Amplifier problem... or maybe audiocard?

**l1nk** · 08-03-2007, 06:44 AM

Hi all, I'm experiencing some problem with my carpc -> amplifier connection.

I have a miniITX motherboard with integrated 6 channels audio (L-R front, L-R rear, Central/LFE).

I've directly connected 4 of the 6 outputs channels of the motherboard, to the 4 line inputs of my amplifier (kenwood KAC849).
So when configuring (via software) the soundboard to exit on 4 channels all the stuff works greatly :-) and I have frontal and rear channels workin good. No noise/buzz, nothing strange.

Recently I buyed an amplified bazooka.
I'd like to connect to the soundboard as already done for the other channels so I started configuring soundboard to exit on six channels, i.e. enabling the central/LFE output.

When I connect the LFE soundboard exit to the bazooka input the bazooka works good and I like very much this new sound and the big bass I got :-D

There's only a little problem :-(

When not hearing music I can clearly hear a low freq buzz costantly even if mute volume on windows... This buzz is always present even when listening to music or movies, though overtopped by the sounds, I can hear it's annoyng presence :-(

This disturbing buzz disappear if I connect the bazooka to the line out of my kenwood but in this way I lost the 6 channel configuration :-( because I'm getting the signals for the bazooka from a combination of front/rear channels.

Maybe an impedance problem?? Is the soundcard audio outputs compatible (for impedance, level) with the high impedance inputs of my amplifiers (even kenwood and bazooka are connected by their high impedance line inputs).

Many thanks for your help.

**durwood** · 08-03-2007, 10:44 AM

buzzing or alternator whine?

Sounds like a possible ground loop problem. are the amplifers sharing the same ground point? Otherwise pick up a groundloop isolator and install it on the bazooka tube.

**l1nk** · 08-03-2007, 11:02 AM

Originally Posted by durwood

buzzing or alternator whine?

Sounds like a possible ground loop problem. are the amplifers sharing the same ground point? Otherwise pick up a groundloop isolator and install it on the bazooka tube.

Thanks durwood for response.

Seems to have nothing to do with the car, but related to the pc instead :-( Or, as already said, to the connection between pc and bazooka.

The Kenwood 4 channels amp have his ground on a screw on the left side of the car's body; the bazooka tube have his own ground on a different screw on the right side. The ground is the same, only taken at two different points of the car's structure.

**volfiregon** · 08-03-2007, 12:01 PM

I would suggest that probably you would have to connect a Low Pass Crossover Filter or High Pass Crossover Filter. How many Watts does the Bazooka play ? .

**l1nk** · 08-04-2007, 06:15 PM

Originally Posted by volfiregon

I would suggest that probably you would have to connect a Low Pass Crossover Filter or High Pass Crossover Filter. How many Watts does the Bazooka play ? .

Is a BTA100, integrated 100W amplifier.

Seems to be something related to car's ground and the MB.
I tried to directly connect a wire from battery - pole to the gnd of an audio jack of the mb and the noise plays louder... It does not disappear but is more louder. It plays louder when I connect the "-" pole of the car's battery to every metallic part on the motherboard, either audio aoutput jacks or serial port or usb output's box... or the screw's holes.
Could be a solution but it plays louder, dont disappear

**XC-C30** · 08-04-2007, 07:58 PM

Originally Posted by volfiregon

I would suggest that probably you would have to connect a Low Pass Crossover Filter or High Pass Crossover Filter. How many Watts does the Bazooka play ? .

A sub that outputs watts?? I want such a sub too!!!! Where can I get one?

**pancit175** · 08-04-2007, 09:03 PM

I use to have that problem untill I went digital/optical. I know thats not a solution, per say. But I figure I'd propose that as a possibility.

**l1nk** · 08-05-2007, 03:25 AM

Originally Posted by pancit175

I use to have that problem untill I went digital/optical. I know thats not a solution, per say. But I figure I'd propose that as a possibility.

My mb also have spdif output and I think I could use that instead of analogs... but for this kind of connection I need to add a decoder or something like that... it's correct?

**rijndael** · 08-05-2007, 06:59 AM

Originally Posted by l1nk

My mb also have spdif output and I think I could use that instead of analogs... but for this kind of connection I need to add a decoder or something like that... it's correct?

that is correct. you will need a head unit (or other device like an Alpine PXA-H701...kinda expensive) that can demodulate the digital signal back to analog for the sound output.

i recommend going with the advice people are mentioning here about a ground loop isolator. all you do is place that isolator on the RCA jacks from your computer, then from the isolator to your amplifier via another RCA cable. i dont know how much shipping is to where you are at, but here in the U.S., its only 15 dollars at an electronics store, and its small, so it shouldnt be much.

**pancit175** · 08-05-2007, 07:59 PM

Originally Posted by l1nk

My mb also have spdif output and I think I could use that instead of analogs... but for this kind of connection I need to add a decoder or something like that... it's correct?

Correct. Just keep in mind, if you go that route, that some devices can either accept spdif through an optical cable or a digital RCA cable.