DIY Good Class D amplifier

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#147
Acca said:
Yes,I say in first post.Change 4k7 to 22-47k
Click to expand...

This is a good thing.
How we can calculate our own gain?
I mean, it would be very interesting if we can change gain to obtain a low input sensibility (say: 5Vrms).
This is the case when one want to run the amplifier with a good tube preamp.

I guess I have to see SG3525 datasheet 😎

Edit: is there a way to make this ampli a pure final ampli (voltage gain = 1, only current gain: power buffer)?

Edit2: what about input impedance? I guess it's (very) high, due to the use of input opa, so one can go with single ended tube preamp, that show a not so low output impedance, am I wrong?
 
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#149
iperv said:
This is a good thing.
How we can calculate our own gain?
I mean, it would be very interesting if we can change gain to obtain a low input sensibility (say: 5Vrms).
This is the case when one want to run the amplifier with a good tube preamp.

I guess I have to see SG3525 datasheet 😎

Edit: is there a way to make this ampli a pure final ampli (voltage gain = 1, only current gain: power buffer)?

Edit2: what about input impedance? I guess it's (very) high, due to the use of input opa, so one can go with single ended tube preamp, that show a not so low output impedance, am I wrong?
Click to expand...

Classic resistor divider.
Gain can be 1 at input,but output will change with PSU voltage.
Imedance is very high,as in classic op-amp.
 
#151
Acca said:
Classic resistor divider.
Gain can be 1 at input,but output will change with PSU voltage.
Imedance is very high,as in classic op-amp.
Click to expand...

:up:


Acca said:
And this is for any full power at output.
For example,on single 70V you get about 100W on 4R at input of 0,15V
On single 140V you get about 550W on 4R,at same voltage at input (0,15V).
Click to expand...

Can you please better explain this fact?
I don't understand why.
I'm too much analogist :note:
 
#153
@iperv
It doesn't have feedback.If PSU is 50V on say 20% duty out will be 10V but on 100V PSU 20% duty give 20V at output.In both cases input voltage is same but output isn't.
Max input voltage of SG is +/-2,5V
 
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#155
Acca said:
@iperv
It doesn't have feedback.If PSU is 50V on say 20% duty out will be 10V but on 100V PSU 20% duty give 20V at output.In both cases input voltage is same but output isn't.
Max input voltage of SG is +/-2,5V
Click to expand...


Ok, understood 😎
The input signal make a modulation of the duty, it defines the #% of duty cicle.

Can SG accept +2,5V and -2.5V?
Balanced input?
 
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