Wireless IEMs: Xvive U4 & alternatives

[dave_bass5]

4 minutes ago, Al Krow said:

 

So my 1.0M cable has arrived. Not been able to eliminate the background hum entirely, which is a shame. Volume issues all fine as expected with the TS rather than TRS jacks. The hum seems to be loudest on channel 1 and quietest (but still present) on channels 4 & 5 so we'll be making use of those at the next gig.

I still say it’s faulty. You shouldn’t be forced to do any of this IME. Both ours are plugged in to our desk without any buzz or interference. Granted its not a digital desk like yours, but if your U4 is that sensitive id at least get it swapped over for a new one, just to confirm its normal. 

[Al Krow]

2 hours ago, dave_bass5 said:

I still say it’s faulty. You shouldn’t be forced to do any of this IME. Both ours are plugged in to our desk without any buzz or interference. Granted its not a digital desk like yours, but if your U4 is that sensitive id at least get it swapped over for a new one, just to confirm its normal. 

 

But it's the same issue on two separate brand new U4s - one's mine and one's the singers.

 

Here's the thing:  no hum at all when:

- the transmitter and receiver are both on but the mixer is switched off; 

- the mixer is on and I pick the transmitter up in my hand; 

- with direct headphones into the mixer ie not via the wireless U4.

 

Sounds like some sort of grounding issue related to the mixer & wireless.

 

Any obvious fixes to try out?

Edited January 19, 2023 by Al Krow

[dave_bass5]

21 minutes ago, Al Krow said:

 

But it's the same issue on two separate brand new U4s - one's mine and one's the singers.

 

Here's the thing: no hum at all when the transmitter and receiver are both on but the mixer is switched off. No hum when the mixer is on and I pick the transmitter up in my hand. Sounds like some sort of grounding issue related to the mixer. Any obvious fixes to try out?

No sure if this would help, but have you tried your Boss wireless with that mixer? We know the Boss doesn't have an issue. 

[Al Krow]

12 minutes ago, dave_bass5 said:

No sure if this would help, but have you tried your Boss wireless with that mixer? We know the Boss doesn't have an issue. 

 

Yup I have, but I think it's a separate point? Because the Boss is only getting as far as the inputs, whereas this is an output issue.

 

Edited January 19, 2023 by Al Krow

[EBS_freak]

1 hour ago, Al Krow said:

 

But it's the same issue on two separate brand new U4s - one's mine and one's the singers.

 

Here's the thing:  no hum at all when:

- the transmitter and receiver are both on but the mixer is switched off; 

- the mixer is on and I pick the transmitter up in my hand; 

- with direct headphones into the mixer ie not via the wireless U4.

 

Sounds like some sort of grounding issue related to the mixer & wireless.

 

Any obvious fixes to try out?

What else is plugged into the mixer?

 

Does it still make a noise when you have got just the mixer plugged in and nothing else apart from the U4?

[Al Krow]

37 minutes ago, EBS_freak said:

Does it still make a noise when you have got just the mixer plugged in and nothing else apart from the U4?

 

Yup, exactly this.

[EBS_freak]

42 minutes ago, Al Krow said:

 

Yup, exactly this.

And you've checked the power connection is seated properly?

[Al Krow]

2 minutes ago, EBS_freak said:

And you've checked the power connection is seated properly?

Yup, it's 5V DC. Even tried with just batteries tonight. Same result. 

[EBS_freak]

Hmm, this sounds like a EM and lack of shielding within the unit issue.

[Chienmortbb]

14 hours ago, EBS_freak said:

Hmm, this sounds like a EM and lack of shielding within the unit issue.

EM as in Electro Magnetic?

[EBS_freak]

Yes - could be proximity of some transformers to those outputs thats putting noise on the line.

[Al Krow]

Well I think I've got to the bottom of the Xvive U4 hum and it's (sadly) to do with the Zoom L-8 desk (digital, plastic cased).

@dave_bass5 very kindly popped round tonight with his missus' U4 and his Mackie 802 desk (analogue, metal cased).

What we found was that his U4 also had the same high-pitched hum through the Zoom L8; none of the U4's had the hum (except when the transmitter and receiver were right next to each other) through the Mackie. 

No such hum audible when wired IEMs are plugged into the L-8, but we're looking to go wireless. Guess that means I'm going to be looking for a new desk in the near future - shame, as the L8 has a lot going for it particularly at its price point.

 

On 20/01/2023 at 00:17, EBS_freak said:

Hmm, this sounds like a EM and lack of shielding within the unit issue.

 

As an alternative to ditching the Zoom L8, just wondering whether getting a little wire box (to act as a Faraday cage) to put the U4 transmitters in would work to shield the transmitters from the L8's EM whilst still allowing connectivity between transmitter and receiver?

 

Edited January 27, 2023 by Al Krow

[EBS_freak]

Depends how directional the transmitters are. Do some experiments with some foil. It will tell you if you are on the right tracks or not.

[Al Krow]

37 minutes ago, EBS_freak said:

Depends how directional the transmitters are. Do some experiments with some foil. It will tell you if you are on the right tracks or not.

I was actually thinking along exactly the same lines. Getting mixed results ie works intermittently.

Edited January 27, 2023 by Al Krow

[Woodinblack]

Maybe a ferite bead or something - but it seems more like maybe it is the output of the desk that has the hum (or it is a capacitance issue). If not, maybe a bigger lead.

 

As to directional, the aerial in the U4 is a little bit of bent wire. Actually...

 

[JohnDaBass]

I think @Woodinblack may have a solution. 

Maybe the hum  through the Zoom is originating from a poorly isolated power supply. It would be worthwhile feeding the AC mains cord through a ferrite ring a couple of times to clam the noise entering the Zoom. Many low cost hi fi units use a similar solution rather than redesigning their psu to meet EMC regs in curtain countries. 

[Al Krow]

@Woodinblack - thanks! Agreed it's definitely the desk causing the issue - when the desk is switched off and the transmitter & receiver left on, the hum disappears entirely (unless the transmitter & receiver are placed in very close proximity).

 

@JohnDaBass this is definitely a budget / low cost unit (certainly for a digital desk), however the power for the Zoom is an AC adaptor USB --> 5V DC input on the desk i.e. basically the same as a mobile phone. Does that impact your suggestion?

[JohnDaBass]

1 minute ago, Al Krow said:

@Woodinblack - thanks! Agreed it's definitely the desk causing the issue - when the desk is switched off and the transmitter & receiver left on, the hum disappears entirely (unless the transmitter & receiver are placed in very close proximity).

 

@JohnDaBass this is definitely a budget / low cost unit (certainly for a digital desk), however the power for the Zoom is an AC adaptor USB --> 5V DC input on the desk i.e. basically the same as a mobile phone. Does that impact your suggestion?

Not sure, but have tried a different 5v psu ?

Some of those psu can be quite noisy. 

[Al Krow]

Just now, JohnDaBass said:

Not sure, but have tried a different 5v psu ?

Some of those psu can be quite noisy. 

 

Yeah -  tried a couple of those out and actually come to think of it, I switched to battery power (which the Zoom caters for) and the hum was still present, which I think eliminates the input power as being the cause?

[dave_bass5]

36 minutes ago, JohnDaBass said:

I think @Woodinblack may have a solution. 

Maybe the hum  through the Zoom is originating from a poorly isolated power supply. It would be worthwhile feeding the AC mains cord through a ferrite ring a couple of times to clam the noise entering the Zoom. Many low cost hi fi units use a similar solution rather than redesigning their psu to meet EMC regs in curtain countries. 

Could be on to something.
We also noticed when the receiver was next to the Zoom desk, which was on, it was also causing this interference, even though the transmitter was in the Mackie desk (so it wasn’t coming from that). 

[EBS_freak]

Whats the zoom adapter look like? Presumably it hasn't got a ferrite core on the plug? Also though... didn't I read that you had tried it with batteries? If it does it with batteries, the ferrite core on an adapter won't make much difference. I think it's probably a given the interference is being generated internally in the desk and my money would be on some sort of transformer with some poorly placed sensitive components/inadequate screening.

Edited January 27, 2023 by EBS_freak

[Al Krow]

6 minutes ago, EBS_freak said:

Whats the zoom adapter look like? Presumably it hasn't got a ferrite core on the plug? Also though... didn't I read that you had tried it with batteries? If it does it with batteries, the ferrite core on an adapter won't make much difference. I think it's probably a given the interference is being generated internally in the desk and my money would be on some sort of transformer with some poorly placed sensitive components/inadequate screening.

 

Agreed, Russ.

 

Dave's Mackie 802 - analogue and metal case - didn't have the hum issue at all with any of the three U4s we tested last night.

 

The Soundcraft Signature 12 or 12 MTK is similarly analogue & metal cased, but has 3 configurable aux out and a headphone out, which gives us what the Zoom L8 does (but without the setting store / recall ability that the Zoom has, which is definitely a "nice to have"). And the Soundcraft gear seems to get a good rep online. Sadly I think my flirtation with capable budget digital desks may be coming to a swift end...

[EBS_freak]

The analogue and metal case bit is not really a factor - if the problem noise is generated inside the desk and interferes with an audio path, it's still going to be present across any audio feed to ground. Such things can happen in both analogue and digital desks so don't think this is a digital desk problem!

 

I would wager that it's whats happening in the aux out (which isn't really a true desk aux out - as Zoom have decided to incorporate headphone amps on the out). I would guess its the amplification stage thats causing the issue. You may get some mileage by putting a ferrite call on the cable between the desk and the Xvive transmitter... but you may lose some top end in the audio. Whether that's something that can be perceived, well, it's probably worth a try...

Edited January 27, 2023 by EBS_freak

[Al Krow]

21 minutes ago, EBS_freak said:

The analogue and metal case bit is not really a factor - if the problem noise is generated inside the desk and interferes with an audio path, it's still going to be present across and audio feed to ground. Such things can happen in both analogue and digital desks so don't think this is a digital desk problem!

 

I would wager that it's whats happening in the aux out (which isn't really a true desk aux out - as Zoom have decided to incorporate headphone amps on the out). I would guess its the amplification stage thats causing the issue. You may get some mileage by putting a ferrite call on the cable between the desk and the Xvive transmitter... but you may lose some top end in the audio. Whether that's something that can be perceived, well, it's probably worth a try...

Cheers Russ - could you or @JohnDaBass recommend me a suitable ferrite ring / supplier to thread the cable through please, and I'll gladly give it a go?

[EBS_freak]

A bunch off ebay would be a starting point I guess.