noisy preamps?

Forums Forums Qu Forums Qu troubleshooting noisy preamps?

This topic contains 20 replies, has 9 voices, and was last updated by Profile photo of Dwight Dwight 7 years, 4 months ago.

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  • #36385
    Profile photo of jet1968
    jet1968
    Participant

    just listening to L/R through headphones and with nothing plugged in to the desk, all preamp gains set to 12 o’clock, all faders at unity (0) and headphones at 11 o’clock there seems quite a bit of noise (hiss) If I crank a channel’s preamp gain to about 3 0clock it starts lighting the gate threshold around -40db. My question is, is this a normal level of noise? I appreciate I’m summing the noise by having all faders up at once but still seems a bit noisy to my ears? Anyone else confirm this?

    #36386
    Profile photo of Stix
    Stix
    Participant

    Do you have the pads on all channels off? If you have any pads engaged combined with high gain settings you will get a lot of noise.

    #36390
    Profile photo of Ermep01
    Ermep01
    Participant

    From the knowledge base:
    Known issues – Other:

    Some USB noise can be heard on the ST3 input channel when the top panel ST3 mini-jack input is selected as its source and nothing is plugged in.
    Mute this channel or turn its fader off when it is not being used. The noise is not present when an audio source is plugged in.

    #36392
    Profile photo of jet1968
    jet1968
    Participant

    Thanks, but st3 is muted and still noisy

    Stix – where do i find the pads?

    #36393
    Profile photo of eotsskleet
    eotsskleet
    Participant

    i’m not sti but i know where to find the pads for channel gain reduction: Select an Input channel, go to the processing-screen, choose the first register “preamp” there you will find the “PAD” for Gain Reduction.

    #36394
    Profile photo of jet1968
    jet1968
    Participant

    are you talking about the rotary dial? I know about that one, thats the one I’m using

    #36395
    Profile photo of MarkPAman
    MarkPAman
    Participant

    No, it’s a (picture of a) little switch. See page 16 of the manual, top right photo.

    This is only with dSnake input:

    Channel Preamp source
    Local (red Gain) – Rear panel Mic/Line sockets
    feeding the internal Qu mixer preamps. These are padless
    preamps featuring wide gain range.

    dSNAKE (yellow Gain) – Remote preamps located in
    an AR2412 or AR84 AudioRack on stage or other
    remote location and connected to the Qu dSNAKE
    port via a Cat5 cable. These preamps include Pad
    switching.

    #36396
    Profile photo of eotsskleet
    eotsskleet
    Participant

    ou now i see.. page 16 on the manual… the “PAD” Button is only available for the AR-Racks Preamps! (is that true?)
    If you use the Qu-16 without a AR-Rack then you would not have the possibility for Gain-Reduction by PAD! But then that should not be your Problem!

    Do You have the same noise when you have plugged in a channel? Can you tell that there is only one channel that generates that noise or does it only start if you turn the volume of all channels up?

    #36397
    Profile photo of jet1968
    jet1968
    Participant

    seems to be across all channels when you crank the gain on each channel. (whether plugged in or not) can someone else check if theirs does the same? turn up preamp gain knob on any channel until around 40db of gain or above, do you see the gate meter lighting up and when you listen on headphones can you hear noisy hiss?
    thanks

    #36399
    Profile photo of jet1968
    jet1968
    Participant

    to add to above, playing with the PAFL settings and reducing the PAFL trim obviously reduces the hiss on headphones but the fact remains when you crank the input gain you induce a lot of noise.. just got my 01v96 out to compare and it seems a lot quieter at similar levels

    #36405
    Profile photo of GCumbee
    GCumbee
    Participant

    I wont have my demo unit back till the weekend so it will be then before I can test this. I had not noticed that there was no pad on local inputs. I can’t understand why this was not included. On this level of console it seems that would be a given and if they can do it with a AR box connected why not with local inputs? Not a lot of people will be using this with a remote stagebox.

    #36406
    Profile photo of GR-PDX
    GR-PDX
    Participant

    Missing a pad does seem like an oversight. You can dial down to -5db on the rotary…maybe they thought that was good enough? Leaves you 65db of gain range.

    Anyway, I hadn’t really noticed noise much. I tried as OP suggested, and there definitely is additive noise from preamps; it increases as you bring faders up. But I would expect that.

    My test, to try to get some kind of consistency: Shure SRH840 phones, phones level maxed. L/R at 0db, channel 1 at 60db gain, fader at 0db. Mute and unmute channel 1.

    Doesn’t seem to me to be an inordinate amount of noise is added for that level of gain. So far I seem to end up with about 28db gain for most mics, even dynamics. Haven’t tried a ribbon yet, though.

    HTH,

    #36409
    Profile photo of jet1968
    jet1968
    Participant

    hmmmm, if I use your settings (60db of gain) it sounds like I’m stood next to Niagra falls – very loud hissing. Are you sure you’ve got LR to PAFL turned on in the setup menu? Also, do you see the green gate meter climbing up as you turn up the gain? At 60db, my meter is lighting up the bottom quarter of the scale

    #36410
    Profile photo of jet1968
    jet1968
    Participant

    also, there is crackling sound in headphones when turning preamp knob backwards and forwards. Not very noticeable through external speaker, but definitely in headphones

    #36411
    Profile photo of jet1968
    jet1968
    Participant

    had a go at making a short video to show whats going on, listen to the hiss from the headphones at the end
    http://s90.photobucket.com/user/jonnybass1968/media/MOV_0101_zps7818dc02.mp4.html

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