DIY Good Class D amplifier

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iperv

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Joined 2008
Acca said:
Mag amp isn't bad as doctormord say.I tried it without feedback,and sound is ok for me.
You can use any PSU,boost can't increase voltage on electrolytes because speaker reactive energy is small to do this.As I say,first try on 150khz.I make mag amp in halfbridge and pushpull,and it don't require PSU cap's.SMPS directly power it.But this is for sub and mid's because sw. freq. is cca. 35khz
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Very good.

So I go with standard pcb and standard schematic (the corrected ones, of course).
Linear 80V single ended.

To complete my design I have to choose output mosfets.
Any suggestion on the best choice for 100W/4ohm/80V single supply?

Saluti.
 
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iperv

Member
Joined 2008
Acca said:
Yes,can be implemented,but I don't tried on this,but tried on similar amp.
+/-100V give 1kW on 4R
You should use totem pole at IR outputs for this power.
Click to expand...

Thanks for previous suggestions.

I don't understand which is the right formula to use to obtain the correct rms Po.
Fom here:

Pse(PEAK) = Io^2*RL = (Vo/2Rt)^2*RL = ¼(Vo/Rt)^2*RL = 2 • Pse(RMS)

So: Pse(rms)=80V*(80V/4)/2=800Wrms (??)

EDIT:
with +-100V: (200*200/4)/2=5000Wrms (??)

I think we have to consider the efficency too:
With an eta=90% we have:
800W*0.9= 720Wrms
5000W*0.9= 4500Wrms

So what?
 
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iperv

Member
Joined 2008
Acca said:
So it's not true.
P=U^2/R
R=4ohm
U=Udc/1,4
U=100/1,4=70VAC
P=70*70/4=1225W at input
1225*0,9=1100W at output.Rms.

With single supply calculate U=Udc/2,8

It's formula for half power of resistor placed between +100V and -100V rail.
It's a two 5kW resistor in series,2 ohm each and with 200V across it.
So it is useless.
Click to expand...


Yes, ok.
I forgot to reduce current peak to rms, and forgot that when mos up is on then lower one is off, so I have to consider half voltage.

So: #/(2*1.414) = Vdc/2.8

:cheers:
 
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iperv

Member
Joined 2008
I deepened a bit theory of class D amply,
and seems that an advantage of clocked frequency amplifiers vs auto oscillating is that the first are easily syncronizable.
Of course, I would like to build a double stereo amplifier, in order to mantain up way separate from down way (there are differences on sensibility and I need to regolate volume independently).
I guess I have to syncronize the PWM ICs.
Is this a feature supported by SG3525?

EDIT:
answer is yes:
Synchronizing SG3525 - diyaudio

EDIT2:
/OT ON:
answer is yes, but I don't know how to
OT OFF/
 
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