Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15
  1. #11
    I suppose I could have said 36 or 33; 39 is what I use. Just habit, I guess.

    When summing, the maximum load occurs in those instants when you have a positive signal on one channel and an equal but negative signal on the other. At those moments, the point where the two resistors join will be at about zero volts. So in essence each channel has one resistor from its output to ground. (Not a real ground - just a zero voltage point that exists because the other output is pulling in the opposite direction.)

    So if you have 33-ohm resistors, at those moments you'll have a 33-ohm load on each output. At other times, when the outputs are not so much in disagreement, the load will be higher resistance. This is okay, since these outputs are essentially stiff voltage sources that will drive any load that is not lower than the intended load. These days the intended load is 32 ohms, the impedance of your average headphone.

    In theory, any resistors from 32 ohms up will work. However, you don't want to go too high, for the same reasons very-high-impedance anything is undesirable: susceptability to noise, interference, signal level loss, and high frequency loss.

    Edit: I hope this is obvious, but maybe not: when I say 33 ohms or higher, I'm talking about summing a headphone output. With a pro-type line output minimum resistance is 600 ohms (620 isthe closest standard value) and with a consumer-type line output, probably about 2.2K.

  2. #12
    New Member
    Join Date
    May 2009
    Location
    London, England
    Posts
    6
    Thaks for all the help folks. I was with you Karl up to that last post at which point my brain melted and poured out my ear onto the floor beside me I have not had any problems yet but once my brain is back where it belongs I will make a lead as you recomended. If I understand correctly the lead I have made is fine, I just need to add two 39 ohm resistors, one each in left and right signal wires before soldering them to the 2 pin and the Ipod will be protected.

  3. #13
    New Member
    Join Date
    May 2009
    Location
    London, England
    Posts
    6
    I have found some 39 Ohm 0.25w Carbon Resistors on ebay. Will they do the job?

  4. #14
    Right. Just so there's no confusion, the resistors go IN the right and left signal lines - you have to break the connections and insert the resistors - not ACROSS signal and ground.

    The Ebay resistors would work, but that seems like a lot of trouble for two resistors. We have a Radio Shack in every suburb, do you? Or can you track down a local electronics repair person? They'll have some resistors. Remember, anything from 33 ohms to at least 1,000 ohms will work, as long as they're both the same. Wattage doesn't matter - we're talking thousandths of a watt here.

    Looking at me, you'd know that my brains dribbled down to my waist many years ago.

  5. #15
    New Member
    Join Date
    May 2009
    Location
    London, England
    Posts
    6
    Job done. Managed to solder the two resisters onto the 2 pin, then one to the left and one to the right signal lines, I put shrink sleeve on any exposed wire on the signal-in side of the resisters and squeezed it all inside the XLR case, nice and tidy and all works well.
    Thanks for all your help Karl, thanks for everyones help, it was much appreciated, even the parts I dont understand, yet. Cheers, Kibble.

Page 2 of 2 FirstFirst 12

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Subscribe to us on YouTube