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Discussion Starter #1
Hi Guys,

Ive had a bit of a play around with the software and got a bit of a feel for it, but wanted to ask those that actually used the device before if its a good thing to use to create an LT?

Also if you wouldn't mind could you add a run down on what you did..

Cheers.
 

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Discussion Starter #2
Also, what are the negatives of the unit?

Does it cause a thump at turn on?
 

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Discussion Starter #5
Also, what are the negatives of the unit?
I know the unit outputs pro levels, which I believe my Quest 3004 can handle (theres a button for lowering the gain - I think thats all that is required).

And I believe the unit works better with pro levels on the inputs? Is that correct.

The Behringer MX882 is what Im planning to use to Sum the LFE + L & LFE + R and possibly up the inputs to the DCX to pro levels.

Just wanting to be over cautious and ask as many questions as I can before I jump in and possibly buy the wrong combination of kit.

Any thoughts?
 

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The DCX can do anything eq wise that can be done so yes it's the right device.

To use it you will need an amp with trims or XLR-RCA with -12db attenuators.
 

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Discussion Starter #7
The DCX can do anything eq wise that can be done so yes it's the right device.

To use it you will need an amp with trims or XLR-RCA with -12db attenuators.

Thanks for the reply.

I have been looking through the Quest 3004 documentation and have found the following.

There is input trims on the front and there is a gain selector on the back.

amplifier performance
• Amplifier gain
The amplifier should always be operated with the input
level controls set at maximum. The only departure from
this practice is where the internal filters/crossover is
engaged in a bi-amp configuration, where it may be
necessary to turn down the high frequency side of
the amplifier. If the amplifier needs to be calibrated, to
match a mixer line level output, the gain switch on the
back of the amplifier can be switched to the correct
line level.
On the back of the unit the gain setting options are:

7. Selectable Gain Settings
Adjustable input switching for 1.4V, 32 dB or 26 dB make system calibration easy.
What option should I be using given the output of the DCX ? What is the 1.4V setting and how does it compare to the other two options ?
 

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Discussion Starter #8
Can anyone confirm ?

Thanks for the reply.

I have been looking through the Quest 3004 documentation and have found the following.

There is input trims on the front and there is a gain selector on the back.



On the back of the unit the gain setting options are:



What option should I be using given the output of the DCX ? What is the 1.4V setting and how does it compare to the other two options ?
 

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7. Selectable Gain Settings
Adjustable input switching for 1.4V, 32 dB or 26 dB
The 26dB and 32dB settings are fixed gain settings that assume the pro standard input. So, for an input level of 0dBu (=0.775vRMS), the output of the amp will produce a voltage gain of 26dB or 32dB depending on the switch setting.

The 1.4V setting is a sensitivity setting (as opposed to fixed gain) that says the amplifier will produce its full power output (i.e. 1100watts @4ohms) with 1.4volts input. The 1.4v is a broadcast standard where 1.4v=0VU.

The DCX output will be at the standard pro level, so I would choose either 26dB or 32dB. If 32dB peaks your limiters, then drop to 26dB.

The MX822 can also set any level you wish, so I don't see that you have any problems. It's all balanced and all at pro levels.

brucek
 

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Discussion Starter #10
Thank you.

The 26dB and 32dB settings are fixed gain settings that assume the pro standard input. So, for an input level of 0dBu (=0.775vRMS), the output of the amp will produce a voltage gain of 26dB or 32dB depending on the switch setting.

The 1.4V setting is a sensitivity setting (as opposed to fixed gain) that says the amplifier will produce its full power output (i.e. 1100watts @4ohms) with 1.4volts input. The 1.4v is a broadcast standard where 1.4v=0VU.

The DCX output will be at the standard pro level, so I would choose either 26dB or 32dB. If 32dB peaks your limiters, then drop to 26dB.

The MX822 can also set any level you wish, so I don't see that you have any problems. It's all balanced and all at pro levels.

brucek
 

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Discussion Starter #11
Found a good post on how to create LT's using the DCX (and other such devices)

http://www.htguide.com/forum/showpost.php4?p=125637&postcount=3

Most of the better digital EQ boxes, e.g. the Behringer DEQ2496 or DCX2496 can do it with ease.

The LT can be replicated as the sum of 3 filters - two band (bell shaped) filters and one 12dB/octave shelving filter. The first band filter changes the Q of the box/driver to 0.7 at it's Fb. The shelving filter changes the response to Q=0.7 at the new desired Fb. The second band filter sets the Q to whatever you want it to be, e.g. Q=0.5, at the new Fb.

In practice, you may not even need the band filters. Just use a shelving filter to boost the lows. If the final response curve looks the way you want it to, it doesn't matter how you get there or what kind of fancy name you give it. It's all just EQing the bass response to be the way you want it.
 

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Discussion Starter #12
I ended up sending an email to Quest to see what setting they recommend, and they said to use the 1.4V setting.

, I wish I knew more than mooo all about electronics :p

The 26dB and 32dB settings are fixed gain settings that assume the pro standard input. So, for an input level of 0dBu (=0.775vRMS), the output of the amp will produce a voltage gain of 26dB or 32dB depending on the switch setting.

The 1.4V setting is a sensitivity setting (as opposed to fixed gain) that says the amplifier will produce its full power output (i.e. 1100watts @4ohms) with 1.4volts input. The 1.4v is a broadcast standard where 1.4v=0VU.

The DCX output will be at the standard pro level, so I would choose either 26dB or 32dB. If 32dB peaks your limiters, then drop to 26dB.

The MX822 can also set any level you wish, so I don't see that you have any problems. It's all balanced and all at pro levels.

brucek
 

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Discussion Starter #13
I found a very helpful post that explains the math behind the decision to use the 1.4V setting for gain on the Quest 3004 (in my case).

http://www.controlbooth.com/forums/sound/8797-use-plus-4-minus-10-4-10-switches.html#post102969

Lets hope its right :clap:

Re: Use of plus 4/minus 10 (+4/-10) switches?
Almost. :)

I was working through the math of this the other night for a project. +4dBu is a voltage signal, referenced to 0.775 V. Thus, 4 dBu is actually 1.228V. (4 = 20*log(V/0.775); thus 0.2 = log(V/.775) and V = 0.775*(10^0.2))

-10 dBV is also a voltage signal, but referenced to 1V. So this signal would be 316 mV (-10 = 20*log(V/1); thus -0.5 = log(V) and V = 10^-0.5 = 0.316).

Thus, the difference in voltage would be: V = 20*log(1.228/0.316) = 11.79, or approximately 12 dB difference in signal strength.

THe short answer to your question is that almost all consoles reference their outputs to 4dBu, unless noted. Most IEM gear will probably have a switch on it. So just set the switch to +4 dBu and plug it up.
__________________
Mike Benonis
Grad Electrical Engineering '14, Virginia Tech
Electrical Engineering '09, The University of Virginia
KI4RIX
http://www.benonis.net/
 

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explains the math behind the decision to use the 1.4V setting for gain on the Quest 3004 (in my case).
I don't see how this encourages you to use the 1.4 volt setting?

The DCX has a max output pro level of +22dBu = 9.75 VRMS. math = (0.775 antilog (22 / 20).

So if the amp setting of 1.4 says that full power output is reached when 1.4 volts is at the input, what will happen when you feed the amp 9.75 volts (+22 dBu)?

brucek
 

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Discussion Starter #15
To be honest its from piecing all the information together and trying to join the dots together. I admit I know very little about electronics.

I have been told in this thread that DCX would out pro levels and that to bring it down to consumer levels it would need to be attenuated by 12dB. The math above, I thought, showed that by using the 1.4V sensitivity would in effect account for this 12dB difference. It also shows that at pro levels (+4dBu) that the output would be below 1.4V, so never able to achieve full output.

Also I emailed quest about using pro level inputs into the amp and they said to use the 1.4V setting.

The figure of +22dBu you list below is the first I have seen in reference to the DCX. Can you link to this for me please?



I don't see how this encourages you to use the 1.4 volt setting?

The DCX has a max output pro level of +22dBu = 9.75 VRMS. math = (0.775 antilog (22 / 20).

So if the amp setting of 1.4 says that full power output is reached when 1.4 volts is at the input, what will happen when you feed the amp 9.75 volts (+22 dBu)?

brucek
 

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Discussion Starter #16
The MX822 can also set any level you wish, so I don't see that you have any problems. It's all balanced and all at pro levels.

brucek
Ill be using the MX882 to mix channels on the input side to the DCX. I had a look at feeding the outputs of the DCX back into the MX882 but from what I could see that would end up creating a feedback loop if I used the main outputs which I intend to.
 

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I have been told in this thread that DCX would out pro levels and that to bring it down to consumer levels it would need to be attenuated by 12dB.
No, you will be using all pro levels and all balanced. There is no need to convert to consumer level. No attenuation required.

It also shows that at pro levels (+4dBu) that the output would be below 1.4V, so never able to achieve full output.
No, the +4dBu refers to the nominal pro level, just as -10dBv refers to nominal consumer level. The max levels are listed in the device manuals.

The MX882 spec sheet (download here), and the DCX is the same (download here). Both +22dBu max out.

brucek
 

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Discussion Starter #18
How have you come to that? Im lost.

I will be using the Integra DHC-9.9 which has XLR outputs. But I assume this is a consumer level product and will not output pro levels?

I may also integrate my 2ch rig with the HT rig and would then need to mix single ended (RCA converted to XLR) with the LFE from HT via the MX882.

The DCX works best a pro levels so I could use the MX882 to raise the levels to pro levels.

The quest 3004, i have ****. I had assumed if i feed it the pro levels from the DCX that it would have a fit. And that I would need to compensate for the 'pro' levels.



No wonder people pay extra to just buy consumer level goods that do it all for you. Too much stuff to work out for most people I would imagine.

I must say you have thrown a spanner in the works. Your telling me different information than what the equipement manufacturer is telling me.

No, you will be using all pro levels and all balanced. There is no need to convert to consumer level. No attenuation required.


No, the +4dBu refers to the nominal pro level, just as -10dBv refers to nominal consumer level. The max levels are listed in the device manuals.

The MX882 spec sheet (download here), and the DCX is the same (download here). Both +22dBu max out.

brucek
 

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How have you come to that? Im lost.
The MX882 can set any level you want. You want pro.

I had assumed if i feed it the pro levels from the DCX that it would have a fit.
It's a pro level amp. I see no reason for it to have a fit if you send it pro levels. They provide a sensitivity and fixed gain switch along with a GAIN Input switch to calibrate mixer line levels to amplifier input sensitivity.

No wonder people pay extra to just buy consumer level goods that do it all for you. Too much stuff to work out for most people I would imagine.
The pro equipment gives you options.

I must say you have thrown a spanner in the works.
You may be worrying about it too much. If one setting doesn't work, try another.

brucek
 

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Discussion Starter #20
Thanks for your help.

I guess Im just confused as the Quest guys told me to use the 1.4V sensitivity setting.

The MX882 can set any level you want. You want pro.


It's a pro level amp. I see no reason for it to have a fit if you send it pro levels. They provide a sensitivity and fixed gain switch along with a GAIN Input switch to calibrate mixer line levels to amplifier input sensitivity.


The pro equipment gives you options.


You may be worrying about it too much. If one setting doesn't work, try another.

brucek
 
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