Dec 6, 2012 7:15 AM
Line 6 XD-V35 loud buzzing help needed!
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Jan 14, 2013 9:20 AM by
Johnny4x 
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.. tried last night switching power supplies.. made no difference
. Again though, you have sparked another theory... it looks like the power supplies are not earthed.. I'm guessing that could be the problem, but there is no obvious way of earthing the units.... if I can find a more robust and earthed 9v supply somewhere - ill try that! ... arrrgggg.....Cheers Ron..
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No need to mess with alternative power supplies, John...
Your swap has absolutely cleared them of any involvement.
(It was always going to be a long shot anyway, triggered by my experience with one such faulty switched-mode plug-pack that was superimposing a massive mains-frequency ripple onto what was meant to be its smooth d.c. output.)
Incidentally, to answer your query, there's no way you should ever defeat their lack of an earth pin by adding a "ground" or "earth" to any part of a system that features the sort of "fully floating" powering that's deliberately engineered into XD-V systems.
As I find it almost unthinkable that a new XD-V35 receiver should exhibit these symptoms as a fault, I'd suggest a "one component at a time" check, if you'll just bear with me.
That the problem only arises with phantom applied (and given that you've already tried a variety of XL cables) strongly indicates that it originates from some sort of "mis-connection" between the output of some device and its connection to your mixer.
Start with nothing at all connected to your mixer's inputs, but with its phantom power switched on.
If the buzz then returns on plugging in ONLY the XD-V35 receiver by itself, then I'm afraid your receiver does have an internal fault that will require attention (...warranty?) from Line 6, possibly via the "Contact Us" link at the bottom of this page.
I'm betting that it doesn't...
Which would lead us to methodically add your sources (subsequently powered and switched on) to your mixer inputs, but only one at a time, ...until the device that's actually causing the racket turns up.
The most likely culprits are unbalanced sources such as iPods, tablets, computers, samplers, sequencers and/or other replay devices connected via jacks or RCA plugs.
It's frequently the case that such an unbalanced device works really sweetly for years, ...right up until another power supply (such as for your latest radio mic) arrives and (as luck would have it) is physically positioned at the one spot in the entire universe that guarantees the perfect induction of mains frequency into the unbalanced device's cable to the mixer.
Aaaargh!!!!
The good news is that this type of problem is fairly easily solved by either
- Simple re-arrangement of the device's physical location, or
- Converting the offending device to being "pseudo balanced", by wiring its signal "hot" (tip) to pin 2 and signal "cold" (sleeve or shield) to pin 3 of an XL male connector (with nothing wired or "shorted" to pin 1) ...and running it into a suitably attenuated mic input.
Here's hoping.
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Hi John
That's a very curious problem. I suspect that your mic cables may have "pin 1" connected to the "shell". Can you measure with an ohmmeter from the shell to pin 1. This should give a very high ohm reading (in the millions of ohms). If it doesn't then there is a problem. Open up the connector and you should see a wire running from pin 1 to a u shaped lug on the top of the connector where the screw goes in. If it's there cut it.
Ron's idea of lifting pin 1 altogether should work as well but it's my second choice.
You don't need to worry about the power supply having an earth ground. It's designed to operate this way. It finds a ground through the audio connection (unless you use Ron's method
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Whoa! Hold up there, Gents...
Heartfelt apologies for not making it plain enough.
Just to be absolutely clear about this...
There's absolutely NO way I'd endorse the connection of any XD-V (or other balanced output equipped) receiver via the "pseudo-balanced" pin 2 & 3 XL adapter cable that I've suggested solely as a possible solution to buzz and/or hum emanating from other RCA or jack-plugged external sources.I'd also forgotten about the "rogue" (problem creating) XL connectors and cables that used to be supplied with the offending removable link that Don's so helpfully pointed to.
(I throw myself before the mercy of the Court, Your Honour, on the grounds that I've relied exclusively on Neutrik XL connectors for the last three decades or so.)
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Great "clue", John...
The DI has effectively isolated a rogue "signal earth to chassis earth" connection that we're now almost certain exists somewhere in your wiring of the V35 receiver to the desk.
The dreaded "earth loop" strikes again, exactly as Don and I feared.
While the DI is an effective temporary "work-around", I'm sure you'd rather not have it doing just this, so now we're looking for a short-circuit from a cable's earth to one of its signal "legs" (being those wired to pin 2 or pin 3 of the XLs in question) ...and in the event that no problematic "link" or "short" is actually visible inside the connectors themselves, maybe you have a cable that's been "spiked" or punctured, creating such a short-circuit somewhere along its length.
Using the "Ω" setting of a multitester (as Don's already suggested) is one way of quickly identifying the culprit, but if you don't have access to one of those, compare the sound of a phantom powered mic that delivers a nice "full and fat" sound via its own cable and desk channel with how it sounds connected via the V35's cable with the V35's "suspect" cable re-patched to that "good" mics input.
Faulty cabling will yield a lower-level and "thin" (lacking bass) sound from that "good" mic and input channel.
Happy hunting.
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Just so, Don...
But (regrettably) the malady isn't confined to the Orient.
My experience of cheap "ready-mades" tallies with both yours and the one Alan Hardiman's illustrated in the blog I've linked above.
Not only that, but I've found that the number of earthing "myths" out there almost exceeds the number of road crew personnel !
For the benefit of readers seeking clues from this conversation in respect of its "buzz" and "buzzing" tags, one particular anomaly (that took us an eternity to track down) arose from the use of a Canare dual-sexed XL stage box, (superb hardware) twenty of which we'd ordered pre-wired from a highly reputable pro audio supplier.
It turned out that whoever did the actual wiring went to a huge effort to ensure that a "buss bar" interconnected all of the number 1 pins, ...as well as interconnecting each and every "spare" pin of the single multi-way connnectors that would attach to the respective "spare" conductors of the ten superb Canare star-quad multicore cables we'd ordered with the stage boxes.
That was in addition to the "break out" from each of the star-quad cables' discrete earths being beautifully and dutifully soldered to its correct and separate pin 1.
(It turned out that there are still some so-called "textbooks" out there that encourage exactly this form of vandalism.)
The result: Some gigs entirely buzz-free, but with some gigs perplexingly requiring a bewildering array of earth-lifting, transformer isolation and DI arrangements for any clean audio to eventually be obtained.
THE MORAL OF THE STORY:ALWAYS keep every "pin 1" separate from any other termination whenever standard 3-pin XL connectors are employed for audio, without exception, ...unless (of course) you're seeking a particularly devious form of revenge on the recipient/s of those connectors.
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oh my word... I haven't a clue what I'm doing.. but you guys are sooo helpful - I do wish this had just worked out the box!
Anyways, I went over to the hall this afternoon, and chose a cable to butcher.. I opened it up, and saw an "earth" looking wire ... so cut it. Now I have re-read the post here.. and I'm not entirely sure thats what I was meant to do..
Plugged the unit back in - but still buzzed.
I even went to Maplin today (electronics store) and spoke to a knowledgeable guy there.. he told me most of what you guys are saying, but also suggested that the unit just didn't like Phantom Power (the mixing desk is a "Spirit" and phantom power is not per socket but on/off for the whole desk)
In addition, I pulled every input out of the desk today, and the v35 still buzzed when the only unit plugged in - but that was with my cut wire.. I need to do that again with a regular xlr, will get back re that!
Please don't lose patience! I feel I have more 'twiddling' I can do - I need to try moving the v35 away from the desk etc... so maybe there is still hope.
Pic attached of butchered cable (cut at both ends)
Arrg!
John
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Sorry John, for not being absolutely clear...
"Earth-lifting" (which shouldn't be necessary here) would require that the "shield" (the bare copper you've correctly identified) remain attached at the female (receiver output) end of the cable, only being cut to prevent "double-connection" (an "earth loop") to both the mixer's and the receiver's chassis.
What you've done is to convert your cable into a totally unshielded pair that's almost guaranteed to buzz,
...HOWEVER...
It looks very much as though the connector pictured above has the majority of its remaining (bare copper) shield wire hanging off the silver metal of its external "chassis", ...meaning that we now have pictorial evidence that it was, almost certainly, one of the earth-loop creators we've been looking for !!!
(Naturally, if all your cables are similarly constructed, they're all potential sources of similar problems with any gear.)
The correct "fix" involves configuring both ends of the cable so that the cable's bare copper shield can only come into contact with pin 1 and NO other metal whatsoever.
The pin 1 connection should be soldered as solidly as the other two pins, the normal technique being to reduce its length so that it's the shortest wire of the three, the reduction in length being for the sole purpose of ensuring that it absolutely cannot contact any metal other than its "own" pin 1.
An easier retrofit (for the XL connectors at both ends of your existing cables) would involve a really sharp set of side-cutters being used to "clean out" all of the excess copper shield that's connected to the chassis (flat metal) while leaving it soldered exclusively to pin 1 ...and then using a small strip of electrical insulation tape to fully insulate all of the bare copper that you've left attached to that pin 1.
Having done all that, your cables will (at long last) be CORRECTLY terminated such that they can successfully operate all of the gear in your inventory, whereas a special "earth-lifted" cable would not work with powered microphones.
As for the "knowledgeable guy" at Maplin, (trust me) ...he ain't.
Phantom power is so named because balanced connections (such as the XL male on the back of your receiver) can't "see" it. It should have NO effect whatsoever, PROVIDED the balanced wiring is correctly terminated...
...As you are just about to ensure.
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Hey John
Just think how smart you'll be in the future once you get this all figured out
My guess is that connector connects the ground wire (which you do need) to the shell (which shouldn't happen).
Do you have a cable that is made with real Switchcraft or Neutrik connectors?
Have you tried it in a different mixer?
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AARGH !!!!!!!!!!!!!
Sorry, Reason413, ...but your post perpetuates exactly the sort of earthing "myth" I was talking about earlier in this discussion and stands as a shining example of precisely the sort of "audio voodoo" that needs to be stamped out.
In any case, what better Season is there for a good burning at the stake?
(Ahem...)
As Don's so patiently pointed out yet again, your misunderstanding arises from yet more of those damn cables with the sort of dodgy wiring and assembly that I hadn't encountered for years, ...right up until this post, in fact.
Be assured that (as Don and I have indicated earlier) it remains a demonstrable and incontrovertible FACT that no audio equipment with a balanced output needs to "like" phantom powering, the very name of which is testimony to its irrelevance when correctly wired.
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Two pieces of good news, John !
- The holidays are great and
- You don't need "those exact cables", indeed well-priced ones can be sent to your door from (among others) either of these:
http://www.studiospares.com/leads-xlr/xlr-male-female-5m-lead-neutrik-china/invt/590140/
http://www.thomann.de/gb/cordial_cam6bk.htm
I've only included the genuine Neutriks on rugged cable from Thomann to give a price comparison. I've found that the "Yongsheng" Ningbo Neutriks, when assembled "Studiospares-style", (i.e. no spurious pin 1 to chassis shorting) work really well, as you'll see from other UK users' reviews on their site.
The other Chinese-made "budget" leads in their catalogue are indeed a few quid cheaper, but you risk being back where you started!
An online order placed today will probably be at your place before New Years Day, so (with any luck) a successful outcome may be part of your Happy Hogmanay.
Hae a wee malt or two for me, eh Laddie !
Slainte!
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Read this first:
http://producingforaliving.blogspot.com.au/2010/09/microphone-cable-wiring-101-connecting.html
Different balanced-output audio gear exhibits different earthing schemes.
(As Don Boomer has been at pains to point out, Line 6 have opted for a "fully floating mains-earth-independent" system that's analagous to being run from batteries.)
It is therefore to be expected that, when applying the "positive" side of 48v DC "phantom" power equally to pins 2 & 3, with its "negative" side being carried by pin 1, any cabling that INCORRECTLY (I'll say it again,
"INCORRECTLY" ...as confirmed by, among others, no lesser bodies than the Audio Engineering Society and the International Standards Organisation) attaches the negative side to the chassis in addition to its correct pin 1 destination, will draw a response (or not) that's entirely dependent on the earthing scheme of the actual equipment in question.So the good old Samson's trouble-free operation is indeed irrelevant ...and...
...we're FAR from being alone in "still blaming the cables".
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Great question !
Because, with nearly all microphones, (powered or not) their case is, in fact, already connected connected to pin 1 as a "shield" that keeps stray RF from affecting the mic's internal circuitry.
That's an entirely different application from connecting the output of another device that accepts external power while also sending signal via cables that have "phantom" DC applied to them.
You've put your finger on the fundamental root cause of the misunderstanding that gave rise to some mic cables being supplied with the very incorrect wiring we're talking about. Those cables will work very well with microphones of all types, but ONLY with microphones.
Accordingly, the only way to have an inventory of XL cables that will satisfactorily run all balanced audio gear is to "seek and destroy" any "pin 1 to case" connections in them.
May the force be with all who are on that noble mission !
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"In the finest traditions of the Service", Steve...
...Exactly as I've come to expect from Line 6 !
I am, however, wondering if Line 6's Quality Assurance section actually has any of the cheap and nasty "pin 1 and chassis-wired" cables in its inventory?
Given that I hadn't struck one for years, I was curious enough to "create" one before packing for a Seasonal gig yesterday and ...guess what?
Using it and applying 48v phantom power via the "global" switch on a variety of small mixers yielded textbook earth loop buzzing when it was connected to the output of any of my randomly-selected XD-V70 receivers, ...but only from some of those mixers.
I guess the most revealing analysis was provided by my tiny and "bulletproof" Sound Devices MixPre D, (a portable field mixer with comprehensive facilities) which would not ever yield buzzing from my receivers when just "on its own" being powered by its internal AA batteries.
When, however,
- Connected to some mains powered "downstream" systems ...AND
- It also had its Sound Devices "universal" mains supply energised and connected to its Hirose "Ext Power" connector,
would yield buzz on applying phantom to my "freshly butchered and dual-earthed" XL cable, (but only with some of those downstream devices) regardless of whether its front-panel "Power Selector" switch had it running from its internal AAs or external power.
Finally, here's hoping Santa is as good to you and yours as he's just been to me...
All the very best (and a hearty "Ho, Ho, Ho !") to all from Down Under.
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