timtheenchanteruk Posted January 16, 2007 Share Posted January 16, 2007 I have a few cheap passive DI boxes, which work quite well. my question is, can I use them backwards, ie turn a balanced signal into an unbalanced, or will it just not work.I ask because something I am doing for a friend needs a monitor, which has been borrowed, but only has unbalanced inputs, having worked in this venue before unbalanced cables of more than a meter or so causes horrific buzz problems. can I do it this way, is there something else I can use/do to solve the problem, or do I need to find another monitor?? Link to comment Share on other sites More sharing options...
Chris Beesley Posted January 16, 2007 Share Posted January 16, 2007 It all depends on the DI box ... what make/model is it? Link to comment Share on other sites More sharing options...
timtheenchanteruk Posted January 16, 2007 Author Share Posted January 16, 2007 possibly not much use, but its a LEEM DIRECT-BOX, model DR40possible the older version of the NDR40here Link to comment Share on other sites More sharing options...
StevieR Posted January 16, 2007 Share Posted January 16, 2007 You need a passive DI to unbalance a signal - i.e. its got a transformer in it. The EMO E520 is one we use for that purpose. Steve Link to comment Share on other sites More sharing options...
mikepoll Posted January 16, 2007 Share Posted January 16, 2007 OK, just going through in my head an idea so anyone feel free to correct me, but:Balanced Signal:Pin 1: GroundPin 2: SignalPin 3: Inverted Signal Now as Pin 3 just carries an exact replica of pin 2 (just inverted) to change balanced to unbalanced could you not:Presuming going XLR to Jack.Either: Pin 1: Jack SleevePin 2: Jack TipPin 3: N/C(Or:Pin 1: N/CPin 2: Jack TipPin 3: Jack Sleeve) The second arrangement would actually give a signal with twice the amplitude but the effect would still be the same would it not?I accept any issues of impedance matching may not be accounted for is this solution but would others agree that this could work as a back up option? Link to comment Share on other sites More sharing options...
StevieR Posted January 17, 2007 Share Posted January 17, 2007 Now as Pin 3 just carries an exact replica of pin 2 (just inverted) to change balanced to unbalanced could you not:Presuming going XLR to Jack.Either: Pin 1: Jack SleevePin 2: Jack TipPin 3: N/C(Or:Pin 1: N/CPin 2: Jack TipPin 3: Jack Sleeve) Not quite, I'm afraid. For the first arrangement you are essentially sending an unbalanced signal and negating the noise-cancelling effect of the balanced signal. Over a long cable run you will hear the difference! Second arrangement may produce odd results. Not suite sure as I've never wired it this way. Thinking about it though, you are essentially grounding the cold (inverted) signal and lifting the earth from the signal source. You should still get the signal through but possibly with some background noise or hum. Steve Link to comment Share on other sites More sharing options...
mikepoll Posted January 17, 2007 Share Posted January 17, 2007 Yeh, ok about the first option, neglected to think about why the balenced signal was there :P I guess with the second one it would be quite dependant on how the destination treated the signal, whether it actually used the sleeve as the ground and referenced the signal to it... in this case it would work; or whether it just assumed (as standard) that the sleeve would be a ground 0V and used its own internal ground reference to compare to therefore haveing the same effect as the first option and defying the purpose of the balenced signal. Thanks for the thoughts though! Link to comment Share on other sites More sharing options...
broadcast_techie Posted January 17, 2007 Share Posted January 17, 2007 I have in the past used a cheap cpc DI box to go from the pa desk out into my camcorder (canon xl1) which worked ok, however I wasn't at any great distance... Kris Link to comment Share on other sites More sharing options...
lonfire Posted January 17, 2007 Share Posted January 17, 2007 or just buy a line balancing transformer and stick it in your own project box.. look at cpc code AV08743.. do people think that'll work? I'm looking todo something similar.. all the description says is MATCHING TRANSFORMER - F XLR TO 1/4" rgdschris Link to comment Share on other sites More sharing options...
GreatBigHippy Posted January 17, 2007 Share Posted January 17, 2007 I have used a behringer DI box for this purpose so it is possible. I think stageline passive DIs can be used this way too. The problem with any non DI solutions is that if you have any unbalanced equipment without a DI box between that and the other end then the whole run is unbalanced. (ooops just seen that the post after that which says just as much!)Another option (if you have the kit available) is put use one of the minimixers like the behringer or makie ones with a single or two mic inputs. That way they can even have some baisc eq on thier mix :) Link to comment Share on other sites More sharing options...
David A Posted January 18, 2007 Share Posted January 18, 2007 Yes it will work absolutely no problem. Link to comment Share on other sites More sharing options...
timtheenchanteruk Posted January 18, 2007 Author Share Posted January 18, 2007 am I right in thinking though, just for future referance, that it wouldnt work with an active (phantom powered) DI, as ther wouldnt be any phantom coming from the outputs of the mixer Link to comment Share on other sites More sharing options...
dbuckley Posted January 19, 2007 Share Posted January 19, 2007 No, it wouldn't work because unlike a transformer, electronic circuitry does not work backwards. Link to comment Share on other sites More sharing options...
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