Behringer UltraDrive DCX 24/96 or Other Digital Loudspeaker Management Systems

[SonicBooMan]

DCX2496 Noise/Hiss

Hi all,

I just bought a Behringer DCX2496 Digital Crossover, and had everything connected to my Dayton RS Dipole Phoenix (RS 8" & RS shielded tweeter). I only built the MTMs, not the woofers...that will be done when the RS 12" comes along.

The MTM sounds good, except for one minor/major problem.

What I noticed bothers me quite a bit. The DCX seems to produces noise/hiss. It sounds to me similar to pink noise, but at a lower dB. When I turn up my amp to "realistic" listening level, between -30 to -10dB, I can hear the hissing sound 10ft away, during quiet passages. And when I don't play any music, I hear it also. In addition, I heard some instruments being distorted on the tweeter, which I'm guessing is caused by the DCX.

When my amp's volume control is at -60 to -80dB, I can still hear the noise at about 2 feet away. Also, when I muted the input of the DCX, the noise is still there; when I muted the DCX's outputs, the noise was suppressed, but not eliminated. When I turned the DCX off or disconnect the output, no noise, even when I cranked up the amp's volume.

Monte Kay said the DCX is noisier than Linkwitz' electronic crossover. But I didn't understand what he meant until I used one. I may keep it for testing/tuning purposes, but for my final speakers, I would not want to use the DCX. I called Behringer's tech support and told him how I tested the unit. He seems to think I received a defective one. I don't think I've got a defective unit; I think this is what I'm getting for the price...a noisy digital crossover.

I don't have any amps with XLR connectors, so I made some XLR-to-RCA cables. Could this be a possible cause of the noise?

If someone has any suggestion of suppressing the noise, please let me know.

Thanks,

SonicBooMan

[RonS]

SonicBoomMan, I've also got the DCX, and am experiencing the same thing. I haven't had much time to look into it, but will call Behringer soon.

I'm hoping that Davey will chime in here, as he has one too. Mine is not too noisy, I have to get pretty close to the speaker to hear it. It is a different kind of hiss from normal analogue amp noise.

Ron

[Davey]

Ron/BooMan,

This is normal for the DCX. You have to remember that we audiophiles are operating this thing in a totally different configuration than the folks in the pro world. The "fix" is a straightforward concept....you have to get the signal level inside the unit much higher so it's well above the noise. You do this by using a post-DCX multi-channel volume control or adding fixed attenuators of 10-20db on each of the outputs and using a conventional pre-DCX two-channel control.

Also, when constructing XLR-RCA cables (or using adaptors) on the outputs disable the pin 1-3 connection so the DCX doesn't auto-increase the gain by 6db internally.

Some DCX users have noted crackling/noise problems above and beyond this "normal" noise and have traced the problem to a faulty connector(s) on the ribbon cable that connects the rear board to the DSP board.

These are common issues that have been discussed on various forums for the past few years. The DCX is a nice unit, but it's not really Behringers fault that most of the non-professional users out here don't know how to operate it properly.

Ron, regarding the Marantz reciever.....I don't have any first-hand experience, but there are a couple of members on the DCX forum who've used it successfully in this configuration. I'm not sure what kind of driver loads they have.

Cheers,

Davey.

[RonS]

Thanks Davey. I'm using AES digital in to the DCX, so no problem with having sufficient levels coming into the unit. I don't find the noise objectionable, in my case I have to move pretty close to the speaker to hear it. At this point I still don't have any post DCX attenuation, so I'm running the digital input at -15dB. I had thought that that was the cause of the hiss, so I wasn't going to concern myself with it.

Cheers,
Ron

[SonicBooMan]

DCX 2496 Noise/Hiss

OK, thanks Davey...

In the XLR connector, I jumpered pin 1 to 3, as the DCX's manual instructed. Is this what you mean by disabling pin 1 and 3?

Also, I don't quite understand which instruments you are referring to when you said use either the "post-DCX multi-channel volume control or adding fixed attenuators of 10-20db on each of the outputs and using a conventional pre-DCX two-channel control."

Could you give me examples of these, either by pictures or brand/model # or websites which list the devices?

Thanks for all who replied.

SonicBooMan

[Doug Lockwood]

"In the XLR connector, I jumpered pin 1 to 3, as the DCX's manual instructed. Is this what you mean by disabling pin 1 and 3?"

The manual is for pro audio. You want to cut the wire that shorts pin 1 and 3. Having pins one and 3 open will cause the DCX to have 6 db less gain.
This will improve the system Signal to noise for Consumer audio amplifires, that have more gain than the pro amps.

If the 6db attenuation isn't sufficient, an attenuator on the output can be used. This can consist of a pot / stepped attenuator or a fixed attenuation. I personally haven't found that necessary for my system.

HTH

Doug

[SonicBooMan]

DCX 2496 Noise/Hiss

OK, I disconnected pin 1 (shield) from pin 3 (-V) on one side. And I do hear a lower noise level. So I'm going to disconnect pin 3 from 1 for all the outputs.

Does this applies to the inputs as well? In other words, should I go ahead disconnect pin 1 from 3 for the inputs?

Thanks,

SBM

[Davey]

On the inputs it doesn't matter since there is no internal circuitry to sense a single-ended input.

Davey.

[SonicBooMan]

Ron/Doug

I disconnected pins 1 from 3 for all outputs. The noise/hiss is lower than before. In addition, I just noticed that each output has a gain control. It can be adjusted to +/-15dB. I increased the gain, and noticed the increased noise. Now I set mine to -10dB. This seemed to help reduce the noise, in addition to disconnecting pins 1 from 3 on all outputs.

Am I doing the right thing, Davey?

Thanks,

SBM
P.S. I'm new to all this stuff; so bear with me if I sound somewhat audiophile illiterate...

[Davey]

You're going the right direction. The internal attenuators are operating in the digital domain which is not preferable to analog attenuation...in this case. Ultimately you'd want to perform all the attenuation outside the DCX box. You could add fixed attenuators to each of the six outputs or use a six-channel volume control which how I operate mine. In that case all the noise is effectively "removed" and you won't hear anything from your speakers but silence.

If you're using a digital input (as Ron is) you're fairly limited in how to implement a proper volume control without using a six-channel type.

Make sense?

Davey.

[SonicBooMan]

Davey,

Could you provide the model/brand of volume control you're using for all 6 outpus of the DCX2496? It looks as if I may have to do something similar. The fixed RCA attentuator can be expensive, especially the higher dB ones. By the time I spend the money for 6, it may equal or exceed the cost of a volume limiter.

Thanks,

SBM

[Davey]

Well, mine is a Davey brand Model 1......yeah that's it. It's a six-channel VCA control using Analog SSM2018 chips. It's a prototype, but I've have a better design that I'm working on.

Yeah, I wouldn't buy commercial attenuators, but you can easily put a few resistors inside an XLR connector or a little box for just a few dollars. Until you get a multi-channel volume control that would be the way to go.

Davey.

[Paul W]

Davey,
Do you know of a way to fix the "frying bacon" intermittent connector noise? Hard-wire the ribbon cable? I have reseated the connectors in my 2496 three different times and the problem returns after a few weeks/months. Last time I also used a contact cleaner...but that lasted only two weeks!

I'm about to send this thing skittering across the street!
Paul

[Davey]

Boy, I dunno Paul. I haven't had a bit of problem with mine so I'm afraid to touch it.
Did you read the long thread on Diyaudio.com? It seems like I remember one of the fellas on there building a new ribbon cable with supposedly better "quality" connectors and not having any problems.

Maybe you should sell it to some unsuspecting person?

Davey.

[jdybnis]

I seem to remember that the ribbon cable was a red herring. Someone on diyaudio tracked it down to the XLR. I can't remember the fix. You should read the threads over there anyways. There is one big one in the loudspeaker section and one in the digital section. Lots of good info.

[Paul W]

I haven't read all of the threads (some statements are just too wild-eyed) but I did read about the XLR connectors. I could not find any problem in that area, only with the ribbon connectors.

Selling it "as is" would be my only disposal option...and I am satisfied with it other than this one problem...so I'll keep looking for a more permanent solution.

and yes...if your's ain't broke, don't fix it!

[Paul W]

Behringer...credit where credit is due.

A follow-up...

After being screwed by Porter Cable (tools) and Best Buy within the past 12 months I almost didn't even try working with Behringer but I did. Here's to good customer service...

I was ready to pitch my DCX2496 because of the intermittent noise problem. I wrote Behringer a "squeeky wheel" email and received a reply within about 3 hours. Even though my unit was 2 years old (well out of warranty) they offered free repair. I turned down free repair because I didn't want the downtime. Then they offered free replacement with a new unit...which I accepted. Replacement unit arrived (looking brand new, down to the protective plastic sheets over the LCD panels) but I was concerned because the date code on the replacement was nearly the same as my original...both mid 2003. Sure enough, after 8 days, the replacement started frying.

The Behringer customer service guys immediately promised to have a unit with a current date code identified, checked out and sent to me. Next day they said they didn't have any current production (in Washington state)...was it okay to repair my original? I said yes, provided it stayed fixed.

The repaired unit arrived three weeks ago and I immediately popped the hood to see what they had done...new output board but nothing else visible. I pressed for details and they said they had "corrected a problem with intermittent shorting between the output board and the chassis". (I had heard of one pro-sound guy who put "fishpaper" between the output board and chassis on 5 units out of the 50 he was using.)

The repaired unit has been operating every day without so much as a peep...so it seems reseating connectors, bending tabs on the XLRs, etc may just be exercising an intermittent between the output PCB and the chassis.

What surprised me far more than the problem/solution was the attentive and immediate customer service...the Behringer guys were on it "like white on rice".

Porter Cable, Best Buy, anybody out there?

[thylantyr]

Intermittent noise is documented on DIY forums, the fix
is easy. Reseat the ribbon connectors even if they are glued.

My new DCX started to have intermittent noise after
the first week. I reseated the connectors and the problem never came back.

[Paul W]

thylantyr,
At first reseating the connectors worked for me too but the problem kept returning more and more often. Based on what Behringer CS told me, and the fishpaper report, I now believe reseating just moves the output PCB relative to the chassis...flexing a marginal short through the paint. What is the date code on your unit? They've probably corrected this in later production.
Regards,
Paul

[thylantyr]

Date code: 0307

[Paul W]

Mine is 0304 (April 03). The replacement they sent me (which also developed the noise problem) was 0307...same as yours.

[Arctophile]

The manual is for pro audio. You want to cut the wire that shorts pin 1 and 3. Having pins one and 3 open will cause the DCX to have 6 db less gain.
This will improve the system Signal to noise for Consumer audio amplifires, that have more gain than the pro amps.
<snip>
Doug

Sorry to come to this a bit late, but I am about to make some leads to connect my DCX to a receiver (RCA inputs), and I'm unsure about which pins to connect. As I understand your post, I only need to connect pins 2 & 3 on the XLR end - is that right?

Thanks,

//Adam F

[Davey]

Use pins 1 and 2. Pin 1 to your RCA outer and Pin 2 to your RCA center. Pin 3 leave unconnected.

Davey.

[Arctophile]

Thank you sir

//Adam F

[JonFo]

XLR Attenuation?

Hi guys and gals,

I also have a DCX (and DriveRack260), see my bass management write-up for details.

I want to correct the gain structure around the DCX, as I currently run about -7db of cut in the input stage (within the DCX).
The amps do not have gain management, so I need to cut via something else as has been discussed above.

I have a question about attenuators for XLRs (I use balanced in amps - Sunfire).
Would something like this one -10DB XLR attenuator at Sweetwater work?
I'm concerned that it's a low-z mic attenuator.

Besides hacking the cables (I'm Lazy and not the greatest at soldering), what purchase options are there?

Thanks,

[JonFo]

OK, I got ahead of myself, there are some options. Silly me, one is already sitting in my rack. The Behringer MX882 can also be used as a 6x6 level matching rig as well as the mix mode my current one is used for.
All I need to do is buy one more. And at $100, a good deal.
See: http://www.americanmusical.com/item--i-BEH%20MX882.html