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Old 4th June 2011, 09:13 PM   #31
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Originally Posted by luka View Post
for what I can tell, only shutdown noise you get is if your supply for fets falls before main goes low enough
I am using the circuit off the datasheet so all should be OK component wise.

The power off crack improves with VAA and VSS decoupling from 10uf to 22uf. Sometimes after half a dozen power offs it disappears of its own accord !
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Old 4th June 2011, 10:48 PM   #32
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Found this in the datasheet concerning hard clipping.
R1 is the input resistor:

Note that this condition also limits the maximum
audio input voltage feeding into R1. If this
condition is exceeded, the amplifier stops its
oscillation during the operation period. This
allows a 100% modulation index; however, a
care should be taken so that the high side
floating supply does not decay due to a lack of
low side pulse ON state.
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Old 4th June 2011, 11:25 PM   #33
luka is offline luka  Slovenia
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hard clipping is always a problem, I guess IRS is part of the amps that stop osc. while they need to output one or the other rail...and the problems that come with that
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Old 4th June 2011, 11:32 PM   #34
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hard clipping is always a problem, I guess IRS is part of the amps that stop osc. while they need to output one or the other rail...and the problems that come with that
If the input voltage exceeds the max triangular wave voltage then the output will switch high and stay there until the input voltage falls again or Vbs discharges completely.
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Old 4th June 2011, 11:34 PM   #35
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btw, what is your input resistor value anyway?
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Old 4th June 2011, 11:38 PM   #36
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btw, what is your input resistor value anyway?
3k3 as per datasheet.
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Old 4th June 2011, 11:40 PM   #37
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and what kinda peak voltage must you put to it, to clip the amp?
have you every try any different resistor value and/or gain?
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Old 4th June 2011, 11:45 PM   #38
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and what kinda peak voltage must you put to it, to clip the amp?
have you every try any different resistor value and/or gain?
I havent altered the values from the datasheet. Gain is 14.

I am used to class AB amps accepting hard clipping so this is a bit strange.
I can understand why the problem occurrs just not sure of a solution.
I suppose I could put back to back zeners on the input to reduce the input voltage to safe level.
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Old 4th June 2011, 11:48 PM   #39
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I would use limiter... even AB amps uses them, since hard clipping does no one any good, so one should stay away from it
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Old 4th June 2011, 11:51 PM   #40
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I would use limiter... even AB amps uses them, since hard clipping does no one any good, so one should stay away from it
Thats true.
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