Group Outputs / Mix Outputs Signal Strength

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This topic contains 15 replies, has 7 voices, and was last updated by Profile photo of [XAP]Bob [XAP]Bob 5 years, 3 months ago.

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  • #52945
    Profile photo of shadow
    shadow
    Participant

    Newbee question, first it should be known I am not a professional audio engineer.
    I am looking to use my QU-32 to record to an analog multitrack tape deck (Teac A3440).
    The Mixer is brand new and I am still learning my way around it. While experimenting
    with the outputs I have observed that the signal strength at the mix outputs is considerably
    lower than that of the group outs. I need to push the output faders on the mix outs to near max
    and I still have a weak signal, could it be a Pre/ Post fader setting or a limitation of the
    ports themselves. I am using all unbalanced equipment and patch cables. I am hoping it is in the
    mixer setup. As the QU does not have any local direct outputs only to USB, what would be the best
    ouputs to use to send the signal to the Tape Deck?

    #52946
    Profile photo of markie
    markie
    Participant

    Group, Mix, Matrix outputs – Balanced XLR line
    level outputs for the mono and stereo mixes, for example to
    feed monitor amplifiers, external processing devices, delay
    fill speaker systems and recording devices. These use low
    impedance, high quality differential driver circuits for
    connection to +4 or 0dBu equipment. Maximum output is
    +22dBu.
    Professional equipment provides ‘balanced’ connections for
    maximum interference rejection over long cable runs. If you
    are connecting to ‘unbalanced’ equipment then make sure
    the XLR pin 3 (signal cold) is linked to pin 1 (signal ground)

    I’m not sure if this could be a help to your problem or not. I hooked up a set of bose array speakers to the main outs left and right and used a 1/4 inch unbalanced to a balance xlr and got all kind of noise it sounded low and so on. Maybe you could talk to a place like guitar center and ask them the questions and see what they say.

    #52947
    Profile photo of shadow
    shadow
    Participant

    Thanks for the quick reply. I do have all the correct adaptors and cables for the the outputs to defeat the balance wiring.
    they are all the same configuration, You would think that the mix output signal would be the same as the group outs if the output faders are equal on both. Thanks, I will continue to ask around.

    #52949
    Profile photo of GCumbee
    GCumbee
    Participant

    We learned many years ago that the practice of shorting pin 3 or 2 to 1 was not necessarily a good or correct practice. Many manufacturers discouraged this practice. Dbx was one. Rane put out a document showing the correct methods. Reasoning was that in a differential output that shorting the negative to ground was in fact an electronic short therefore not good on the circuit chip. Overheating or failure or distortion could be expected.

    This practice works on transformer circuits since they are passive.

    I have not run full measurement tests on QU series products but haven’t noted any problems in my installations. I haven’t used groups though as outputs.

    #52954
    Profile photo of DoctorG
    DoctorG
    Participant

    At the risk of insulting someone’s intelligence, let me explain how a balanced signal connection (XLR) works.

    An XLR connection uses two signals that are out of phase with each other. The positive-going signal is on pin 2, the negative-going signal is on pin 3, and pin 1 is ground. When connected to either a proper transformer-coupled or differential amplifier circuit, the negative-going signal is inverted and added to the positive-going signal, giving a signal twice as large as the positive-going original. Any externally-generated noise signals induced into the signal wires will be in-phase in both wires, and the inversion process effectively subtracts one noise signal from the other. This further enhances the signal/noise ratio in a balanced circuit.

    To use an XLR cable with an unbalanced circuit, the proper way is to use pin 2 as the signal and pin 1 as ground, leaving pin 3 un-terminated. You don’t get the 2X signal boost, or the induced-noise reduction, but this avoids the problem of grounding out the negative-going signal on pin 3. In most cases, this grounding should not cause problems, but it could. At any rate, grounding it does not help in any way.

    With regard to the original issue – low signal levels at the Mix outs, I can’t help but think that the Mixes have not been set up properly. The inputs must be assigned properly to each mix and the levels of each signal into the mix must be set as desired. The Mix Masters then control the overall mix output level.

    #52955
    Profile photo of Dick Rees
    Dick Rees
    Participant

    [Quote] Newbee question, first it should be known I am not a professional audio engineer.
    I am looking to use my QU-32 to record to an analog multitrack tape deck (Teac A3440).
    The Mixer is brand new and I am still learning my way around it. While experimenting
    with the outputs I have observed that the signal strength at the mix outputs is considerably
    lower than that of the group outs. I need to push the output faders on the mix outs to near max
    and I still have a weak signal, could it be a Pre/ Post fader setting or a limitation of the
    ports themselves. I am using all unbalanced equipment and patch cables. I am hoping it is in the
    mixer setup. As the QU does not have any local direct outputs only to USB, what would be the best
    ouputs to use to send the signal to the Tape Deck? [/Quote]

    The user manual says that the max outputs of the mains, mixes and groups are all the same: +22dBu. So you are correct in assuming that the problem is very likely in the setup/routing.

    If you want to connect balanced and unbalanced equipment you can use the Rane white paper on cabling/connections for a guide or you can use some kind of BALUN such as an EbTech “Hum Eliminator” (despite its somewhat misleading name). A pair of such two channel devices will serve and can be a valuable addition to your gear locker for many applications. I have three of them in my kit.

    http://www.ebtechaudio.com/hedes.html

    http://www.rane.com/note110.html

    Remember that you will experience some signal loss in the conversion, but it will be slight and acceptable.

    #52959
    Profile photo of Andreas
    Andreas
    Moderator

    Just for curiosity: Why do you intend to record on tape in 2015?
    Still have my Tascam 34 and 38 along with all the dbx gear for sentimental reasons, but never thought about recording something new on that vintage stuff.

    #52961
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    Given the ability with free software on any ‘OK’ laptop to record many many tracks…
    And play them back to overdub…..

    I agree with the ‘why tape’ question, but am interested in the problem – I guess the routing isn’t quite behaving as expected. Have you tried the siggen? Have you used the same cable for each channel/output as a test?

    If you have a stagebox then patch the same output to each mix/group etc in turn as well…

    #52963
    Profile photo of Dick Rees
    Dick Rees
    Participant

    An XLR connection uses two signals that are out of phase with each other.

    This would be more correctly stated as “of opposite polarity”, but in the context of the OP makes little difference as it is unrelated to the topic.

    #52964
    Profile photo of shadow
    shadow
    Participant

    Thanks for the input, connectivity is not the issue here, I am using RCA to XLR adaptors that are jumped across the pins as recomended by A&H. Just to be certain I have swapped out the adaptors and cables (this in a constant), No change in output signal, I think it is still in my routing settings, experimentation will tell. I will however look into the Rane configuration, as I would not want to let the smoke out.

    #52965
    Profile photo of shadow
    shadow
    Participant

    OK, for those of you that question why I choose to record with old technology? Here is my best answer. HOBBY, I still have all of the audio (HI-FI) equipment that I purchased new in the late 70s & 80s. This vintage equipment is all in Mint Working Condition and still in OEM spec (Thanks to the quality of the era & a little TLC), I have since scrapped out most all of the equipment that I acuired from the mid-90 on up.
    Can I use current technology? Yes, and I will at some point, However, I would still want to utilize my Vintage “Reel to Reel”. If you seen and could listen to my equipment you would be stunned. Would I still have this issue on new professional equipment , the answer is yes.
    With a little help from the experiance on this forum, I Will learn the intricacies of the Qu-Desk.
    That being said, Thanks for the help so far and keep it coming. (Be part of the solution / LOL).

    #52969
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    Hobby is a good reason 🙂

    Do you have a stagebox?
    Have you tried using the signal generator to act as a reference level for the outputs?

    How are you measuring the levels?

    #52982
    Profile photo of shadow
    shadow
    Participant

    I do not have a stage box, and I have not used the signal generator. The way I found the output strength discrepancy I was attempting to dub from a CD to Tape and monitoring the VU meters on the TD. With the inputs and outputs constant I switched the outputs from the Mixer
    and the signal was stronger from the Group Outs. I will try using the siggen as soon as I get an opportunity. I will let you know what the
    result is.

    #52986
    Profile photo of Dick Rees
    Dick Rees
    Participant

    With the inputs and outputs constant I switched the outputs from the Mixer and the signal was stronger from the Group Outs.

    There are/can be several gain staging adjustments between the ins and outs.

    #52987
    Profile photo of GCumbee
    GCumbee
    Participant

    Are the groups getting in mono which would increase the signal by approx 3-6db?

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