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Thread: Caution! Non-standardisation in audio interconnects - left/right channel reversal

  1. #1
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    Default Caution! Non-standardisation in audio interconnects - left/right channel reversal

    On a number of occasions over the years I've been aware of a Left - Right signal reversal. Using pop music as a test source, it's impossible to detect this reversal because there are no rules about which instruments should occupy particular positions across the L-R sound stage.

    But for classical music, with rare exception, the musicians are arranged in a rigid plan from left to right, just as you would hear them in the concert hall playing a contemporary western symphony or similar*. It beggars belief that a commercial CD could be mastered with L and R transposed, so what is the problem?

    It seems that the issue is that many - perhaps most - 3.5mm jack to L - R phono cables are incorrectly wired inside or colour coded outside. There is a perfectly clear standard of how the unbalanced stereo three-way jack plug should be connected and it is the top picture here. The tip (marked 3) should be left channel, the ring (marked 2) right and the body (marked 1) the common ground. But the tip and ring connectors are frequently interchanged.

    How can you be sure that the marked left channel really is left? If you buy a fancy expensive interconnect will it be wired correctly? Is this somehow related to cable length? The answer is that, in my experience you should completely disregard the colour coded left and right identifiers on the phono plugs (or sockets). Just don't believe that left is correctly marked as left, and right as right. Ideally test the continuity with a multimeter; the tip should connect to the left channel. And no, price doesn't seem to be an issue, nor brand, nor length. I have been caught out on this a few times and now I always check with a meter and correct the colour markings before using a 3.5mm interconnect cable.

    What happens if you don't have a multimeter? You could arrange a bulb and battery. Or you could play classical music and check that the violins are really on the left side. Or you could download this little channel identifier. Here is the embedded clip and here is the downloadable file. Burn it to CD and then you can check your entire system. Here is a brilliant web + video walk through by Sir Simon Rattle of the modern orchestra.

    (Clips to follow with pictures).

    *Note: the position of the piano (and maybe other soloists) may not follow this general rule if they have a significant individual role in the performance. and/or the composer and/or conductor have their own particular preferences for orchestral seating. But the violins are (as far as I know) always on the left side, as a block.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

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    Default Picture of incorrect phono lead

    Here is a picture of a very typically incorrectly assembled 3.5mm stereo jack to twin phono plugs lead. The tip of the jack plug should be the left channel. The low resistance on the meter confirms that it is incorrectly wired to the red plug. Of course, you can use this lead but you should re-mark the red plug as the black one and the black one as the red one, perhaps with nail varnish or a small label. I wish I could say this was a rarity but it's not. It first came to light a few years ago when I couldn't get a new audio test system to self-calibrate. The reversal of one of the channels confused it and having wasted time on that I've checked every 3.5mm lead I've used since.

    I assume, but this is a guess, that if you pay for an expensive interconnect (I don't have any myself) that you could be reassured about internal wiring, but I would still check before use. This issue is so basic I cannot understand why it's not QC controlled at the production factory.

    Here is our L-R channel identifier made on my PC headset microphone ...

    Loading the player ...


    You can download a WAV version to burn to CD here

    >

    P.S. Just as I made this a Lancaster bomber (perhaps the last remaining) flew very low over the house at perhaps 300 ft .... wonderful sight and sound
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    Alan A. Shaw
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    Default Fluke DVM

    Nice 8060A. I have one of those but unfortunately some of the functions no longer function. The price of repair seemed a bit steep for the amount of time I use it now.

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    Default Red is Right, Black is Left but whose right and left?

    Quote Originally Posted by A.S. View Post
    .. I wish I could say this was a rarity but it's not. .....

    I assume, but this is a guess, that if you pay for an expensive interconnect (I don't have any myself) that you could be reassured about internal wiring, but I would still check before use. This issue is so basic I cannot understand why it's not QC controlled at the production factory.
    ..
    It is not as rare as one thought to be. My previous Preamp's was wrongly wired. I have seen a tri-wiring speaker with external crossover mixed up the tweeters connection.

    There are also some confusion as to whose left and right it should be! Sometimes, even the very basic causes confusion to audiophiles. And thanks for the clip, now I know iPad,s internal speakers are in stereo.

    Btw, isn't it more convenient to label the wrongly wired right channel red connector as left instead Tip? Case of technical people thinking differently?

    ST

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    Default Jack plugs and balance connections (ring-tip-sleeve)

    Quote Originally Posted by STHLS5 View Post
    ...Btw, isn't it more convenient to label the wrongly wired right channel red connector as left instead of (as you have marked it) Tip? Case of technical people thinking differently?...
    Actually there is a reason for this.

    If you look back over my post you'll see that I mentioned using this type of cable in my audio test-rig and I also mentioned the word unbalanced. In fact, although doubtless the primary use of this type of interconnect is for (unbalanced) L-R audio with a common ground, there is another completely different use to which it could (rarely) be put to use. That is as a balanced to single-ended (unbalanced) adaptor.

    Referring to the full article on wiring ring-tip-sleeve jack plugs here you can see that in a single-channel balanced system the tip could carry the hot or plus signal, the ring the cold or minus signal and the sleeve the ground or shield. And balanced (hot, cold, ground) connections are common in PA and recording work when long signal lines are in use (as it rejects interference better) and also in test equipment. So, in my test jig there was no left or right channel (test equipment is single channel) but there was a balanced circuit which generated a hot and cold balanced signal. If these were inadvertently reversed because of incorrect construction of the cable, the test equipment was completely mystified. As was I for a few hours. That's all there is to it.

    Incidentally, studio microphones uses a balanced hot-cold-ground system. One reason why it's daft to obsess about 'absolute phase' at the recording end is because it's possible that due to error some or even all microphones and/or cables could be wired out-of-phase (hot to cold, cold to hot) and this may be very difficult to detect in a multi-mic arrangement. Individually an out of phase microphone or cable would still function perfectly and sound exactly the same as in-phase.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

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    Default

    And here is another incorrectly wired 3.5mm jack to twin phono cable. This one is much longer. So that's about a 25% chance that the cable you buy has the tip wrongly wired to the right channel when it should be the left channel.

    Incidentally, a close look at the printing on the cable suggest that this was intended for the hifi market ..... image how easy it would be to attribute a miraculous 'improvement' in sonic quality due to nothing more than a channel swap.

    >
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    Alan A. Shaw
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    Default AES Standard - the wiring of XLRs

    This may be off topic so please feel free to delete.

    In your earlier post you mentioned about XLR connectors. My understanding is that in the olden days pin3 used to be hot and microphones XLR connector's pin2 was always been hot. This was done to protect the drivers from bottoming out when a strong pressure on the microphone's condenser may causes the driver to move backward and damaging them.*

    To prevent drivers damage and also to ensure that drivers moves out when it receives a signal the pins were reversed for microphones. However, the current AES standard is to have pin2 to be hot for all XLR connection. So, I am just curious whether phono jacks were deliberately miswired? I remember reading somewhere that some equipments deliberately select pin3 to be hot.

    ST

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    Default Red is Hot, Black is Cold - crazy inconsistency

    Quote Originally Posted by A.S. View Post
    Actually there is a reason for this....

    Referring to the full article on wiring ring-tip-sleeve jack plugs here you can see that in a single-channel balanced system the tip could carry the hot or plus signal, the ring the cold or minus signal and the sleeve the ground or shield. ..........

    According to Pro Co Sound (who bulilds audio interface products) - Engineering Specifications states that the colour code for hot is red and for cold is black. If the tip is hot then red should be hot. Maybe, this is why you find longer cables to be "miswired" because they were probably used in recording industry rather than home audio where red is right and white is left.

    According to their standards:-

    Audio signal wiring typically involves three connections:
    SHIELD a/k/a common, ground, screen
    HOT a/k/a high, positive, phase
    COLD a/k/a low, negative, antiphase

    In general, Pro Co regards a red conductor as HOT and a black conductor as COLD, and wires all connectors to accepted industry conventions:

    • Two-pole connectors (1/4' phone, 3.5mm mini, RCA phono, etc.): HOT conductor to tip, COLD conductor and SHIELD to sleeve.
    • Three-pole connectors (1/4" phone, 3.5mm mini, 'TT', etc.): HOT conductor to tip, COLD conductor to ring, SHIELD to sleeve

    ST

  9. #9
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    Default Confusion upon misunderstanding ....

    Well maybe they do, but they are in my view reverse-wiring compared to other standards. And as I have shown, length has no influence over this - the short interconnect was also wrong.

    STORY SO FAR: Even the audio industry cannot (seemingly) decide how to connect a 3.5mm jack plug to two phono plugs. You MUST be on guard for channel reversal.

    The final arbiter of this must be an IEC standard or equivalent.
    Alan A. Shaw
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    Harbeth Audio UK

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    Default Red/Black vs Red/White Vs Red/Blue

    Alan,

    It appears there are two color codings for 3.5mm Jack (TRS)to RCA cables. One is Red and Black, and the other is Red and White. My headphone's 3.5mm to RCA cable is Red and White. The red colour is for right channel and the white is for left channel.

    I have another set of cables but that is Red and Black and here the Red is Left channel. I only realized that after reading your post. All the while I was thinking there was something wrong with my computer's sound card.

    Did you find the case of wrongly wired interconnects only applies to Red and Black RCAs? My old RCA interconnects were Red and Blue colours.

    ST

  11. #11
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    Default No, there is no 'standard' for 3.5mm to phono cables channel id: fact

    Quote Originally Posted by STHLS5 View Post
    ... It appears there are two color codings for 3.5mm Jack (TRS)to RCA cables. One is Red and Black, and the other is Red and White. My headphone's 3.5mm to RCA cable is Red and White. The red colour is for right channel and the white is for left channel. I have another set of cables but that is Red and Black and here the Red is Left channel. ...
    This is all barmy.

    Allow me to show you the rather nicely packed, low-mid priced, major electronics brand, 3.5mm to twin phono cable that sparked all of this issue when I bought it a while ago, to use with my audio test system. It conforms to your previous comment that as it is coloured white and red at the phono end (rather than black and red), you argue that there should be certainty over its internal wiring and that the tip should be left channel. Conversely you argue that had it been colour coded black/red according to the specification you mention, it could have been wired with the tip to the red phono, what would seem like a channel reversal.

    Unfortunately, it's all too easy to disprove this theory and I am unshaken in my original position which is, regardless of whether one considers red and black to be right and left or red and white to be right and left there is no assured consistency across cables regardless or brand, length or any other factors. There is complete chaos over this rather small, but important point. You cannot and must not assume that the tip is wired to a particular channel whichever 'specification' you chose to believe in.

    The attached picture shows the cable that started the concerns. Not only is the tip wired to the right channel (incorrectly, it should be left as discussed earlier in the Wiki article) but the picture printed on the rear of the packet compounds the error.

    Enough proof? You have to ask yourself, if the audio industry can't even get this most basic issue of left-right channels correct, can you believe anything you read other than that from real, hands-on end users? And where amongst all the highfalutin audio cable talk in the media do you see basic issues like this mentioned - and how many interconnects have duped their owners?

    >
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    Alan A. Shaw
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    Default Stereophile test disc

    Or you can just buy/borrow/steal/download a Stereo Test Disc, like Stereophile's Test Disc 2, which includes channel separation and phase tests. Both should indicate whether you've got cables that are faulty or cables that were mixed up by the user on initial connection. HTH.

    {Moderators comment: you should check out every such cable incl. to mp3 player etc.}

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