Behringer DCX2496 Questions

[DougL]

The Behringer DCX2496 is a great unit, and I have my prototype speakers up and running using it. Now I need to take the next step.

I looked in the manual before I bought the DCX, and saw it had mike facilities on input C. Based on that, I bought the measurement microphone.
After trying to use it with Speaker Workshop, it appears that the microphone preamp is only active in the Time testing.
While buying a microphone preamp is not the end of the world, I was wondering if someone else could confirm that I need to buy a microphone preamp.

Doug

[petervv]

hi Doug,

>I was wondering if someone else could confirm that I need to buy a microphone preamp

You're right, the mic input is only used for automatic time delay adjustment, you need a seperate mic amp to do measurements.

regards, Peter

[janneman]

If you supply a couple of mA's via a resistor to pin 4 of the large flatcable going to the analog output board (X14), relays 2B and 2C energise. That activates the mic preamp at the C input.

The amplified signal can be picked off from pins 9 & 10 of the smaller flatcable on the input area. (X13).

Jan Didden

[audio-kraut]

Since we are on topic - another question. I am having problems with the xlr outlets of my dcx - they start a nasty noise in the lower band. Wiggling the outlets helps to solve it for a while. I have tried resoldering, which works for a month or so, then problem reoccurs.
Suspect bad soldering points.
Is ist advisable to remove the pc board mounted xlr connectors and replace them with panel mounted ones, and wire those to the board?

[janneman]

I dunno, hard wiring doubles your chances for bad solder joints.

Is the PCB under some mechanical stress? That is known to loosen solder joint, or at least make them unriliable, after some time.

Jan Didden

Edit: I have located and used an exact replacement for the Behringer back panel XLRs from Farrnell. If anyone is interested I can look up the order number.

[audio-kraut]

No jan, just the "stress" of the xlr plug ins. Started showing symptoms after about the third month I had the unit.
Are those replacement connectors of a better quality - i.e. metal?
And yes, I'm interested. Have to do something to cure the problem long term, thanks.

[Paul W]

The "frying egg" noise seems to be caused by the ribbon PCB connectors. Try reseating them.

This happened to mine in channel 6...reseating the connectors fixed the problem...after another couple of months it started in channel 3. Sure would like to find a permanent cure!

[audio-kraut]

Thanks for the terminology - describes the problem very well. Yes, I sure would like to find a permanent solution too. Will try again. Maybe cleaning the contacts and then somehow fasten the ribbon band connector - haywire and silicon?

At least - I know theres others out there, maybe we should develop a ten step program for the dcx

[audio-kraut]

I think I found the problem for the frying egg syndrom.
Just happened to reoccur, so took unit out and inspected it - no problems with ribbon connectors, solder joints - all nice and tight. Then I noticed: The little metal tabs that on the outlets hold the xlr plug in position were flat against the xlr housing - no spring action to seat the xlr connector properly.
Bent the tabs down 1/8" and reinserted unit into chain - and all noise gone.

[janneman]

For those who are interested in those things, I ran a sim on the DCX2496 output filter (the 2nd order anlti-aliasing filters implemeted in opamps on the output boards). The attached graph shows the freq/phase curve (labeled "stock") and the passive filters I am going to put in (labeled 'mine' - how original!).
The stock has about -.2db at 20kHz but some 30degr phase shift. The passive has about -.5dB @ 20kHz but less phase shift.

Jan Didden