Output Trim

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This topic contains 29 replies, has 10 voices, and was last updated by Profile photo of volounteer volounteer 3 years ago.

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    Profile photo of Hugo


    Thanks ! That’s what I’m looking for !!!


    Profile photo of The Cat
    The Cat

    Keith, thanks for the explanation about the analogue and digital signal levels. Much appreciated.

    Profile photo of volounteer

    @KeithJ A&H

    wrt @hugo reply you gave

    can we use the DCA to raise the gain? How much?
    I only need 12dBFS more into the LR but would like more to have some wiggle room.

    Profile photo of KeithJ A&H
    KeithJ A&H


    The DCA level uses a fader and the fader goes to +10dB.
    More importantly however, why do you need to raise the dBFS level?
    I only ask as dBFS does not directly relate to analogue output level – which is what I’ve been thinking you wanted to adjust.
    Was it instead that you wish to adjust digital output level?
    Did you read through the article?


    Profile photo of volounteer

    @KeithJ A&H

    I want to raise the dBFS level so that I can use the output lights on the upper right to be a meaningful guide to our sound levels in dB SPL so we dont have to keep hand measuring them. We have plenty of signal level in volts going to the power amp. If we raise the dBFS would could always lower the power amp to match that new level.

    But our main usage has only one person speaking and not always very loud. We typically see signal detected and then one or two other lights might come on but the range there at the bottom is very wide and not useful for us.

    Profile photo of Dave Meadowcroft
    Dave Meadowcroft

    Your gain staging is all wrong from what you describe and you may be looking for the wrong solution. This is what I would do…

    Turn your power amps right down so nothing is coming out.
    Select and switch on PAFL on the channel the mic is connected to.
    With a reasonable level going into the mic (people who insist on whispering or won’t speak directly into it should never be given a mic!) set the gain so it’s generally around the top of the green. If the first couple of orange LEDs light occasionally that’s fine.
    Now turn off PAFL and raise your main LR fader (assuming you’re coming directly out of there) to 0. You should now see the same level on the meters that you did when PAFL was on. This is what you wanted, and is how it should be, so now you can set your amps.
    Slowly raise the input sensitivity on your power amps until you have a usable level without feedback – still with a reasonable signal going into the mic.
    That’s it – you’re set, well for one channel anyway!

    This is assuming you don’t have a crossover or anything in between the mixer and the amp of course.

    Your amp probably has a max input of 4dBu. The max out on the SQ is 22dBu. So you need to lose around 18dB at the amp to match max levels which using this method we’re achieving with the amp sensitivity controls. If the amp/speakers are overpowered for the space then you’ll be lower than -18 on the amps. If they are underpowered then you will be reducing less and risk clipping at the amp/speaker if you do drive a signal close to max out of the SQ.

    Hope that helps!

    Profile photo of Dave Meadowcroft
    Dave Meadowcroft

    Forgot to say, also raise the channel fader to 0 after turning off PAFL along with LR.
    Also, make sure there are no DCAs, drastic EQs or heavy compression/make up gain involved!

    Profile photo of SteffenR

    we told him already what to do, many times…
    but he is not able to do it

    Profile photo of volounteer

    @dave Meadowcroft

    Thanks. I will see if I can get the MD an A1 to do that.
    We are making some changes so it may be feasible.
    Already added the acoustic treatment to help.
    Next is to REring out the room.
    Hopefully they remove all the EQ on mikes and reset them to best avoid feedback.
    I had suggested we do something like you noted to end up with all the faders closer to zero as the norm.

    The ampS are in another frame next to the mixer and i/0 gear for CDs and tapes.
    Do not know their max level so would have to research that.
    Will have to check again as it was left over from the old analog mixer, but we may have 4 amps and EQ boxes.
    Most of them are flat but one does have some bass cut on it.
    There might be a cross over somewhere as I think I heard they have subwoofers hidden somewhere. TBD.

    The gain staging may be wrong.
    From my very old days I would say the staging is correct and the mixer is deficient.
    Although we do need to reset the staging with all the changes that have been happening.

    As to the whisperers, we have no control. This is a church.
    If they have random people talking you get some who whisper and some who hold the mike as low as their arm will let them.
    The main pastor we can handle by slowly riding the faders.
    Some of the guest speakers and even deacons seem to think it is artsy-craftsy to switch from whisper to yelling.
    And some of them will wander away from the pulpit too.
    I wonder if seminaries encourage this odd method of talking as there are a lot of them who do it.

    Again to the wide DR we need to do something more to compress that wide range way down.
    So DCA and compression and make up gain may be necessary. An SQ would be easier than the Qu but that was not in our budget.

    And as @SteffenR has noted, folks have given many good suggestions, but not all are feasible in the situation where we have to do the best we can without our being able to dictate use of the HVAC, or choosing who gets to speak at a mike or some other similar suggestions.

    From my perspective the Qu is an erroneous design for what I would expect it to be able to do, but I see where AH would rather get folks to buy SQ or other more expensive gear. OTOH the Qu is a great device that does an awful lot at a very reasonable price for what it can do. Just wish it did a little bit more:) And that we had an actual audio profession in the church not just a bunch of advanced amateurs.

    Profile photo of Dave Meadowcroft
    Dave Meadowcroft

    Good luck with it – I’d offer to help but I’m in England so not really practical 😅

    Find out the models of the amps, speakers and crossovers / EQs, if there are any, and I’ll be happy to look up the specs and give you calculated settings for all of them that will be a good starting point – it will still need setting up properly for the room with a measurement mic and your outputs EQ (or inline EQs if they are there) using RTA.

    You mentioned Room Treatment did whoever fitted that not measure the acoustics of the room before, during and after? If not they could have caused more problems than they solved.

    There is nothing ‘deficient’ in the SQ, or QU for that matter, in fact the SQ is right up there with many of the very best consoles on the market and sounds incredibly good. It’s got to be a set up/understanding issue.

    Profile photo of Mike C
    Mike C

    @ volounteer

    In many of your post including the one you just made you reveal how little you actually
    know about the complete configuration of the churches sound system.

    So without knowing that how can you possibly think you can optimize the system in any shape or form.

    I’m guessing it’s a complete hack job of an install and set up at this point.

    Profile photo of volounteer


    I am finding out more about the system.
    Unfortunately nothing is DOCUMENTED. From before the time any of us arrived.

    They are going to have the dealer come in yet again to tweak things.
    I am hoping to identify things they need to do, other than what the MD might be considering.
    A total optimization is unlikely, but I do hope that significant improvements can be made.

    As to hack job I would say only if AH dealers are hacks.
    It is more we got a problem so make one change now. Repeat every couple years.

    That became many changes that accumulated and need to be redone as a whole now.
    I am trying to take a more system wide view of things to see what I can get done.
    All I can do is make suggestions and argue my case.
    The decisions are made higher up the food chain.

    All of us inherited the analog AH mixer and gear.
    Not sure why they upgraded to the Qu as the MD does not really know digital.
    It is possible the analog board was too old and was getting noisier.
    MD does know mixers very well and has some understanding about acoustics that led to the paneling which is helping a lot.
    But he is really a musician and not a tekkie.
    He filled in as A1 when the main guy was travelling a lot for work.
    Our A1 has just semiretired so has more time to give the church and is taking over the responsibility for the system.

    I think that whoever put in the old analog AH mixer (42 channel?) also inherited the power amps and switching gear to cycle things on/off properly along with the cassette tape system and probably the CD devices to record and another for playback.

    Profile photo of Mike C
    Mike C

    Anyone who really knows what there doing could walk in there and start
    going through the equipment, following the cabling, putting a little test signal
    here and there into the system and figure out what’s going on in an hour or so.

    In less then a days time figure out what’s working, what’s not, what you need, what you don’t need and have the system working better than ever.

    As for dealers of any equipment unfortunately how skilled there in setting up the equipment they sell can very from one extreme to the other.
    I have doubts about yours!

    I have been involved with some churches who were just about ready to replace everything
    because the system in place while good equipment was just so poorly set up, configured and operated they had been convinced replacing everything would fix all the problems.
    When all was said and done it just needed completely gone through, properly set up, maybe some maintenance work, maybe a little upgrade here or there and the system was better than ever.

    For example one had glaring speaker mis-wiring issues that had to have been that way
    since the system was installed by a “professional” company, said “professional” company
    had been called back a few times for ongoing issues with the system all the while saying the system meets the spec and was working fine.

    Took me about a minute with a mic saying check one two to start pointing to speakers
    that were not working properly and the rest of the day on a lift rewiring the speakers and configuring the system.

    Profile photo of Mike C
    Mike C


    Find out the models of the amps, speakers and crossovers / EQs, if there are any, and I’ll be happy to look up the specs and give you calculated settings for all of them that will be a good starting point – it will still need setting up properly for the room with a measurement mic and your outputs EQ (or inline EQs if they are there) using RTA.

    Over the course of time I have asked him many times for equipment info, makes, models, ect. or to at least post a few pictures of the equipment and overall installation of the system.
    Never got anything other than vague descriptions at best and I don’t think we’ll ever get any more then that.
    All in all it’s a lost cause!!!!!!!!!

    An SQ would not fix any of their issues and would be more board then they could comprehend.

    Profile photo of volounteer


    I would have to do an inventory.
    But we need to have that for ourselves so I will work on that.
    I can get items that are visible. Not sure all have the info on them. Some do for sure, dont recall looking at the others.

    The dealer is supposed to use special mikes and a computer program (smaart??) to re-ring the room for all the changes that have been made. I hope they get him to reEQ all the mikes that heavy heavy bizarro EQ on them now. So much is cut out you could just lower the gain 6-8dB and get the same effect.

    A lot of the cabling disappears into two holes in the wall.
    Good luck following that.
    Not sure we need to do that as it comes out under the stage and we do know what stage inputs match our inputs.
    And the stage ouputs seem to match the monitors and the wedgies.
    If there really are subwoofers they are under the stage and I have no idea how to get there.
    With all the bass cut from the HPF I dont see why subwoofers are even there.

    I would agree that we need to go through everything and document what we really have then fix any mistakes that might exist.
    I think there are no gross mistakes just rough edges that need adjusting with the acoustic panels, new mikes, yada yada.
    If anything the audio team is in much worse shape. Admittedly they jumpstarted everything from ground zero when covid hit and shut things down using two people including a secretary that seems to know more about video as she edited and posted videos before we went to livestream, and one kid who is very smart, plus an assistant pastor who ‘tries hard’ and seems to learn fast although possibly from the kid.

    The problem is time as most people who volounteer have jobs and this is a freebie when they donate time to help do anything.
    So they prioritise things and others get deferred. Also what they think is important is not always what I think is needed.

    Cant say how skilled the dealers were. Pretty sure there have been at least 3 maybe 4 over the years. And one more recent one used for at least 3 jobs, maybe some more before I joined the church. Just wish somebody had written down what they did.

    The one tech I did see live is adequate, or better. He has a lot of experience and seems to know what he was doing. He might be a superstar but he took some shortcuts , which might be good (I cant say), to do things I would have expected to be done differently. Maybe he was trying to save us money by not burning more of his hours that we would be charged for. I dont think he did anything wrong, he just did it differently than the ‘book’ would have described it. Maybe the book needs updating. Do not see any problems with what he did and things were definitely better after he did them his way.

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