Confused by pre-post

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This topic contains 5 replies, has 4 voices, and was last updated by Profile photo of johnc johnc 5 years, 4 months ago.

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  • #54420
    Profile photo of johnc
    johnc
    Participant

    A novice has a question. In a simple setup on a GLD-80 board. lp1 is sent to Aux1. It would seem that if the send is made pre then the lp1 fader would have no effect on the level sent to Aux1 whereas if pre is off then the lp1 fader would very the level. It seems the lp1 fader has effect in both cases.

    What am I missing ??

    #54421
    Profile photo of Edi
    Edi
    Participant

    Hi John,

    When you are mixing to Aux 1, the channel fader is the aux send knob you may be used to on an analogue console. In the analogue world you also had to turn the Aux knob independent of pre/post if you wanted to send signal to the aux bus.

    Try the following: Set the send to Aux1 mix as pre, now press mix button on master LR mix. Channel faders show now the main mix levels. Lower fader for IP1 to -infinite. No signal is sent to main mix. Now press mix button for Aux1. Channel faders now show the levels sent to the Aux1 bus. If you now raise fader for IP1 it is if you turn the analogue Aux knob. You send the pre fader signal (because the fader for the main mix is still completely lowered!) to the aux bus.

    In a aux post fader configuration you would not send any signal to the aux bus, as long as the channel does not send signal to the main LR mix.

    Hope this helps.

    Best regards,
    Edi

    #54422
    Profile photo of johnc
    johnc
    Participant

    Thanks Eli,

    Let me set up a different scenario. Suppose you have lp1 driven by a monaural music source and Aux1 and Aux2 feeding into monitor speakers A and B respectively. Aux1 relates to lp1 PRE and Aux2 relates to lp1 as post (not PRE). Now we press Aux1 mix and set the lp1 level to -40 and then press Aux2 mix and set lp1 to -20. These values are both stored and if we press the Aux mix buttons back and forth the lp1 fader will jump back and forth between -20 and -40.

    But it would seem that the PRE setting on Aux1 would force it to read the lp1 level as -0 ( ignoring the fader) while Aux2 would take the signal at -20 under the control of the fader (post fader). Is this correct or does pre and post only have effect elsewhere?

    #54427
    Profile photo of beartech
    beartech
    Participant

    Hi John,

    I don’t want to assume anything, so please pardon me if I state the obvious. Make sure when you are selecting pre/post that you are doing so with the Mix button of the respective Aux mix lit. As to your question about the IP1 to AUX 1 pre and Aux 2 post, I would expect that the listening level in Aux 1 would vary and be lower than Aux 2 until the IP1 fader reaches -20db in the Main mix. At this point they should be the same level.

    My logic is that IP1 is set is set 20db lower in Aux 1 than in Aux 2. Once you overcome that difference, the volume should be equal. The IP1 feeding Aux 1 is always at 0db (pre). If you set the IP1 fader to 0db in the main Mix it will cause the Aux 2 level for IP1 to be 20db above Aux 1. therefore when IP1 is set to -20 in the Main Mix they will be equal. I hope this helps.

    #54429
    Profile photo of FBCW
    FBCW
    Participant

    I think the fact that the fader becomes the send level for the current aux mix is confusing you.

    Try this: Press select on the channel you want to send to your aux mix. Press the processing button to the right of the touchscreen. Now tap on the routing tab, then select the tab containing your aux mixes. You should now see an LCD screen full of virtual knobs.

    These knobs represent the send levels to each aux send. This should be somewhat familiar to you if you have used an analog desk. Remember that, whether pre or post fader, you still have a send level for each aux on each channel.

    When you press the mix button on an aux send, the fader represents the send level FOR THAT AUX SEND, not the ‘fader’ that a post fader send respects.

    I really think the aux routing tab on the LCD screen will help you because you can pull up that screen for any channel, then press the mix button on an aux and visualize the relationship between the virtual knob on the touchscreen that controls your aux send level, and the fader that becomes representative of that virtual knob when pressing the mix button on an aux strip.

    Hopefully this helps!

    -Brian

    #54430
    Profile photo of johnc
    johnc
    Participant

    Thanks guys and collectively you have cleared this up.

    It was not clear to me when looking at the block diagram in the manual that the fader that can be routed to the Main aux has special status.

    I understood that the single fader on each input channel could be used to control multiple sends by using the mix button on the receiving auxes (sp?). What was unclear was that the send to the Main aux had special status and that the pre and post switch on all the other sends was relative to it. I assumed that all the sends and the “virtual” faders created for each aux had equal status wherein the pre/post would have simply taken each respective virtual fader in and out of the circuit.

    As it is, the actual implementation is necessary to create special effects (reverb, etc) that can be either fixed to the input or varies relative to the Main output. It all makes sense now.

    Thanks again. This is a great forum and again I appreciate your patience and your help.

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