Audio experts, static from power amp at startup

[scottmandue]

Tested the source and the speakers are new so I am down to the power amp.

Symptom: At power on a slight crackling or static (like cellophane being crunched into a ball) comes through the speakers.

Exact same static comes through at start up with the source set to Aux., CD, (static is constant when switching source) speakers are relatively new (under a year).

What think ye?

Thanks in advance,
Scott

P.S. Obviously (from the title) I suspect the power amp, and therefore a bad capacitor... power supply or signal path?

P.S.S. It only happens for ten or twenty seconds until the system warms up so it is not the end of the world but it bugs the heck out of my OCD self.

[scottmandue]

Nobody?

[imcarthur]

Originally Posted by scottmandue

I suspect the power amp, and therefore a bad capacitor... power supply

I believe that you probably answered your own question here. I am not a tech but it sounds like a cap in the power supply.

Ian

[LeeH]

More info would be helpful... What kind of amp? Integrated? Power amp + preamp? Receiver? Brand and model?

[scottmandue]

Originally Posted by LeeH

More info would be helpful... What kind of amp? Integrated? Power amp + preamp? Receiver? Brand and model?

Automobile system, pre out of new Alpine head unit to new SS Soundstream amp in trunk to new speakers in door.

It only last for 10-20 seconds at startup,but stays consistent when I switch between souses (Aux, bluetooth, USB, tuner, CD) until it goes away.

[rusnak]

I would call Soundstream and let them know.

[john70t]

Is there a (+12v) inline filter to throw at it?
Is the amp ground separate from the engine ground? Both clean and tight?

Sorry, I know nothing in this.

[Cajundaddy]

Sounds like power amp capacitor...

[LeeH]

Can you hook the speakers up directly to the head unit to take the amp out of the mix?

I'd then try something like running a cable directly to the amp's input (ie... a 3.5mm to rca cable plugged into your phone or ipod.

Doing the above should allow you to isolate which component is causing the issue.

Does it do this every time? So, if you have the car running and turn the power off on the unit, then turn it back on do you get the same results? Or, does it only happen when you've started the car. What I'm thinking is, if it's the latter, then maybe something in the car's electrical system is energized temporarily at start up.

I second the question about the 12v in line noise filter. I bought an external Sirius satellite box that had lifetime service. Hard wired it in my car and had a nasty buzz. Put something like this in the mix and now it's silent:
Pie 12 Volt 12 Amp Noise Filter | eBay

[908/930]

Did you try unplugging the RCA connections from the amp and then turning it on? If it makes the same noise without any input it narrows down the amp (bad caps or solder joint), is the AMP and the head unit grounded at the same place and same connection for power? if not it can cause ground loop.

[908/930]

Could also be a bad contacts on the relay inside the amp.

[futuresoptions]

Originally Posted by Cajundaddy

Sounds like power amp capacitor...

Or a cold solder joint

[scottmandue]

Originally Posted by LeeH

Can you hook the speakers up directly to the head unit to take the amp out of the mix?

I'd then try something like running a cable directly to the amp's input (ie... a 3.5mm to rca cable plugged into your phone or ipod.

Doing the above should allow you to isolate which component is causing the issue.

Does it do this every time? So, if you have the car running and turn the power off on the unit, then turn it back on do you get the same results? Or, does it only happen when you've started the car. What I'm thinking is, if it's the latter, then maybe something in the car's electrical system is energized temporarily at start up.

I did try plugging my phone (RCA to 3.5) playing Pandora and I thought I did not hear the noise... so I figured it was the head unit.. so I bought the new Alpine... can't tell you how pissed I am the sound is still there

OK, so I will try unplugging the RCA to the amp and see if I still have the static... and run a test with my cell phone again.

Amp is in the trunk and head unit is in the dash, I presume they both ground to the chassis.

I am only running the RCA pre-out of the head unit, I would have to pull the dash to get to the speaker out of the Alpine, all unused wires are taped off at the ends to prevent shorting.

I also suspect a component running at at startup... but this is a 1995 Miata with crank windows and not a lot of electrical accessories and the static is not consistent... it goes in and out then after a few seconds goes away all together.

I will try soundstream but the amp sat in the garage for a couple weeks before I got it installed... then I got the new head unit and installed it... so it has been a couple months since I bought it.

[LeeH]

You never said whether or not the noise is only there for a few seconds when the car starts vs the stereo starting.

If you've been driving and turn off the power to the head unit, then turn it back on do you get the noise again?

If you start the car with the radio off, drive for a while, then turn on the stereo do you get the noise?

If you turn the car on, hear the noise, let it run its course, then turn the car off and immediately restart do you hear the noise again?

Same results on warm and cold starts?

Do you have an external 12v power supply that you can use to energize the stereo equipment. Maybe pull the battery from your other car so the stereo equipment is isolated from the car's electrical system?

The ebay noise filters are cheap and easy to install. Took the noise from my radio - but it was a different noise - I had the whine/hum that's tied to engine speed... sounds like an audio tachometer.