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Odd popping sound
by unc417 on 2013-02-04 19:10:37

I have 7 v70 handhelds. A while back, I started hearing an odd and intermittent sound, initially I thought it was a bad guitar cable. I eventualy found the sound in 3, so far, of my handhelds.

I can't seem to reproduce it on demand, and it doesn't always seem to be at the same level.  I've gone through the trouble ticket process and hope to find some answers here instead.

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It'sa subtle popping sound throughout the clip.

1 of the receivers is on the original firmware, the rest have been updated to 2.02 I think it is.

Using RF1

Usually use the L6 model but have tested with the sm58 model too.

I have connected a flash recorder directly to the receiver using TS cable and still found the noise, otherwise I'm using xlr to the mixer.

Wifi is present and I was going to test with wifi being powered off but was assured by support wifi would not do this. Reception also has been perfect, no signal issues at all.



Re: Odd popping sound
by RonMarton on 2013-02-05 02:57:15

Having listened to your helpful sample, the fact of that "splat" being not only irregular, but also being evident in several handhelds seems really weird !

You're right, it does sound for all the world like a wiring-induced intermittency and I'm inclined to be with Line 6's support team in their backing of your original "gut feeling" that the problem's physical in origin ...rather than any artefact of the wireless transmission system.

None of which helps you !

So, with very little to lose, why don't we start by looking at possible "physical connection" issues ?

As it happens, there's a bit of routine maintenance that I've just done upon the "Anniversary" or "1st Birthday" of my V70 handhelds having entered service...

...and it's become a routine I've taken to doing annually on lots of equipment, ever since (back in the 1970s) the humidity of my coastal location (and, possibly, vibrations) caused the near simultaneous arrival of "splat", "shash" and "fizz" problems in many of our "first generation" of screw-on "multi-pattern-interchangeable-capsule" condenser mic systems.

  1. Carefully unscrew so as to detach the entire mic-capsule from the handheld's body;
  2. Dip a cotton "bud" applicator into eucalyptus oil (I am an Aussie, after all...) and "roll-squeeze" its tip against the bottle's side so only very little oil is "free" on the surface of the cotton "ball" at its end;
  3. VERY carefully polish (and VERY gently depress) the ends of the mic capsule's "pogo stick" pins with the ever-so-slighly eucalyptus oil-dampened end of the applicator;
  4. Be equally careful and gentle in then wiping along the concentric copper "ring contact" paths inside the transmitter's head with a similarly eucalyptus oil-moistened applicator;
  5. Use as many fresh applicators as it takes to finally return zero residue, then "towel off" the contact surfaces with an un-moistened applicator's end, prior to
  6. Finally (and very carefully) re-assembling the handheld/s.

Some use kerosene-based "WD-type" contact cleaners for this sort of work, but (patriotic considerations aside) I find that eucalyptus oil leaves less "dust attracting" residue on the contacts.

Both are equally water-repellent and corrosion resistant, but eucalyptus smells a whole lot nicer.

(Incidentally, diluted roughly 5 to 10 parts water to one part oil, it's also a great solvent for "liberating" the urethane "sponge" and metal components of mic windscreens from their accummulated dirt, while leaving a pleasant scent instead of the "beer and tobacco" odour that often infects hard-working vocal mics.)

Here's hoping that this effects a "cure"...



Re: Odd popping sound
by unc417 on 2013-02-06 07:19:13

Thanks. I'll try that.



Re: Odd popping sound
by unc417 on 2013-03-16 10:43:04

Sorry for the delay. I did the cleaning process you described but it has not made a difference.  Any other ideas?

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-16 12:42:18

Damn.

The sound in your sample definitely has an "analog" character to it, but I'm afraid its persistence after your "clean-up" of the handheld's internal contacts means you'll now need to investigate your entire signal path from sources to output/s.

It seems to me that the really hard bit will be "catching" it when it's actually persistent enough for a methodical "down the line" check that should commence directly at the back of a receiver while it is actually in the act of misbehaving.

This will require an entirely separate monitoring system to be "on standby", so that the offending receiver's XL output can immediately be transferred from its existing "normal" mic input to another mic input for interrogation, preferably at a high monitoring level, ...which will probably require the use of something like a headset hanging off another small mixer.

Should this set-up reveal the problem to be evident at receiver's back panels, I'm afraid all three of your affected systems will need to be the subjects of Line 6 service tickets, using the "Contact Technical Support" and "Open A Support Ticket" links that flow from the "Support" link at the bottom of this page.

(Given the difficulties you've had in "triggering" the fault, I reckon you may be without them for quite a while, as the Line 6 technical crew will probably need large amounts of both patience and luck to find the fault.)

If, however, (as I'm hoping) your three receivers prove to be "clean" at their back panel outputs, then some interstage connection or circuitry "downstream" is to blame.

I'd start with the "one by one" removal of any unbalanced (RCA or jack) gear that has its outputs connected to your system, in the hope that one such device is adding the offending racket.

Should that not prove to be the case, then more "instant" interrogations such as those I described for your receivers may subsequently be required.

These should be performed in "block diagram" order of the signal path, starting with a driving of the separate monitoring system from your mixer's "direct outs" and/or "pre outs", then methodically moving through a "loud" interrogation of every connection point.

Patience and luck would seem to be the watchwords once again.



Re: Odd popping sound
by unc417 on 2013-03-16 12:53:56

I've already gone through the trouble ticket system. They had no useful information to give, short of sending them systems in for investigation.

At my last band rehearsal, Wednesday, I was using 4 of the 7 systems. I noticed the popping sound in all 4, and maybe a coincidence, it seemed worse than it had ever been before.

I've never been able to duplicate this noise myself, by putting high levels into 1 mic at a time, at a midweek time when I have the auditorium to myself. It always seems to be when several systems are in use and high levels going into all of them. Perhaps another coincidence though.

I came to the forum rather than sending systems off to L6 because given the number of receivers affected, I'm not convinced this is an isolated issue. I believe it to be a design flaw common to most or all systems, not likely since nobody else seems to be affected, or something environmental.  I have no idea what that would be though.  Between the 3 systems mentioned earlier, and the 4 involved this week, I believe most or all of my receivers are having this issue.

It isn't coming from anything downstream, such as the console, because the recordings I made were made by connecting the recorder directly to the receiver output.

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-16 14:07:28

My apologies for forgetting the initial description of your clever flash recorder connection. Sorry.

I can confirm the "solidity" of Line 6's XD-V system architecture as I regularly use my two racks of four XD-V70s simultaneously at levels from conversational to heavy metal ...and very often have my one XD-V75 as a ninth contributor (mostly, but not always, set to RF1 as you do), but I've never experienced anything like this.

Given the timing between "plops" or "splats" and the unique transient nature of the sound in your sample, I'm now wondering about other microwave activity in your local area, ...specifically something that's not the more "normal" WiFi and/or Bluetooth that's routinely "laughed off" by the RF1 four-frequency scheme.

Could a local airfield, heliport, military or law enforcement base have upgraded its radar gear at the time your problems started ?

Did the problem commence when a microwave link dish "sprouted" from a local rooftop ?

Should something along those lines be at the heart of this issue, P180 directional paddle antennae orientated to back-reject an offender such as those could well help.

As you've upgraded to the later firmware and if you're unsure of such a source's existence and/or direction, it might then be worth spending half a day in the auditorium with all systems running to listen for a "splat" and your eyes looking for a coincident RF "spike" on a specially set-up receiver's "Channel Scan" display.

That "miner's canary" receiver would have just one (perhaps borrowed) stand-mounted P180 antenna connected, allowing you to aim it as a "direction-finder" to help locate the compass bearing, if not the exact source, of such spurious RF. 



Re: Odd popping sound
by unc417 on 2013-03-16 19:13:02

This is a very rural area, there are no commercial properties around like what you mention nearby.

I'm also in a concrete building if it makes any difference. The handhelds completely stop working as soon as I move into another room. 

I would be willing to do that experiment, if I knew of a p180 around that I could borrow.

Again, is it a coincidence that I've only ever found the splat when multiple systems are running with fairly high levels? I've never been able to find it with just a single system running.



Re: Odd popping sound
by RonMarton on 2013-03-17 02:50:50

"I'm also in a concrete building if it makes any difference. The handhelds completely stop working as soon as I move into another room."

That vital information rules out external radar or microwave, as any that was strong enough to penetrate your set-up would most likely be on the verge of "cooking" anything that lives outside, ...leaving aside the fact that such an operation would also be illegal to the point of felony.

So now we'll need details of

  1. The deployment of your receiving antennae. What type, how many, physical locations and method of connecting to the receivers.
  2. Does each receiver operate from its own dedicated Line 6 "wall wart" power supply and if not, are you certain that each has access to half an amp (500mA) of ripple-free and regulated 9 volts D.C. ?
  3. Whether or not you routinely operate all of your transmitters on high (10mW) power.

If the answer to (3) above is "yes", a trial with all of them operating in "Battery Save" may prove worthwhile, provided your receivers' front-panel diagnostic LED columns indicate that the lower power is enough to deliver solid RF at "showtime".

My reasoning is that anything that attenuates RF is also capable of reflecting it.

So, given that you've observed definite attenuation from material in your walls, the more RF you "spray" at them, (more transmitters switched on, each "spraying" RF at higher power) the greater the likelihood of multiple reflections creating truly weird cancellation and re-enforcing "nodes".

It's just possible that the cumulative and highly random effect of such re-enforced nodes hitting your receiving antennae may be "swamping" the receivers' RF input stages, especially if those receiving antennae are physically close to a wall or corner.




Re: Odd popping sound
by unc417 on 2013-03-17 18:37:31

1.  I have 2 antenna chains.  The standard included antenna connected to 2 receivers, one a chain of 4, one a chain of 3.  This is using the included rg59 cables and terminators on the last receivers. I considered buying paddles initially, but with my setup I never have anything less than 5 green signal led's so I decided to save my money and skip the paddles.  The individual A/B reception bounces a little bit, but the led's are always solid. The antenna are about 10 feet in front of the back wall and about 6 ft off the floor.

2. Each receiver is using it's own included wall wart.

3. I always use power save.

That makes sense about reflecting signals, but I can't be the only one using these mics in a block wall environment? My analog sennheiser and shure gear haven't had any issues like this, I don't know if their lower frequency would make them more or less suceptible to this though. If you are correct and this is a result of rf multipath, wouldn't I hear the splat regardless of audio level going in to the mic?

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-17 19:46:33

"That makes sense about reflecting signals..."

Not any more, it doesn't !

Not radiating just 3.3mW with receiving antennae hundreds of wavelengths away from any possible reflectors, ...unless, of course, yours is the only auditorium on planet Earth with a steel mesh and checker-plate floor and ceiling, ...or someone's taken to wearing aluminium foil.

Based on your excellent reception in "Battery Save" mode, I'm also heartily in agreement with your decision to forgo the expense and complication of paddles.

As to the level of audio affecting the splatting, to my mind that can only be relevant to something analog, hence my query about possible power-supply induced current starvation, something that your use of individual wall warts has also ruled out.

I reckon that those wall warts should also prevent such artefacts coming in via the mains ...and that carrier frequencies are most unlikely to have any bearing on the matter.

"If you are correct and this is a result of rf multipath, wouldn't I hear the splat regardless of audio level going in to the mic?"

Possibly not, given the nature of digital "silence" and/or the likely elimination of random contributions via the encoding process.

"A very rural area"...?

...Hmm...

A real long shot, but we're at the "desperate" stage here.

Any electric fences working close by, such that their "earth stake returns" may be coupled via the building's earth to the mixer and PA systems' grounding ?

That way the "splats" would always be there, but would require the "un-muting" of several low level systems for the cumulative effect (of them "traveling back" up the signal earths) to eventually be heard. 





Re: Odd popping sound
by unc417 on 2013-03-17 19:55:23

No, no electric fences nearby.

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-18 10:21:15

I've now had the chance to raise this in a "brainstorming" session with four really experienced broadcast-engineering members of the TV Outside Broadcast ("Remotes") crew that have been both colleagues and friends of mine for decades.

On hearing about the issues we've already covered, they remain as mystified by this as you and I are, ...with just two suggestions for further investigation.

First, one from the Broadcast Engineer whose specialty is microwave link systems. He suggests that I ask you whether any BNC connectors in your LMR-195 antenna wiring may have their outer shells in contact with support (or other) metalwork.

Even though I pointed out that the pains you've taken to follow Line 6's recommendations "to the letter" make this highly unlikely, we all agreed that there'd be no harm in checking such 'basics" anyway.

The second concerns the "health" (or otherwise) of the AC mains power to your entire audio rig.

I'm sure you'll share our feeling that it would be crazy to spend hundreds of bucks on a "computer grade" AC power conditioner with enough isolated and filtered mains outlets for all of your amplifiers, your mixer/s and all devices connected to it/them ...when doing so may not solve the problem.

We just wonder if anyone in your community may

  1. Have such a device for their home or office multimedia set-up and
  2. Would be willing to "power down" and lend it to you for a session of testing.

The team's third suggestion only applies if either of the first two effects a cure, in which case they suggest I send you a bill to cover the cost of our beers.



Re: Odd popping sound
by unc417 on 2013-03-18 20:28:38

No, there is no contact on the shells.

I have a power conditioner for the mixer and other equipment, but because of the number of outlets and the number of devices I have, the receivers are not on it.  I can change that.  Does it make any difference if I use a power strip or must each receiver have it's own receptacle on the conditioner?

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-18 21:30:13

As I thought, all seems correct with your BNCs and short lengths of LMR-195 coax.

Even better, a tiny glimmer of very faint light may now almost be visible at the end of this seemingly interminable tunnel.

Theoretically, the earth-independent wall warts powering the receivers should not require any form of isolation (as you currently have) and so them being "paralleled" from a common power strip should be irrelevant and/or present no problems of any kind.

All other things being equal, the "normal" procedure for most sensitive equipment would be to have every device that has an earth pin run from its own independent, fully isolated and separate outlet of the power conditioning device...

...BUT...

NOT audio systems.

It is indeed good practice for audio gear to have the protection afforded by a device that protects it from variations in voltage and frequency, as well as from the spikes, superimposed switching signals, splats and "spurgles" that may arrive through the mains wiring...

...however...

Earthed mixers and the "input-related" gear immeditely connected to them (sources, outboard effects, replay devices etc.) MUST all derive their mains earths from the same point.

The standard way of doing this is to first ensure that the power conditioned outlet that's to feed them is capable of delivering enough current (usually a "no brainer" as input-related devices draw very little) and then to have all of those devices powered in parallel from the one receptacle via power strips.

(Part of the reason for running "earth independent" balanced audio signal wiring to the more current-sapping power amplifiers or powered speakers is that those are then able to be powered and conditioned from points closer to where they "live".)

From what you've just reported, it now seems possible that your current powering arrangements may have some of your input devices deriving their earths from different points, being different outlets of your power conditioner...

...which could be compromising the RF shielding of the devices in question via routes such as earthed chassis and/or signal wiring.

Here's hoping...



Re: Odd popping sound
by unc417 on 2013-03-18 21:40:09

I should have included the specifics of the current setup a little better. Just to be sure we're on the same page:

The a/v installers mounted a heavy duty (not sure of the model specifics without looking) power strip in the desk, which is plugged in to the wall outlet. This is a dedicated receptacle on it's own 20amp circuit.  The rack mount conditioner is connected to the main power strip. The line6 power strips are then also connected to the same main power strip.

Are you suggesting I should move the line6 strip to a receptacle on the conditioner?

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-18 21:44:07

Does the rack mounted power conditioner itself have only one outlet that then feeds all the other gear via power strips ?



Re: Odd popping sound
by unc417 on 2013-03-18 21:48:56

The rack mount conditioner, with 8 receptacles, is nearly full. It is powering the mixer, outboard preamps, cd recorder, a couple sennheiser analog receivers.



Re: Odd popping sound
by RonMarton on 2013-03-18 22:03:37

Right, eight mains outlets (receptacles) on the rack-mounted power conditioner...

Which may or may not have earth isolation between them, ...so...

Assuming there's no power amplification in your mixer, try a possible re-allocation of your earthing by "cascading" as many power strips as you need to power all of the input-related gear you've just mentioned (including all radio mic receivers) from just the ONE outlet receptacle of your power conditioner.

(There's very little chance of an overload as their total current consumption should be well under that outlet's rated maximum.)



Re: Odd popping sound
by unc417 on 2013-03-19 08:27:00

It's a eta pd8l. I had planned to replace it with a Furman PL-8C this year but other expenses came up and it wasn't a very high priority. I'm not familiar with that brand but we used a reputable a/v installer and I've had no reason to believe it to be an inferior unit.

It is not a powered mixer, it's digital also.

I'm not sure I understand. You want everything, mixer, receivers, cd recorder, the entire desk powered off of a single outlet on the conditioner? 



Re: Odd popping sound
by RonMarton on 2013-03-19 12:57:32

ETA Systems are part of MiTek.

I'd not bother replacing their EPD8LR with the Furman PL-8C, as (to my mind) the improvements you'd notice would largely be cosmetic.

Here's the way I'd have arranged the power distribution allocation, which is the scheme that I'm suggesting you now try:

ETA PD8L 15 amp rear socket #1 to have a multi-outlet power distribution strip (or strips) connected to it.

The following input-related devices to be powered from the outlets of those distribution strips which receive their conditioned and protected power from that first rear panel socket of the ETA PD8L:

  1. Mixer.
  2. Any or all external pre-amps.
  3. Any or all outboard reverberators, delay and/or sound effects units, graphic equalizers and similar processors.
  4. Any or all record/replay devices such as CD, DVD, BlueRay and/or video systems.

The PD8L's remaining seven rear outlets to be used for sensitive devices that are either

  1. Guaranteed to have earth-independent balanced XL male connections to the audio system, such as your Sennheiser and Line 6 radio mic receivers, OR
  2. Are NOT in any way connected to the audio system, such as monitors, computers and/or visual display units. 


Re: Odd popping sound
by dboomer on 2013-03-19 16:37:31

Can you try switching to RF2 mode and checking to see if the popping continues?



Re: Odd popping sound
by RonMarton on 2013-03-19 16:42:30

...And preferably before you've gone to all the trouble of re-building your mains-powering "world".



Re: Odd popping sound
by unc417 on 2013-03-19 16:47:05

I will rearrange the power connections as it was suggested.  I am reminded of the Christmas Lights connections on Chevy Chase' Christmas vacation....

Yes I can use rf2. Although I am using wifi in the facility. The AP is about 10 feet from the receivers.  Do you anticipate problems? I can shut the wifi off for a couple services if needed. Some congregation members may be inconvenienced but troubleshooting is more important. 

Thanks



Re: Odd popping sound
by RonMarton on 2013-03-19 23:59:05

" ...and checking to see if the popping continues?"

Is the main point of Don's very clever suggestion of listening to find out if a total switch to RF2 clears the problem.

Although I've never experienced problems (nor have other 2.4GHz users reported problems to me) when access point base stations and/or mobile devices have been more than a metre or two (3 to 6 feet) away from my XD-V transmitters and/or receivers running RF1, ...it may still be worth trying a shut down of that local access point, just to "eliminate it from our enquiries, Sergeant".

Incidentally, my suggested change to your powering arrangements may well bear fruit in the future, when other "semi-pro" or "domestic" audio gear arrives to be fed into your console.

I've often taken to labelling a " future expansion" power strip (with "spare" outlets available) that's running from the "common earthed" primary output of such power conditioners as being for "Audio Gear Only".

Following your excellent suggestion, I will also add a sign to such installations that reads "Not For Use By The Griswold Family".




Re: Odd popping sound
by dboomer on 2013-03-20 12:38:21

Yes I can use rf2. Although I am using wifi in the facility. The AP is about 10 feet from the receivers.  Do you anticipate problems?

Not if you scan and find open channels.




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