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Old 06-22-2019   #1
 
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Default Help with noise/hiss issue

Ive recently "gone active"
Setup is
2015 Mustang
Ford sync3 head unit
Pre-amp outputs flattened in forscan and taken from factory amp harness
Dayton DSP-408
2x Alpine PDX-v9 amps
Morel Elate 3ways (2◊200w wfr, 2x100w mid, 2x100w twt)
2x Kicker 43CWRT122 12" subs (2◊500w)

My previous setup non-active had no noise.

After switching, at first i had a constant hiss even at zero volume, coming from all speakers mainly noticable from tweeters. I have to lower the master volume on the dsp to 40 (of 66) to get it to an acceptable level. This is without engine running.

I re-routed power cables to avoid running in parallel with any rca cables. This made zero difference.

I then tried a different ground, again no difference. Ground is bolted into bare metal point and is solid. The length of cable to it could be shorter though, about 0.5m of 0awg and then another 0.5m of 4awg from a distribution block to each amp. Not sure if thats worth trying to shorten as it will make installation awkward.

The RCAs I've been using are rubbish and just what i had lying around. I replaced the primary one running the length of the vehicle to the dayton with a better but not great cable and the hiss at zero volume disappeared. Result.

Except that as soon as i add even 1 level of volume the hiss comes back. Obviously once i get to level 4 it's not noticable but i know it's there.

Next steps are to replace all the rcas with high quality cables. (Including cables from DSP to amps)

My questions are, what is the reason replacing just this one cable got rid of it just at zero volume? And is it possible that replacing the rest will get rid of it completely?

Or is it just the DSP at fault and i need a better unit, audison or helix.

Thanks for any input/advice
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Old 06-22-2019   #2
 
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Default Re: Help with noise/hiss issue

You can test the RCA noise by "shorting" the RCAs. Connect the R and L of the same channel.



Sounds like gains might need to be messed with. Not sure if input voltage has anything to do with it. Your DSP outputs at 3.5V, and your amp's max input voltage is 4V.

I have hiss with my setup if I don't reduce my input gain, and I have a 6V DSP output into a 6.5V max input voltage.

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Old 06-22-2019   #3
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Default Re: Help with noise/hiss issue

I went through a similar situation as you recently. Passive, zero noise but as soon as I went active, noise. My hat goes off to the engineers of the passive crossovers.

I would turn the gain down all the way on your amp and see if you get noise. Next check the gain output of the tweeters on your DSP instead of the DSP volume.
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Old 06-23-2019   #4
 
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Default Re: Help with noise/hiss issue

Quote:
Originally Posted by sparkymustang View Post
Ive recently "gone active"
Setup is
2015 Mustang
Ford sync3 head unit
Pre-amp outputs flattened in forscan and taken from factory amp harness
Dayton DSP-408
2x Alpine PDX-v9 amps
Morel Elate 3ways (2◊200w wfr, 2x100w mid, 2x100w twt)
2x Kicker 43CWRT122 12" subs (2◊500w)

My previous setup non-active had no noise.

After switching, at first i had a constant hiss even at zero volume, coming from all speakers mainly noticable from tweeters. I have to lower the master volume on the dsp to 40 (of 66) to get it to an acceptable level. This is without engine running.

I re-routed power cables to avoid running in parallel with any rca cables. This made zero difference.

I then tried a different ground, again no difference. Ground is bolted into bare metal point and is solid. The length of cable to it could be shorter though, about 0.5m of 0awg and then another 0.5m of 4awg from a distribution block to each amp. Not sure if thats worth trying to shorten as it will make installation awkward.

The RCAs I've been using are rubbish and just what i had lying around. I replaced the primary one running the length of the vehicle to the dayton with a better but not great cable and the hiss at zero volume disappeared. Result.

Except that as soon as i add even 1 level of volume the hiss comes back. Obviously once i get to level 4 it's not noticable but i know it's there.

Next steps are to replace all the rcas with high quality cables. (Including cables from DSP to amps)

My questions are, what is the reason replacing just this one cable got rid of it just at zero volume? And is it possible that replacing the rest will get rid of it completely?

Or is it just the DSP at fault and i need a better unit, audison or helix.

Thanks for any input/advice
Are you talking about head unit volume or dsp volume? I don't guess it matters much, whatever volume control it is that unit is where that noise is coming from.
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Old 06-23-2019   #5
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Default Re: Help with noise/hiss issue

In my Challenger I had the same problem. Almost exactly. Turned out it was the factory amp and all the troubleshooting was a big waste of time. Try plugging something into the DSP directly, use the system without the factory stereo and see if the hiss is still there.
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Old 06-23-2019   #6
 
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Quote:
Originally Posted by Souths1der View Post
In my Challenger I had the same problem. Almost exactly. Turned out it was the factory amp and all the troubleshooting was a big waste of time. Try plugging something into the DSP directly, use the system without the factory stereo and see if the hiss is still there.
Ok so I've just done this and zero hiss at any volume with my phone as the source into the dsp.

I've been bypassing the factory amp so thats not even in the game. Does this now mean it's caused by the headunit and everything past the dsp is fine?

Is this a case of there's nothing i can do about it? Or are there things i can try? Not afraid to take headunit out and tinker.
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Old 06-23-2019   #7
 
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Default Re: Help with noise/hiss issue

Quote:
Originally Posted by sparkymustang View Post
Ok so I've just done this and zero hiss at any volume with my phone as the source into the dsp.

I've been bypassing the factory amp so thats not even in the game. Does this now mean it's caused by the headunit and everything past the dsp is fine?

Is this a case of there's nothing i can do about it? Or are there things i can try? Not afraid to take headunit out and tinker.
If there was no noise from the h/u before the dsp install, I doubt there is an issue with it... And if there is no noise when using your phone to dsp, then the issue can't be dsp or amp related.

I am thinking something ground related... DSP ground vs h/u ground, etc.. Try grounding the dsp to the same place as the h/u.

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Old 06-23-2019   #8
 
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Default

Quote:
If there was no noise from the h/u before the dsp install, I doubt there is an issue with it... And if there is no noise when using your phone to dsp, then the issue can't be dsp or amp related.

I am thinking something ground related... DSP ground vs h/u ground, etc.. Try grounding the dsp to the same place as the h/u.
Dsp is in boot, any problem just running a cable to the head unit ground? Would be the length of interior.
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Old 06-23-2019   #9
 
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Default Re: Help with noise/hiss issue

Quote:
Originally Posted by sparkymustang View Post
Dsp is in boot, any problem just running a cable to the head unit ground? Would be the length of interior.
For testing purposes, no problem.

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Old 06-24-2019   #10
 
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Default Re: Help with noise/hiss issue

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Originally Posted by DavidRam View Post
For testing purposes, no problem.
ok so i ran the DSP ground to the same point the head unit is grounded. no difference.

but obviously the amps are still grounded in the trunk.

Is it worth disconnecting the head unit ground point and running it to the amp ground in the trunk instead so all are grounded in the same place?
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Old 06-24-2019   #11
 
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Default Re: Help with noise/hiss issue

I see two potential sources of noise here. One source could be a ground loop related to the remote that plugs into the DSP if you have it but if this happens with the engine off than itís likely not that. Second thing I thought of is the gain settings for the amplifier channels driving the tweeters and mids. How did you set your gains on your amplifiers? Did you set the gains for maximum power or did you use the gain to level match the tweeters to the mids, the mids to the midbass, and the midbass to the subwoofer? If you have a massive amount of attenuation in the DSP for say the tweeters because the amplifier gains are high and they are projecting a higher noise floor from the amplifier, well that could be your issue or part of it. You need to turn the gains down on the amplifier and raise the level controls for those speakers within the DSP. You want the DSP sending a good strong signal to the amplifier with the gain control on the amplifier set as low as needed so that it isnít also amplifying unwanted background noise. The level control within the DSP 408 for the tweeters, midrange speakers, and midbass speakers should be set to as close to 60 as you can and use the amplifier gains to level match the speakers to each other relative to the subwoofer output. Only use the level control within the DSP to make small fine adjustments for say left to right tweeters or midrange.

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Old 06-25-2019   #12
 
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Default Re: Help with noise/hiss issue

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I see two potential sources of noise here. One source could be a ground loop related to the remote that plugs into the DSP if you have it but if this happens with the engine off than itís likely not that. Second thing I thought of is the gain settings for the amplifier channels driving the tweeters and mids. How did you set your gains on your amplifiers? Did you set the gains for maximum power or did you use the gain to level match the tweeters to the mids, the mids to the midbass, and the midbass to the subwoofer? If you have a massive amount of attenuation in the DSP for say the tweeters because the amplifier gains are high and they are projecting a higher noise floor from the amplifier, well that could be your issue or part of it. You need to turn the gains down on the amplifier and raise the level controls for those speakers within the DSP. You want the DSP sending a good strong signal to the amplifier with the gain control on the amplifier set as low as needed so that it isnít also amplifying unwanted background noise. The level control within the DSP 408 for the tweeters, midrange speakers, and midbass speakers should be set to as close to 60 as you can and use the amplifier gains to level match the speakers to each other relative to the subwoofer output. Only use the level control within the DSP to make small fine adjustments for say left to right tweeters or midrange.

thanks mate, I didn't buy the remote as I'd read it was common for it to add a lot of noise as you are suggesting.

The gains are set very modestly but only by ear and not pushed to limits at all yet, i don't have the kit to do it any other way at the minute. I set the DSP volume to remove the hiss then adjusted the gain. I will have a go at doing it the other way, high dsp volume & lower amp gain later on. From memory gain had to be at zero to remove the noise in the tweeters i think at decent DSP volume.
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Old 06-25-2019   #13
 
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Default Re: Help with noise/hiss issue

Quote:
Originally Posted by sparkymustang View Post
thanks mate, I didn't buy the remote as I'd read it was common for it to add a lot of noise as you are suggesting.

The gains are set very modestly but only by ear and not pushed to limits at all yet, i don't have the kit to do it any other way at the minute. I set the DSP volume to remove the hiss then adjusted the gain. I will have a go at doing it the other way, high dsp volume & lower amp gain later on. From memory gain had to be at zero to remove the noise in the tweeters i think at decent DSP volume.
I've got a feeling than that this isn't it but its worth at least trying so that the noise floor is as low as possible. Like others said, if you are not getting noise with the engine off or with a different source as the input than I would suspect its the main source input causing the noise and the amplifiers are just doing what they are designed to do, which is amplify the signal and unfortunately any noise input too.

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Old 06-25-2019   #14
 
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Default Re: Help with noise/hiss issue

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Originally Posted by JCsAudio View Post
I've got a feeling than that this isn't it but its worth at least trying so that the noise floor is as low as possible. Like others said, if you are not getting noise with the engine off or with a different source as the input than I would suspect its the main source input causing the noise and the amplifiers are just doing what they are designed to do, which is amplify the signal and unfortunately any noise input too.
noise is there even with engine off.

really frustrating if that's the case. although there was no hiss with just a single amp and passive crossovers with the same head unit. it's only since removing the crossovers and adding the dsp & second amp that the noise has appeared. i suppose more power = more noise maybe?
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Old 06-25-2019   #15
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Default Re: Help with noise/hiss issue

I believe its the factory amp then.

I had the same problem. Not that big of a deal for me. I listen to XM and then music apps (Spotify, Poweramp) on my phone, I never listen to FM or AM radio. So I just switched to the XM app on my phone as well. I have the bluetooth HEC for my Helix, so I just had my phone connected to it for music and my car at the same time for calls. When a call would come in the helix would automagically switch. That solution worked for me anyway.
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Old 06-25-2019   #16
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Default Re: Help with noise/hiss issue

Maybe start by turning the tweeter amp gain all the way down, and DSP gain up...
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Old 06-25-2019   #17
 
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Default Re: Help with noise/hiss issue

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Originally Posted by Holmz View Post
Maybe start by turning the tweeter amp gain all the way down, and DSP gain up...
yep ok, so i've just gone and approached it like this, even with amp gain at 0 DSP needs to be at 40 for it to be unnoticable (but still there if put ear to speakers).
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Old 06-25-2019   #18
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Default Re: Help with noise/hiss issue

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Originally Posted by Souths1der View Post
I believe its the factory amp then.
Not even wired in bud
Quote:
Originally Posted by sparkymustang View Post
Ok so I've just done this and zero hiss at any volume with my phone as the source into the dsp.

I've been bypassing the factory amp so thats not even in the game. Does this now mean it's caused by the headunit and everything past the dsp is fine?

Is this a case of there's nothing i can do about it? Or are there things i can try? Not afraid to take headunit out and tinker.
Iíd be looking to maximise signal from the headunit and also from the dsp, then have gains as low as can be

Daft question... can you lay your hands on a line out ground loop isolator? Might be worth stitching (guessing factory headunit isnít on RCAís, so may need a bit of soldering) one of those into the circuit and see if it cures the noise issue?
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Default Re: Help with noise/hiss issue

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Originally Posted by dumdum View Post
Daft question... can you lay your hands on a line out ground loop isolator? Might be worth stitching (guessing factory headunit isnít on RCAís, so may need a bit of soldering) one of those into the circuit and see if it cures the noise issue?
funnily enough i have one on order, should arrive tomorrow.

will this not distort the signal though? i thought i'd read somewhere that it has a negative affect on quality.
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Old 06-25-2019   #20
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Default Re: Help with noise/hiss issue

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funnily enough i have one on order, should arrive tomorrow.

will this not distort the signal though? i thought i'd read somewhere that it has a negative affect on quality.
Not in my experience, itís basically a 1:1 transformer inline with the signal, I donít go a bundle on them and normally Iíd rather find a solution as in my experience itís normally a component along the way and Iíve never had induced noise I couldnít cure, but if itís a unique component thatís not easily repaired and it cured it I would go with it 👍🏼 I hope it sorts it for you
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Default Re: Help with noise/hiss issue

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Not in my experience, itís basically a 1:1 transformer inline with the signal, I donít go a bundle on them and normally Iíd rather find a solution as in my experience itís normally a component along the way and Iíve never had induced noise I couldnít cure, but if itís a unique component thatís not easily repaired and it cured it I would go with it 👍🏼 I hope it sorts it for you
well i think i've narrowed it down to the head unit itself which is Fords sync3 heavily built into the car, climate control etc all in there so not an option to replace unfortunately.

that's great if it doesn't affect the signal. i only ordered it out of curiosity to see if it helped at all, thinking i wouldn't actually use it.
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Old 06-25-2019   #22
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Default Re: Help with noise/hiss issue

Are there any specs for that amp's SNR?
(Those numbers are usually in the 80s to ~115 dB range.)
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Originally Posted by Holmz View Post
Are there any specs for that amp's SNR?
(Those numbers are usually in the 80s to ~115 dB range.)
112db according to their website

https://www.alpine.co.uk/p/Products/SingleView/PDX-V9
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So i plugged in the ground loop isolator and it made no difference at all. I tried it at the head unit and also between the dsp and amp.

I also temporarily grounded the head unit at the same clean ground point as the amps & dsp. Again no improvement.

Its a constant hiss, not a buzz.

at zero volume its silent but will occassionally appear for a cpl seconds then go quiet again.

At volume setting 1of30 on headunit the hiss is loud. It doesnt get louder with the head unit volume setting. It stays a constant volume.

The dsp volume control makes the hiss quieter and louder. All the way down to setting 40of66 to get it to go away which seems very low.

Replaced/rerouted rcas, no difference.

Plugged in my phone directly to the dsp input and the sound is clean, no hiss.

Unplugged rcas at head unit and no hiss.

Any other suggestions to look at?
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Old 06-27-2019   #25
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Default Re: Help with noise/hiss issue

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Originally Posted by sparkymustang View Post
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Plugged in my phone directly to the dsp input and the sound is clean, no hiss.

Unplugged rcas at head unit and no hiss.

Any other suggestions to look at?
My interpretation is that this hiss appears to be coming from the HU.
Wires do not generally hiss...

in theory the thermal noise does hiss, but if the iPhone is on the same RCAs up front, then you can test that... the theory is a small amount of hiss, and only dependent on temp.
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