Member
Join Date: Jan 2007
do you have a complete schematics ?
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Old 10th January 2009, 05:37 PM   #4
Sponkii is offline Sponkii  Denmark
diyAudio Member
Join Date: Dec 2008
Default pwm..

No... i have already made a schematic an put it on a breadboard, working fine at 120kHz.. the only problem rightnow is how to drive my haflbridge or fullbridge..

i have a regulatet +/-7v supply and a +/-24v supply, they share the same 0...
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Old 12th January 2009, 11:35 AM   #5
acid_k2 is offline acid_k2  Italy
diyAudio Member
Join Date: Oct 2006
1) driving a speaker directly from LM833 is not a good idea.
2) +- 24V will give you theoretically only 72W RMS (289W in bridgemode) on 4 ohm speaker; and half power on 8 ohm speaker 36W halfbridge, 144W fullbridge).
3) which mosfet driver do you think to use?
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Old 20th January 2009, 07:08 AM   #6
Sponkii is offline Sponkii  Denmark
diyAudio Member
Join Date: Dec 2008
Default Acid

The reason i connected the LM833 to the speaker (a small one) was just to tes if it worked..

I'm not totaly sure wich fets im gonna use, but i have a couple of different ones i want to try, just so i find what i think that suits me ..
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