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Need DIY assistance -- Kev or Zilla??

Discussion in 'Pro Audio Equipment' started by Cucco, Dec 20, 2005.

  1. Cucco

    Cucco Distinguished Member

    Okay - so my PreSonus Central station has gone flakey. The rackmount portion works fine, but the gain control on the remote is terrible. It scratches and cuts out on both or either channel on its own.

    I shouldn't have expected anything more though from PreSonus...

    Anyway, before that even happened, I had thought about putting a stepped attenuator in anyway. Now that it has happened, I think that's a no-brainer.

    First - how easy is it to replace an attenuator?
    Second - where can I get a good stepped attenuator (stereo)? (I know I'll have to drop a decent amount of $$ for a good one)
    Third - given all of the above, would somebody out there with better soldering skills than my own and further knowledge of attenuators be willing to do it for a fee?

    Thanks guys!

  2. iznogood

    iznogood Guest

    one : easy

    two : http://www.dact.com (second to none)

    three : without a doubt!
  3. Kev

    Kev Well-Known Member

    that suprises me as I didn't expect that signal would actualy pass through the remore unit
    one should never make assumptions about how things are made
    ... must always lift the lid to be sure

    the part may be replacable but I'd have to see inside ... and then the part would need to be available

    I suspect it may just be a dual ganged potentiometer ... :roll:

    The DACT alternative is one fine idea
    even if you do change over to another controller the DACT box can always find a use elswhere. ( I can explain )

    Also there is Goldpoint Switches

    My DIY Factory site has a little info and I am working on more but it is a slow old process so I don't have a solution described in full yet.

    Mk1 is the simple passive attenuator ... from dual ganged pot to dual stepper switch like DACT or Goldpoint.

    MK2 is the VCA based unit with remote controller ... wired

    Mk3 will be a multi relay box with either wired or IR remote control ... like the MKI it is a PASSIVE signal route and will have some user preset features like ... dim, cut, mono ... left, right
    This is being developed with great assistance from Mikkel S.
    It will also be expanded for input switching and multiple outputs (active)

    So in the long run it will do the same sort of thing as the PreSonus Central
    mine will be quite different in method and will probably not have the SPDF or AES functions ... Mikkel says otherwise ... so you never know
  4. Zilla

    Zilla Active Member

    I have no direct experience with this presonus unit. I don't know whether the volume control is an analog pot, or some kind of encoder that controls a vca or dac digitally. The dact attenuators are good and compact, but presonus tends to stuff their chassis' chucky corner tight. Don't know if even the dact would have room inside. Need to look under the lid.

    Based on other presonus gear I have seen, I would expect that there are too many other compromises in that unit to warrant another $100-300 in mods. I would be inclinded to just build a new monitor controller all together.
  5. Cucco

    Cucco Distinguished Member

    Hey guys!

    Thanks for the input.

    I'm really quite interested in keeping the Central Station. Despite other crap from Presonus, I have been quite impressed by this unit so far.

    Unfortunately, the audio does travel to and from the remote control unit and therefore does go through the remotes attenuator. I've cracked the case and, while it doesn't appear to be cram packed (actually it's wide open), the problem that I see is that the attenuator is at the bottom of the slanted unit. I'll take some photos and measurements and let you guys know.

    Iznogood - if everything looks like it would work, could I send it to you via post and have you gather the part(s), perform the work and ship it back? I would gladly pay if it's not TOO expensive. (I know the part works out to around $50-$75 USD - please feel free to factor in your reasonable charge for labor - I'm not about screwing people for their efforts...)

    Thanks guys!

  6. Kev

    Kev Well-Known Member

    get pictures of that attenuator

    so very disapointing that the audio does pass through the remote

    it is very likely that a replacement part can be fitted
    also very possible that a better than original (Alps perhaps) could be fitted

    there must be a good Tech near to you
  7. iznogood

    iznogood Guest


    i would be happy to help..... but i'm far away from you.... in denmark....

    so i guess it would be alot cheaper for you to find someone in the states...
  8. Zilla

    Zilla Active Member

    did you want to put the att. in the main unit or the remote?
  9. Cucco

    Cucco Distinguished Member

    In the remote.
    Pics coming tonight.
  10. Cucco

    Cucco Distinguished Member

    Sorry for the delay in posting pics.

    Here the are...

    (Dead Link Removed)
    (Dead Link Removed)
    (Dead Link Removed)
    (Dead Link Removed)

    It appears that there is enough room for just about any other attenuator. It also appears that several points are soldered to the board but only 3 are traced to anything else. One of those obviously appears to be a ground.

    Is this typical, only 3 connections? Hell, that should be pretty easy!

    Thanks guys!!!

    Jeremy :cool:
  11. Kev

    Kev Well-Known Member

    three connections per layer

    signal, ground & slider

    I don't think that those bottom connections and tracks are the only ones.

    Difficult to see but I suspect there are more directly below the green four layer pot ... right next to the 10 pin IDC / Ribbon connector.

    I don't know why there is 4 layers ... two stereo controls perhaps.
    Perhaps they are using two layers to form one ... for reliability ?
    Wait ! :shock:
    could be set up as a balanced attenuator sort of thing.

    Should be easy to find and fit a suitable unit here.

    DE-soldering the old one will be difficult as these are plate through holes.
    An experienced tech can do this.
    The novice should be careful about heat build up on those solder pads and plate through holes ... doing the PCB damage.

    I would use both Solder Sucker AND Solder Wick techniques.

    You need to find the resistive value of this thing
    look for markings on the side 10k ... 20k
    could be low at around 500 or 1k if this is a balanced attenuator thing
    I haven't found a likely suspect online yet ... but I'll keep looking.

    Do they have a spare part you can buy ?
  12. dpd

    dpd Active Member

    maybe DC offset?


    This sounds like a problem not with the attenuator, but a leaky capacitor in series with the attenuator which can be changing the DC offset into the next stage of circuitry. Just for fun, I'd check that possibility out. If a cap is in series with the attenuator, replace them and listen to the results. Very simple to do, very inexpensive and quick. Cheap fix while you are considering the better attenuator.

    I've had pretty dismal results my pair of PreSonus DCP-8's. One has lost its memory and scrambles its settings on every power-up cycle. Both seem to have low-level transient bursts that get into my Rosettas. PreSonus can't fix them any more. Plus, I believe that they sound like crap, too - I haven't yet recorded anything without them in the chain but I'll bet things sound much better the next time I do a recording.

    Thanks for the info - I was seriously considering one of these things for my studio that suffers from not having a good talkback system. Sounds like its time to look elsewhere.
  13. Kev

    Kev Well-Known Member

    Re: maybe DC offset?

    excelent advice
    seriously this makes lots of sense and I should have suggested it

    you wouldn't expect a pot to be scratchy this soon and the DC through the cap is very good thinking

    good to see someone is looking at this with a clear head

    thanks to dpd
  14. Zilla

    Zilla Active Member

    Looking at those pics confirms my initial feeling: start from scratch.

    Interesting comment about blocking caps. Makes me wonder why you would need them in a supposedly passive circuit.
  15. Cucco

    Cucco Distinguished Member

    Thanks guys!

    I appreciate all the tips.

    One thing though - with all due respect - I don't want another device and I don't want to build one. The thing is, I really like the device as it is. I don't like that the remote is causing troubles. I might have them repair/replace it as it's under warranty, but I still want the stepped attenuator.

    In general, I haven't noticed any degradation of the sound by its passing through it (if it's there, it's minimal) and the converters are actually halfway decent. (Neigh, they're actually damn good! They're no Lavry's or Benchmarks, but they're every bit as good as Apogees!)


  16. dpd

    dpd Active Member

    About 25+ years ago I built a stereo preamp from scratch (why I admire Kev so much - he sticks with it!). The 1st model used a 24 position attenuator built with 1% metal film resistors and a pretty good switch. I just never thought that 24 positions was sufficient. So, I went out and bought a monster 32 position dual-deck Shallco switch with silver contacts and massive wipers. Then, I designed my own attenuator profile - not linear, not quite audio taper and built it with high end 1% metal film resistors (non-magnetic leads, etc). That thing still works to this day. There is zero crosstalk and it tracks great between the two channels. Heck, even made a beefy knob out of aluminum stock and sand-blasted it. BTW, the switch has a very nice feel.

  17. Kev

    Kev Well-Known Member

    Oh ... SO ... Sweeeet

    I love DIY
  18. dpd

    dpd Active Member

    Hey, Kev, if I can dig up the design folder, do you want me to send you the information?

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