Behringer X1204USB problem

[Steve St.Laurent]

Just received a brand new Behringer X1204USB mixer. When using the stereo inputs (5/6 or 7/8) if I put the level on +4 in approximately 20 seconds I start getting bad crackling in the audio. If I change the level to -10 and then back to +4 it goes away. I am not getting a clip signal and it does this no matter how low the initial signal is sent to the board. This happens through headphones, on the audio outs and even happens on the USB out. I recorded it and saw that the signal on the + side of the wave is what's dropping out and where the crackling is coming in. Here's a screen shot of the wave:



and here's a link to the audio http://www.motosportsdesign.com/stevest/crackling.mp3 . I contacted Behringer's tech support through email but they aren't too helpful. I run a 16 channel sound board at our church with no problems but this is for me personally and I haven't set one up from scratch before. Is there something I could be doing wrong or is this just a defective unit. Everything else seems to be working fine. The 2 sets of stereo inputs (5/6 & 7/8) do not have a gain or level knob they just have a push button that selects either -10 or +4 whereas all the mono inputs have regular gain knobs - and none of those produce this crackling issue.

Thanks in advance for any help.

[Enzo]

Sounds to me like a defective unit. I cannot think of any reasonable explanation of why this would be proper function. The fact the gain is a switch instead of a pot is irrelevant. if that were all it took, every switch on it would be noisy.

The customer service people there are not generally techies.

[pecorporation]

Work the gain switch in & out several times real fast and see if that helps. If it does, this switch needs cleaned with a deoxidizing cleaner.

[Steve St.Laurent]

Tried the gain switch in and out and that didn't help.

After a little more troubleshooting though I have narrowed the issue further. If I put a drum machine on the same ports and the problem doesn't happen. The problem does happen if either my Digitech RP500 or my acoustic guitar are plugged in. I'm going to scrounge up another audio device here tomorrow that I can get to 1/4" cables to test some regular music on those ports. The RP500 works fine if I plug it into two of the mono inputs. It seems like there is a digital processor that's doing the level change on those stereo ports (+4 or -10) and it's getting overloaded with the guitar sound and causing it to freak out.

[Steve St.Laurent]

I was able to find a CD player that I was able to hook up to those same inputs - guess what, it worked fine. So it only seems to happen with a guitar input - ideas? I was hoping to use one of the stereo ports for my RP500 as it's setup for that. I could just run it on two of the mono channels if I have to but then I'm using up 2 of my 4 mono channels

[Steve St.Laurent]

Ok, this is probably a stupid newbie question but in the X1204USB manual it shows the level options on the stereo inputs as +4 dBu (studio level) or -10 dBV (home-recording level). On the board itself it's just shown as -10 or +4 which is what made me assume it was just an either or gain/level setting. The specification also show the impedence of those jacks to be 20 kOhms whereas the RP500 lists the 1/4" outputs at 500 ohms. Should I just be running those lines at the -10 setting (where it works correctly and doesn't break up). The thing is that at the -10 setting with the RP500 cranked all the way up I only get a very weak signal when I isolate that line (-20). I did find that I can use the 3 band EQ on that line to boost that signal to the 0 range.

[Steve St.Laurent]

Just heard back from Behringer. It doesn't state it in the manual but the +4 setting on the stereo inputs is for balanced signals only. I was using an unbalanced signal which is why it wasn't working on the +4 setting. Thanks for the help guys.

[BigDaddyD]

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