Dx-38 usage question..

[Coytee]

The Dx-38, has a set of input LED's. These monitor the signal coming in I suppose. There are 6 of them in a column. Starting at the bottom, they're marked -30, -24, -18, -12, -6 and "clip".

The directions say:

To simultaneously achieve maximum headroom and minimal noise, the DX38 has to be properly integrated into the gain structure of the entire audio system.

You can set the desired input level of the DX using the two INPUT controls (1). Therefore, operate the system at the highest signal level that is to be expected in the further operation. Slowly turn the INPUT control (1) clockwise while continuously monitoring the level meters (the LED's) for peak readings. The optimal value for program peaks lies between -12 db and -6 db. The CLIP-LED's indicate clipping of the AD-converter and should not light at all or at least only very briefly. When driving the DX38 below the mentioned range, its outstanding S/N ratio is not optimally used, resulting in probably audible system noise. (above emphasis is mine)

Ok, now it seems to me whoever wrote this has never had a pair of Jubilees hooked up to his system. For me to get those lights up to the suggested levels, the speakers are reallyyyyyyyyyy starting to talk to me. I typically don't have ANY of the LED's lighting up, or if I'm cranking it, it might get up to -18 and perhaps peak at -12

At risk of exposing how anal I can be on something silly, one thing I absolutely do NOT care to do, is take the adjustment knob and simply crank it up 100%. I want to keep it at 12:00, or "unity" as I think it was called by Trey. It might be irrational, but I don't like doing it []

Any suggestions on how to bump the LED's yet prevent my ears from being blown out?

Would the following work...?

I have around 8 db's of attenuation applied to my dbx amp (1V input sensativity) as opposed to zero attenuation to my McIntosh amp (2 1/2 V input sensativity)

Is it possible (desirable) to retract the attenuation of the dbx amp so it's zero, and flip over to the McIntosh amp and BUMP it UP by 8 db's , thereby giving the SAME difference as I currently have, but allowing the signal strength to be higher?? (I admit not knowing if I can even BUMP it like that)

My fear is those gymnastics happen AFTER the input meters

This is a different animal for me to deal with since we're not dealing with line signals but the preamp's output signal and its variability.

Am I making a mountain out of a molehill? I can't say I hear any noise, then again, I never heard the 90 Hz muddy sound from a standing wave I had in the room until Mike found it, displayed it and eliminated it.

[DrWho]

What preamp do you have? And what do you have driving it? Keep in mind that the Dx38 is a system controller for live sound reinforcement....where SPL's on the order of 130dB from the mains are the norm. You've gotta have a lot of headroom to achieve this output and keep things clean sounding at 70dB.

As you mentioned, there is nothing wrong with turning down the gain of your amplifiers to then allow you to crank up the preamp (and thus better saturating your DACs). Just be careful that you don't crank the preamp to a point where it's no longer behaving linearly - as can often be an issue when interfacing between "home" and "pro" gear.

That said, you're probably right about that mountain...

[mas]

Perhaps I am missing something here...but you want the 'clip indicators' to light??

I think in this case you may indeed be making a mountain out of a molehill here...no LEDs flashing simply indicates that you are not overdriving the unit and that the signal being passed is well within the linear operating range of the unit.

It ain't broken! Don't fix it! []

With all due respect, I think its time to quit tweeking and time to start enjoying![]

I should have such 'problems'! [][]

[BiggerIsBetter]

This is the same dilema that comes up a lot in conversatino about the Behringer digital unit. In summary, you want the highest level input (without climping) in order to maximize the amount of bit available. The best solution requires a volume control after the processor (which means know you need 2 since you are biamping)....hense the whole dilema.

Either, do the best you can with the adjustment you have on your amp (i.e set to minimum and maximize the input to the processor) and put your head in the sand OR read everything that has been written about this for the Behringer on the various forums, prepared to be fustrated and have a head ache.

[Coytee]

Gotcha on the mountain.. []

To finish out your questions:

What preamp do you have? Peach

And what do you have driving it? Huh? do you mean cdp? or 110V household? []

As you mentioned, there is nothing wrong with turning down the gain of your amplifiers to then allow you to crank up the preamp (and thus better saturating your DACs).

My amps don't have gains. I was referring to the INTERNALS of the DX, make the db adjustments (much like I have my solid state amp knocked down -8 db right now)

Hey look at me Mom... I'm typing in Blue, like Mr. Roy uses... [H]

[Coytee]

Perhaps I am missing something here...but you want the 'clip indicators' to light??

Oh, no... but the manual says "to achieve maximum headroom and minimal noise... the optimal value for program peaks lies between -12 and -6db. I don't get it anywhere near there... much like saying maximum power on your car is while traveling at 90 MPH and all I can do is put around at 6 MPH (I'm not sure if that's a perfect analogy [])

I think in this case you may indeed be making a mountain out of a molehill here...no LEDs flashing simply indicates that you are not overdriving the unit and that the signal being passed is well within the linear operating range of the unit.

It ain't broken! Don't fix it! []

Gotcha!

With all due respect, I think its time to quit tweeking and time to start enjoying![]

I should have such 'problems'! [][]

neener neener []

[PrestonTom]

I have become confused here, especially with the analogy to the Behringer.

On the Behringer if you are feeding it an analog signal (which is not the preferred method). The Analog-to-Digital (ADC) conversion has two features that are critical. One is the voltage range over which it functions (about 8-10 volts) and the second is the number of bits it has in the conversion (about 24 bits). You want to fit as much of the dynamic range (the range of voltages from the source) into the range (and number of bits) that the ADC provides. Failing to do this means you are not using all the bits avaliable and you are increasing the quantization noise (in effect). If you exceed the range (voltage) then you are not encoding the higher levels. This second problem is clipping the signal and results in harmonic distortion. I am asumming the DX-38 is also accepting an analog input.

The further complication that was referred to regarding home vs pro in home systems the output of the source or whatever (not the phono prior to a pre-amp) is line level for home systems (about one volt, roughly). Although some CD players are hotter and put out about 2 volts (roughly). However, Pro equipment puts out a much larger voltage (8-10volts). Consequently an ADC in a pro system has an ADC set up to accept a much larger range of voltages. This larger range (from a home system) can be accomplished with a preamp (with sufficient gain).

Is this a big deal .....

The noise floor in your living room will certainly exceed the quantization error on either a 16 bit or 24 bit ADC. Even if you are only using 10-12 bits you are probably quite safe (each bit is 6dB). Consequently, err on the side of using too few bits and avoid the clipping. So leaving 12dB or "room" would be potentially loosing 2 bits. This is not the end of the world.

If the truth were told: anything improvement beyond 14 bits or so (if you are using all of them) is typically not perceived under the best of conditions (headphones in a sound attnuated environment). When listening through speakers in a realistic environment, folks talk about the "improvement" with 18-24 bit recordings, there is reason to be skeptical about this claim.

-Tom

[DrWho]

to put it another way Richard....do you hear any noise?

[ben.]

Follow their instructions. By calibrating your system's dynamic range so that the loudest SPL is still giving you peaks at -6 or -12 dB relative to clipping within the unit, you'll ensure optimum operation. There's a linearity to be found when devices are operating near their nominal levels, though. If you only crank it every now and then, it may be worthwhile to readjust levels so that you have a "cruising along" setting that runs the inputs hotter, and a "no one else is in the house and the neighbors are gone, too" setting that has lower input sensitivity.

Mike - 130dB? I hope you're talking about at 1m... I fear for the future of live music if not...

[DrWho]

yea, definetly 1m... []

The thing I fear is the slow increase in output capability of the less expensive sound equipment and all the DJs that like to run everything into clipping all the time...Just a few weeks ago I set up a few systems on campus for DJ's that just happened to be capable of 140dB at 1m. Never did I think providing a system with headroom would be such a mistake. I come back to check on things a little bit after the show started only to find every amp nearly solid red. Since then I now brickwall everything to 120dB at 1m to keep things from blowing up (both equipment and peoples' ears) [6]

*sigh*

(does it really sound "good" to them???)

[ben.]

It's true. Cheap power and heat sink type (credits to PWK on that) power handling capabilities of speakers are "trickling down" so stupid SPL is becoming more economical and therefore attainable to folks ill equipped to handle the responsibility.

[Coytee]

to put it another way Richard....do you hear any noise?

I admit to not hearing anything. Then again, I never heard the 90 Hz node that was muddying up the room until Mike came by, heard it and showed me how to eliminate it.

I've learned that I don't know enough about the technical stuff (and never will) to understand if something is being used to its fullest potential.

For all I know, my system is maxed out but on the flip side, I might have room for 50% improvement by simply maximizing a couple key components, ala, the Dx-38.

so, for me, the only way I figure out what's on the other side of a rock... is to turn it over! []

[DrWho]

How bout this...do you notice a change in the noise floor with

everything on versus everything off? The easiest way to check this is

to plug and unplug the speakers with everything on...if you don't

notice a difference then you have nothing to worry about []

[Coytee]

When I unplug my speakers, I notice about a 150 db drop in noise...[] at least, that is what Marion calls it...

[]

Interesting that you say that... I'm under the impression that since I've got a tube amp involved, that I should NOT 'unplug' that speaker from it ?? (K402)

[DrWho]

hmmm, guess you need to throw the tube amp away then [][]

In that case, listen to the difference with everything on compared to just the amps off. []

[Trey Cannon]

That's my boy Who...

Die tub amps die....[6]