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Seeking clarification on Zoom R16 1/4" input jack in XLR combo plug: Balanced or not?

Discussion in 'Converters / Interfaces' started by quesne, Aug 15, 2015.

  1. quesne

    quesne Active Member

    Hello All:

    I have a very simple question regarding the Zoom R16 XLR combo input jacks.

    The Zoom R16 documentation appears to state that when you use an XLR connection to the combo jack, it is a balanced signal. The documentation is not so clear on whether the 1/4" port provides a balanced TRS connection. If I could find a schematic of the input bus for the R16, the answer would be easy to see.

    I have seen conflicting info in a few forums regarding this, and I was hoping to find out for sure. Does anyone know the answer to the question? Or (better yet) is there a schematic out there that someone can share?

    Thanks in advance for any assistance :) Quesne

    These are the only descriptions I see of the input ports from the user manual:

    XLR/standard phone combo jack x8
    Input impedance:
    (Balanced input) 1K balanced, 2 hot
    (Unbalanced input) 50K unbalanced
    1 equipped with Hi-Z switch, input impedance 470k (Hi-Z on)
    2 equipped with phantom power switches
    Input level: –50dBm < continuous < +4dBm

    Supports input from a variety of sources, including guitars, mics and line level instruments. The 8 onboard jacks, which accept XLR and standard phone plugs, include one high-impedance input and two with 48V phantom power. From high-impedance guitars and basses to dynamic and condenser microphones and line-level devices like synthesizers, many sources are supported.
  2. paulears

    paulears Well-Known Member

    Why not plug a jack in and stick a meter on it? Tip to sleeve should be the same as ring to sleeve if it's balanced. If the ring to sleeve is a short, then its unbalanced. I'd bet it's unbalanced.
  3. quesne

    quesne Active Member

    Thanks very much. When you say "Tip to sleeve should be the same", what exact units am I measuring? Voltage while powered on? Ohms? Continuity?

    Please clarify and I will test. Thanks :)
  4. paulears

    paulears Well-Known Member

    Ohms - that's what you are after. Expect a dead short!
  5. Boswell

    Boswell Moderator Distinguished Member

    Test with Zoom power off. If the ring-to-sleeve meter reading is zero (short circuit) or infinite (open circuit), the input is unbalanced. Only if it's the same as tip-to-sleeve is it balanced.
  6. quesne

    quesne Active Member

    Thank you very much for the info, paulears and Boswell. I just made the recommended measurements on a balanced cable. It was plugged into the channel 8 input of my unpowered Zoom R16. Here are the results. I would appreciate help in interpreting the results:

    On 2000K ohm setting
    T - R = 92
    T - S = 47
    R - S = 44

    On 200K ohm setting
    T - R = 91.9 (slowly and consistently rises approx 0.1 per second)
    T - S = 47.0 (stable)
    R - S = 43.7 (slowly and consistently rises approx 0.1 per second)

    On 20K ohm setting (or lower)
    T - R = infinite
    T - S = infinite
    R - S = infinite
  7. quesne

    quesne Active Member

    Just adding a quick note: I found this article from 2011 that seems to refer to the 1/4" inputs on the Zoom R16 as balanced TRS. I don't know much about the reliability of the source, but I thought it was worth posting here for any other folks searching for similar relevant info :)

  8. paulears

    paulears Well-Known Member

    Balanced then! Useful to know - probably a simple balanced pad, so a mono plug into it just shorts the ring to sleeve, which nobody would be aware of.
  9. quesne

    quesne Active Member

    A couple more pieces of info for the interested....

    As per gecko zzed on the homerecording.com forum, the Zoom site shows the R16 specifications here:


    Note this:

    Input 1-8
    Type: XLR/TRS combo jacks

    Also, I found this on page 11 of the operation manual: "You can connect cables with XLR and monaural phone plugs (balanced or
    unbalanced) to the INPUT jacks."

    That also seems to indicate that the 1/4" connection supports a balanced connection.

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