Gainclone makes my speakers go POP when lights turned off

[chylld]

Hi all,

I've built my gainclone from chipamp.com's stereo LM3886 kit. The sound quality is amazing, tons better than my AV receiver, however unlike the receiver it has a tendency to make the speakers go "POP" whenever a light switch in the house is turned off.

The pop happens whether the input signal cable is plugged in or not.

My gainclone is the only device affected by this popping, and I'd be happy to hear any suggestions as to how to mod the GC to suppress the popping. The last thing I want to have to do is buy a UPS just for this purpose!

Thanks in advance.

[darkfenriz]

Show us your grounding connections.

[Peter Daniel]

Check this link: LM3886 very prone to mains noise

[nigelwright7557]

Interference from lights being switched on can come from two sources.
1/ Through the mains into your equipment.
2/ Transmitted through the air as RF or EM into your equipment.

Theearthing can be perfect but if your PSU doesnt filter out spikes then the noise will still get through.

[Shhhtack]

Apparently chip amps are sensitive to voltage spikes on the mains. I built an lm3886-based amp and experienced the same problem. I replaced my AC receptacle with one that incorporated a filter and the problem was mostly solved. I say MOSTLY because if the voltage spike is high enough the problem still occurs. But this only happens now during electrical storms.

[chylld]

Yeah I found some of these filter IEC sockets on the Altronics website, unfortunately I've already put in the big IEC+fuse+switch one so the cutout is too big for the filtered unit

I bought a big orange metal powerboard from bunnings, that has filters in it apparently but didn't help at all.

Thankfully, Altronics has a mains filter kit which purportedly eliminates pops and spikes from entering the hi-fi system, at $42 it's expensive just to fix a few pops but it's the best option I have at the moment.

This of course assumes that the noise is coming from the mains! Although I really doubt it's coming from the line-in, since the pop is the same volume whether I have the volume set high or low... if it was an irregularity on the line-in, I'd imagine that the pops would increase with the volume.

[AndrewT]

Hi,
Most chipamp circuits major on how simple they are to assemble.
Consequently they omit many of the "normal" practice circuits/components that most designers fit as standard.

Have you fitted filters to the input end of the power amp? DC block and RF attenuator.
Have you fitted a filter to the speaker terminals? Thiele network.

[ashok]

Maybe RF sensitivity. Do you still have the problem ( or reduced) if you take the amp far away from that room and operate the same switch ?

Is your amp on a wooden base with no cover at all ?

[jaycee]

if you built a true gainclone, it has no RF stopper on the input, so you will pick up the field.

The data sheet suggests 220pF between the inverting and noninverting input of the chip to prevent this.

[Dr.EM]

A filter like this could be used:

http://www.rapidonline.com/Electroni...g-filter/64492

So you wouldn't need to change your inlet.

Check its shielded (ideally in earthed metal enclosure). If not, try and shield the inside of the box with foil/copper clad boards or at least use shielded wire for the input.

Add RF filtering at line in. Together should sort the problem out