Qu Separate Gain amd Trim control

[damcleanParticipant]

Hi, I have 2 questions:
1) We have a QU-24 and I’m wondering if it is possible to set gain and trim independent of each other.

2) I am investigating getting an SQ6 to act as our main mixer and then connecting it to our QU24 and having the QU24 act as our livestream mixer. The user guide for the QU24 suggests that in this setup changing the gain/trim will actually change the remote side gain. Is this true? Said another way, we want the SQ6 to beable to set the analog gain (preamp) and then send the digitized signal to local channels as well as the QU24 and then on the QU24 have the ability to adjust the local trim without effecting the SQ6.

Thanks

[volounteerParticipant]

@damclean

Sounds more like an SQ question for that forum.
I did not read the Qu manual that way. What did you see that made you think that.

My read says if you send digital channels from SQ6 to Qu that you can trim the usbb digital +/- 24dB on the Qu.
Do not see how that could affect the SQ to make a change there.

There are lots of trims. You could trim the DO by off to +10dB. Trim PAFL yada yada.
But you seemed to imply the usbB trim. Is that what you meant?
Does the Qu go next to the livestream and not somehow back to the SQ?

[damcleanParticipant]

Thanks for the response!

So the connection to SQ6 would be over the DSNAKE ethernet port, not USB.

Looking at the block diagram, each channel processing cluster has a trim. https://www.allen-heath.com/media/Qu-24and32-block-diagram_V1.8_1.pdf
It would be nice to have separate control of the preamp gain, and the trim. However it seems you can only control this trim for USB sources.

The documentation seems to suggest that when the channel source is “local”, meaning rear panel, then gain knob will control the preamp gain. When it is set to dsnake, it will remotely control the preamp gain on the connected device. When the source is USB, the knob will control the trim.

I have not seen documentation on what this knob does when the source is another console – i.e. the SQ6. I am wondering if the gain knob in this case will control the remote premamp gain as it does with a typical dsnake device. I would prefer it to control the trim. I am also wondering if I can get manual control of TRIM in anycase.

Not sure if this cleared that up.

Here is a copy paste of the text from the reference guide. The photos aide in how I arrived at my understanding as well (Page 29) https://www.allen-heath.com/media/Qu-Mixer-Reference-Guide-AP9372_10.pdf:

Source lets you choose one of four sources as the
input to the channel. Press the Fn key to open the
Source screen.

…

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

dSNAKE (yellow Gain) – Remote preamps located in
an AudioRack on stage or other remote location and
connected to the Qu dSNAKE port via a Cat5 cable.
The AudioRack preamps include 20dB Pad switching.

[damcleanParticipant]

Quick followup. From my understanding, when the QU24 is connected to an audiorack and set to source inputs from the rack, the gain knob will control the preamp gain on the audio rack. The connection to the SQ console, from my understanding, reuses this feature in the QU console. That is to say that I dont think the QU console has any understanding that it is connected to an SQ console, it will treat the SQ console as if it is an audio rack. Ergo my suspicion that the gain knob would try and change the SQ preamp when really I would want it to control the trim.

What I want is to beable to set the GAIN on the mixer which has the mic connections, and then leave the gain constant at a good but safe level. The channel will then be split, one going to the primary mixer and the other going to the secondary mixer. I then want each board to have the ability to change the trim, as if it were the gain, without effecting the other board. If the SQ is the source, then I need the QU gain knob to control the QU trim and not try and control the SQ gain. If the QU is the source, I want to beable to adjust its GAIN and TRIM seperately. I know the SQ has a way to control gain an trim seperately, but I dont see if the QU has a method.

[volounteerParticipant]

@damclean

you may be right. I see your concern. But I do not see a definitive answer in the manual.

My intuition says it would not be controlling trim on anything but the box it is on as that would have been a lot of extra work for AH to pull off and the Qu does not seem to rate such extra effort.

We feed our livestream from a mix on the Qu. Once that is set nothing seems to be able to change it and the livestream has its own gain control to tweak the outgoing audio. Note: That I do not do the livestream and am going on what the A2 told me and showed me. And that is how I read the block diagram too.

What I want is to be able to set the GAIN on the mixer which has the mic connections, and then leave the gain constant at a good but safe level. The channel will then be split, one going to the primary mixer and the other going to the secondary mixer.

I then want each board to have the ability to change the trim, as if it were the gain, without effecting the other board.

If the SQ is the source, then I need the QU gain knob to control the QU trim and not try and control the SQ gain. If the QU is the source, I want to be able to adjust its GAIN and TRIM separately. I know the SQ has a way to control gain and trim seperately, but I dont see if the QU has a method.

I do not see a problem. One of us may be overthinking this issue.

[damcleanParticipant]

Right now we also feed the stream with a mix. I would double check what you said… for us the gain does change everything… as it should when you look at the block diagram. Even if the knob changed the trim and not the gain.

The mix has its own fader for each input to the mix, but that’s all it has, it doesn’t have its own trim or eq ect. We are getting by right now, but it is a bit arduous at times.

With regards to the remote gain control: I read somewhere that when connected to dsnake the gain setting controls the remote preamp. Which would make sense. But I can’t find it in the reference manual, maybe it’s written in some other supporting document. But it needs to be done this way. The audio rack converts the signal to digital. You need a way to control the preamp gain to set the voltage range before the adc. It would have been a design requirement for A&H otherwise the value of the audioracks feature is severely impaired. You can also control things like phantom power and I think polarity as well. All the source analogue settings need to be forwarded to the audio rack. I just want the ability to also change the local trim :p

[volounteerParticipant]

@damclean

I confuse easily.

The dsnake comes in digital. The ADC is in the preamp before the channel strip.
There is a trim that affects all the outs from that channel but the mix out has its own fader and is not affected by the other.
We feed the livestream from the Qu mix. We set that level and then changes are done in the PC merging audio with the video and sending on to both the radio station and the livestream.

My block diagram shows FX PEQ GEQ compress delay then fader for the mix and a balance.
But no extra trim but why would you need

another

trim?

I hear what you are saying but do not grok your problem. We have many problems but they are more people problems:)
Our main one seems to be balancing the inputs during soundcheck to set the mix faders feeding the livestream.
I think that might have been fixed with an average setting for anything we have on stage and then the livestream fader tweaks it.

With regards to the remote gain control: I read somewhere that when connected to dsnake the gain setting controls the remote preamp. Which would make sense. But I can’t find it in the reference manual, maybe it’s written in some other supporting document. But it needs to be done this way. The audio rack converts the signal to digital. You need a way to control the preamp gain to set the voltage range before the adc. It would have been a design requirement for A&H otherwise the value of the audioracks feature is severely impaired. You can also control things like phantom power and I think polarity as well. All the source analogue settings need to be forwarded to the audio rack. I just want the ability to also change the local trim :p

Can you cite where you read that. I have not seen it. It may be out there somehow but I do not know how to do that if so.
Maybe this is an SQ feature. We only use the Qu. Sounds like you are really needing to control the SQ not the Qu.

[Mfk0815Participant]

There can only be one console which controls the analog gain of a preamp. In the mentioned environment only the console which is directly connected to the preamps, the SQ, can control the analog gain. The other, the QU, will have only the possibility to adjust the digital trim of the channels of the QU.

[damcleanParticipant]

Thanks for the responses guys.

@volounteer, I am not talking about output trim, I am talking about input trim. Yes, you will fine the output has eq, compression, ect. ect, but those are settings for the entire mix. If I get a second sound board, each channel will take one channel as a source from the first soundboard via dsnake (or slink from the SQ perspective). It will be grabbed right before the TRIM and send to the second board. That way the second board has full control, it can set per channel EQ, FX, the works. However, will it have control of the trim? Thats the question.

It matters to have trim control, it helps you set the volume range of your faders. I dont want one sound board to change the trim and have it effect the other. The documentation for the QU suggests strongly that you dont get to chose if you are changing the preamp or if you are changing the trim, it is done automatically. See page 29 https://www.allen-heath.com/media/Qu-Mixer-Reference-Guide-AP9372_10.pdf

The SQ gives you the ability to change gain and trim seperately, but the QU doesnt seem to allow you.

@mfk0815: How are you so sure? Have you tried this?

[volounteerParticipant]

@damclean

not sure what your real problem is. our Qu has two places to set gain on the input channel strip.
One looks like ‘trim’ where I set the dB gain in the screen after selecting the channel.
The other is the fader that can go up a modest ways and all the way down to nothing.

We set the gain for each mike and then fine tune with the faders as needed.
AFAIK we do not use what is on p29, but perhaps the MD did that behind the scenes.
I do know that I can adjust the preamp gain from the screen when truly needed.
But normally I just need the faders.

I see no way to automatically change anything from another device on the Qu.

p63 and p68 discuss AMM and midi control which is the only thing automatic that comes close to what you are describing
but you never said AMM nor midi so was that an oversight or do you think the SQ has some ESP ability to change the Qu?

[Mfk0815Participant]

@damclean Since I never worked with a QU I am not 100% sure. But, digital trim is part of the channel processing for any console I know, eg dLive, SQ, GLD, so why should it be different for the QU. And it makes no sense when it is not implemented like this. There is one gain master for the analog gain and the digital trim is individual for each connected console. That’s how it works.

[damcleanParticipant]

Take a look at the block diagram. This is the info path: From XLR input you first have a preamp gain, which is an analog gain which sets the voltage level for the adc. It then goes through some digital routing and gets to the channel processing cluster. Then the first element in the channel processing is a trim, this acts as a course gain adjustment in the digital domain. Than after some eqs and other processing you have the fader, which is more fine tune as you suggested. It can then be sent to various mixes ect and finally outputted.

If we were to connect two boards together, the connection would be a digital one. The path would go through the preamp of one board and then be split after digitization, one leg going into the trim on one board and the other into the trim of the second board.

Ideally we would have these boards act independently. To act independently we need the gain to remain constant as the gain is the only setting that effects both boards. We don’t want someone to adjust this gain unless the absolutely need to, as if they do it will effect the other board.
However you sometimes need this coarse
adjustment when the faders arent enough. In most cases the trim would be adequate, you don’t need to modify the preamp gain. Since each channel has a trim as the first digital element each board can most of the time function independently. However, unlike the SQ, the QU doesn’t give you the ability to modify the trim specifically. It automatically decides if your “gain” is changing the preamp or the trim, depending on what the source is.

I hope that clears it up.

To explain my other concern. One handy accessory you can buy is an audio rack which allows you to have a set of XLR ports in a box connected to the QU via Ethernet. What you do is you have your xlr cables connect to thjs box under the stage, and then you only need one cable running from the stage to the mixer, and this cable is an Ethernet cable which can travel a long ways without any analog degradation as it’s already digitized. This connects using the dsnake port. Now, I know for a fact that when you do this, and you change the gain knob on the QU for one of the channels going to the audio rack, what you are doing is changing the preamp gain in the audiorack, you aren’t changing the preamp gain on your board, nor are you changing the trim. This is what page 29 is talking about.

If I were the engineers at A&H and I was trying to find an easy way to enable this board to board connnection I would
Just reuse this audio rack functionality. That would suggest that changing the gain knob would change the preamp gain of the connected mixer just as it changes the preamp gain of the audio rack.

[damcleanParticipant]

@mfk0815: From what I understand on those other series board you have the ability to specifically control gain and trim separately. The QU series is annoying in that it sort of automatically selects what you are adjusting. You don’t get the choice to control trim and gain independently. Depending on your source you either control 1) the preamp gain (if you are using an xlr port at the rear)
2) the trim (if you are using USB as a source)
3) the remote preamp gain (if you are using an audio rack over dsnake).

It’s this third option that has be worried, as the qu-sq connection setup is virtually identical to an audio rack setup. Dsnake device source selection makes the gain setting change the remote gain, so it stands to reason that if it’s another console is connected using the dsnake path than the gain setting would change the connected consoles preamp gain.

[Mfk0815Participant]

If you have a closer look at the block diagram of the QU you will see that there is an analog gain in the local analog inputs as well as on the analog inputs of the stageboxes AR2412, AR0804 and AB168. But if you look at the Input channel block diagram you can see between source selection and insert point the “trim pol” block. This tells you that the QU also have separate analog gain and trim. I think, the trim is not directly accessible on the QU to simplify the handling for not so experienced users, because the may be confused about those to controls. And for the QU the SQ connected via dSake is not a preamp source like the stageboxes.
I assume that the communication protocol between QU and SQ will tell the QU that the signals coming from the SQ to the QU cannot be handled like signals coming from a stagebox. So the QU can react and do not allow the user to set the preamp gain at all. Its handled like the signals are coming from a USB source.

Conclusion: The SQ will be the Master of the analog gains for the local inputs of the SQ or connected stageboxes, and the connected QU only gives the user the possibility to adjust the digital trim of the QU, the QU cannot control either the analog gains of the SQ nor the digital trim of the SQ.

There is only one System I know in that price range with a flexible handling of the gain master. There you can define which console is the Master of the analog preamps but this system do not come from A&H. But that’s another story.

[damcleanParticipant]

Yes, Your description of the block diagram is what I have been describing this whole time, and your conclusion is the behavior I would want. I am writing this forum post precisely to confirm if your conclusion is true.
I have given an explanation on how the QU might not behave in that way. To be honest, what I am expecting that the gain knob in the QU would do nothing OR that the QU would try and set the analog gain of the SQ but it would have no effect… meaning the gain knob in this mode would try to do something but in effect it would just do nothing. Either way, anything other than your conclusion is undesirable to me.

This is an important part, if your conclusion is true than I am happy and would proceed with writing up a proposal of buying the SQ and using the QU as an auxiliary mixer… but it doesn’t sound like you are able to confirm that it’s true?

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