Which RCA's?

So I just watched the video regarding single end rca vs. differential input rca. I looked up my Arc XDi and of course it has differential inputs, and so does the PS-8, but I don't see that listed for the Helix SPXL1000. Head Unit is Kenwood DDX9903S.

Do I need both single end and twisted rca's?
From hu to dsp?
dsp to arc amp?
dsp to helix amp?

Also, any brand recommendations (and best place to purchase) would be appreciated as well! As always, thanks in advance for your help!

Bobby K.

If the headunit put out a differential signal, I would say to use that type of RCA since that long run would be the most susceptible to picking up noise. Since the MS8 and amps will be so close together, I don't think it's worth worrying over and would just get some decent standard RCAs.

http://www.darvex.com/store/pc/RCA-I...nnects-c53.htm

Thanks Al! I posed the question to Kenwood regarding the output from the HU.

The kenwood is most likely not differential output, but you can impedance balance it to take advantage of twisted pair with screen.

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Originally Posted by chad

The kenwood is most likely not differential output, but you can impedance balance it to take advantage of twisted pair with screen.

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Can you explain how to impedance balance? I mean I know what impedance is... so do you mean that the two twisted pair conductors will see an equal impedance?... and how do you go about doing that?

In order for twisted pair with a balanced receiver to cancel noise both lines have to have the same (nearly exact if not exact) impedance characteristics, if they do not then the noise induced on each line will have different levels, frequency response, phase shift, etc and will not cancel out with the balanced receiver. You do not have to have an inverting signal on the inverting leg, it will work without. The reason it is called balanced is referring to the balanced impedance, balanced differential means balanced impedance with differential audio signals on each leg.

Here's a helpful doc.... https://drive.google.com/file/d/0Byu...ew?usp=sharing

Fig 2.4 is what I ended up doing in my car.

Quote:

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Originally Posted by chad

In order for twisted pair with a balanced receiver to cancel noise both lines have to have the same (nearly exact if not exact) impedance characteristics, if they do not then the noise induced on each line will have different levels, frequency response, phase shift, etc and will not cancel out with the balanced receiver. You do not have to have an inverting signal on the inverting leg, it will work without. The reason it is called balanced is referring to the balanced impedance, balanced differential means balanced impedance with differential audio signals on each leg.

Here's a helpful doc.... https://drive.google.com/file/d/0Byu...ew?usp=sharing

Fig 2.4 is what I ended up doing in my car.

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Excellent info.. Thanks for sharing.

So looks like one would have to either obtain the schematic or break open their headunit to find the appropriate component values in order to implement this.
What problems did you solve by doing this? Did you fab up a small external box to house the components to achieve this or implement it within the existing headunit chassis?... Maybe you documented these efforts elsewhere you can link us to?

That was over my head, lol. If I use twisted, shielded RCA's, will that cover all possible scenarios of balanced/unbalanced, input/output between equipment pieces?

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Originally Posted by Truthunter

Excellent info.. Thanks for sharing.

So looks like one would have to either obtain the schematic or break open their headunit to find the appropriate component values in order to implement this.
What problems did you solve by doing this? Did you fab up a small external box to house the components to achieve this or implement it within the existing headunit chassis?... Maybe you documented these efforts elsewhere you can link us to?

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I did it in a project enclosure and used the service manual at first. Then, out of drunken boredom I measured the components int eh HU to get a tighter match on my add-on components.

Reasoning behind it is that my Honda is quite electrically noisy and I also do Ham radio stuff so any "more" RF rejection is a good thing. my HU is my processor and my amp has differential inputs so it only made sense to go balanced all the way back..

I used Gepco 61801 EZ cable, the drain (shield) is attached to the HU ground and the receiving end is left disconnected and heatshrinked off. The RCA's at the receiving end have the black (impedance corrected "inverting" side) attached to the sleeve and the signal side attached to the pin.

I described the setup a couple times (I think) on DIYMA but I do not believe I have any pics.. I have no way to really find the thread as I do not have login credentials there anymore after the password debacle.