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Converting unbalanced to balanced signals.

Discussion in 'Recording' started by FUBARd, Sep 29, 2009.

  1. FUBARd

    FUBARd Guest

    I've been making music on synths, drum machines, bucketts and my computer for about 15 yrs now yet I've got no formal training. I realize that for long cable runs, it’s best to use balanced cables to reduce noise and grounding problems. What about cable runs (15 to 25 ft) to gear with unbalanced outputs like vintage synths? I think DI boxes are an option but I also understand that the 'affordable' ones color the sound in a negative manner. Additionally I've got about 20 channels I need to do so with on a tight budget. Is there a 'cheap trick' to making cables to convert bal to unbal while maintaining they’re functional integrity? Perhaps a DIY project of some sort?

    I've searched and surprisingly; not much on this. Maybe I'm the only one that doesn't know... :-?

    THANX!
     
  2. natural

    natural Active Member

    Assuming that these 20 cables go to inputs on a mixer that also accepts balanced inputs, why are your keyboards upwards of 25 feet away from your mixer.
    Take steps to better plan your space where a majority of these devices are within an acceptable range.
     
  3. AudioGaff

    AudioGaff Well-Known Member

    You get what you pay for. You want no color / high qulaity and cheap? Well, you don't get both. Most decent to great DI boxes have a transformer and few other components. Most of the cost is in transformer. The crappier the transformer, the cheapr the cost, and the crappier the sound.

    What you likely need is something like Ebtech makes that is specific to converting unbal to bal and -10 to +4 as well as the other way around.
     
  4. djmukilteo

    djmukilteo Well-Known Member

    FUBARd:
    To be honest...FWIW...and...IMO..with most vintage or older electronic equipment that are unbalanced you should be able to connect them unbalanced directly into your mixer unbalanced and get just as good a sound as long as the cables are good instrument type cables (TS) with good unbroken shielding and good positive connectors and jacks....even RCA type cables if they are relatively good quality and make good connections at the jacks work perfectly OK....any noise you might pickup is going to be in the form of AC which is usually a proximity effect....keep them away from noisy items....move the cable around or check the cable for poor or broken shielding.
    Balanced is fine and is preferred and all but it won't make the signal any better it will only protect the signal better from noise....it doesn't inherently make things sound better or cleaner...especially higher output devices like sythns and the like. If the equipment is unbalanced then that is the way it was designed to match the transmission characteristics and impedance. A slong as both ends match that your good to go....
    If you want to get some inline style isolation transformers, there are all kind out there that will convert Hi-Z to a balanced mixer input....sometimes those do help!
    Distance is really a matter of voltage drop which translate better to wire gauge, but unless you going down the street.......distances like your talking about shouldn't be a problem with good 18 or even 16 gauge conductors...
     
  5. Kev

    Kev Well-Known Member

    yep a DIY project

    start with a simple quality audio transformer
    10K ohms sort of thing

    check out the Rain Library - we have told you that before

    then look up the app notes and white papers at Jensen Transformers

    a simple transformer will help to get that Fully Floating Differential feed - balanced - with all the good noise cancelling goodies
    but it doesn't get you from -10dbu to +4dbu ... nor +4dbm

    you will need some active components for that
    but that is no often needed

    there is enough info out there
    and here
    - cos I've posted it many times

    use the search
     
  6. Link555

    Link555 Well-Known Member

    http://www.analog.com/static/imported-files/data_sheets/ssm2142.pdf

    This may be a cheaper option, but you will need a power supply, and they don't work both ways like a XFMR.
     
  7. Boswell

    Boswell Moderator Distinguished Member

    For runs of 20-25ft from active outputs, don't bother trying to wire up unbal-balanced converters or DI boxes. Spend the money on good-quality unbalanced cables fitted with metal TS jack plugs. For the sort of signal levels you are talking about, you will be OK as long as you route the cables sensibly, e.g. not running parallel to mains leads.
     
  8. Kev

    Kev Well-Known Member

    Thanks Link

    yep
    that's the SSM2142 driver chip
    been around a long time and my balancing boxes do use them ... you will find my PCB's on the net if you search

    the receiver chips are SSM2141 and 2143 ... slightly different headroom with the 43 set for more

    THAT Corp also have these sorts of things and BurrBrown have some too (not drop in replacements though)
     
  9. FUBARd

    FUBARd Guest

    Thats quite a lot, thanx! Looks like I've got some reading to do.

    Natural: thats exactly what I meant. :) And I've tried several setups yet what Ive got is best so far. There are several large pieces in here.

    djmukilteo: I agree, like on the CS-15 which is noisy even in headphones with the volume down :)) but I'd like to keep em all sparkely 'up top'.

    Audio Gaf: Thats what I was sort of thinking of but am scared of their 'sound'

    Kev: You're freaking me out and I LOVE IT but you've got to dumb it down for me a little as I've only put together a few paia kits.

    Link555: I like your link and I think that'd be exactly what I'm looking for if I had just a bit more experience in building something out of such charts.

    Boswell: Ive already done so with %90 "wrapped" cable and Neutrik connects. I like the idea of not spending more money but I still need to get this mono signal into balenced XLR inputs. Ive bought some XLR connects for this purpose; to simply split the neg to ground AND neg but I was hoping maybe for something a little sophisticated.

    Everyone: but maybe it's not nessecairy, I've got 110v power and when I reorganize my cabeling, I'm planning to leave power on the floor, suspend midi & cv a two feet off the ground and suspend my audio cables about four feet off the ground and a foot from the wall with wood shelving around my perimeter. Thats after I make my purchase of the 1000' roll of shielded cable for the permanent install. Do you guys think this type of spacial seperation would benifit the signal quality over my 'rats nest' to any audible degree?
     
  10. Kev

    Kev Well-Known Member

    quality cable and connectors always

    nothing wrong with a bit of physical separation from the power cables

    track down noises and earth issues one at a time and solve them

    otherwise it all builds up to a problem
     
  11. djmukilteo

    djmukilteo Well-Known Member

    What type and brand of shielded wire are you getting for the installation?
     
  12. FUBARd

    FUBARd Guest

    Here's the cable. It's Dayton. Seems like the kind of thing that there's only so manny mfg plants in china making the same thing and selling to a hundred companies to markett diferently. But then again WTF do I know.

    http://www.parts-express.com/pe/showdetl.cfm?Partnumber=100-240

    It LOOKS like the same stuff I see in all the snakes and other installs and the PRICE is right. Is there better stuff out there that's not MONSTERously expensive?
     
  13. Kev

    Kev Well-Known Member

    that looks a bit like Belden 9401 ... or the single equiv of 8723 (can't remember the #)
    it's a foil sheid with drain and good for perminant install paths and for where things don't get moved or stepped on much
    looks to be ready for a Krone block (punch down)

    I do use a lot of 9501
    but I also tend to replace often as I change things

    for Mic cable I only use Canare Star Quad or Belden equiv
    other brands are out there ... Mogami etc

    use a cable ready for being stepped for that stuff under your feet near the Keyboard stands etc
     
  14. Link555

    Link555 Well-Known Member

    You pay for things like flex and braided shield.

    The RC is the most important spec when it comes slew of the audio signal.

    They don't mention that on the link you provided.....

    What you do see it is a foil shield, that is ok for no moving installs, but will not handle the abuse of gyrating singers and moshing crowds.

    Second they do say:

    Stranded bare copper conductors (7/30 per conductor)

    That 7 strands of 30AWG cable to make 22 AWG, 7 strands is not as flexable. Infact it the smallest number or strands you can have.

    Cannare CA-L-2T2S has 60 strands!
     
  15. djmukilteo

    djmukilteo Well-Known Member

    I thought FUBARd was using that shielded pair wiring for mic lines permanently installed in the walls of his room?
    Maybe I got that wrong....
    Typically that stuff is used in conduits or raceways for mic runs in theater's and school stage projects up to control rooms...that sort of thing.....I don't think you want that laying around under foot though....if it's out of the way or bundled in some sleeving like Roundit or spiral wrap and run around the perimeter of the room that would be fine I would think...
     
  16. FUBARd

    FUBARd Guest

    YES DJMUKILTEO, What I would use it for would be for the forementioned install idea. NOT for anything that moves like miking or guitars exc. Mostly between synths, drum machines, FX, computer exc. I'm asking as my wife n I are finally buying a house soon and I'm already planning the studio install. But if the most important factor isnt even listed perhaps I should look elsewhere. Suggestions?
     
  17. djmukilteo

    djmukilteo Well-Known Member

    I think that type of wire within reasonable runs 100-200 feet is perfectly OK...it's done all the time commercially...especially if your running from say a main junction box in a control room out to the live or practice room to mic outlets or a distribution floor box or wall box. Much less expensive and more permanent than buying pre-built snakes and running those in the walls.
    The only thing better would be maybe larger gauge 18 or 20 or more stringent shielding...95-100%...Just make sure you separate the mic and line level stuff from each other so you don't get any bleed over from the line level stuff into the mic level stuff...if you're not using conduit....keeping them around 6" to a foot apart in the open is always the right thing to do....that's all I would do like you described earlier....power separated from line level stuff separated from mic level stuff....nothing long and parallel!
     

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