Friday, April 3, 2009 5:59:44 PM
All kinds of clicks and pops could be heard through my speakers. Not very nice at all! I did a bit of searching and thought a mains filter would cure it. Well the mains filter did have an influence but not enough.
After seeing some fellow chip amp builders having a low pass RC input filter in their amps I decided to give it a shot. A knowledgeable DIY Audio forum member wrote that to eliminate HF noise an input RC filter with a time constant (= product of R and C) of 0.5 to 1.5μs is very effective at cutting HF noise. I got a 680 ohm resistor and a 1500 pF capacitor (EMZ KP) giving me a time constant of ~1μs and a cut-off frequency of ~156 KHz.
I soldered the RC filters in place and now there is silence. No pops, no clicks. Silence, and Loud Jazz of course.
Now I really have finished my chip amp there's another amplifier I'd like to make...
Ever since I got my LM3886 chip working (aside from the pops & clicks) I've been eyeing another DIY amplifier. BrianGT from chipamp.com, whom I bought the LM3886 PCBs from, has another set of PCBs available: Aleph PCBs. With these PCBs one can make a mini-Aleph. A mini-Aleph is a ~10 Watts amplifier. Only 10 Watts? Yes, but 10 Watts is enough to get you into serious trouble with your neighbours and it's a class A amplifier. Apparently class A amplification is the bee's knees...