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Author Topic: DCX2496 Behringer Crossover (redux)  (Read 5793 times)

Ryan Lantzy

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DCX2496 Behringer Crossover (redux)
« on: November 27, 2006, 03:54:21 pm »

Rather than reply to the million page long thread I'll just link it.

http://srforums.prosoundweb.com/index.php/t/9398/6617/

OK.  More bad news/good news depending on how you look at it.

Upon setting up for a show last week I had the frying bacon rear it's ugly head again.  I thought I had solved it initially.  Boy was I wrong.

The frying bacon sound was intermittent and would start with out warning.  And note, it has absolutely nothing to do with being to close to the metal frame with stuff grounding out to that.  Nothing.

The problem is the ribbon cable as Ivan had found previously with his units.  After much pushing and prodding I narrowed it down to that.  The kicker is, I can't for the life of me figure out specifically what problem with the ribbon cable causes it.  It seems that the cable is glued down from the factory.  When I first opened my unit, that glue had been undone by either vibration, temperature changes, or improper application.  I didn't bother to re-glue it, but tucked the cable in neatly which mostly immobilized it.

Well, after some more shaking around in a rack for a month or so, the cable wiggled loose again.  It seems that when the cable moves it causes the noise... I'm not exactly sure why.  I examined the header and the point at which the cable is "pinched" or crimped on to the teeth of the header.  I could see no visible issues.  Looked like every other IDE hard drive style ribbon cable I'd ever laid eyes on... and those IME infrequently go bad with light handling.

The weird thing is when the cable moved independent of the chassis/boards it caused the issue.  If it stayed in a particular spot I could elicit the frying bacon sound.  If I jiggled it quickly I could hear pops/crackles at very high amplitudes +15 or  so dBu.  It was fairly random though... moving back to the same posistion would not always cause the frying bacon sound.

It is my guess that the ribbon cable has either: a worn connection, an improperly crimped end, or a break/short somewhere along it's length.  Bad ribbon cables seem to be a thorn in the side of modern electronics... from what I've read of other manufacturers issues... though, IME I have had only one or two go bad on me in about 10 years of working with computers.

I can't tell for sure (I'm no electronics expert) but I think the cable is a digital connection.  The noise seems digital in nature and after talking to a few local EE guys the thing that a bad ribbon cable could cause communication errors and bit error rates to go up causing the noise floor to rise.  That would explain why it still passes audio with the frying bacon noise in the background.  That is a total guess though.

I used hot glue to fasten the cable down... And I used it quite liberally.  I also reinforced the connection point to the I/O daugther board with hot glue.  The cable is completely immoble now.  I can shake, smack, drop the unit with zero ill affects.  No noise, no snaps crackles or pops.  Since the thing is out of warranty anyway I tossed it down the basement steps a few times.  Still works like a charm.

It is sad that such a great unit otherwise has to be hampered by a faultly cable that Behringer probably buys wholesale off the same suppliers as everyone else.  It's probably a cheaper part but who knows.

P.S.  While I still consider this a good value if you don't need absolute reliability I will discontinue purchasing these.  I have 3 right now.  Two are doing EQ for my monitors and one is doing EQ and xover for my side fills.  Only one has exhibited the frying bacon sound.

For me they are non-critical.  I *could* get buy running the sidefills in full range and EQing the monitors with the graphic.  It's inconvenient and not optimal... but I've seen worse failures.  For my FOH, I use a dbx DR260, and while I hate the front panel interface, the thing has been rock solid reliable for me.  I would not have it any other way as my FOH cabinets require biamping, delay, and param EQ.

As time and money allows I'll probably upgrade to something like a DR480/xilica/Sabine/Protea.  I wouldn't recommend the Behringer unit unless you have a risk mitigation plan or are a weekend warrior without much liability.  One of these on FOH could be a dealbreaker if it went down and no backup was available.

Edit: clarity
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Ryan Lantzy
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Re: DCX2496 Behringer Crossover (redux)
« Reply #1 on: November 27, 2006, 05:45:06 pm »

Ryan Lantzy wrote on Mon, 27 November 2006 14:54

Rather than reply to the million page long thread I'll just link it.

http://srforums.prosoundweb.com/index.php/t/9398/6617/

OK.  More bad news/good news depending on how you look at it.

Upon setting up for a show last week I had the frying bacon rear it's ugly head again.  I thought I had solved it initially.  Boy was I wrong.

The frying bacon sound was intermittent and would start with out warning.  And note, it has absolutely nothing to do with being to close to the metal frame with stuff grounding out to that.  Nothing.

The problem is the ribbon cable as Ivan had found previously with his units.  After much pushing and prodding I narrowed it down to that.  The kicker is, I can't for the life of me figure out specifically what problem with the ribbon cable causes it.  It seems that the cable is glued down from the factory.  When I first opened my unit, that glue had been undone by either vibration, temperature changes, or improper application.  I didn't bother to re-glue it, but tucked the cable in neatly which mostly immobilized it.

Well, after some more shaking around in a rack for a month or so, the cable wiggled loose again.  It seems that when the cable moves it causes the noise... I'm not exactly sure why.  I examined the header and the point at which the cable is "pinched" or crimped on to the teeth of the header.  I could see no visible issues.  Looked like every other IDE hard drive style ribbon cable I'd ever laid eyes on... and those IME infrequently go bad with light handling.

The weird thing is when the cable moved independent of the chassis/boards it caused the issue.  If it stayed in a particular spot I could elicit the frying bacon sound.  If I jiggled it quickly I could hear pops/crackles at very high amplitudes +15 or  so dBu.  It was fairly random though... moving back to the same posistion would not always cause the frying bacon sound.

It is my guess that the ribbon cable has either: a worn connection, an improperly crimped end, or a break/short somewhere along it's length.  Bad ribbon cables seem to be a thorn in the side of modern electronics... from what I've read of other manufacturers issues... though, IME I have had only one or two go bad on me in about 10 years of working with computers.

I can't tell for sure (I'm no electronics expert) but I think the cable is a digital connection.  The noise seems digital in nature and after talking to a few local EE guys the thing that a bad ribbon cable could cause communication errors and bit error rates to go up causing the noise floor to rise.  That would explain why it still passes audio with the frying bacon noise in the background.  That is a total guess though.

I used hot glue to fasten the cable down... And I used it quite liberally.  I also reinforced the connection point to the I/O daugther board with hot glue.  The cable is completely immoble now.  I can shake, smack, drop the unit with zero ill affects.  No noise, no snaps crackles or pops.  Since the thing is out of warranty anyway I tossed it down the basement steps a few times.  Still works like a charm.

It is sad that such a great unit otherwise has to be hampered by a faultly cable that Behringer probably buys wholesale off the same suppliers as everyone else.  It's probably a cheaper part but who knows.

P.S.  While I still consider this a good value if you don't need absolute reliability I will discontinue purchasing these.  I have 3 right now.  Two are doing EQ for my monitors and one is doing EQ and xover for my side fills.  Only one has exhibited the frying bacon sound.

For me they are non-critical.  I *could* get buy running the sidefills in full range and EQing the monitors with the graphic.  It's inconvenient and not optimal... but I've seen worse failures.  For my FOH, I use a dbx DR260, and while I hate the front panel interface, the thing has been rock solid reliable for me.  I would not have it any other way as my FOH cabinets require biamping, delay, and param EQ.

As time and money allows I'll probably upgrade to something like a DR480/xilica/Sabine/Protea.  I wouldn't recommend the Behringer unit unless you have a risk mitigation plan or are a weekend warrior without much liability.  One of these on FOH could be a dealbreaker if it went down and no backup was available.

Edit: clarity


I'm ASSuming that it's an IDC (insulation displacement connector). While there are literally bazillions of good IDC connections in use all around us. Anybody who has been in the business long enough to do some decent volume will have seen or experienced a problem or two, preferably in other companies products.  Cool

It can be as simple as a bad batch of wire, bad connectors, bad tooling, or faulty machine set up. Usually the designs are competent, but this is not a good area to cut corners.

If you had three hands you could identify the bad line(s) with an ohmmeter, but you might as well assume they are all questionable. It's not uncommon to brute force repair these by soldering where the IDC blades pierce the insulation, or course you shouldn't apply so much heat that you distort the connector housing.

Unless they have found a cable source so cheap that they don't work, these are usually routine repairs to just replace with a new good batch of cables. These are not expensive in bulk but a PIA to one-off.  

Just about every audio manufacturer has experienced cable problems from time to time. How they support the product in the field is important. Did you try to get a replacement cable from service?

JR
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Tom Reid

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Re: DCX2496 Behringer Crossover (redux)
« Reply #2 on: November 27, 2006, 06:09:00 pm »

Old IT closets with punch down blocks give me the willies too.
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Scott Deeter

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Re: DCX2496 Behringer Crossover (redux)
« Reply #3 on: November 27, 2006, 06:38:41 pm »

Ryan Lantzy wrote on Mon, 27 November 2006 15:54



I can't tell for sure (I'm no electronics expert) but I think the cable is a digital connection.  

Since the thing is out of warranty anyway I tossed it down the basement steps a few times.  Still works like a charm.

Edit: clarity


OMG Ryan, I'm sorry but I'm LMAO between these 2 lines you wrote.
All I can picture is someone taking apart a piece of gear, not knowing what the hell's in there, hot gluing, then to top it off, throwing it down steps a few times for a reliability issue test. Laughing  Laughing  Laughing

Clearly you should contact Uli with this Razz
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Re: DCX2496 Behringer Crossover (redux)
« Reply #4 on: November 27, 2006, 07:02:55 pm »

Tom Reid wrote on Mon, 27 November 2006 17:09

Old IT closets with punch down blocks give me the willies too.

A properly executed IDC connection is gas free and quite good, at least for the first few decades. Laughing

JR
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Ryan Lantzy

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Re: DCX2496 Behringer Crossover (redux)
« Reply #5 on: November 27, 2006, 10:07:12 pm »

Scott Deeter wrote on Mon, 27 November 2006 18:38

Ryan Lantzy wrote on Mon, 27 November 2006 15:54



I can't tell for sure (I'm no electronics expert) but I think the cable is a digital connection.  

Since the thing is out of warranty anyway I tossed it down the basement steps a few times.  Still works like a charm.

Edit: clarity


OMG Ryan, I'm sorry but I'm LMAO between these 2 lines you wrote.
All I can picture is someone taking apart a piece of gear, not knowing what the hell's in there, hot gluing, then to top it off, throwing it down steps a few times for a reliability issue test. Laughing  Laughing  Laughing


Very Happy  Yeah... that wasn't my shining moment in Quality Assurance testing... I mostly just wanted to see if I could shake it loose.  I figured... my amp racks have taken stage dives on accident so this was a good test.  Laughing

It's not that I CAN'T tell if it's a digital connection.  There are IC's near the inputs and output XLR connectors on the I/O board.  My *guess* is that they are ADC/DACs respectively and then that is all sent over to the DSP board.  Honestly, when I was working on it I just didn't feel like looking up the ICs to see what they were.

I could be totally wrong.  They might be somekind of output driver, and all the connections are analog.  The cable was 24 pins I think.  That worked out nicely for for 9 digital signals 18 pins, power, ground, a voltage reference for the converters and some sort of serial link to control other junk.  Roughly speaking.  It's just a guess.  Maybe I'll do a little more investigating and take some pictures.

Quote:

Clearly you should contact Uli with this Razz


Well, I'm sure they are aware of the issue.  I'm pretty sure Ivan contacted them with his faulty units.  And the issue is known.

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Ryan Lantzy
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Re: DCX2496 Behringer Crossover (redux)
« Reply #6 on: November 27, 2006, 10:10:16 pm »

John Roberts  {JR} wrote on Mon, 27 November 2006 19:02

Tom Reid wrote on Mon, 27 November 2006 17:09

Old IT closets with punch down blocks give me the willies too.

A properly executed IDC connection is gas free and quite good, at least for the first few decades. Laughing

JR


Punch blocks are pretty standard in telecom apps.  I've used 110 blocks for numerous ethernet installs... never had an issue.  Hell, all the wall jack plates I've seen for RJ-45 use 110 style punch downs.  They are dang reliable IMO.

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Ryan Lantzy
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Re: DCX2496 Behringer Crossover (redux)
« Reply #7 on: November 27, 2006, 10:25:57 pm »

John Roberts  {JR} wrote on Mon, 27 November 2006 17:45

I'm ASSuming that it's an IDC (insulation displacement connector). While there are literally bazillions of good IDC connections in use all around us. Anybody who has been in the business long enough to do some decent volume will have seen or experienced a problem or two, preferably in other companies products.  Cool


I didn't know the technical name, but looked that up and I think you are right.

The one in the DCX is like this:
http://en.wikipedia.org/wiki/Insulation-displacement_connect or

Quote:

It can be as simple as a bad batch of wire, bad connectors, bad tooling, or faulty machine set up. Usually the designs are competent, but this is not a good area to cut corners.


About 8 or so years ago when i was working in college at a local computer shop we had an entire batch of floppy drive cables miswired from the factory.  We cooked more than a few motherboards and drives with those faulty cables.  We kept trying new cables thinking that an entire batch gone bad was impossible.  We relied on the keying they provide on the header which was a bad idea.  You live you learn... we should have been following protocol and looking for the red wire to match pin one.  Duh.  This is a little different... but sucks just the same.  (BTW, pin one is almost always near the power connector on a disk drive, but not always... fun huh?).

Quote:

If you had three hands you could identify the bad line(s) with an ohmmeter, but you might as well assume they are all questionable. It's not uncommon to brute force repair these by soldering where the IDC blades pierce the insulation, or course you shouldn't apply so much heat that you distort the connector housing.

Unless they have found a cable source so cheap that they don't work, these are usually routine repairs to just replace with a new good batch of cables. These are not expensive in bulk but a PIA to one-off.  


I could probably just replace the cable myself.  The really really dumb thing (IMO) is that the cable header is just a punch block on one end, and a detachable "male/female" end on the other.  So to replace it, I'd have to rip up the cable from the permanent (soldered) punch down block and press a new one in, which I've done.  Or, I'd have to desolder the punch block from daughterboard.  Blah.  Not worth it.

Quote:

Just about every audio manufacturer has experienced cable problems from time to time. How they support the product in the field is important. Did you try to get a replacement cable from service?


I have no doubt that if this were under warranty it would be covered in full by Behringer.  I doubt they would send me the cable because it's my guess that it's considered part of the daughterboard sub assembly.  It is "semi-permanent" as those punchdowns aren't really designed to be used more than once.

They would probably offer to fix it, but it would probably be nearly as expensive as just buying a new one... which I'm NOT doing.  Or maybe send me the whole daughter board with semi-permanent cable pre-attached.  Which... may only cost $100 but a brand new one is like $250.

I should probably just call and ask.  I just don't care enough to do so at this point.
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Re: DCX2496 Behringer Crossover (redux)
« Reply #8 on: December 05, 2006, 09:18:40 am »

Do new DCX2496 units have the same problems? Or has Behringer changed the unit to prevent these issues?
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Ryan Lantzy

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Re: DCX2496 Behringer Crossover (redux)
« Reply #9 on: December 05, 2006, 08:15:28 pm »

Robert Fielder wrote on Tue, 05 December 2006 09:18

Do new DCX2496 units have the same problems? Or has Behringer changed the unit to prevent these issues?


My two newer units have not given me any problems...  It remains to be seen however.  The bad unit I had is circa 2003.  The new ones are date stamped April 2006.  The older unit worked fine for about 3 months.  My new ones are approaching that age now.  Time will tell.

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