rfi

[Shiva6150]

Just wondering how to get rid of radio interfearence in a SW/AM/FM receiver caused by a set of computer speakers that have a class-D amplifier. The rfi is from the high speed switching mode of the amplifiers output section, possibly the switching power supply they use too, would ferrite beads kill the noise? The radio is used with the speakers for fm sometimes because they do sound VERRY good and the fm on the receiver is so good it gets stations that even high end car stereos have trouble with, warm midrange, smooth treble, good bass with great tight woofer control, wonderful with classical music, and just incredible with raga and my hindu religious music. IMO it sounds like a good tube amp. But on some fm channels, I get that nasty rfi that class-d is soo well known for. SW is useless because of it, suprisingly its not a problem with MW/LW.. Other than the rfi issue I'm prety impressed with these new class-D amplifiers. All the warm and smooth tube goodies without the heat and power bill. I will be building up a high powered class-D soon. I have had 3 of these things so far and loved the SQ on all of them, first was an ipod boombox from altec lansing, the imt-800.. what a BEAST! HUGE power, all class-D, then a cheap set of sony computer speakers, 5w class-D, still have them and those realy do sound like tubes and have good drivers too, rigged them up to run on 4 aa batteries and left it on 24/7, those batteries lasted a WEEK! at full power! , then I was hooked on class-D for sure since its possible to have good power with incredible efficiancy and better sound than I ever hered from any other ss amp technology, and on the CHEAP!. My latest system is a set of philips spa-7210 computer speakers with 40w of class-D goodness. Like the sonys they have that warm tubey sound but with more bass and extended treble because of sepearte tweeters and more than enough power to annoy the neighbors. Who woulda thought ss would sound this good for so little $$! My tube amp is getting lonely..LOL Never in my life did I ever think ss could sound as good as or better than valves, but now I can say that. Thanks to class-D. And in cheap systems of all things. I'm just blown away by this new ss tech. Now to fix the line noise problems. Would a ferrite bead on the output line of my radio knock out the noise, its not on all channels, just particularly bad on my classical station and one of the local stations.

 

[marce]

If it is the class D amp then there is somthing wrong because even though they can be noisy, that noise should be contained within the switching loop on the PCB and not be transmitted. There is a thread on EMC and class D that may help.