Behringer DCX2496 digital X-over

[Pano]

Originally Posted by SY

Check the Jensen app note that zigzagflux linked.

Yes, I've read it. Still doubt it makes much difference for short line applications. Long lines, sure.

I'll wait to see hard evidence that it makes a difference in this application.

[zigzagflux]

Originally Posted by Groundloops

I wonder if this simple SE output from the AK4393 datasheet is useful, especially for short interconnects. Seems that no output capacitors are needed ...

Depends on what you feed, I suspect. You have shown a difference amplifier, which does remove the DC, but it also can add its own output offset voltage (dependent on the opamp used). Most off-the-shelf amplifiers will have some series capacitor somewhere in the input circuitry, so this offset will effectively be removed.

If your amp is using a non-gapped amorphous core input transformer (like mine), this circuit will saturate the transformer.

[Viper_user]

Hi i have a question of going from XLR out to RCA in,
do you recommend this solution?
Balanced Wiring (3.9kΩ & 1.9kΩ)

And when fireing up DCX does the last used preset start?

[Pulse-R]

you don't need the resistors,.

if you connect 1 and 3 pins, then the DCX reverts/uses unbalanced mode.

also, yes the last settings are used, even if not saved in a memory location.

[Viper_user]

Ok thank's Pulse! Does that solution activate a digital attenuation and some bit loss?
If i understand oehlrich right, all kind of volume adjustments happen in the digital part

I consider also this solution to bypass output stage during this method: passive output stage for DCX2496 It seems very nice! Would the output be ~10dBV (0.32V RMS)? If so, does this solution activate the digital output attenuation?

Thank's

[peterhenk]

All,

I would like to know if the following is feasible.

Remove the complete output of the DCX2496, connect the dac outputs directly to the xlr connectors (no filtering of the DC voltage etc.) and replace the output with input transformers in my amp (see picture).

The advantages would be:
- very few parts (no caps) in the sound path.
- fully balanced until my single ended amp.
- DC voltage eliminated (though at the other end of the cable)
- expensive but few parts..... so very fair price!

All this inspired by the application note by Jensen transformers on connecting balanced and se equipment.

Thank you for your input.

Peter

[canever]

Hi, it works only on the paper.
Change the output is not like change the bulb in a lamp.

The trafos works caring to the impedances seen by the primary and by the secondary. The ratio of the transformer is the key of this matter. You cannot forget. Otherwise the trafo doesn't work properly.

In your suggestion you don't care about the impedance matching. By the trafo you reflecy to the primary the impedance of your amps by the ratio2 of the trafo.

It works only, probably doesn't "sound"; only if you are lucky and the amps match the output impedance of the DACs. Study the data sheets and you will understand.

Better if you place the trafo inside the DCX. Look for a trafo with a center tap, and you place a "stupid" RC cell on this center tap, 33-47uF/10K is a classic. 10K or different depending on your amps, and you have to change the uF.

This RC filter:
1) helps a lot to clean the signal ... even if close to 75-100KHz you can ear a sweeter sound with the cell installed
2) matches the input impedances of your amps.

It is a classic, purist, solution to the DAC matter. The datasheet almost of all DACs describe this solution.

[peterhenk]

Canever, Thank you for the reply.

Will study the RC filter solution this weekend! I will still need a receiver end at the amp side though ;-(

I did study the data sheets (does not mean I understand all of it ;-) of my amp and the Jensen application note (attached) on crystal voltage out DAC's as I understand that the AKM dac's on the Behringer have a similar DC output.

The amp boards have an input circuit I wanted to change (wanted to mod this part anyways) to match the load of the line + trafo.

[fredsonqc]

Hi,

You need to charge DAC output with around 1k Ohm
You need to filter RC as well
A lot of people who used output transformers directly had DAC failed in time...

I use Jan Didden DCX outputs (find in Pilgham shop), passiv and activ, and all my amplifiers have input transformers inside chassis).
That is the best CMRR way. I remoove the input cap in amplifier replacing by transformer.
Pilgham Audio - DCX passive upg.

I modified up today around 15 DCX, all mods I appreciate were with Didden way; never use,please, selectronic mods! All of them are bad for different reasons,trust me. i tryed a lot of mods...

For input transformers You need tu use them with max 1 feet cable long to amplifier. (CMRR 30dB) that is the worse solution after lonely adapter cable.

But If You need to use transformers close to DCX, all in a separate box for example, not the best but better solution is to use output transformer as JT-11-EM .(CMRR 60dB max)
JENSEN TRANSFORMERS, INC. - LINE OUTPUT TRANSFORMERS

Finally, If You need to adapt pro level (from DCX outputs, no mods) with consumer level (RCA input amplifier) You need to step down 12dB with 4:1 input transformer as JT-10KB-D (CMRR up to 120dB!)

For my part, ragarding this point, I did that for DCX input since I remooved (of course) the E/S daughter board and have XLR pro level outputs from my preamplifier. I use Cinemag transformer that I made made (CM25101) to feat with the AK4393, means You need a midle point on secondary to analogique ground of AK.

For DCX output,Your choice will be the best with input transformer in chassis of amplifier (end line always) with JENSEN JT11-P-1,well known, almost for me :-) (CMRR around 107dB!)
I use the PCB version (1HPC)
JENSEN TRANSFORMERS, INC. - LINE INPUT TRANSFORMERS

my 2 cents

FRED

[pinkmouse]

Originally Posted by fredsonqc

A lot of people who used output transformers directly had DAC failed in time...

Hi Fred, do you have references for this, it's not a problem I was aware of.