S&L Posted April 4, 2014 Share Posted April 4, 2014 just taking the opportunity to clear up a few niggles on my maintenance list. This problem first appeared at a gig just before christmas. the vocal mic, when played through front of house at line check sounds thin, all top and no mid and bottom like a terrible cheap mic connected.the chain went mic > xlr cable > multicore > analogue desk.it just exibited on this specific channel (5 on the multicore). being pressed for time we swapped the mic cable and mic, packed them away for checking and the problem disappeared. I checked mic and cable after gig - no problem. New years eve I tried the same mic again (different cable) same channel on the mulitcore (5) - same thing happened at line check. I swapped the gear for another set AND another multicore channel and all was fine. after new year I went right through our gear, tested every cable and the multicore and found one mic cable with an intermittent connection between pin 2 and 3 - I threw out the cable. I tested each mic for sound through a desk and they were all fine. the problem went away. then last friday the problem came back. same chain, same original mic, different multicore channel. swapped cable and mic, the problem persisted. swapped multi core channel (was 8, changed to 9) and the problem went away - and no other multicore line in use (including channel 5) had a problem. digital desk set up this time. now on a show night with tight set up times, I don't have time to do endless testing on the night and this isn't a huge problem since I always try to have spare multicore channels, spare cables and spare mics available even for a small bar gig. I have the time between shows to go through and test gear again but if everything tests ok for continuity and sound again, what am I looking for?and more importantly, what sort of a sound transmission problem results in sound passing but only thin top end sound? other channels, sound fine, the channel effected changes, the problem persists with different desks, differnet mics, different cables. What's everyone think..ever heard this before? Link to comment Share on other sites More sharing options...
timsabre Posted April 4, 2014 Share Posted April 4, 2014 Sounds like an intermittent fault on the multicore - either pin 2 or 3 broken can sound "thin".Is it a good quality multi? It's usually the tails that start to break, but by bending the cable different ways the fault can be intermittent.That's my guess anyway. Link to comment Share on other sites More sharing options...
MarkPAman Posted April 4, 2014 Share Posted April 4, 2014 and more importantly, what sort of a sound transmission problem results in sound passing but only thin top end sound? Sounds as though you have a "one-legged" connection. i.e. either the + pin 2 or - pin 3 connection is missing. Your problem tracking it down suggests that it may be an intermittent problem (as cable breaks often are) and of course, you may have more than one. A cable tester that can indicate intermittent faults such as Behringer's CT100 can help here. Link to comment Share on other sites More sharing options...
Just Some Bloke Posted April 4, 2014 Share Posted April 4, 2014 found one mic cable with an intermittent connection between pin 2 and 3 - I threw out the cable. I'm so old I can remember the days when we used to get the soldering iron out and fix it! :) Link to comment Share on other sites More sharing options...
sam.spoons Posted April 5, 2014 Share Posted April 5, 2014 Me too but I think S&L meant a 'connection' (so a short?) between 2 and 3. If it wasn't in the connectors it implies physical damage to the insulation somewhere, definitely a 'throw it out' moment http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif Link to comment Share on other sites More sharing options...
S&L Posted April 5, 2014 Author Share Posted April 5, 2014 re throwing out - laziness on my part but a soldering iron takes time - actually I threw it ina box I have labelled cable sick bay --which implies I may repair it but the box becomes a dumping ground - one spare afternoon maybe I will remedy that. re CT100 I purchased one recently and had high hopes but alas it has an intermittent problem itself - if you lean on almost any cable it makes and breaks - so I have gone back to using my rat sniffer - I keep meaning to take the ct100 back to cpc but haven't gotten round to it - strange state of affairs because I have a battered old tester with rotary selector (silver? behringer?) which is still going strong though the rotary switch is starting to get a little wobbly. re shorting 2 to 3 sounding thin - I had no idea that was how a short like that exhibited itself - that means more than likely the short is at the desk end - it's a thomann multicore so not brill but has been ok up to now - and feels robust - actually its trailing cables feel chunky, are well numbered and it cuts about 3 minutes or so off the time it takes to wire up my old loudest.com multicore (in the cupboard). probably the thing to do next is ignore it, wait for it to happen again in the field and take apart the end of the multicore end in question - reassemble and see if it cures. then I WILL have to get the soldering iron out! Link to comment Share on other sites More sharing options...
timsabre Posted April 5, 2014 Share Posted April 5, 2014 A short between 2 and 3 sounds like silence. A break in either 2 or 3 (but not both) sounds thin. Link to comment Share on other sites More sharing options...
S&L Posted April 5, 2014 Author Share Posted April 5, 2014 A short between 2 and 3 sounds like silence. A break in either 2 or 3 (but not both) sounds thin. ah ok - so I am looking for an intermittent break. Link to comment Share on other sites More sharing options...
sam.spoons Posted April 5, 2014 Share Posted April 5, 2014 My mistake, of course a short would result in silence. Open circuit on 2 or 3 could still allow some thin weak sounding bleed via the remaining conductor and ground. Link to comment Share on other sites More sharing options...
Cheeseweasel Posted April 6, 2014 Share Posted April 6, 2014 When pins 2 or 3 of a balanced line are disconnected, the signal is still carried by capacitance between the broken leg and the cable shield - i.e. it has the effect of putting a high-pass filter in the signal chain, hence the weak, toppy sound associated with one-legged cables. Link to comment Share on other sites More sharing options...
Generalhammond Posted April 7, 2014 Share Posted April 7, 2014 I would re-solder the socket of channel 5 on the multi then cut the plug off the tail and refix further down the tail. Link to comment Share on other sites More sharing options...
kgallen Posted April 8, 2014 Share Posted April 8, 2014 When pins 2 or 3 of a balanced line are disconnected, the signal is still carried by capacitance between the broken leg and the cable shield - i.e. it has the effect of putting a high-pass filter in the signal chain, hence the weak, toppy sound associated with one-legged cables. That's useful, because for any meaningful cable capacitance between a core and shield, this would imply that the break was towards the source end. A break at the other (sink?) end would mean very little cable coupling and thus just a signal ~6dB down on expected. Maybe the amount of "thinness" can help work out how far through the cable unless the connector can be found to be at fault :P Link to comment Share on other sites More sharing options...
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