[ontopofm]

Originally Posted by jonywalker

Then it is the noise of its own. Normally such aftermarket amps have S/N rate higher than 90dB, even my PDX with 76dB doesn't have any noise if input is disconnected. Above 90dB should be noisefree absolutely. I assume your car engine was off during the test otherwise the electric magnetic interruption could also be a possible noise origin.
So you could send back you amp.

is that volume independent? because the music is quite loud when i plugged back the inputs at the borderline of hiss/no hiss

[ontopofm]

Originally Posted by Technic

And this is after setting the amp gain to the absolute minimum, correct?

correct

[Technic]

Originally Posted by ontopofm

correct

What is that "line driver" that you got?

[ontopofm]

Originally Posted by Technic

What is that "line driver" that you got?

Phoenix Gold TLD22

[Technic]

Originally Posted by ontopofm

Phoenix Gold TLD22

Did you try this device?

You will need to make RCA plugs out of the OEM underseat wires to use this device, and that is assuming that the OEM amp outputs to the underseat subs do not exceed the maximum input level of this device (5V).

[ontopofm]

no, i havent try it, i need to get some RCA cables
i have the Amp Interface Adapter laying around so im going to use it
oem amp --> amp interface adapter --> line driver --> alpine amp
hope it will works

[jonywalker]

Originally Posted by ontopofm

no, i havent try it, i need to get some RCA cables
i have the Amp Interface Adapter laying around so im going to use it
oem amp --> amp interface adapter --> line driver --> alpine amp
hope it will works

you said your amp still had noise even if the input was disconnected, and the amp gain was set to the minimum. If that is true then nothing could help.
My hiss issue is different from yours then my hiss comes from HU, using line driver could lift S/N, thus eliminates the white noise.

[Technic]

Using the low level inputs instead of the high level in this amp could definitely prove if the amp itself is the problem, or it was "hissy" high level inputs.

[jonywalker]

Originally Posted by Technic

Did you try this device?

You will need to make RCA plugs out of the OEM underseat wires to use this device, and that is assuming that the OEM amp outputs to the underseat subs do not exceed the maximum input level of this device (5V).

Hi Technic,
do you know a simple way to make an amp like PDX with differential balance input only to accept RCA input from a line driver or a alpine CDA HU?

[Technic]

Originally Posted by jonywalker

Hi Technic,
do you know a simple way to make an amp like PDX with differential balance input only to accept RCA input from a line driver or a alpine CDA HU?

The great thing about balanced input amps is that it takes non-balanced inputs as well. It is the other way around (non-balanced inputs amps accepting balanced inputs) that can't...

[ontopofm]

the line driver is in, it reduces the hiss a lil bit
do you guys not get any hiss at all even at high volume?

[scooby9]

Any updates on the "hiss" issues?

[Technic]

Originally Posted by scooby9

Any updates on the "hiss" issues?

There is a very noticeable "hiss" in a PDX 4-100 that I just installed, even without any inputs. In my case, it is the amp that most probably is bad as a PDX 4.150 that I also have does not have any hiss at all with the same power/ground/RCA/speaker connections.

[fdiprete]

Originally Posted by Technic

There is a very noticeable "hiss" in a PDX 4-100 that I just installed, even without any inputs. In my case, it is the amp that most probably is bad as a PDX 4.150 that I also have does not have any hiss at all with the same power/ground/RCA/speaker connections.

Damn.

Hearing about these hiss struggles makes me appreciate my old alpine amps that are dead silent. I just took it as a given.

[Technic]

Originally Posted by fdiprete

Damn.

Hearing about these hiss struggles makes me appreciate my old alpine amps that are dead silent. I just took it as a given.

After some tests I'm pretty sure that this hiss is coming from some OEM module of the car when it is on, as the other PDX amp (4.150) that I have is also showing some hiss after re-testing. It seems to me now that when I tested the 4.150 that module was off (the car was off), so it made me think -incorrectly now- that I have a bad 4.100. But additional tests with different scenarios showed that regardless of the amp there is a very subtle hiss and even some times a faint whine that goes on and off at different times, like there is something else turning on and off even when the car is not running. None of these noises vary with engine speed or they increase with volume, so alternator or fuel pump interferrence is out of the picture. All this testing is done without any inputs to any of the amps...

There are still a couple of things that I can do to try to further minimize the hiss to acceptable levels, with better cables, shorter grounds and speaker wires, and better layout of all the components. I will not be able to completely eliminate the hiss as I'm using the Cleansweep remote volume at 75%, so I can use the OEM volume controls but that's acceptable for me.

[Technic]

In my hiss case, the PDX 4.100 was bad. A brand new one solved the issue...

[sierrajulietgolf]

I have spent months installing an Alpine system in my BMW 325ci. Being a convertible, everything required customized fitting and a tight squeeze for all wiring, fun, sort of... This included the amplifier, so I was very happy when I found the Alpine PDX-4.100...fit PERFECTLY in the factory CD changer fitting in the trunk.

So problem 1...I had the same problem with Channel 2 on the amplifier...terrible noise, above any regular level of system hiss. Amp ground is alright, still present with RCAs detatched. Realized it was the amp when I switched the outputs for channel 1 and channel 2, and the noise switched from right side to left side speakers. Alpine suggested I switch out the amp for a new one.

Problem 2...second amp solved the channel 2 problem, but now I have low level noise in all channels. With the volume high you cannot notice the noise, but not all songs are naturally loud, and any break in a song makes this noise apparent. Alpine suggested that the amp is broken and I should return for another...seriously?!

I am going to try amp #3, purchased from Crutchfield with a full, 30-day return policy. If the problem persists, I am going to switch to a new brand. I am not, as of now, satisfied with the quality of Alpine amplifiers.

Update: I saw a few posts on here about Line Drivers. Would a line driver from the Alpine CDA-X100 HU to my PDX-4.100 solve this issue??

Thanks for your help!

[Technic]

Originally Posted by sierrajulietgolf

I have spent months installing an Alpine system in my BMW 325ci. Being a convertible, everything required customized fitting and a tight squeeze for all wiring, fun, sort of... This included the amplifier, so I was very happy when I found the Alpine PDX-4.100...fit PERFECTLY in the factory CD changer fitting in the trunk.

So problem 1...I had the same problem with Channel 2 on the amplifier...terrible noise, above any regular level of system hiss. Amp ground is alright, still present with RCAs detatched. Realized it was the amp when I switched the outputs for channel 1 and channel 2, and the noise switched from right side to left side speakers. Alpine suggested I switch out the amp for a new one.

Problem 2...second amp solved the channel 2 problem, but now I have low level noise in all channels. With the volume high you cannot notice the noise, but not all songs are naturally loud, and any break in a song makes this noise apparent. Alpine suggested that the amp is broken and I should return for another...seriously?!

I am going to try amp #3, purchased from Crutchfield with a full, 30-day return policy. If the problem persists, I am going to switch to a new brand. I am not, as of now, satisfied with the quality of Alpine amplifiers.

Update: I saw a few posts on here about Line Drivers. Would a line driver from the Alpine CDA-X100 HU to my PDX-4.100 solve this issue??

Thanks for your help!

So, are you using an Alpine HU with these amps? How are you routing the RCA cables from the dash to the trunk?

[sierrajulietgolf]

Yes, Alpine HU connected via patch cables directly to the amplifier. They are routed on the left side of the vehicle (all low gauge, red power wires are on the right side of the car). Noise is still present even with the patch cables unplugged. And in testing, I routed the patch cables essentially OUTSIDE of the car to ensure they were not the problem, picking up signal noise running inside the car. Technic, you seem very knowledgeable about system setups and have had experience with the PDX-4.100, any ideas? Could you explain a little more about the Line Driver? I could always install one and see if it works, Crutchfield is amazing with its 30-day trial/return period. Thanks!

[Technic]

Originally Posted by sierrajulietgolf

Yes, Alpine HU connected via patch cables directly to the amplifier. They are routed on the left side of the vehicle (all low gauge, red power wires are on the right side of the car). Noise is still present even with the patch cables unplugged. And in testing, I routed the patch cables essentially OUTSIDE of the car to ensure they were not the problem, picking up signal noise running inside the car. Technic, you seem very knowledgeable about system setups and have had experience with the PDX-4.100, any ideas? Could you explain a little more about the Line Driver? I could always install one and see if it works, Crutchfield is amazing with its 30-day trial/return period. Thanks!

What are you using as the ground point, direct battery connection or a chassis ground close to the amp?

A line driver cannot be used to eliminate that kind of noise. You need to find the source of that noise first.

[sierrajulietgolf]

Ground point is right next to the amplifier, back left portion of trunk. It is grounded to a specific BMW grounding point, brown wire BMW multi-ground is grounded here as well. I have seen SO many posts online about this specific amplifier and this problem. I find it hard to believe it is the product. One of my ideas is that this amplifier rests right below the BMW AM/FM antenna module. I have previously rule this out though since I did not connect the antenna turn on lead to my HU as I only use Sirius.

[Technic]

Originally Posted by sierrajulietgolf

Ground point is right next to the amplifier, back left portion of trunk. It is grounded to a specific BMW grounding point, brown wire BMW multi-ground is grounded here as well. I have seen SO many posts online about this specific amplifier and this problem. I find it hard to believe it is the product. One of my ideas is that this amplifier rests right below the BMW AM/FM antenna module. I have previously rule this out though since I did not connect the antenna turn on lead to my HU as I only use Sirius.

Before requesting another replacement amp, change the ground point and/or move the amp to another place to see if the noise goes away.