---------- > From: Compliance West <[email protected]> > To: [email protected] > Subject: EN60065 requirements > Date: 1996¦~11¤ë17¤é AM 07:07 > > To: Audio safety aficionados > > Reference: EN60065:1993 and similar IEC, UL, and CSA standards > > Just a few thinks to chew on. I encourage a response from everyone, > especially those involved or associated with European or North American > safety agencies. > > > In our lab, for the sake of simplicity, we perform audio testing by > injecting white noise from a CD player into a graphic equalizer, adjusting > the EQ bands at flat response for frequencies 200Hz - 4kHz, and -12dB for > other frequencies. Comments? Should it not be -18dB at 12kHz and -24dB at 26kHz ??
> > 2. Clause 4.2.6 describes loading the amplifier to 1/8 maximum power, using > the signal described in 4.1.5. Assuming max power is determined by finding > the point where there is an increase in THD at clipping. How does one > accurately determine this point with a white-noise signal input? Are there > THD meters that can do this, and if so, how much do they cost? (sorry for my > ignorance here). Also, > since the THD of white noise would fluctuate (since white noise is random), > at what point would one determine that clipping had been reached? The noise source of course is white, but after passing through the filter described above the noise is no longer white, but pink. It should be possible to see clipping occurring on the scope. > > In our lab, the clipping level is determined by amplifying a 1kHz sinusoidal > signal and looking for clipping on an oscilloscope. The input voltage to > the amplifier is set at RATED (not 1.06 times rated). If it is possible to > measure THD of white noise, I am guessing that clipping (say, defined as > THD>10%) would come at a lower output power level than clipping of a > sinusoid, due to the random nature of the white noise - causing peaks that > would clip as the output signal approaches the DC bus rails. Comments? >
