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Studio wiring insert/return issue?!

Discussion in 'Recording' started by funkyape, Oct 20, 2005.

  1. funkyape

    funkyape Guest

    This is my first post - so hello to everybody!

    I have a problem with one of my studios and wondered whether anybody would be able to shed some light on my issue! We have a problem with fairly drastic gain output drop when we patch any outboard equipment through the insert/return points on the patchbay.

    We have a multicore from the Soundcraft Ghosts' insert point (Tip=Hot) going into a Bantom Patchbay (no rear connectors - soldering onto patchbay) with return and screen on the bottom patchbay (S and T repectively) and the send to the top patchbay point above (also on T) and half-normalised. On paper, this seems correct with patchbay and mixing desk manuals. (unless anybody tells me different and the manuals are wrong?!)

    Anyway, it is not the desk because we can patch some insert cables direct from the desk into any of the compressors/gates etc - so it has to be a patchbay/wiring issue.

    is there something i've missed here? Or are there any recommendations as to what to try? Any help greatly appreciated - before I go bald!
     
  2. Cucco

    Cucco Distinguished Member

    Hey funkyape!

    Welcome to RO. I think you've come to the right place! :cool:

    I would be glad to help you, but I'm having a hard time understanding your exact wording. Perhaps some pictures/diagrams would be good and also, whenever possible, try to use the universal terminology and no abbreviations.

    Someone here should be able to help if everything makes good sense. Believe it or not, several of us still work with patchbays!!!

    Kev??Zilla??

    Cheers,
    Jeremy
     
  3. funkyape

    funkyape Guest

    Cheers Cucco

    Mmmm - Let's see if I can word it better?!

    As stated above - we have a signal gain drop whenever we plug any outboard (compressors/gates etc) into the signal path (via the patchbay). By experimenting, we have so far concluded that the desk and outboard all work fine - because if we plug them in the signal path with a standard jack-to-jack insert cable they work fine.

    However we don't use a jack-to-jack patchbay for the shear amount of inputs we have bantom patchbays (which are the bare-wired solder onto the patchbay PCB type - and therefore have no connectors on the rear of the patchbay).

    Therefore the wiring we have used MUST be wrong - however we have follwed the desk manual (soundcraft Ghost) and the supporting document for the patchbays (ISOPATCH SIGNEX)?! And we still get the drop in signal gain when we patch cables into the patchbay for the external studio equipment. (NOTE: this is only happening with the insert/return connections)

    So, in summary - I am after any suggestion as to if we have been given the wrong information by either Soundcraft or Signex or I've missed something out!!!!!


    For the more technically minded the wiring currently works like this:

    32 channel Soundcraft desk has 32 jack insert/send sockets with jack plug (tip=hot or + or RETURN) (ring=cold or - or SEND) - going into the bantom patchbay.

    The Bantom patchbays are wired with insert send on the upper patchbay hole and return on the bottom with them all HALF NORMALISED on the PCB boards - so sound travels through them normally with no cables plugged in (and no loss of signal)


    The cables wired onto the PCB inside the patchbays (AND THIS MAYBE WHERE THE PROBLEM IS?) are:

    RETURN (or hot) and SCREEN/GROUND wired onto the (Tip and Screen) solder points on the bottom patchbay socket AND the SEND (or cold) soldered onto the top patchbay also onto the (Tip) solder point.

    Hope that makes sense?! On paper this is meant to work fine (and it does to a point) - but as mentioned earlier everytime we plug in outboard we get a considerable gain drop - which almost makes the outboard un-usable.

    If you're still awake then thanks for any help or pointers to try and solve this head scratcher?!
     
  4. 43hertz

    43hertz Guest

    32 channel Soundcraft desk has 32 jack insert/send sockets with jack plug (tip=hot or + or RETURN) (ring=cold or - or SEND) - going into the bantom patchbay.



    Funkyape,

    I'm not positive I'm understanding your description right, but here's what I think might be wrong based on how I read your description. In the quote above, you say that "(tip=hot or + or return) (ring=cold or - or send).

    I don't have any experience with a Ghost but this would seem to be non-standard as compared to every other 1/4" insert jack I've ever seen where the tip=send, not return. Do I read your description wrong or is possibly the Ghost wiring totally non-standard?

    Best of luck with your problem. It appears to my fairly untrained mind that you may be sending signal from the board into the output of the outboard equipment. I'm not sure why you would get any signal at all this way unless it's feeding back through the half-normal. Any help anyone else?

    Gary
     
  5. Reggie

    Reggie Well-Known Member

    How much level loss are you talking? Say you send a sine wave through the whole chain, how many db are lost at the end?
     
  6. funkyape

    funkyape Guest

    The OUTPUT level from the outboard equipment drops to approx half the INPUT gain coming from the desk into the outboard. Obviously to combat this we have to whack the output 'make-up' gain to maximum "just to hear the effect" of the outboard working!? Does this help?
     
  7. Kev

    Kev Well-Known Member

    half ?
    ... for some that would be -6dB

    and
    -6dB
    is an indication of being ONE LEG'ed

    I think this is a balanced / unbalanced sort of issue.
    USE a balancing method to interface your Soundcraft Ghosts' insert t and from the Bantom Patchbay.
    see the Rane library for ideas.
     
  8. RemyRAD

    RemyRAD Well-Known Member

    That is exactly it! Your inserts are unbalanced, the patch Bay is balanced, along, possibly with your processors/effects. Sounds like it's 6 DB low or more since you do not have a complete circuit. It's possible that patch cords that are just tip and sleeve, for inserting, may be the ticket?
     
  9. Cucco

    Cucco Distinguished Member

    Kev -

    Isn't half -10dB?

    J.
     
  10. dwoz

    dwoz Guest



    erm.....no. But I can see where you could easily get that misperception.


    also, what the heck is a "bantom" patchbay? is that a new manufacturer? I have seen lots and lots of "Bantam" patchbays, and even lots of "TT" patchbays :)


    dwoz
     
  11. Cucco

    Cucco Distinguished Member

    Umm... well, when you double the amplitude, you add 10 dB. This is not rocket science, just common knowledge. One would assume the reverse to be true.

    How is this a misconception?

    BTW - I'm assuming he is referring to the Bantam type plug (or TT). It appears it's a mis-spelling.

    J.
     
  12. RemyRAD

    RemyRAD Well-Known Member

    Oh well, voice-recognition is not perfect, like our audio, for those of us who are lousy typists.

    I think we were talking about 1/4" because, for change, you guys really weren't talking about size?
     
  13. Kev

    Kev Well-Known Member

    that's why I said it like I did
    " ... for some that would be -6dB "

    I didn't want to start that discussion here.
    so for this thread
    loss of one leg of the balanced line is likely to drop the signal by 6dB
     
  14. dwoz

    dwoz Guest

    see, kev is talking about VOLTAGE, and that might be different than the "FLAVA" of db that you're talking about.


    dwoz
     
  15. dwoz

    dwoz Guest

    and remember, there are about 19 flavors of Db......


    dwoz
     
  16. dwoz

    dwoz Guest

    sorry you didn't duck that brick cucco....yes It was all about banatam TT patchbays....


    dwoz
     
  17. Cucco

    Cucco Distinguished Member

    Well, yes and no.

    There's one dB. One and only one.

    However, it's how it's measured in relationship to various other items, such as voltage, full-scale and so on... (you obviously know - no need for a physics lesson here...)

    Since the original poster referenced his ears as his source of measurement, I naturally assumed that he was referring to straight, old-fashioned dB. In which case, increasing by 10 DOES in fact double (and the inverse of course).

    However, if he were measuring dBVa, then yes, this would be the case.

    In any situation, Kev is right - it does sound like a balancing issue. (which also sounds right since the poster also referenced to poles of his cable connected to the same point on the patchbay.)

    J.
     
  18. funkyape

    funkyape Guest

    Sorry lads - didn't mean to start an arguement!!!! :)

    Thanks for the suggestions - I'll try unbalancing the bantam patch leads tomorrow and see if that makes a difference? It's certainly a good shout!

    I'll let you know the outcome....
     
  19. Kev

    Kev Well-Known Member

    that's fine
    all big boys here

    Levels is difficult as it needs more words to keep people on the same thought and spec

    yes many applications of the db and we should say things better ... dBm, dBV, dBFS and so on dBSPL
    even dBREF

    go to Rane and look some stuff up

    so easy to get confused.
    so don't hold onto a single thought too tightly as people here will use short hand to comunicate.
    easy to get side tracked

    it's all good
     
  20. freakydave

    freakydave Guest

    Ghost

    The Ghost inserts are unbalanced, tip is return, ring is send.
     

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