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2017 Toyota 86. Focal Utopia M, Audiofrog GB, Mosconi Zero
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Discussion Starter · #1 ·
So it seems that most higher quality amps all tend to have differential inputs on the RCA connections. That sounds great, but how useful really is it?
I say that because I can't seem to find a single headunit that outputs in that way to allow the amps to take advantage of it.
Am I just misunderstanding the way the headunits are outputting their signal? Or do you only get to take advantage of this tech when you are using something like a dsp in between that converts to the differential signal?
It sounds like it should be something very useful, but if your typical longest runs in the car that are the most prone to picking up noise (HU to amps/DSP in the back of car) can't take advantage, it seems to me like it may not be as useful as it seems at first glance.
Someone please enlighten me!
 

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Nope. You’re right. I don’t know of any radios that have balanced preamp outputs. They’re all single ended. Twisted pair rcas offer no benefit from the single ended radio output to DSP input.

The place where this matters is between the DSP and the amp. Like you said, having differential outputs on the DSP, and differential inputs on the amp, you want to use twisted pair rcas to take advantage of the signal noise reduction.
 

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That is what Im talking about for years. With very short runs of RCA cables from DSP to amps and with possible toss-link connection between HU and DSP, there is really small chance of inducted noise issue, especially if cables are routed carefully avoiding parallel runs with electrical...but IMHO that is something every installer should look for. The only other benefit is higher signal voltage, but with todays head units deliver between 4-8V it isnt a thing to die for
 

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Discussion Starter · #4 ·
Nope. You’re right. I don’t know of any radios that have balanced preamp outputs. They’re all single ended. Twisted pair rcas offer no benefit from the single ended radio output to DSP input.

The place where this matters is between the DSP and the amp. Like you said, having differential outputs on the DSP, and differential inputs on the amp, you want to use twisted pair rcas to take advantage of the signal noise reduction.
Makes sense to me. Dsps also typically have a very high output voltage compared to a headunit as well, so it seemed strange they wouldn't be the ones integrating it
 

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Differential inputs are designed to work with EITHER single ended outputs or balanced outputs. Lots of factory systems use balanced outputs to reduce the likelihood of noise. It's silly that aftermarket head units don't do this, but even with a single ended output, these dramatically reduce the potential for noise.

Years ago, head units and the inputs of processors and amplifiers were single ended and literally every system had noise. At the end of an installation, battling ground loops was just SOP. That's where star grounding and all of this searching for the ground problem came from. Now, with differential inputs, the power supply ground is rarely the problem and that's why so many of these noise troubleshooting threads include "I tried regrounding everything and running a 000 gauge cable from the battery to the ground and I did the big three and I replaced the RCA cables and...I still have noise."

Because that's not the problem anymore.
 

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Differential inputs are designed to work with EITHER single ended outputs or balanced outputs. Lots of factory systems use balanced outputs to reduce the likelihood of noise. It's silly that aftermarket head units don't do this, but even with a single ended output, these dramatically reduce the potential for noise.

Years ago, head units and the inputs of processors and amplifiers were single ended and literally every system had noise. At the end of an installation, battling ground loops was just SOP. That's where star grounding and all of this searching for the ground problem came from. Now, with differential inputs, the power supply ground is rarely the problem and that's why so many of these noise troubleshooting threads include "I tried regrounding everything and running a 000 gauge cable from the battery to the ground and I did the big three and I replaced the RCA cables and...I still have noise."

Because that's not the problem anymore.

I agree there should be more options for balanced signals coming out of headunits….

a vehicle is such a noisy environment it is a prime candidate for balanced audio lines.

differential definitely helps with noise reduction in my experience even coming from a single ended headunit output but a real balanced line seems to make much more sense to me for a vehicle…
 

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I agree there should be more options for balanced signals coming out of headunits….

a vehicle is such a noisy environment it is a prime candidate for balanced audio lines.

differential definitely helps with noise reduction in my experience even coming from a single ended headunit output but a real balanced line seems to make much more sense to me for a vehicle…
Use the speaker level outputs. Those are balanced.
 

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I think the main reason for OEM headunits being differential is down to cost of materials and additional complexity.

Having to run shielded single ended cable could cost more when everything else is single core.


Sent from my Pixel 5 using Tapatalk
 

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I think the main reason for OEM headunits being differential is down to cost of materials and additional complexity.

Having to run shielded single ended cable could cost more when everything else is single core.


Sent from my Pixel 5 using Tapatalk
Pretty sure that isolating the signal from ground by 6V and being able to further eliminate noise by simply twisting some cables AND being able to have the head unit adjust the output voltage automatically when an amp is plugged in are the factors driving this decision. The fact that it's cheaper probably figures into the decision too. But single ended inputs and shielded coaxial cable is dumb AF in a car in which that audio ground is the same as every switch and module in the car.
 

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I don’t know of any radios that have balanced preamp outputs. They’re all single ended. Twisted pair rcas offer no benefit from the single ended radio output to DSP input.

The place where this matters is between the DSP and the amp.
Yes all aftermarket headunits are single ended. The rcas between the headunit and DSP matter just as much as between the DSP and amp. Headunit is single ended. That means that if the DSP has balanced inputs, you need(SHOULD) use twisted pair rcas to take advantage of the DSP input circuitry. If the DSP has single ended inputs, then you need(SHOULD) use shielded coaxial rcas to take advantage of the DSP input circuitry.
 
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