Is is a 20kHz 3,1V sine wave mixed with a 440kHz 0,3V sine wave.
There are small amounts of unavoiadable remaints of the switching frequency left on the output on class D amplifiers. It cannot be heard and it does not affect tweeters. Let me explain why.
The switching frequency current and power
A typical tweeter inductance is 30uH and that alone will represent an impedance of 80 Ohms. Adding the tweeter DC resistance of typical 6 ohms we end up with 86 ohms resistance to the 440kHz signal. The current in the tweeter will then be 0,3v/86= 0,0035A (3,5mA). Calculating the power we get 0.0035*0.0035*86=0,001W
On top of that I don't think it is neccassary to say that 440kHz is very very far from being audible either.
The high frequency audio signal
The 20kHz signal is 3,1V and the AC resistance (impedance) of the 30uH coil is 3.8 ohm. Adding the DC resistance og 6 ohms we get 9,8 ohms.
The current in the tweeter will be 3,1/9,8=0,316A. Calculating the power we get 0.316*0.316*9,8=1W
To sum up the math in words.
The signal we see in the oscilloscope does not look that nice. The 440kHz frequency is only about 10 times smaller than the 20kHz auido signal.
But because of the inductance in the tweeter the power delivery of the high frequency is 1000 times smaller. Even when a fairly small 3,1V 20kHz signal. At higher sound levels it will be many thousands time smaller. Its neglible.
0,001W power is way to little to matter at all. Also understand that this power is continous from the moment the amp is turned on. It is not something that changes. It is constant and independant of the music signal. It will heat up the tweeter by something like 0,01 degrees. I haven't seen anyone claim that a 0,01 degree constant temperature difference has a huge impact on the sound yet.
This supposedly damaging high frequency noise is the last grasping at straws to disqualify class D amplifiers.
I have here explained why it has no effect.
Why cannot you explain why it is so bad?
There are small amounts of unavoiadable remaints of the switching frequency left on the output on class D amplifiers. It cannot be heard and it does not affect tweeters. Let me explain why.
The switching frequency current and power
A typical tweeter inductance is 30uH and that alone will represent an impedance of 80 Ohms. Adding the tweeter DC resistance of typical 6 ohms we end up with 86 ohms resistance to the 440kHz signal. The current in the tweeter will then be 0,3v/86= 0,0035A (3,5mA). Calculating the power we get 0.0035*0.0035*86=0,001W
On top of that I don't think it is neccassary to say that 440kHz is very very far from being audible either.
The high frequency audio signal
The 20kHz signal is 3,1V and the AC resistance (impedance) of the 30uH coil is 3.8 ohm. Adding the DC resistance og 6 ohms we get 9,8 ohms.
The current in the tweeter will be 3,1/9,8=0,316A. Calculating the power we get 0.316*0.316*9,8=1W
To sum up the math in words.
The signal we see in the oscilloscope does not look that nice. The 440kHz frequency is only about 10 times smaller than the 20kHz auido signal.
But because of the inductance in the tweeter the power delivery of the high frequency is 1000 times smaller. Even when a fairly small 3,1V 20kHz signal. At higher sound levels it will be many thousands time smaller. Its neglible.
0,001W power is way to little to matter at all. Also understand that this power is continous from the moment the amp is turned on. It is not something that changes. It is constant and independant of the music signal. It will heat up the tweeter by something like 0,01 degrees. I haven't seen anyone claim that a 0,01 degree constant temperature difference has a huge impact on the sound yet.
This supposedly damaging high frequency noise is the last grasping at straws to disqualify class D amplifiers.
I have here explained why it has no effect.
Why cannot you explain why it is so bad?
