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  1. #1
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    Balanced and unbalanced at patch panel?

    I need to run both balanced and unbalanced signals to a patch panel that feeds an audio router. The balanced is a snap but what inputs to use for the unbalanced (RCA)? Would it be +ve and shield or +ve and -ve? How will this affect my router if I were to select one of these unbalanced sources at the router and send the signal through to a balanced destination and vice versa? A dissertation would be real nice on this. I read the FAQ on cancelation but it did not help with my problem but only touches the edge.

    Thanks for any suggestions!

  2. #2
    What router? What does its manual say you should do?
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

  3. #3
    Senior Member SC358's Avatar
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    Hey YoJo - Welcome!

    Cross patching and routing balance and unbalance is a bad idea - totally (imho). You could wire the patchbay(s) as long as:
    1- the router accepts unbalanced wiring.
    2- You only route unbalanced to unbalanced and balanced to balanced.

    If audio level and quality is NOT an issue then you can wire it however you want and accept the consequences later.

    If you care about audio quality then don't mix the two.


    In order to get around this you'll have to spend for audio converters.


    SC358
    Relationships are based on compromises - behavior accepted is behavior repeated.

  4. #4
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    I like the converter idea!

    This is the kind of answer I was looking for. I just knew I could get a professional attitute here. Can I get a suggestion on the converter? Rack mountable is preferred. Do any of you have experience with this? What are the other pitfalls?

    Thanks again! I'm going to like it here. Hopefully I won't be a leech forever.

  5. #5
    Senior Member SC358's Avatar
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    I've used products by RDL (Radio Design Labs) which I would rate as pro-sumer. They've always been reliable and a decent price of about 150USD. There are some others that cost more but I really have a problem understanding why should it cost so much when there's not that much to the circuitry (this is just my own stubborness). If I did not find them reliable, I would not use them (or at least complain to RDL).

    RDL has FP-BUC2 Balanced to Unbalanced Converter and FP-UBC2 Unbalanced to Balanced Converter. I've used www.markertek.com to make my purchases. If you find a place that has them cheaper please let me know. Each unit also comes with plastic interlocks (kind of like a version of plastic velcro) which I think works great on a 2 or 3 Rack Unit (RU) blank panel where you can mount about 6-8 RDLs in the back of a rack.

    If you need a professional type and can spend the money, I've used ATI MM100 matchmaker, which goes for 449USD at B&H Photo. This unit is 2 in 1 which goes Unbal to Bal AND Bal to Unbal. If you purchase 2 units, you can additionally purchase a 1 RU mount adapter for them.

    FYI: Due to the change of formats, this little converter now cost more than VHS machines (and replaced by dvd player/rec) which were the main purpose of buying these gadgets.

    Pitfalls: In regards to the RDL you should position these so that the variable potentiometer is accessible in case you need to give it a bit of a tweak when they're rack mounted. Use reference tone to balance the gain structure or as best as possible with the machines you're working with. Just remember in troubleshooting that this interface is now part of the audio path.

    Btw, thanks for the vote of confidence.
    SC358
    Relationships are based on compromises - behavior accepted is behavior repeated.

  6. #6
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    Problem solved!

    The MM100 is a brilliant idea! I couldn't find any info on the rack mount but emailed ATI for that info. I'm on a roll now!

    I'm in process of replacing the 20 year old GV audio and video routers and DAs with Miranda NTWs. Already have some of their HD/SDI stuff and it works well. We're looking forward to running it all with one control panel rather than split vendors.

    On the FYI, I know replacing some equipment might be cheaper but some are not replaceable such as the laserdisk machine and a few others which I will look into replacing. Sometimes, management types (no offence to anyone here) would rather pay to fix a problem than replace the cause hardware. Go figure. It's just that the GV stuff is no longer reasonably maintainable.

    SC358, Your ARE the one eyed man!

  7. #7

    patch panel

    What SC358 said. The only proper solution is a transformer to change unbalanced things to balanced (and balanced back to unbalanced if you have unbalanced inputs).

    For what it's worth, if this comes up again, if all your inputs are balanced you can get pretty close to true balanced performance even if some of the outputs are unbalanced. (In theory, it actually makes no difference whether an output is balanced. But you know what they say about "in theory...")

    Going backwards from a balanced input, wire everything as if it were balanced through the batch bay and back to the source. At that point, if the source is unbalanced, connect the + wire to the signal out, the - wire to the shell or sleeve of the connector, and either connect or don't connect the shield to the chassis (that is, you need to experiment for least hum).

    It's a matter of reference points. A piece of equipment with a balanced input does not see its own chassis as the reference point. It sees each wire as the reference point for the other. Wiring both back to the source, and then grounding one wire there, insures that the balanced input will "see" the same signal the unbalanced source is putting out.

    So: if you're strapped for cash, unbalanced outputs are ok, as long as all inputs are balanced and all wiring is balanced from the unbalanced output forward, especially at the patch bay.

    If you're not strapped for cash, get the RDL modules. They're outrageously priced, but in the context of the overall cost of a system they don't count for much.

    BTW - I assume you're talking line level signals. Putting mics in a patch bay is a bad idea and putting mics with phantom DC power in a patch bay is a very bad idea.

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