Members Unalaska Posted January 31, 2010 Members Share Posted January 31, 2010 ...is a great article talking about how combining (NOT splitting) signals, say Left and Right MAIN outputs into a single MONO feed. It also explains a way to make such a cable using resistors. So I did this, being bored and not working tonight I thought I'd stay in and do something productive. It's made from a small project box from radio shack with a male XLR output and 2 8" tails with 2 FXLR's. Inside the box are the resistors and the 2 cables are ziptied to the side wall as a strain relief. It took a while to do the 1st one but I plan on doing 1 or 2 more as a handy thing to have around. Resistor values were taken from the Rane site (470ohm and 20K, I had to use 2x 10K's in series since the shopping mall radio shack has a rather limited selection). The 20K goes across pins 2 and 3 on the output XLR and when I check the wiring with a behringer cable tester it shows continuity between pins 2 & 3, using the Audiopile tester (1 pin at a time) shows everything is normal. Any ideas? Link to comment Share on other sites More sharing options...
Members Unalaska Posted January 31, 2010 Author Members Share Posted January 31, 2010 So here is a pic of the 2 I made. geeky I know, whatever... The MXLR jacks are cheezy but fit the little box, the 8" sections of cable were from Lackey I think. I have a big box of cables with no ends, i use it for wierd little projects like this. Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 31, 2010 Members Share Posted January 31, 2010 The cable testers use different methods of detecting, and cannot be used to test a cable like this. There should be 4 of the 470 resistors, one in series with pin 2 and 3 on each input line pairs, and the 20k between pin 2 and 3 on the output. Actually, the 20k resistor is unnecessary. I usually use 1k rather than 470 ohm because it better matches the drive characteristics of most line driver stages, but 470 ohm will work with the possible problem of excessive distortion at high drive levels. Link to comment Share on other sites More sharing options...
Members dboomer Posted January 31, 2010 Members Share Posted January 31, 2010 The resistor values are not critical. I usually use 1k as well. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted January 31, 2010 Members Share Posted January 31, 2010 ...The 20K goes across pins 2 and 3 on the output XLR and when I check the wiring with a behringer cable tester it shows continuity between pins 2 & 3, using the Audiopile tester (1 pin at a time) shows everything is normal. Any ideas? Try turning the lights off... I suspect you see a dim bulb on the Bugcatcher from the resistors. Link to comment Share on other sites More sharing options...
Members Scodiddly Posted January 31, 2010 Members Share Posted January 31, 2010 Looks like a handy thing. Lots of times for little shows I've been stuck with a Mackie mixer into a mono system, and being able to sum L and R would have been nice for CD or iPod playback. Link to comment Share on other sites More sharing options...
Members Dookietwo Posted January 31, 2010 Members Share Posted January 31, 2010 So here is a pic of the 2 I made. geeky I know, whatever...The MXLR jacks are cheezy but fit the little box, the 8" sections of cable were from Lackey I think. I have a big box of cables with no ends, i use it for wierd little projects like this. Well done. Looks like they are made to last. Dookietwo Link to comment Share on other sites More sharing options...
Members trevcda Posted January 31, 2010 Members Share Posted January 31, 2010 Just out of curiousity; how would this affect phantom power if this box got used to combine inputs or otherwise used on channel inputs? Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 31, 2010 Members Share Posted January 31, 2010 Phantom power would pass through, you would want an isolation transformer to block this if the outputs bare from a source like a Mackie Mixer (especially). Link to comment Share on other sites More sharing options...
Members Unalaska Posted January 31, 2010 Author Members Share Posted January 31, 2010 Good to know about the values. I had to use 4x 680ohm on the 2nd one because I bought the only 470's they had in stock. I figured it was "close enough" and if there was an issue I'd fix it later. It's desgined not for mics but for mixer outputs or EQ outputs to a mono rig. I want to do one more attached to a patch panel with 2XLR inputs in a mono amp rack. mark, I'll look again in the dark... Link to comment Share on other sites More sharing options...
Members RoadRanger Posted February 1, 2010 Members Share Posted February 1, 2010 I just stick the resistors in the xlr connector shells (two 1k in each xlrf) and don't bother with a resistor across the balanced line (the 20k in this case). Perhaps not as robust but I don't use my "Y" cords to fly speakers . Link to comment Share on other sites More sharing options...
Members trevcda Posted February 1, 2010 Members Share Posted February 1, 2010 It's desgined not for mics but for mixer outputs or EQ outputs to a mono rig. Understood. But if I had one of these in a tool box, I'd bet it would a matter of days before one of the guys tried to use it to combine tom mics on one of the smaller systems. Link to comment Share on other sites More sharing options...
Members Scodiddly Posted February 1, 2010 Members Share Posted February 1, 2010 Understood. But if I had one of these in a tool box, I'd bet it would a matter of days before one of the guys tried to use it to combine tom mics on one of the smaller systems. Combining same-model mics isn't any big deal. We do it for orchestras now and then, and it works just fine as long as the mics are exactly the same. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 1, 2010 Members Share Posted February 1, 2010 Would work just fine to combine similar mics. Link to comment Share on other sites More sharing options...
Members Unalaska Posted February 1, 2010 Author Members Share Posted February 1, 2010 I'll Y together tom mics without anything special, they are identical mics and I've never had an issue. So what's the 20K ohm resistor across pin 2 and 3 for anyway? Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 1, 2010 Members Share Posted February 1, 2010 I'll Y together tom mics without anything special, they are identical mics and I've never had an issue.So what's the 20K ohm resistor across pin 2 and 3 for anyway? My best guess is for providing some terminating of the source line perhaps for reducing or damping ringing on a transformer balanced input. Link to comment Share on other sites More sharing options...
Members Unalaska Posted February 1, 2010 Author Members Share Posted February 1, 2010 Never thoght of that, I doubt any of the gear I use is transformered input but it's nice to be safe... Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 1, 2010 Members Share Posted February 1, 2010 Never thoght of that, I doubt any of the gear I use is transformered input but it's nice to be safe... Even if it is, it's not all that critical. In fact, the termination will be different for every type of transformer. Link to comment Share on other sites More sharing options...
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