Tim Paul Posted May 2, 2013 Report Share Posted May 2, 2013 I've got a shoot coming up where I need to hook my LMa up to the truck for talent IFB. I'm betting the truck can send me a dry line. However, they have not yet found a truck, so I can't talk to them to confirm. I'm hoping someone can help me with a schematic to make a wet/dry XLR adapter cable. Thanks! Quote Link to comment Share on other sites More sharing options...
soundslikejustin Posted May 2, 2013 Report Share Posted May 2, 2013 ...what? Are you trying to use the LMa to transmit TO a truck radio? Or trying to use a truck radio mic with the LMa as a transmitter? Quote Link to comment Share on other sites More sharing options...
Jim Gilchrist Posted May 2, 2013 Report Share Posted May 2, 2013 ...what? Are you trying to use the LMa to transmit TO a truck radio? Or trying to use a truck radio mic with the LMa as a transmitter? Truck = TV production truck or audio production truck. Dry line = just audio no dc bias current. Wet line = an output with both audio and dc on it. A standard analog phone line is a wet line, for example, as are intercom lines. It's been some time and somebody else might have a better answer, but I think a pair of 1 uF 200v 10 uF 50v. caps in line will block phantom on a line. If the caps are polarized, the plus side should point to the truck or source of phantom power. It's been long enough that I can't remember if there's a better way if you're worried about a typical telco wet pair. Best regards, Jim Edited to reflect the values I found in my notes. Quote Link to comment Share on other sites More sharing options...
soundslikejustin Posted May 2, 2013 Report Share Posted May 2, 2013 Truck = TV production truck or audio production truck. Dry line = just audio no dc bias current. Wet line = an output with both audio and dc on it. Intercom lines are "wet," for example. Best regards, Jim Interesting. I've never heard them referred to like that. Haven't done that much truck work, though. Thanks for the lesson! So in that case, a 'wet to dry' adaptor would be something like a capacitor-based DC block, and a 'dry to wet' would be akin to a DC injector (Bias-T style) or something...? Quote Link to comment Share on other sites More sharing options...
Jim Gilchrist Posted May 2, 2013 Report Share Posted May 2, 2013 Interesting. I've never heard them referred to like that. Haven't done that much truck work, though. Thanks for the lesson! So in that case, a 'wet to dry' adaptor would be something like a capacitor-based DC block, and a 'dry to wet' would be akin to a DC injector (Bias-T style) or something...? It's been a while since I used that part of my brain, Justin, and I remembered some things, so I edited my post. Something like the Berringer Ultra-DI 100 would also work as would any line level capable isolation transformer, like the VMS-4 that Vark Audio makes. Best regards, Jim Quote Link to comment Share on other sites More sharing options...
Hartley Posted May 2, 2013 Report Share Posted May 2, 2013 Put a 10uf 50v non polorized electrolytic cap in line with pins 2 and 3 of the xlr line. You can find them at Radio Shack. You can use an inline connector or a small box with a cable coming out both sides. Quote Link to comment Share on other sites More sharing options...
Tim Paul Posted May 3, 2013 Author Report Share Posted May 3, 2013 Awesome, thanks guys! Quote Link to comment Share on other sites More sharing options...
Audio Daddyo Posted May 6, 2013 Report Share Posted May 6, 2013 The majority of Sat trucks I've worked with tell me they can't give me a dry IFB feed. I use either a Sescom IL-19 http://www.markertek.com/Audio-Equipment/Audio-Processing/Audio-Hum-Noise-Eliminators/Sescom/IL-19.xhtml or my whirlwind 3 way splitter and make sure you connect your LMa Tx to the XLR output that has the isolation transformer on it. http://www.markertek.com/Audio-Equipment/Audio-Interface/Mic-Splitters/Whirlwind/SP1X3.xhtml Andy Quote Link to comment Share on other sites More sharing options...
Jack Norflus Posted May 6, 2013 Report Share Posted May 6, 2013 The majority of Sat trucks I've worked with tell me they can't give me a dry IFB feed. I use either a Sescom IL-19 http://www.markertek.com/Audio-Equipment/Audio-Processing/Audio-Hum-Noise-Eliminators/Sescom/IL-19.xhtml or my whirlwind 3 way splitter and make sure you connect your LMa Tx to the XLR output that has the isolation transformer on it. http://www.markertek.com/Audio-Equipment/Audio-Interface/Mic-Splitters/Whirlwind/SP1X3.xhtml Andy I had a sat truck fry the transformer of a whirlwind imp 1X3 splitter by sending me a wet line - the truck operator thought that it was dry. Quote Link to comment Share on other sites More sharing options...
Tim Paul Posted May 6, 2013 Author Report Share Posted May 6, 2013 Andy, you just answered my question... I have a couple IL-19's, I was going to ask Jim if they would do the job. Thanks for answering my question before I even asked! I may build a barrel with caps just to keep in my IFB kit, but it's nice to know I don't have to build it right away. Thanks again guys! You have all been a huge help! Quote Link to comment Share on other sites More sharing options...
Audio Daddyo Posted May 9, 2013 Report Share Posted May 9, 2013 Interesting Jack. Ive used my splitter many times over the years to dry out the IFB feed and it is still working today. Andy Quote Link to comment Share on other sites More sharing options...
Jack Norflus Posted May 9, 2013 Report Share Posted May 9, 2013 Interesting Jack. Ive used my splitter many times over the years to dry out the IFB feed and it is still working today. Andy Not sure what happened - I pluged in the wet line and smoke came out of the box.That was the first and last timei used it on a wet line. Quote Link to comment Share on other sites More sharing options...
mikefilosa Posted May 10, 2013 Report Share Posted May 10, 2013 It has been decades since I did this process, and have completely forgotten how we achieved it back in the early 90s. I thought we used drypair adapters somewhere in the chain... I think RTS PLs can pack as much as 50v down the lines.... Would the Shure A15BT work in this capacity? http://www.fullcompass.com/product/435414.html?utm_source=googleps&utm_medium=shopping&utm_campaign=googleps&gclid=CP3T-onDircCFdJ9OgodIEoAEA The link claims it can also serve as an isolation transformer - might be a less expensive way to achieve the result. Based on previous good results of course -- Does anyone have a thumbs up for this inline solution? MF Quote Link to comment Share on other sites More sharing options...
Peter Mega Posted May 10, 2013 Report Share Posted May 10, 2013 Not sure what happened - I pluged in the wet line and smoke came out of the box.That was the first and last timei used it on a wet line. Ahh yes, the smoke they put in at the factory came out!! Quote Link to comment Share on other sites More sharing options...
Audio Daddyo Posted May 11, 2013 Report Share Posted May 11, 2013 Not sure what happened - I pluged in the wet line and smoke came out of the box.That was the first and last timei used it on a wet line. That would probably scare me off too although I will continue to use mine until I see smoke. ( : Andy Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted May 12, 2013 Report Share Posted May 12, 2013 I have always used a Whirlwind Splitter isolated output for Wireless IFB. Also great for splitting the signal to different devices. I run the IFB into my 664 to feed my IFB transmitter on a Aux and also create a custom headphone preset so I have it in one ear as well, therefore I dont need to take up an IFB box. Quote Link to comment Share on other sites More sharing options...
mikefilosa Posted May 17, 2013 Report Share Posted May 17, 2013 FWIW, and for "the Archives" - The Lectro T4 IFB transmitter has RTS opportunities built into it's selectable inputs. Via dipswitches you can dry out an RTS line AND select one or the other available channels for transmission. MF Quote Link to comment Share on other sites More sharing options...
DanieldH Posted May 17, 2013 Report Share Posted May 17, 2013 For reference: PSC provides a model of their barrel adapters for "line drying". http://www.professionalsound.com/specs/barrels.htm Quote Link to comment Share on other sites More sharing options...
Tim Paul Posted May 19, 2013 Author Report Share Posted May 19, 2013 I tested out my IL-19's with 48v phantom power, sure enough according to the meter no power passes thru. I made a short XLR jumper with 10uf 50v non-polarized electrolytic caps in line with pins 2 and 3. According to the meter the cable is still passing about 42v. What am I missing to make this cable work? Quote Link to comment Share on other sites More sharing options...
rofin Posted May 19, 2013 Report Share Posted May 19, 2013 According to the meter the cable is still passing about 42v. What am I missing to make this cable work? It's a combination of the very high meter input impedance and a miniscule capacitor leakage curent. As soon as you load either or both legs to pin 1 it will act as you expect. As a by the by, you don't need non polarised caps. Polarised with the + towards the phantom is fine. Rob Quote Link to comment Share on other sites More sharing options...
soundmanjohn Posted May 20, 2013 Report Share Posted May 20, 2013 ANd if you want to get really fancy, there's always this box: http://www.studio-tech.com/product_m72.html Regards, John Quote Link to comment Share on other sites More sharing options...
Tim Paul Posted May 26, 2013 Author Report Share Posted May 26, 2013 Just to follow up, the IL-19 worked like a charm. No dry line was available from the truck. Not an issue though... two days of live shots and not a single IFB issue. Thanks again guys! Quote Link to comment Share on other sites More sharing options...
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