This is a misnomer that has been generated around the web.
But there is an element of concern because of the very high efficiency of altec drivers.
Keep in mind the drivers I use are much more efficient than yours and noise
would be a bigger issue in my case.
Two important steps to succeed with a digital crossover like the dcx.
1) pump maximum signal into the crossover to ensure the signal is converted
to attain maximum resolution
2) attenuate the output signals from the behringer feeding the power amps.
If the amps you are using have an attenuator knob you are good to go.
The amps I purchased for my setup did not so I needed attenuators between the xo
and the power amps. I purchased these from Scott Endler and they work like a dream.
My system uses a stock behringer unit with the highest efficiency drivers altec
made and there is NO noise. Nothing. Dead silent. Which is creepy when the music
kicks ins. It's all about proper gain staging and listening to GM, bfish, old guy, pano and
all the other nut cases who visit here when you want to design a speaker system correctly.
Thanks, Steve. My system will use domestic HiFi SS integrated amplifiers. One amps' 'pre-amp out' will connect to the crossover input. The crossover outputs will connect to the respective 'main amp in' of the 2 or 3 amps used.
Will this arrangement be OK? Would a simple boost stage between the pre-amp and crossover be necessary?
Marshall.
Opinion is only as valid as its verifiable supporting evidence.
Do the power amps have a volume knob?
Yes means you have no worries.
No means you might have a bit of tweaking to do...maybe...maybe not.
Also you say you're going to use the pre out of an integrated amp to feed the crossover?
So you have no plan to use the power amp in the integrated amp?
It's all about gain structure, Marshal. If not used right, the DCX (and some other pro gear) can be noisy. But not if you do it right.
Here is a little something I wrote on the subject. Pano's Scribblings
Steve, I think the volume control on these integrated amps is in the pre-amp stage.
What would I need to do?
Marshall.
Opinion is only as valid as its verifiable supporting evidence.
Pano,
Thanks for the gain-staging articles. I used to write policy, procedural and work instruction documents and I am impressed by their clarity of yours.
Flattery aside, here are the integrated amp specs. I have to work with:
Amp 1 - 'Pre-amp out' (1Volt) which would be the drive to the crossover.
Amp 1- 1Volt into the Main(power)-amp > 35W RMS per channel(8 Ohm)
Amp 2 -1Volt into the Main(power)-amp > 50W RMS per channel(8 Ohm)
Amp 3- if used, similar to Amp 1.
Do I need to provide boost for the input and attenuation for the output of the crossover or is there a way to make this all work in a home application using the crossover without add-ons.
Marshall.
Opinion is only as valid as its verifiable supporting evidence.
Thanks Marshall. I used to translate user manuals into French and we always tried to make them better than the originals. Sometimes we actually succeed.
With a sensitivity like that it's not going to be easy to stay clean. These pro crossovers are really meant for power amps with a volume control up front. Even if you were to modify the DCX to bring the outputs down to the same level as the DAC chip output (about 1.7V RMS) you'd want to attenuate before the amp. I certainly need to in my rig.
On the older integrated amps I've owned, the volume seems to be the last thing in line. So for example coming in the tape monitor is subject to volume control. You think yours are not like that?
Of course you could build attenuation into your cables.
EDIT: Come to think of it, 1V out of the preamp seems low. A CD player is usually 2V out. Do you have a way to measure this?
With only the DCX spec sheet to go by...Originally Posted by mah
+22dBu max input (and output) = ~9.7V, so disregarding EQ cut/boost, 1V in should produce 1V out. Both (really all 3) connections are low-to-high Z too, so no problems with loss or loading. Should be a smooth insert. You may have to tweak the gain a bit on the 2nd amp to balance the output for relative gain.
RE noise, I suspect you'll have some, but mostly from the amps. The common setup uses amps at full gain with adjustment at the pre level, which invariably leads to HF hiss (thermal noise) audible during quiet passages or between cuts. Your planned setup (may) beat that rap. If not, you can join the rest of us that learn to ignore it.
Added
I'd check your amp 1 I/O loop to ensure the level varies with the volume control. I have an old (Kenwood) with that loop, and it doesn't...
"[I]We're going all the way, till the wheels fall off and burn[/I]!"
Bob Dylan, from [I]Brownsville Girl[/I]
[I]"Time wounds all heels"[/I]
John Lennon, referring to the Nixon/Hoover deportation fiasco.
Yep, 1 volt in will give you 1V out. If you don't change the gains inside, it is unity gain (no change)
Of course once you start dividing up the spectrum, each output is now a fraction of the full spectrum and thus lower in level. That will be very dependent on signal and crossover points, of course. Driving the DCX with a hot input helps keep the signal up out of the noise floor. The noise floor has been a big problem for folks using the DCX straight into power amps with no attenuation.
It really was not designed to be used that way - that's its major drawback for home Hi-Fi use.
Right, there's one thing that I just remembered any user should know:
Section 5: Audio Connections
The BEHRINGER ULTRADRIVE PRO DCX2496 has standard electronically balanced inputs and outputs. The circuit design has an automatic hum suppression with balanced signals and is able to operate, without problem, even at highest levels. Externally- induced mains hum etc. is thus efficiently suppressed. The servo- function, also automatic, recognizes the connection of unbalanced pin assignments and changes the nominal level internally so that there is no difference in level between the input and output signals (6 dB correction).
Feeding an unbalanced input on a power amp....well this means the behringer kicks up the signal when it recognizes an unbalanced connection. I forgot to note that the attenuators I purchased also presented a balanced load to the behringer, tricking it into thinking it is feeding a balanced input...thereby preventing the signal from being doubled. Easy to do with resistors....but necessary to get the best result possible.
The confusing part of behringer's documentation is the part in section 5, figure 5.1 where they say for unbalanced use pin 1 and pin 3 have to be bridged...which is simply not true...they should probably re-word that.
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