Speaker Pop & Capacitor

**jstrain** · 04-19-2004, 08:29 AM

I just transferred my empeg into a 2003 Miata with the Bose system. I was able to save myself alot of wiring headache (as well as precious trunk space) and use the existing Bose amp setup, rather than installing my aftermarket amp. My only problem is speaker pop when I shut the car off. Most research tells me that putting a capacitor on the empeg's input will keep it running for an extra few seconds while the amp shuts off, and thereby eliminate the speaker pop.

My only problem is that I have no idea how to actually do that. I can install a stereo, but I'm not sure how to physically wire the capacitor in. Do I just solder it inline in the 12v input line? Also, do I need a diode as well? Can one still purchase this stuff at Radio Shack, or will I need to mail order the $2 worth of parts?

Any info on how to physically put this in would be much appreciated.

Jeremy

**lgbr** · 04-19-2004, 11:34 AM

My best guess is that the power is cut off right as the cd player is cut off. Try using a multimeter to see if the power lead to the amplifier is hot when the car is off. If not, then that's your problem.

Capacitors are very easy to install. Simply cut the power wire and put the capacitor on it, then ground the capacitor.

**nick9871** · 04-19-2004, 10:52 PM

How big of cap should you use? And When I do a search what is all this stuff I find about a relay setup and what not? Can you really use just the capacitator?

**shakes** · 04-19-2004, 11:31 PM

excuse my ignorance but what do you mean by empeg?

anyway ... i don't think a capacitor will help you. for starters, in order to prevent speaker pop, you want your amp to turn off before, or at the same time as your sound card. if the sound card powers down first, you will get that wonderful pop. ... so doing anything to extend the amount of time the amp is on probably won't help.

even if that were the fix ... even a 1farad capacitor (those big ones you see in audio stores) would only provide you with power for a split second ... probably not even over one. search around in the threads regarding tank circuits and look for the equation Ricky posted a number of times.

you definately won't get any help from a cap you'll find at radio shack.

in my setup, i have my external usb soundcard and my amp's ignition wire both being fed from a relay, which is activated by the power cable coming off my ITPS. so the Soundcard and amp turn off at the same time. Additionaly, I have a EQ that my audio signal passes through which is hooked straight up to the ignition wire. So it turns off when the car turns off (45 seconds before the amp/soundcard turn off) so that also prevents the pop (no sound passes through the EQ when it's powerd off)

anyway ... i don't know your setup ... but find a way to turn your sc and amp off at the same time...

**JC-S60** · 07-29-2004, 11:26 AM

As I understood it, the amp doesn't loose his power for some seconds (internal capacitors of teh amp maybe?), which causes it to still amplifie the 'pop' produced by powering down the computer (or 'empeg', which must be some audio-device)...

To avoid this, you could postpone the power off of your computer (by putting a relay that has a capacitor to keep it closed for some time after power is cut to it)...

OR

Put a relay between your speakers and the amp that cuts of the signal of the amp to the speakers at the moment you cut the power (ignition).

Joa

**Squid** · 07-29-2004, 12:48 PM

I have a laptop with a USB Audigy 2 NX... and it was powering down at the
same time as the amp and creating a horrific thump.

To solve my speaker thump.... I put together this little relay circuit to fix it.

I powered up the audigy with a relay instead of the straight switched 12 volts
and a capacitor to delay the action of relay when powering off.

The delay all depends on the size of the cap and the current draw of the
relay... I'm using a smaller relay that draws about 50% less than a typical
"car" relay, so I get more time... which is only about 1 second but more than
enough to allow the amp to power down.

The input diode keeps the voltage from cap going across the relay instead
of just dissapating elsewhere..

So power up your Empeg with this little gizmo and it should delay the turnoff
for a fraction of a second. The amp should shutdown enough to stop
it from still powering the speakers and thus avoiding that thump!