QU32 No output, possible DAC failure?

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This topic contains 10 replies, has 7 voices, and was last updated by Profile photo of KeithJ A&H KeithJ A&H 2 years, 8 months ago.

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  • #89815
    Profile photo of Yamin

    Hello there everyone, I have got a QU32 with no output. Everything is patched correctly, signal goes in I can see it on the meter but there is no output from any mix bus or master L/R (signal is seen on the led when AFL is pressed). It was working perfectly the night before and nothing was changed when powered up the next morning. I have done all the resets but the problem has not resolved.
    I am assuming that the DAC has failed as looking at the block diagram it shows that the metering also happens before the DAC (why signal is seen on the meter).

    1. What chip is used for the DAC on QU32?
    2. Where is it situated? Is it on the main board or somewhere else? Looking at the main board I couldn’t find any DAC chips which I am familiar with.

    I also noticed that something on the other side of the output board (when viewed from inside cover removed) was quite warm. I cannot see what it is without removing the whole output board. I thought it might be due to the power supply being there but it feels freakishly warm but not boiling hot.

    This is probably a long shot but it would be great to get hold of a service manual for the QU32, there are no authorized re-sellers here and sending the whole unit to get serviced would be quite a burden. I am a qualified electronics engineer.

    I hope someone could shed a light on this, your help would be greatly appreciated.

    Profile photo of Mike C
    Mike C

    Just to trouble shoot a tiny bit deeper have you tried the headphone output?
    Have you tried another device of some sort plugged into the outputs, powered speaker, headphone amp, power amp and speaker?

    Have you tried a firmware update/re-load?

    Profile photo of BRS

    And also made sure no PAFL is active – that often used to get me before I mapped a softkey to “Clear PAFL” (and then it lights if any PAFL is on).

    Yeah, try other outputs to see if any are working – mixes, headphones, ALT outs etc. etc.

    Profile photo of Yamin

    Yes I have tried updating the firmware, checked everything else in my signal chain – cables, speaker etc. No output from headphone output either.
    I should add another event company which has got a QU32 is suffering from the same symptoms.

    Profile photo of Mike C
    Mike C

    I take it you tried the headphone out while in PLF/AFL mode.

    In your first post I take it that you can see input level metering
    I assume on the channel meters and you can see PFL/AFL metering
    on the main meter.
    Do you see main output LR level metering when not in PFL/AFL?
    ( the block diagram does show the metering taken in the digital path)

    Was the rest you did the full hard reset?

    Just asking…any chance all the mixes and main are assigned to muted
    DCA groups?

    That all said it’s sounding like the mixer had a major sudden death failure.
    I have never seen a schematic for a QU or opened mine up but I doubt
    that all the DAC’s are on one common chip.
    I’m really guessing here but maybe the circuit that clocks the DAC’s is
    the fault.

    Profile photo of Yamin

    Hey @mikec, Yep I can see the LR level metering even when the AFL of the master buss is not pressed.

    I did a hard reset powered up the mixer while pressing the reset button + setup button. I also made sure that in fact it did reset all the saved scenes were gone.

    There were no DCA’s involve 😉 . I have gone through that muted DCA scenarios couple of times my self.

    I really hope I could get a schematic diagram so that I could make sure even if I have to replace the board I am replacing the correct board. It would be such a shame to discard this nice console.

    Profile photo of volounteer


    Where did you buy it from?
    Is there a dealer in the Maldives?
    Could a dealer repair it cheaper better than you trying to find and replace the correct board/chip/connector/yadayada

    If you find a detailed schematic or a service manual do post that here for the rest of us to know.

    Profile photo of Yamin

    Yeah there are no authorized dealers here.

    Profile photo of Gordon

    I know this is a long shot, but it may be worth mentioning.

    Make certain that all mono channels did not accidentally get un-assigned to L/R.

    While in normal L/R mix mode, (LR is lit and mono channel layer is active,) press the “Assign” button to make sure that all channel select lights are lit up. This indicates routing goes to L/R.

    Profile photo of Jos

    I have also got Qu32 I’m aslo having same problem. As there no output coming from the mixer. Could anyone please help?

    Profile photo of KeithJ A&H
    KeithJ A&H

    Hi @Jos

    Sorry to hear you’re experiencing something similar – you can contact us directly using https://support.allen-heath.com about this and we’ll be able to figure out what’s going on.


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