Class D Technology

Talking about Spread-Spectrum during cold war could put you in a prison (top secret).  Today all CDMA cellphones (Verizon, Sprint etc.) use spread spectrum.  It is interesting application for class D, especially when receiver reacts only to average value (no keying needed).

There is about 1% of switching voltage noise on the speaker cable

You need to rethink this.
Look at the switching noise ringing on the test square waves Stereophile show when they don’t use their special Audio Precision’s auxiliary AUX-0025 passive low-pass filter to hide the switching noise ringing from view.

This is what’s on the speaker cable on the $7K Anthem Statement M1 monoblocks, and it more like 20% of the wave form.

Without Audio Precision’s auxiliary AUX-0025 passive low-pass filter
http://www.stereophile.com/images/1212AM1fig02.jpg

With Audio Precision’s auxiliary AUX-0025 passive low-pass filter
http://www.stereophile.com/images/1212AM1fig03.jpg

Cheers George

Stereophile test shows about 0.5Vp-p  - that is about 1% since switched voltage is in order of 50-80V.  It comes from the fact  that output filter is 2-pole making it -40dB/decade while switching frequency is about decade above filters cutoff frequency suppressing noise by 40dB.  -40dB is 1%

As I posted before, speaker cables have no chance to radiate for many reasons.  Tweeter won't play 500kHz,  not only because of membrane inertia but also because of its impedance rising extremely high.

Switched voltage 50-80V represent the highest output voltage.  They show switching noise riding on a very small signal.  This signal of 1V peak represents 63mW of the root frequnecy + harmonics on the 8 ohm speaker.

Sorry your wrong kijanki, the switching frequency to signal ratio follows the signal level in a proportional manner. and that 20% pod SF noise in the links I provided above, the SF noise does not disappear at certain levels of playing, it stays proportional to the level your playing.

And I didn’t ask you about tweeters playing 500kHz, but seeing you mentioned it, ask the poor sod I had to replace both the Wilson 8’s tweeter diaphragms on, because they were blu’ed with heat abuse from this 500kHz noise. They still worked but never sounded quite right, but they did when I replaced them. BTW he won't use a Class-D again, until he's convinced that the SF noise won't harm his tweeters again. 

Cheers George