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XD-V75L Hiss
by tccc on 2012-05-12 07:32:15

Hi all,

Racked up the full 14 V75 systems last night ready for use in the theatre night week, came to test them out with all the beltpacks up and running, and noticed a slight hiss on every channel when connected to the mixer. Admittedly it's when there's quite a bit of gain applied, but if it was at a volume to record a conversation from some distance away, you'd hear it (I know this isn't a likely use, I'm just giving it as an example!)

Initially I thought it was just the lavalier, so I tried another and it was the same. Then I disconnected the mic completely, and the hiss was still there. Connected a standard mic straight to the mixer channel to check that it wasn't just preamp noise - totally silent even with full gain.

So, thinking it was somehow related to having all the power cables and XLR looms cable-tied inside the rack, I removed one receiver and just connected it straight to a mains socket using one of the supplied Line 6 9V adaptors, and a single (short) XLR cable going straight to the mixer - still the hiss is there. If you leave the receiver on, and turn off the beltpack, silence again...

Any thoughts?! Can someone else (Ron?) verify if this hiss is just the nature of the kit? I'm not really expecting it to be an issue in normal use, I'm just surprised that they're not totally silent given the technology.

Thanks!



Re: XD-V75L Hiss
by dboomer on 2012-05-12 10:38:22

Well nothing is totally silent, but they are about 10dB quieter than any other wireless units.  I'm assuming you don't have any XDV hardware issues as they all are acting the same.

A lot will depend on how close to the mouth you can get the lavs.  You could also try boosting the output in the receiver, in the setup menu.

Are the power supplies for the receiver and for the mixer on the same service?  Do your clear cables have the shells connected?

There's gotta be an answer.  Please stick with me and we'll solve it.



Re: XD-V75L Hiss
by tccc on 2012-05-12 11:06:25

Hi,

Thanks for the quick response on a Saturday! Yes, I've tried multiple beltpacks and receivers, so, as you say, it can't really be a fault as such. I've tried boosting the receiver output, but this also boosts the 'hiss'. I've tried connecting the mixer and the receiver to physically separate mains rings just in case, but it's still the same. The mains adaptors are all as supplied by Line 6, with the filters still attached. I am using euro to UK plug adaptors, but I can't see how that could affect it really. I also have 3 which were supplied with US adaptors, and these are the same too.

All very strange! I can't see it being an issue in the theatre, as the lavs will be in the hairline. I was just quite alarmed at how much background hiss there was compared to a wired mic, and I could have sworn that the hiss wasn't there when I first tested the units at a small concert last week! I've even just tried separating two of the receivers (they were rackmounted using the joining strip, etc) but it made no difference. Puzzled!

I know it's hard to compare volumes, but basically, connected to a Yamaha 01V96, with the preamp gain set halfway, and the channel and main fader at 0db, you can hear a reasonably loud hiss when the beltpack is on, regardless of whether a microphone is connected. Pressing the mute button virtually elimates the hiss.

Anything spring to mind?!

Thanks.



Re: XD-V75L Hiss
by RonMarton on 2012-05-12 17:30:39

Sorry about the zone-related time delay of this reply, Theatre-Hissers...

...But I'm hoping  that something I've noticed in adapting and connecting my huge variety of sources to TBP12 belt-packs may be of assistance.

(Click on the pink pic at left for details of my rig.)

Being all in the bit-mapped digital domain, the processing inherent in these belt-packs isn't the dreaded "Automatic Level Control" compressor of analog gear, nevertheless one of the (very few) artefacts I have regularly observed sounds remarkably like the automatic application of a staggering amount of gain in the absence of "identifiable" (hence encodable) signal waveforms being input at "decent" levels.

If you thing the hiss with nothing connected is objectionable, you should hear the racket when an unterminated XLF (mic socket) to TA4F (belt-pack socket) adapter cable is moved around or "scrunched up", ...it can range from a deafening "waterfall" to an entire avant-garde soundscape !

Now, despite me being an almost lifelong Yamaha fan, their early 01/02 "V" and "R" consoles did have some of the noisiest, dirtiest-sounding and nastiest-clipping mic preamps I've ever experienced, in keeping with the ongoing paucity of their cumbersome, tiny and hard to read LCD menu navigation, ...none of which is relevant to this discussion.

Nor is Yamaha's subsequent reaction in endowing subsequent generations of their mixers with industry-leading sonic transparency and clear, ergonomic operation, at prices relatively far lower than their predecessors.

(If your thinking, however, that I'm hinting at replacing an old 01V as soon as money allows, ...you'd be damn right ! Yamaha LS9's are like 01V's on stereoids, ...only much sweeter-sounding, staggeringly more powerful and far easier to use.)

http://www.yamahaproaudio.com/global/en/products/mixers/ls9/

(When dreaming, ...why not dream BIG ?)

While we're ruling things "out", you've done a great job of proving that mains supply and rack (or any other) wiring also have no bearing on this artifact.

Which brings us back to your fabulous MKE-2 mics, or, to be more specific, quality of sound from their TBP12's and their XDV-75 receivers when they're actually being fed spoken word, as distinct from merely picking up ambient room noise.

Betcha that you won't hear anything other than the performance, the whole performance and nothing but the performance, while an actor is actually speaking.

Nor will any "pumping" or "breathing" of ambient noise be audible between speeches.

It's just that this form of bit-mapped digital input processing renders obsolete the old analog starting-point estimation technique of "preset the input trims till the room noise sounds about right".

Speaking of room noise, I've found it well worth experimenting with the XD-V's "Environment" settings in rehearsal, particularly when given simultaneous overlapping contributions from large numbers of participants. (Yes, I do hate teleconferences.)

I've found "Environment" to have been a really useful tool in such situations, once you're used to adjusting the gains upwards upon switching in the harsher "Speech" mode in the event that you decide to employ it for almost automatic "multi-gated" mixing.

It is, however, much more than just a "gate", ...playing with it being by far the best way to evaluate its dynamic, multi-parametric operation and its consequent appropriateness (or otherwise) for your individual situations.



Re: XD-V75L Hiss
by tccc on 2012-05-12 18:11:32

Hello again Ron!

To be honest, I've been sat here trying to test my newly-racked suite of 14 XD-Vs on my own, and it's remarkably tricky to do so with only yourself available to speak into the mic! In the end I resorted to playing music in a room (fairly loudly), and placing a couple of beltpacks (some with MKE-2s, some with cheap lavs) and then heading back downstairs and listening to the channels on headphones. Obviously an awful lot more gain is required when they're being used on an ambient basis like this, but the hiss was quite noticeable there, both when the signal was silent and when music was playing. I'm just wary that everyone else seems to comment on how quiet and clean the V70/V75s are, so I'm wondering if something is going amiss!

I did notice the compressor/gate type option on the receiver menu - I'll play around with that tomorrow. I believe the settings are now Off, Music or Speech on the V75s.

Incidentally, I was quite impressed that with all the transmitters set to low-power, and all the receivers racked with the supplied antennas distributed to two pairs of 4, and two pairs of 3, I was able to take the beltpacks out to the bottom of the garden, and virtually every channel still showed full RF at the receiver. I suspect the paddles will be staying in their box at the theatre tomorrow...

I'll report back after we've had our technical rehearsal tomorrow evening at the theatre, and let you know how the 'hiss' was. If it's still an issue then perhaps one of the Line 6 guys might have a few things for me to try. I notice that there is a previous thread from someone who had a similar issue, but which didn't appear to get resolved (or the original poster didn't respond afterwards).

As a complete aside, the Yamaha 01V96 VCM mixers are on a different planet to the original 01Vs and 02Rs and the pre-amps are very clean and open (and a tad boring!). When it's set in 96k mode, the sound quality is superb (I certainly prefer it to an LS9 which only supports up to 48k), although you'd only really notice the difference if you're using it for recording purposes. I do agree that for live sound an LS9 does add some fairly essential features, not least the option to quickly reset the channel EQ, which the 01V96 doesn't let you do!)

Anyway, I'll report back tomorrow and hopefully all will be well once we're in the venue. If it isn't then I'm not going to be very popular!



Re: XD-V75L Hiss
by RonMarton on 2012-05-13 01:29:19

I just got back from an outside broadcast ("remote" to the Americans) and am "dashing this off" in the hope that you'll see it before your next theatre job...

...Because I feel you really should pack your paddles, as "bench" RF reception offers almost no guidance whatsoever in terms of what might be obtained in actual use.

If it were my stage job, (given a choice) I'd always like to have the option of paddles over whips, for a whole host of reasons, of which I'll only list the most vital three:

  1. There aren't mobile bags of brine (people, "perfect" reflectors/absorbers of RF) running interference at your place;
  2. Amplifier compensation is essential for the cable losses endemic in rigging some antennae for vital lines of sight and
  3. The term itself reflects the fact that true "diversity" (hence the best RF) is best derived from pairs of antennae that are indeed "diverse". I'm referring to the fact that this best performance requires rigging for a given antenna pair to not only "see around" RF obstacles, (whether stationary or mobile) but preferably also to "see" slightly "over and under" them. So, in the case of your P180's, one should be more frontal than its side-oriented "mate", one also being higher or lower than its "mate", with both of their notional "hemispheres" of reception covering the entire performance area, ...while simultaneously "back-rejecting" possible WiFi interference from the public or elsewhere in the venue. This is impossible to achieve with non-directional passive whips that can only be very close to their receiver/s. ...Having said all that, some "weird" performance and receiver set-ups have given me best "walk test" results with one whip being "mated" to a P180 !

Regarding the hiss that prompted this discussion, I'm coming around to the opinion that it may also prove to be the unrealistic nature of your "bench test" that's to blame.

I'd like to hear what happens when, having re-established the gain and headphone settings of your test, you remove an XL female from the rear of an XD-V receiver and replace it with a standard dynamic (non-powered) mic such as a bog-standard SM58.

Be very careful in re-employing the headphones for this test, (indeed don't even have them plugged into their socket when making the receiver/mic swap) as I have a feeling that a standard "Check, one-two" into the dynamic mic will prove to be very loud indeed, maybe even dangerously so.

Should this be the case, it'll prove that an unrealistic "bench-induced" gain structure is indeed at the heart of "grief" that will never be apparent in actual performance.



Re: XD-V75L Hiss
by tccc on 2012-05-13 02:03:51

Hi Ron,

Heading there now - 100m reel of LMR-195, BNC connectors and P180 and P360 paddles at the ready! I'll report back afterwards.

Thanks.



Re: XD-V75L Hiss
by dboomer on 2012-05-15 13:12:09

100m would be well beyond the limit of 100 feet!



Re: XD-V75L Hiss
by tccc on 2012-05-15 15:51:25

Hi,

Sorry, had meant to update this thread yesterday!

The 14 XD-V75s have been behaving well at the theatre. The hiss is still present, but at the required gain for the mics it's inaudible so that hasn't been a problem. There seems to be quite a lot of interference at the venue, but we've still had all 14 channels running quite happily.

Obviously, the 100m reel wasn't to be used as one whole run, just cut into shorter lengths

Ended up with the supplied antennas serving the Antenna B port for each set of receivers (2 sets of four, 2 sets of three), and then 4 paddles serving the antenna A. Although to be honest, I didn't notice much difference compared to just using the supplied antennas for everything. If we were having to cover a larger area then I'd have probably split the racks up a bit so that we didn't have all the antennas close together, but it's fine for this stage.

So all as planned so far!



Re: XD-V75L Hiss
by RonMarton on 2012-05-15 16:04:58

Great news...

Generally, you'll be amazed at the range with just the rubber duckie whips, but the paddles are essential insurance should you even have the slightest suspicion that itinerant interference may turn up later.

Also back-rejection of other possible WiFi is vital for maintaining range in the RF2 scheme, which you'll need to employ whenever more than a dozen channels are to be used simultaneously.



Re: XD-V75L Hiss
by dboomer on 2012-05-16 09:00:55

You will never notice a "sonic" difference using the paddles.  You will just add to the reliability.




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