[digitaldav]

I just got done installing JL Audio XD600/6 using Technic's harness. Also adjusted input sensitivity as per manual. System sounds great but when turned all the way down I hear a slight hissing sound from speakers.
Any thoughts?

[mattyjman]

noise floor from the amp...

[digitaldav]

Originally Posted by mattyjman

noise floor from the amp...

Is that normal?

[Atorsesh]

Is the hiss with the radio/cd and aux? the aux jack is very noisy.

[VP Electricity]

Originally Posted by digitaldav

I just got done installing JL Audio XD600/6 using Technic's harness. Also adjusted input sensitivity as per manual. System sounds great but when turned all the way down I hear a slight hissing sound from speakers.
Any thoughts?

You used an oscilloscope?

I think your gain needs to go down. But this is HiFi, right? Where is your treble control?

[kaigoss69]

Turn the gain down on the channels connected to the mids and tweeters, until you no longer hear the hiss. You probably won't need all the amp's reserves for those speakers and maxing out the gains can introduce unwanted noise.

[kmarei]

An oscilloscope is not needed per manual
Just an AC voltmeter
If you hear hiss when volume is at 0
Then you gain is set too high

[digitaldav]

Even with gain set to 0 there is still some noise. The noise is lower but still there. Could the rca cables be the cause?
Even with treble all the way down, there is still hiss.

[kmarei]

Try unplugging the inputs to the amp, and check for hiss

[VP Electricity]

Originally Posted by kmarei

Try unplugging the inputs to the amp, and check for hiss

That might make it worse since the unloaded inputs can pick up EMI.

Where is your treble control? Should be centered... Still stock speakers?

[VP Electricity]

And the car is a HiFi car?

[digitaldav]

Treble is at center. Subs underseat were replaced last year. Only here the hiss with volume all the way down. Yes, car is Hi Fi.

[Technic]

Originally Posted by digitaldav

Treble is at center. Subs underseat were replaced last year. Only here the hiss with volume all the way down. Yes, car is Hi Fi.

Any hiss with the gain at minimum?

[digitaldav]

There is a slight hiss with gain at 0

[Technic]

Originally Posted by digitaldav

There is a slight hiss with gain at 0

Where your ground is connected?

[digitaldav]

Gounded on the ground block over left rear wheel well.

[Technic]

Originally Posted by digitaldav

Gounded on the ground block over left rear wheel well.

Originally Posted by mattyjman

noise floor from the amp...

[digitaldav]

Originally Posted by Technic

I am going to try swapping out rca cables...

[cdgatti]

Originally Posted by VP Electricity

That might make it worse since the unloaded inputs can pick up EMI.

Where is your treble control? Should be centered... Still stock speakers?

Should unused inputs be 'plugged' with blank rca's ??? For example, the xd600 has 3 pairs of rca inputs, with the hifi harness we are using 2 pair, can noise come in from the unused 3rd pair?

[kmarei]

Originally Posted by VP Electricity

That might make it worse since the unloaded inputs can pick up EMI.

Where is your treble control? Should be centered... Still stock speakers?

so you're saying disconnecting the rca's from the amp side will pick up more noise? that's the first time i hear that
in that case the amp is faulty

[Technic]

Originally Posted by cdgatti

Should unused inputs be 'plugged' with blank rca's ??? For example, the xd600 has 3 pairs of rca inputs, with the hifi harness we are using 2 pair, can noise come in from the unused 3rd pair?

The unused 3rd pair in the XD600/6 is internally connected to CH1-> Ch4 when the input switch is set to 4-input.

[VP Electricity]

Originally Posted by kmarei

so you're saying disconnecting the rca's from the amp side will pick up more noise? that's the first time i hear that

I can't control what you have heard and not heard. But an unloaded, or unterminated RCA input, is an antenna for EMI.

I will quote a paper by Davind Navone and Richard Clarke of Autosound 2000 on troubleshooting noise. (I will fall back on citing an "authority"...)

Unplug the RCA cables from the amplifier/s and mute the signal at the input by using shorting plugs. This will isolate the amplifier from the rest of the car stereo installation. You can make shorting plugs by taking cheap male RCA plugs and soldering the centre and outer terminals together. This shorts out the input of the amplifier/s to ensure that it has zero signal.

Originally Posted by kmarei

in that case the amp is faulty

We all live and learn.