Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 28

Thread: What are the benefits to things that have balanced differential inputs?

  1. Back To Top    #11
    Noob Jdunk54nl's Avatar
    Real Name
    Jacob
    Location
    Phoenix
    Vehicle
    2014 F150 Limited
    Posts
    1,055
    Join Date
    Oct 2019

    Re: What are the benefits to things that have balanced differential inputs?

    Quote Originally Posted by test13371997 View Post
    Yes, differential input still works with single ended outputs. Mess with desmos.com https://imgur.com/a/pTpNdr2. a and b is the "ideal" or exactly what is coming out of the HU. Signal = ground. Since its a differential input, you use unshielded twisted pairs. That means that noise get radiated onto both conductors. So c and d is a and b plus the imaginary noise I came up with. When you do a-b and c-d, you get the same thing. You mention "balanced", but there are no balanced cables with RCAs in car audio. For a cable to be balanced, it needs to have 3 conductors. Which rcas dont have. Those pictures are talking about XLR adaptors and balanced stuff, which isn't a thing in car audio. I dont have anything to say about those pics

    Balanced just means the signal wires have equal impedance to ground (Pin 2 and Pin 3 of a XLR). You can have balanced without 3 conductors as the third conductor (pin 1) of an XLR/TRS/etc. plug is just a ground, this isn't needed to be balanced signal as it has nothing to do with the actual signal.

    I am not 100% sure what your picture is doing or trying to show me.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  2. Back To Top    #12
    Noob Jdunk54nl's Avatar
    Real Name
    Jacob
    Location
    Phoenix
    Vehicle
    2014 F150 Limited
    Posts
    1,055
    Join Date
    Oct 2019

    Re: What are the benefits to things that have balanced differential inputs?

    There is also this from that paper I have linked above, which basically says differential DOES NOT help with noise rejection, only balanced does, which requires both the source and the receiver to be balanced in order to have the required equal impedance to grounds on the signal wires.

    This is page 22 so you can read the whole excerpt as it continues past this picture.

    Attachment 15785





    And this on the bottom of page 16.



    Attachment 15784
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  3. Back To Top    #13
    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
    Location
    Northridge, CA
    Posts
    670
    Join Date
    Aug 2018

    Re: What are the benefits to things that have balanced differential inputs?

    Did you see page 29? Some interesting claims about noise rejection when connecting single-ended outputs to differential inputs, even if the output is not balanced.
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

  4. Back To Top    #14
    Noob Jdunk54nl's Avatar
    Real Name
    Jacob
    Location
    Phoenix
    Vehicle
    2014 F150 Limited
    Posts
    1,055
    Join Date
    Oct 2019

    Re: What are the benefits to things that have balanced differential inputs?

    Right, that seems like specific to using a 2 conductor wire and shield (for 3 pin connector on the receiver end). Does the wording mean it gives 20-30db by being balanced, and an additional 30db by being balanced and differential for 50-60db noise rejection?
    Last edited by Jdunk54nl; 05-24-2021 at 03:27 PM.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  5. Back To Top    #15

    Re: What are the benefits to things that have balanced differential inputs?

    Quote Originally Posted by Jdunk54nl View Post
    Right, that seems like specific to using a 2 conductor wire and shield (for 3 pin connector on the receiver end). Does the wording mean it gives 20-30db by being balanced, and an additional 30db by being balanced and differential for 50-60db noise rejection?
    That is impressive.
    Does that really mean "3 connector" though?
    Or is that the two RCA - plus the shield simply grounded, like some RCAs offer with the center conductor?
    Not that that isn't "3 connections"...

    Sent from my LM-G820 using Tapatalk

  6. Back To Top    #16
    Noob Jdunk54nl's Avatar
    Real Name
    Jacob
    Location
    Phoenix
    Vehicle
    2014 F150 Limited
    Posts
    1,055
    Join Date
    Oct 2019

    Re: What are the benefits to things that have balanced differential inputs?

    Quote Originally Posted by geolemon View Post
    That is impressive.
    Does that really mean "3 connector" though?
    Or is that the two RCA - plus the shield simply grounded, like some RCAs offer with the center conductor?
    Not that that isn't "3 connections"...

    Sent from my LM-G820 using Tapatalk
    It seems, IF my understanding is correct, twisted pair conductor needed with a shield and a way to separate the lo signal and ground noise at the receiving end (one to pin of RCA to pine 2 of XLR, sleeve of RCA to pin 3, and shield of cable to sleeve or RCA and pin 1 of xlr). In my mind that means you must have three separate connection points (Pin 1, 2, and 3) on the receiving end.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  7. Back To Top    #17

    Re: What are the benefits to things that have balanced differential inputs?

    On XLR, yeah - 3 pins. it's kind of the same - but hard to compare because those are balanced signals.

    If you ignore that though, yeah - "shield" is just grounded, conductor A is the signal, and conductor B is the signal inverted.

    We unfortunately don't usually have that with single-ended (unbalanced) sources and amps.

    I've been watching some demos on Star quad cable but so far all have been that "balanced" scenario demonstrating noise rejecting, and it makes sense in that context...
    The two white conductors are the signal, the two blue are the inverted signal - you get a magnetically null sum, and noise is easy to reject.

    I don't think it's possible to take a single ended source and send it down one strand, and send the inverse down the other strand even to get passive noise rejection (without a balanced receiver inverting and subtracting the noise), but I'm going to think on that a bit.

    Basically trying to figure out of it is even an advantage to use star quad cable at all [EDIT: since I'm in the planning of making my own RCA cables with single-ended everything].
    Last edited by geolemon; 05-25-2021 at 04:39 PM.

  8. Back To Top    #18
    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
    Location
    Northridge, CA
    Posts
    670
    Join Date
    Aug 2018

    Re: What are the benefits to things that have balanced differential inputs?

    Quote Originally Posted by geolemon View Post
    Basically trying to figure out of it is even an advantage to use star quad cable at all [EDIT: since I'm in the planning of making my own RCA cables with single-ended everything].
    Isn't the advantage of starquad geometry the cancellation of magnetic interference? I'm pretty sure it's the same as a normal twisted pair but better magnetic interference rejection.
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

  9. Back To Top    #19

    Re: What are the benefits to things that have balanced differential inputs?

    Quote Originally Posted by Justin Zazzi View Post
    Isn't the advantage of starquad geometry the cancellation of magnetic interference? I'm pretty sure it's the same as a normal twisted pair but better magnetic interference rejection.
    Yes exactly - that makes it downright great in a balanced application, like XLR for mics and instruments - two conductors carry the positive signal, two conductors carry the inverted signal. The shield provides passive blocking, and the balanced differential input sums away any induced noise that did make it through the shield.

    But in all the car stereo gear I've had, everything has been single-ended, not differential.

    I just read a thread on a high-end home DIY forum criticizing DIY RCA cable builders who use star quad for unbalanced RCA because:

    1) the shield in coax is a 75 ohm rating, which apparently has a stabilizing effect (I want to find more on this). On star quad, it's not rated. I would have assumed "lower is better", so I'm kind of curious here - but bottom line is it was touted as an advantage for coax.

    2) The shield in coax is braided. It's also braided in most star quad that I've seen, but did see someone complaining about how tough it is to unbraid coax, and how much easier it was to unwind the simply-spiralled shield on their quad cable brand of choice. It does make sense to me that the spiral shield could create inductance where the braid would inherently avoid it.

    3) They measured nearly 4x the capacitance using two strands of quad for positive pin, two strands plus shield for outer. They improved it by using only one of the two conductors "but still measured more capacitance". It was still only 180pF, so I'm not sure this could amount to any frequency limiter.

    I saw another DIY thread where they suggested using all 4 conductors to center pin - I would believe that to increase capacitance further but...
    I found an RC filter calculator that allows pF and will calculate frequency with R and C supplied and so I figured "let's see what 0.1 ohm, 75 ohm, and 150 ohm give us with a 180pF capacitor?"

    [Drum roll here]
    0.1 ohm and 180pF: 8846426426043Hz
    75 ohm and 180pF: 11795234 Hz
    150 ohm and 180pF: 5897617 Hz

    Before you say "that's way above hearing range" (it is) - this is a high pass filter, so in theory that means in all three cases there would be a sloping 6dB/octave attenuation starting way up there - but I couldn't say that a filter whose elbow was THAT far above the used frequency range would/could still provide a 6dB/octave slope. That's a tiny amount of capacitance, so there's only so much available energy to do anything. I expect it's trivial either way - every wire has some capacitance, and of course that doesn't mean "slope".

    I have a feeling BOTH arguments are true:
    1) "Technically, coax is the superior choice for unbalanced RCA applications."
    2) "The differences are so tiny between coax and quad that there's no possible audible advantage either way."

    Sent from my LM-G820 using Tapatalk

  10. Back To Top    #20
    Noob Jdunk54nl's Avatar
    Real Name
    Jacob
    Location
    Phoenix
    Vehicle
    2014 F150 Limited
    Posts
    1,055
    Join Date
    Oct 2019

    Re: What are the benefits to things that have balanced differential inputs?

    So thinking about the picture below more (the correct one).
    Wouldn't this ultimately destroy any balance properties? You have the shield of the cable tied to ground on the receiver end and tied together on the RCA sleeve, so if you measured pin 3's impedance to ground, it should be way less than pin 2's, so no more balance by definition.....

    I am still so confused on this stuff.....The more I think I understand, the more I find errors in my thinking and potentially of others thinking....


    Page 29 from here: https://www.jensen-transformers.com/...ic-seminar.pdf

    Attachment 15778
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Back To Top