Strange problem

**scott_fx** · 07-27-2006, 11:38 PM

shouldn't make a difference but try the mp3 player and radio

**Toehead** · 07-28-2006, 12:16 AM

same result. Thanks for you help though, I appreciate it

Keep the ideas coming!

**scott_fx** · 07-28-2006, 12:36 AM

Originally Posted by Toehead

same result. Thanks for you help though, I appreciate it

Keep the ideas coming!

fill in this chart here:
radio directly to the amp = no noise
computer directly to the amp = no noise
radio + computer (on) + mixer = no noise
radio + computer (off) + mixer = noise
alt. source + computer (on) + mixer = ??
alt. source + computer (off) + mixer = ??
radio + alt source (on) + mixer = ??
radio + alt source (off) + mixer = ??

**Toehead** · 07-28-2006, 08:49 AM

radio directly to the amp = no noise
computer directly to the amp = no noise
radio + computer (on) + mixer = no noise
radio + computer (off) + mixer = noise
computer(off)+radio(off)=noise
alt. source + computer (on) + mixer = no noise
alt. source + computer (off) + mixer = no noise
radio + alt source (on) + mixer = no noise
radio + alt source (off) + mixer = no noise.

**Will Albers** · 07-29-2006, 09:14 AM

A lot of sound cards will switch their outputs to ground when not powered. This causes the ground loop you hear. Thats why many people look for delayed turn on with their amps while the PC powers up. Its completely normal.

I went optical just to avoid it.

**scott_fx** · 07-29-2006, 01:21 PM

Originally Posted by Will Albers

A lot of sound cards will switch their outputs to ground when not powered. This causes the ground loop you hear. Thats why many people look for delayed turn on with their amps while the PC powers up. Its completely normal.

I went optical just to avoid it.

oh oh! that is good to know. hey toehead, try this now. run the radio through the mixer but unplug the computer's rca's from the mixer. does the noise go away? if it does then you'll have to add a way to decouple the rca inputs (that the computer is plugged into) when the computer isn't on

**Toehead** · 07-29-2006, 07:05 PM

Hmmmm.. For a ground loop there must be a path to ground... The only direct way , since the plug goes through the inverter, seems to be through the usb or rca cables..... If I ground the laptop properly, the ground loop should be eliminated, correct?

**pancit175** · 07-29-2006, 07:54 PM

Where did you have the inverter hooked up in reference to your cars power and ground previously? If it was going through the cig lighter, those are subject to alot of noise.
In theory powering and grounding the inverter in a different location may rid your problem.

**Toehead** · 07-29-2006, 08:43 PM

The inverter is hooked up to the battery directly, grounded to the same spot as the amp. I don't think the invertor is adding noise, as there is no noise when the computer is on and there is still the invertor powering everything....

Also, the inverter is a good 2 feet from the laptop... I did this to eliminate any possible interference.

**pancit175** · 07-29-2006, 10:07 PM

So if my understanding is that the noise is only when the computer is off, while still connected to the powered on inverter, then just turn off the inverter while the computer is off and see what happens.
If the inverter is still on, since it creates an oscillating signal for 120AC, then it may be traveling to the sound card output giving you that noise. In theory...