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2 questions, thump and noice.

matsjmatsj Posts: 0
edited June 2007 in PA General Discussion
Hello i´m new here on the forum and i´m hopeing to get some answers on my questions.

My home cinema :

Pioneer dvd ->
Meridian 568 surround processor ->
3 Dbx driverack Pa -> ( 1. Front, 2. center+ sub, 3. rear )
Hypex 5 x ucd 180 -> 5 Jbl 2446h driver+ Jbl 2382A horn 800->20khz.
3 Crown K2 - 8 Jbl 2226h 15\", 40->800hz.
1 Qsc plx 3402 - 4 Jbl 2245 18\" ->60hz.

Now my questions:

1. My girlfriend turned off the Dbx before the amps and there come a HUUUUUUUUGE Thump/ bang from the speakers. Is there something to do to avoid this again ?????

2. I have a light noice in my horn from the Dbx, and a friend on a Swedish forum said i can switch the input gain from 34 db to 17 db inside the Dbx Pa to get ride off the noice. Does someone know about this ??

Except this i´m very pleased with my Dbx.

regards mats


  • Options
    DraDra Posts: 3,777
    #2 - Don't know.

    #1 - Option 1- Others have said to open up the unit and hard wire (by-pass) the switch so that it never turns off.
    Option 2- Put a sticky note saying, \"If amps are on, leave alone!\"
    Option 3- It sounds as if you have no problem putting money into your system, so.... Use a PLC to turn on an off relays in the desired order and with the proper time delays.
    One button on for entire system.
    One button off for entire system.
    Each amp would have its own relay.
    All DRPA's can be on one relay (or 1 each).
    So that would be 5 relay outputs, assuming that all other gear have remotes. You could put these on additional relays or put with DRPA's.
    Raw components, excluding enclosure(s) would run under $600 (USD).

  • Options
    matsjmatsj Posts: 0
    Thank´s Dra for your input. I´m not a money guy, i have bought all my stuff used and worked hard for them :) .

    I have searched the forum for my answers, and found out that there is moore than me who have the power bump :( .

    I will send a mail to Dbx about it and se what they says about it.

    I don´t want to build a powerswitch with relays :evil: for this problem.

    regards mats
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    GadgetGadget Posts: 4,915
    Don't waste your time... DBX will not do anything about this problem.. they can't. Bypass the power switch from the DRPA, and get a UPS unit that will run the DRPA's for a brief few minutes till the amps can be shut down properly. this is for power failure situations...

    As for the internal jumpers I don't know that the DRPA has them.. the 260 does, what position do you have the input sensitivity switch next to the left(mono) input on? It should be on -10 for consumer gear. Do a gain structuring to optimize levels throughout the system and if there is still hiss.. I guess there isn't much that can be done.
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    matsjmatsj Posts: 0
    I sent a mail to dbx last night about my problems.

    I can´t se why that should be a problem for them to fix the power bump ?

    I have the input sensitivity switch on -10 now. My friend on the forum have the DR260. I didn´t have the cash for 4 DR260 so i bought 4 DRPA instead.

    regards mats
  • Options
    skuttaskutta Posts: 1
    To solve #1, I have looked on the web to find products that effectively mute their outputs when power is lost. The idea would be to insert the device between the Driverack PA and the amps. When the power fails, the device in the middle of the signal chain would stop the POP from making it to the amps and speakers. For this to work, the muting would need to kick in almost immediately after power is lost.

    The Behringer Ultralink Pro MX882 looks like it may a good candidate when used as a 6-IN, 6-OUT line driver. The assumption here is the outputs of the MX882 are muted upon loss of power. The 6-IN, 6-OUT configuration effectively provides passthough for each of the Driverack PA's outputs and can be inserted into the signal chain before the amps. The only drawback is the MX822 would not prevent the POP due to the Driverack PA being turned off before the amps are powered down. I have not tried this configuration, so I am not sure if this would work.

    To help with the problem of power failure and turning off the Driverack PA while the amps are on, has anyone tried inserting compressor/limiter between the Driverack PA and the amps? Specifically has anyone tried the DBX 1046? At minimum, it should limit the POP or at least help protect the speakers if the Driverack PA is turned off before the amps.

    Does anyone know the behavior of the DBX 1046 in a power failure situation? If it immediately mutes its outputs when power is lost, it may prevent the POP entirely when placed after the Driverack PA. If the DBX 1046 uses bypass relays, the POP will most likely pass though and it would not a good solution to this problem.

    I know that some of the other DBX products use bypass relays in a power failure situation. There is nothing in the documentation for the DBX 1046 to indicate what happens.

    It is funny that I partially purchased the Driverack PA to protect my PA, but now I trying to protect my PA from the Driverack PA.
  • Options
    GadgetGadget Posts: 4,915
    Guys.. the transient is too fast... the DRPA is a dinosaur and there WILL BE NO UPDATE OR SOLUTION TO THE THUMP! get a UPS for under $50 and keep the DRPA running till the amps are dead... thats THE ONLY SOLUTION AT THIS POINT! DBX CANNOT AND WILL NOT ADDRESS THIS PROBLEM! just like they cannot fix the 260 single device per serial port issue! These units are more than 6 years old now.. they are outdated and DBX is working on new projects to replace the older units, that will address these problems..
  • Options
    wolfgongwolfgong Posts: 74
    Gadget -

    Do you have a ballpark delivery date for the new product(s)?
  • Options
    GadgetGadget Posts: 4,915
    Sorry guys, While I am allowed to moderate this forum and I do get updates from time to time I will always share what I find out.. the new units are still in development and there is no target date or feature list as of now.

    As for version 1.50 it is simply amp and speaker presets.
  • Options
    slywhiteslywhite Posts: 12
    Are we so sophisticated that we can't remember the simple cost free solution to this problem???? Turn Amplifiers ON LAST.. Turn Amplifiers OFF First. Your rack configuration should fix this. Power Conditoner on the top, followed by DRPA and other units and finally amplifiers. Turn everything on from top to bottom. Turn everything off from bottom to top. I thought forums are for sharing useful practical information....
    Gadget gave you this same solution but it seemed to get lost in the rest of his posting.

    Matsj, this issue isn't specific to the DRPA. This noise will happen with keyboard and guitar amplifiers if you plug or unplug while the volume is turned up or down. It will happen when turning off an instrument before turning off the amplifier. It also happens plugging and unplugging connections to and from a mixer.
  • Options
    Depending on how you've set your gain structure you may be compunding the problem. If you have your amp attenuators turned up full then you'll get a lot of background hiss and the turn-off thump will be relatively loud.
    From experience with my DRPA, the turn off thump/pop (when I've accidentally turned the drpa off first) is noticeable but not deafening. That said, I have the system set up such that my amps clip at about 15db output from the DRPA (a tiny bit of headroom from digital clipping the outputs) so the magnitude of the powerdown thump is comparable with a loud (but reasonable) output signal.
    The only problem is you'll have to make sure nobody turns up the controls on the amps. This is the one caveat with setting gain structure, it only takes one person to turn up an attenuator and something could get broken. You could put together a seperate box with 1K or 5K potentiometers to adjust the levels of each output and once adjusted close the box. If you then leave your amp attenuators up full then it should be the best of both worlds.
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    slywhiteslywhite Posts: 12
    I failed to mention that this loud thump you've heard will do a number on high frequency drivers. Sometimes it will absolutely kill them. I did notice that your application is home theater so I'm not certain this will be an issue for you, but for those of us that use compression drivers and the like for live sound reinforcement, depending on how many full range cabinets one is using this can potentially be a minimum $50.00 hit, per cabinet to replace diaphrams. Just FYI.
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    matsjmatsj Posts: 0
    I had 3 Behringer dcx 2496 x-overs before and there were no problem with them. I could turn them on and off and ther were no bump.

    Now i want to know what Dbx can replace the Driverack with :?: .

    Scroll down a little bit to see some pictures. I change the set up often.

    http://www.hififorum.nu/forum/topic.asp?TOPIC_ID=60142&whichpage=14 .

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