head unit hiss (sync3)

[SpArKy]

Ive recently "gone active"
Setup is
2015 Mustang
Ford sync3 head unit (upgrade from MFT)
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 hiss.

Now unless i turn the Dayton right down to volume 40 (of 66) i get a really annoying hiss (not buzz), most notably from the tweeters and midranges. It is a constant hiss with engine off and doesn't change with head unit volume control.

I have done a lot of troubleshooting and the consensus in the audio forums is that it's the head unit that's causing it (or more likely perhaps the installation of the head unit, since I upgraded from MFT myself).

It's not grounding issue. A ground loop isolator makes no difference. I've also grounded the head unit at the same clean ground point as the amps & dsp. Again no improvement.


here are some facts about the issue

• at zero volume its silent but will occasionally appear for a cpl seconds then go quiet again.
• At volume setting 1of30 on headunit the hiss is loud. It doesn't 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, effectively ruling out the amps, dsp or speakers as the cause.
• Unplugged rcas at factory molex and no hiss so not being picked up by the RCAs.

Convinced it's coming from the head unit. I'm about to rip the dash apart and see if anything like the Fakra aerial, wiring for nGauge or anything I've done might be causing it.

Has anyone got a similar setup on a sync3 unit and not had to adjust their levels right down to get rid of hiss?

Thanks for any input/advice

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[StangTime]

Where did you tap into the factory wiring to pull your signals from? Before or after the factory amp?

 

[SpArKy]

Where did you tap into the factory wiring to pull your signals from? Before or after the factory amp?

Before. Factory amp is gone

 

[StangTime]

Before. Factory amp is gone

Have you adjusted the gain on your amplifier too high? You want maximum signal out of the head unit and minimal gain at the amplifiers to avoid amplifying noise. Start by turning your DSP volume down to get rid of as much hiss as possible. Then set your amplifier gains to zero and head unit volume to 80%. Then bring up the gains slowly on the amps to the loudest, cleanest point at which you would listen. Hopefully the noise floor is now reduced when listening at the lower end of the volume control. Forgot to add: You might need to go back and tweak the DSP volume again to reduce any amplification it might be doing to the noise floor.

 

[SpArKy]

Have you adjusted the gain on your amplifier too high? You want maximum signal out of the head unit and minimal gain at the amplifiers to avoid amplifying noise. Start by turning your DSP volume down to get rid of as much hiss as possible. Then set your amplifier gains to zero and head unit volume to 80%. Then bring up the gains slowly on the amps to the loudest, cleanest point at which you would listen. Hopefully the noise floor is now reduced when listening at the lower end of the volume control. Forgot to add: You might need to go back and tweak the DSP volume again to reduce any amplification it might be doing to the noise floor.

where should the amp gains & volume be when I'm adjusting the DSP volume initially? amp gain at zero & volume 80%? the amp gain increases the hiss, but even at zero gain it's still clearly audible.

 

[StangTime]

Hmm. Try this then.... Set all gains - DSP and amps to zero. Head unit at 80%. Bring the DSP up one or two levels. Turn up the amp gain until you hear audio playing. If you hear nothing, then increase the DSP level a bit. Go back and forth between the DSP volume and amp a little at a time with most of the gain being done before the amplifier stage.
If that still doesn't work, you might have gotten a bad head unit. That's all the advice I can offer you.

 

[Racemaster]

More than likely the DSP.
https://www.avsforum.com/forum/90-receivers-amps-processors/3050590-dayton-audio-dsp-408-hiss.html
You can NOT use cheap equipment in these systems.
They are very sensitive to any grounding issues and noise.
Don't expect champagne on a beer budget
All of the rest of your equipment looks of good quality,just get a better DSP and I bet the noise goes away

 

[SpArKy]

More than likely the DSP.
https://www.avsforum.com/forum/90-receivers-amps-processors/3050590-dayton-audio-dsp-408-hiss.html
You can NOT use cheap equipment in these systems.
They are very sensitive to any grounding issues and noise.
Don't expect champagne on a beer budget

was my first thought too but if i use a source other than the head unit, i/e my phone into the DSP input then it plays with no hiss. does that not rule it out? think the morels prove this isn't a beer budget system

 

[Racemaster]

Not sure than.
More than likely is because the phone is not using the same ground as the head unit.
I just googled that DSP review and that is what came up fast.
The Morels and the Alpine should work fantastic I would think.

 

[Racemaster]

One other thing to maybe try is,I used the ground which is up high next to the top left of the factory amp.You will see it when you look up there.It was either a 8 or a 10 mm bolt that attaches the factory wiring from the audio harness.You could make a quick jumper lead and see if it makes any difference.But after reading that review my money is on a noisy DSP.

 

[Cathul]

Are you using the provided remote control on the Dayton? If yes, don't. It's proven to cause hiss in the Dayton.

 

[SpArKy]

Are you using the provided remote control on the Dayton? If yes, don't. It's proven to cause hiss in the Dayton.

nope, read that before i bought it so didn't bother with it.

One other thing to maybe try is,I used the ground which is up high next to the top left of the factory amp.You will see it when you look up there.It was either a 8 or a 10 mm bolt that attaches the factory wiring from the audio harness.You could make a quick jumper lead and see if it makes any difference.But after reading that review my money is on a noisy DSP.

ok, so i have already tried that and it made no difference unfortunately. Mine is RHD though, i'm not sure where the factory amp is on your cars. the ground I re-routed was bolted to the right hand side of the right hand footwell. there were 2, it was the top one. It had 3 or 4 black/grey cables going into it.

Having said that I have just bypassed the DSP which I'm sure i did in the early fault finding stages. The hiss is still there but it's much less "in your face". maybe when i tested before I just listened and heard hiss so ruled it out as the cause. my alpines actually have enough crossover control to run the system actively without the DSP which i may do for a little while until i can get my hands on a better DSP. this one just ticked the few boxes i had (number of inputs/outputs, crossover, time alignment) and can be controlled from an app which was a huge plus for me. I had read that review too, but his is a home audio system and there are plenty of people really happy with their Daytons in the car audio world so just figured his was an edge case.

Am i right in thinking that i'll never get rid of it completely? or should there be no hiss at all? Seriously considering changing the head unit but is a lot of cost and hassle if not necessary.

One thing is for sure, these Morels sound the business with or without hiss at low volume

 

[UserName]

Am i right in thinking that i'll never get rid of it completely? or should there be no hiss at all? Seriously considering changing the head unit but is a lot of cost and hassle if not necessary.

One thing is for sure, these Morels sound the business with or without hiss at low volume

I’ve never used the same dsp that you did so can’t comment on that unit’s particular quirks. I can share my experience with the hiss though. The hiss does come from the head unit and there is nothing you can do about it apart from piping in a different source to your dsp. The hiss is only audible for me if the car isn’t running and the volume is set to zero or the track is paused. I’m also using Morel mids and tweets with dynaudio mid bass drivers. They do get down with a good amount of clean power.

 

[SpArKy]

I’ve never used the same dsp that you did so can’t comment on that unit’s particular quirks. I can share my experience with the hiss though. The hiss does come from the head unit and there is nothing you can do about it apart from piping in a different source to your dsp. The hiss is only audible for me if the car isn’t running and the volume is set to zero or the track is paused. I’m also using Morel mids and tweets with dynaudio mid bass drivers. They do get down with a good amount of clean power.

Which dsp are u using? How much power u running inti ur speakers etc? Details of ur setup would be great if poss.

This is really loud, if i plug straight into the amps its there but much much quieter and what i would call normal in a car setup, these things have signal to noise ratios after all.

With the dsp its pretty loud. The signal to noise on the dayton is on paper better than the helix or audison units so i cant see it being supposed to be like that. Also loads of ppl in other cars using them and are delighted with the features.

 

[UserName]

Which dsp are u using? How much power u running inti ur speakers etc? Details of ur setup would be great if poss.

This is really loud, if i plug straight into the amps its there but much much quieter and what i would call normal in a car setup, these things have signal to noise ratios after all.

With the dsp its pretty loud. The signal to noise on the dayton is on paper better than the helix or audison units so i cant see it being supposed to be like that. Also loads of ppl in other cars using them and are delighted with the features.

There’s nothing wrong with any of the dsps you listed, they’re all respectable brands. At some point your chasing something that may or may not even be perceptible.

The setup is as follows:

JL Fix82 to flatten the factory signal
Helix DSP for processing
Helix Director to control setups and sub volume
Morel MT350 tweets
Morel CDM880 mids
Dynaudio E650 midbass
Pair of Stereo Integrity BM MK5 subs
3 x Mosconi Zero 3 for front stage
Mosconi Zero 1 for sub duty

I didn’t tune it, but the speakers are getting every bit of power they can take while staying in balance with the weakest link. Theoretical maximum output from each Zero 3 is 270 watts rms per channel at 4 ohms. Given the Morels I used are 6 ohm that reduces the output of the amp to 190 watts or so per channel. Obviously they are turned down substantially from the maximum. I think the Dynaudio E650s are getting the full dose. And I am confident the subs are at their limit just running in stereo off of the Zero 1 with somewhere between 450 and 650 watts rms each.

I’m confident that nothing I added causes the hiss because as soon as you unplug the factory source the hiss goes away.

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