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That sounds like the RF is dropping in and out, and you can hear some of the artifacts from the error correction which the receivers seem to employ when the signal strength is low. Have you been able to keep an eye on the RF LEDs at the receiver during the singing? Has anything changed with antenna placement, or are there more WiFi networks in the area than normal perhaps?

Hi, I've posted regarding this several times in the past, but never really managed to get a straight answer, so, a year or so later, I have my fingers crossed..! I run 14 XD-V75 receivers and TBP12 beltpack transmitters, and also have a few handhelds. I've never had any issue with the handhelds, but have had the same issue with the beltpacks from the very beginning. They're unusable in RF1 mode because you get a weird digital error-correction type artifact intermittently on the audio. This occasionally happens in RF2 mode as well, but very rarely, so I just use them in RF2 mode. In either mode, some of the beltpacks give a high pitched whine - regardless of what mic is connected, or even if there's no mic connected. If you ground the transmitter by pressing it against your body, the whine disappears (and audio still passes perfectly fine). All 14 are very early XD-V75 units (apparently from the first ever batch manufactured), and went in to the UK support centre a while ago to have the plastic TA4M input connectors replaced (because the locking notches had worn away), and they were unable to fix the whine issue at the time. Since then, a Line 6 rep posted a while back saying that it was a known issue, and involved replacing a resistor and potentially another component on the TBP12 mainboard. I did call the support team after I'd seen that message, but the UK guys weren't aware of the 'known' problem or fix. So, was there a known fault with the early TBP12s which caused this problem, and is there a definite fix?! Or are there people out there with more recent TBP12s which still experience the same noise? For reference, the receivers are all racked correctly with an XD-AD8 antenna distributor, and P180 and P360 antennas.

Hi Daan, I've reported this several times on here and to tech support, but never really managed to get anywhere. We actually have 14 XD-V75s, which all (apart from one which was replaced recently) have the high-pitched whine to varying extents. As you say - it depends whether it's touching skin or not, and you can silence it by completely cupping the transmitter in your hand. If you want to make it really loud you can put the transmitter right next to the receiver rack! I was told it only affected early V75 units, but obviously that doesn't seem to be the case. I was also told on this forum that it was a known fault, and required a small modification to the beltpack with a resistor added, and some sort of extra shielding where the antenna connects to the mainboard. However, every time I've spoken to Line 6 support in the UK, they've denied all knowledge of this being a known fault, and stated they've never seen it before. I even sent all the transmitters in to their UK centre, who claimed they couldn't find anything wrong with them. If anyone from Line 6 is reading this and willing to finally resolve it, please let me know! I can confirm that shorting pins 4 and 3 doesn't help. Thanks, Daniel.

Hi, That was my feeling given that Don says the whine fix may involve changing some resistors. I guess that might explain why more people aren't encountering the issue - if it only affects early units. I've been using all 14 in RF2 mode this week with various mics, including several scenes with all the mics on stage at the same time. No distortion problems at all, and luckily there was no WiFi in the building anyway, so RF2 mode worked fine. The whine was noticeable on quite a few of the transmitters, so I still need to send those in to the service centre in Rugby for the fix, although when I spoke to them last, they didn't know of the issue or what the fix is. Like Ben, the new pack I bought has no whine whatsoever.

Hi Don, Ah I see. Shame the service centre didn't fix the issue the first time all the packs were sent in, but nevermind! I'll get them all sent back after Christmas when things calm down. Most of mine whine all the time, even when you're not touching the pack at all. It does get significantly worse when you touch near the antenna or input jack though. I agree it's less of an issue on higher-output mics (the Line 6 lav included), but on low-sens Countryman B3s/4060/MKE2s it can be heard during quieter passages.

I've still not had much of a chance to play around further, but I'm due to use about 12 channels for a show next week, so we'll see how it goes! I'd rather fix the whine issue here than send all the packs in to the service centre - Steve/Don, do you know where this spacer gets inserted to stop the whine? Is it to stop the little round metal post from conducting between the RF board and the main board? Thanks, Daniel.

Hi Steve, Thanks for the reply. It definitely happens with red band B3s - mine are all red band low sens versions. It does it with the blue band B6s as well (very low sens). Interesting theory regarding the current - that might explain why it can be intermittent, and perhaps doesn't happen in sound check when the batteries are straight out of the packet. Could it also be the case that the transmitters draw more current in RF1 mode because of the extra RF being generated? That could explain why switching to RF2 fixes it. Any specs available for how much juice the V75 transmitters are able to supply to the connected mic? I'm away at the moment, but I'll investigate further once I get back. The receivers are all just mains powered from the originally supplied adaptors. Thanks, Daniel.

Don, is it not likely that Andy has the same problem with the early transmitters that I have with mine? A high-pitched whine that varies if you touch the transmitter casing and disappears if you cover the majority of the casing in your hand, and is present regardless of a cable/mic being connected or not... sounds exactly the same as the problem I've described before. Daniel.

Hi all, I'm hoping to get time to do a more scientific test with set signals next weekend so that we can try and narrow down exactly what the issue is. I'll do recordings with varying numbers of transmitters switched on to see if that makes a difference. Josep, mine are V75 units, so swapping to those is unlikely to improve the situation for you. I personally still think the problem occurs with increasing RF traffic, which is probably why switching to RF2 mode fixes it. Most buyers seem to be either handheld users or guitar users - both probably only using a handful of channels, and I'd imagine that's why there are few reports on the forum. There are actually a few other times when this has been mentioned in threads, but it's always either been dismissed as user error, or the original poster hasn't followed it up afterwards.

Hi Don, We haven't, although I've had the same issue in schools, theatres, churches, etc, and I can't think of any common equipment which could have caused interference. I need to spend a good few hours with the receiver racks and transmitters over the next few days and try to work out a more scientific way to reproduce the issue with a given set of test tones. Then any artifacts will be obvious by comparing the original file to a recorded output from the receiver, and that's much more feasible for someone at Line 6 to repeat and evaluate. Clearly there must be some specific set of circumstances in order for the problem to materialise, otherwise you'd have many more customers experiencing the issue. Most of our systems were TR versions without a mic, but I do have two of the cardiod lavaliers that I can try - I've never used them because they're obviously not suitable for musical theatre anyway. The serial numbers I posted... are they early units? All from the same batch? If touching the transmitter in a certain way, or holding it close to the receivers, results in RF interference affecting the audio output by way of a high-pitched whine, surely it's not inconceivable that it could also be introducing other artifacts during singing..? RF1 presumably generates a lot more RF traffic, especially with 12 channels in use at once, so that could explain why the problem is either non-existant or much less prevalent when switching to RF2.

Hi Don, I appreciate that - those recordings were just what I had available, and they do demonstrate the issue quite clearly. When I get a chance, I'll happily send some suitable test tones to the transmitters and see if I can replicate the problem. I do feel there's enough information in this thread now for someone at Line 6 to have a concerted effort to replicate the issue at your end. Ben, absolutely - the red clip LED on the transmitters doesn't illuminate when the issue is present, and the receivers never get anywhere near clipping based on the LED indicators on the front. I agree that those capsules simply don't overload unless you scream into them right next to the mouth. I would have agreed that it's likely to be heavy RF that causes the problem, but as I said, it's happened now with just two packs and receivers powered on at a show. It was at a church in the middle of nowhere, with no telephones lines, nevermind WiFi. Puzzling...

Thanks Don - sounds like an easy fix for the whine if that is the cause. Back to the distortion, here's some random short clips from multitrack recordings so that you can hear the problem. Example 1 and Example 2 are from different beltpacks, different receivers, different venue, different day. With Example 2, I then switched all the transmitters to RF2 in the break and we repeated the song before continuing with the rest of the rehearsal. All of the transmitters behaved perfectly after that. Our capsules are a mix of Countryman B3 red-band, B6 blue-band and Sennheiser MKE2 - same issue happens with all. Example 1 is with an MKE2, Example 2 is with a B3. The recordings are pre-fader, so no EQ, compression, reverb, etc. I've normalised the files and saved to MP3. Let me know what you think. Daniel. Example1.mp3 Example2-RF1.mp3 Example2-RF2.mp3

Hi Don, I've not had a chance to test just a single unit yet I'm afraid. We had a concert set up on Saturday evening using two beltpacks in RF2 mode and all was working fine. In the interval, I quickly switched them to RF1 and asked the singers to repeat one of the songs they'd just done as a test, and the distortion was then present straight away. I agree that it's hard to diagnose when everyone is reporting different scenarios. I know that I've definitely never experienced the issue in RF2 mode, even using all 14 channels at once. Granted, perhaps that's due to some other external factor, and perhaps the issue can occur in RF2 mode under certain circumstances. Josep - were your units definitely in RF2 and not RF1 when you noticed the distortion? Don, are you able to share what exactly causes the high-pitched whine on the early units? Is it feasible that it could be linked to the distortion issue? I'm curious as to why switching to RF2 gets rid of the whine. Our transmitters are: D510M6149001038 D510M6149025041 D510M6149014847 D510M6149016001 D510M6149001250 D510M6149017817 D510M6149017770 D510M6149014687 D510M6149017701 D510M6149017497 D510M6149017633 D510M6149015028 D510M6149017428 D510M6149022248 I did speak to Dietmar on the UK support line, and described the high-pitched whine issue, but no-one there seemed to be familiar with it. They have agreed to open an RMA to have another look at the units, so I'll send a couple of transmitters in this week. I'm sure we'll get to the bottom of it eventually! Thanks, Daniel.

Hi, I've now confirmed the issue exists even with just two of my packs running simultaneously in RF1 (with the others turned off). Anacondaq, it certainly sounds like you have the same problem. Do you also have the high-pitched whine from your beltpacks in RF1 mode? (happens with or without a mic connected) Daniel.

Oh mine all do that, but only in RF1. If you encase the transmitter completely in your hands the noise disappears (and not because the signal has dropped out!)

Hi Don, What were the symptoms with the issue your colleague mentioned?

Hi, My understanding from a previous conversation with Line 6 UK is that they were all manufactured on the same day, and they're some of the very first units. One of the serials is 21D510M6149017701, another is 21D510M6149001038. If I give the UK team a call, are they likely to be aware of the issue? All the transmitters have already been in for repair with them once, and they didn't seem to be aware of any such issues. Thanks.

Hi Don, I did another show with them over the weekend, so I had time to play around with them a bit more. 100% - if the transmitters are in RF2 mode they never clip and generally run perfectly (there wasn't much interference, plus the antennas were side of stage, so all 14 channels worked reliably without any drop outs). Once I switched to RF1, the first thing that was obvious was a high-pitched whine on some of the transmitters (with or without a mic attached). Some were still silent, but the majority had a whine to some extent. As soon as there was any reasonable level of singing, the various channels started to clip/distort (sounded like digital clipping to me, but I know you're not convinced!) seemingly without any pattern as to which would distort and which wouldn't. Swapping capsules around didn't help - the issue was definitely with the transmitters. I also noticed that if you hold the transmitter in your hands so that as much of the casing as possible is covered, the whine disappears (and it hasn't dropped out of signal). Back to RF2 and the whine was gone, and no distortion. It seems like there has to be at least 3 of the transmitters turned on before RF1 mode causes issues. Any thoughts?! I suspect the answer might be to call in at Line 6 in Rugby one day and demonstrate the issue.

Hi, Don - the transmitters in use weren't close to the receivers, and 4 sat on the table weren't in use, and again weren't near the receivers. I understand what you're saying, but surely that would only affect the RF performance anyway, I wouldn't expect it to alter the audio path. Plus this has happened on several occasions when the positioning has been different anyway. Sheriton - when I was testing with a random pack the following day, only that pack was turned on, so there wasn't anything still using RF2. I've finished the current show now, so when I get a moment, I'll set everything up at home and test a bit further.

Oh it's a pretty horrible sound! I've got multitrack recordings of various shows it's happened on, so I'll put a link up to a short section tomorrow so that you can hear. Sounds digital to me. The set-up during that particular test was 6 receivers powered-on (with 2 pairs of antennas serving 3 each), 6 transmitters powered-on with Countryman B3 red bands connected. 4 were sat on a table (across the room from the receivers), 2 were fitted to cast (on channels 1 and 3). XLR outs from receivers were going into an M7CL on this occasion. The problem was apparent pretty much as soon as they started singing. Unlocked the transmitters, switched them all to RF2... perfect, so we started the show. The following day I tested them again and they were fine, switched one transmitter at random back to RF1 and it started distorting again when I spoke loudly. Back to RF2 and it was fine. So no, I can't definitely say that it happens if you only use a single unit, but I'll certainly test that out next. It seems unlikely that this can be affecting all V75s, because surely we'd have heard more about it on here from other users by now. I did find one other post from someone who had what sounded like the same issue, but they didn't follow it up. Luckily this venue had no WiFi at all, so RF2 was perfectly fine in terms of reception anyway. In busy theatres we'll need to be able to use RF1 to get a full 12 channels working reliably.

Hi, I discovered something fairly alarming this evening... I've posted a few times regarding the distortion (sounds like digital clipping to me) I get with our set of 14 XD-V75 beltpacks. Trying to diagnose the issue has been tricky, and I'd given up to be honest. It seemed completely intermittent, and wasn't helped by the fact that I'm always in different venues, using different combinations of microphone brands, some shows using more channels than others, etc. Initially I thought it was related to the Countryman mics only, but it turned out to affect others too. Then we sent them in to the UK support guys to take a look at, but they couldn't find any problem. Then I thought I'd fixed it by shorting pins 3 and 4 on all the mics. The clipping only occurs when the talent is singing reasonably loudly (as I've said before red-band Countryman B3s in the forehead position) - I've not noticed it just during dialogue. Receiver normally only has 1 or 2 audio level LEDs lit, and the beltpacks never display the red clip LED when this is happening. I've finally figured it out though. I'm aware that everyone will think this can't possibly be the issue, but I spent a while testing this with different beltpacks, different channels, and it's definitely the cause. Basically, in RF1 I get the clipping. In RF2, they're perfect. Perfectly repeatable by switching backwards and forwards between modes. Whenever I use 12 channels or less, I always put them in RF1 mode. I've just loaded up the show files for recent shows I've done, and every one when I was using the full 14 channels (so in RF2) didn't have the signal clipped. Everything has the latest firmware loaded. So... any thoughts?! Don?!

Steve, You might also want to check that the Dynamic Filter option is turned off on all the receivers, just to rule that out. As Don said, are you sure that they're 20db down at points, or have they just dropped out completely?

The B3s we have are all red-band versions, and the B6s are blue-band, which are even less sensitive.

That's not in the show yet as far as I know ;) I'll pay closer attention to the mics during next week's show, and hopefully at least work out what factors change between the channels that do distort and the ones that don't. I've tied pins 3 to 4 on every beltpack now anyway to lower the resistance. Didn't notice any difference in level whether those two are connected or not though. If nothing else, I'm at least now very familiar with the insides of those beltpacks, especially the little battery cover springs!

That's what I thought... which isn't going to happen with a microphone! Very strange.