I've recently entered the prosumer/pro audio market by buying JBL LSR305 studio monitors and noticed that the tweeters produce constant high-pitched noise (most people apparently call it ‘hiss’) that can be heard even from two metres away. See this spectrogram for a graphical representation. The noise is present with and without input and practically regardless of gain.
Disappointed, I've been researching the issue and it appears that the noise is intrinsic to all Class-D amplifiers and, more worryingly, to all Class-D based monitors. I've learned the basics of audio amplification and the differences between the classes here and found some very helpful information here and here.
Intriguingly, some people claim to either not hear the noise or hear it only when they put their ears right to the tweeters! Could be hearing sensitivity, could be something else.
Naturally, my objective is to remove or at least attenuate the noise, but the question is more general and related to the amplifier itself, hence hopefully relevant.
- Since some people claim to not hear the noise, what variables aside from individual differences in hearing could cause it?
Andy aka wrote: “Class D amps are extremely susceptible to hum on the power feeds to the amplifier […] and any AC voltage superimposed on these rails (ripple aka hum) gets transferred to the speaker.”
- Could it be that my electrical supply is too noisy? (I live in a flat; 230V/50Hz.) If yes, can I buy/build something to filter it?
Some people claim that using a balanced connection solves the issue, others disagree. It's present even with no input, though.
- Can the nature of the input (balanced vs. unbalanced) be related to the issue?