'Hot' signal input to DCX2496 problem

[dabbler]

Hi All,

I have finally recieved my DCX2496 for use in my 3 way dipole project. A few nights ago i plugged my dvd player into the unit and played a CD only to hear the famous frying egg noise spitting out of my dynacos! I opened the unit to check for loose ribbon cable connections (found none) and also noticed that the new units have foam insulation between the boards and the bottom of the case (so nothing suspect there).

I phoned behringer the next day and their response was that the DVD player input is probably too hot and needs to be attenuated with a pre-amp. I also got a lecture on how the dcx is made for use with pro gear not home audio blah blah blah.

So, last night I placed my mixer (with levels turned right down) between the dvd and the unit and connected to a power amp with zero attenuation. Presto, frying egg noise is gone! However, now the input to the DCX is so low that the input LED indicators on the DCX do not even light up. Will this cause any problems with resolution? I also fear I could have a problem with hiss once i hook up my horns to the unit. Is there a better way to deal with this problem?

[Xoc1]

I doubt that a DVD player is capable of overloading the input of a DCX.
A quick check on the input meters will no doubt confirm that the signal level is OK.
Very likely you have disturbed the ribbon cable and this has stopped the output noise.
I bought a broken DCX with the frying egg problem, and the final cure involved me removing the ribbon cable completely, and hardwiring all the connections between the PCB,s
This cured the problem but is not a easy thing to do!

[dabbler]

I plugged the DVD player back into the DCX directly without the mixer and the problem is still there.. SNAP CRACKLE POP! Level is showing around -30db so you are right, no overloading.

With the mixer back in everything works fine

The ribbon connectors on the new units are hot glued in place and feel well secured. I doubt this is the problem in this case. I have read about a problem with the CS8420 chip however i think is only when used with digital input?

[ttan98]

I have a DCX as well, one possible problem is the volume level of all the 6 channels o/p are way up(at its max) and also the inputs( I assume you use analog i/p) to DCX.

When I got mine I config. all the channels first before I connect the DVD. Rather than using the analog DCX inputs I recommend you use the digital o/p from DVD and plug into channel A into the DCX. Config channel A as digital. It sounds better this way.

[Xoc1]

Is the noise limited to certain output sockets or is it all the outputs.
The 'frying noise' is usually limited to certain outputs.
If the noise is on all channels then it is probably an input connection problem.
How have you connected the DVD player to the DCX? Is pin 1 connected to pin 3 for unbalanced XLR input connection as per the DCX manual?

[Pano]

I'm lucky, so far no frying eggs for me.

Unless you have a faulty DCX, there is no way a consumer CD player will over drive it. As noted above, just look at the VU meters.

So there are a few things to do to troubleshoot this.

• Your mixer does not cause the problem. Why? Are you running it in balanced?
• Set the mixer to unity gain. Check the VU meters on the DCX to see that they are the same as when you connect the CD player directly. Still have the problem?
• What is your connector/cable from the CD player to the DCX?
• Are your power amps wide open, or have you turned down the input volume? For best gain structure they should be at 12 o'clock or lower.
• Try the digital input. You'll have to buy or make an RCA to XLR connector. Beware the level going in digital, it will be max! (turn stuff down, first)

[dabbler]

Originally Posted by ttan98

I have a DCX as well, one possible problem is the volume level of all the 6 channels o/p are way up(at its max) and also the inputs( I assume you use analog i/p) to DCX.

When I got mine I config. all the channels first before I connect the DVD. Rather than using the analog DCX inputs I recommend you use the digital o/p from DVD and plug into channel A into the DCX. Config channel A as digital. It sounds better this way.

Inputs and channel outputs are set at 0 gain. Yes i am using analong input but I would like to try digital output. Excuse my ignorance but does the digital cable need an XLR jack into input A or can I use the XLR / RCA adaptor i have in there now? Have never used a digital cable before, dont even know what they look like! Digital output from my dvd player looks like a standard RCA fitting.

If i use digital input, will I need to attenute the signal between the DCX output and the amps?

[Pano]

Yes! To all of those. You should be attenuating anyway - big time. You can use your RCA-XLR adapter.

[dabbler]

Originally Posted by Xoc1

Is the noise limited to certain output sockets or is it all the outputs.
The 'frying noise' is usually limited to certain outputs.
If the noise is on all channels then it is probably an input connection problem.
How have you connected the DVD player to the DCX? Is pin 1 connected to pin 3 for unbalanced XLR input connection as per the DCX manual?

I am using outputs 1 and 4 for testing. When muting output 1, the right speaker is fine, the left speaker spits out frying bacon. When I mute channel 4, left speaker still crackles (with audible distortion in the higher freq) but not as loudly as when output 1 is on. So most of the noise seems to be from channel 1, and alot less from channel 4.

Regarding the pins, I have no idea, I bought my adaptors from here. Is there any way I can find out the pin connections on the adaptors?

[Pano]

You can check them with an ohm meter. Most likely you will find that XLR pin 1&3 are tried to ground, XLR pin 2 is connected to the center of the RCA.

You might want to mute all inputs and outputs. Then unmute and check each channel 1 at a time. Use the same output cable! Is there a difference between the noise of each channel with nothing else happening? Is there any difference in noise with the channel you are testing muted or not muted?

That test will tell us a lot. Then we can proceed to others.