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Zaxcom ZMT3 Hiss


Trey LaCroix

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Hey there, I’m demoing a Zaxcom boom rig for an upcoming project and the system is still new to me.

 

I’m using a ZMT3 into an Ambient UMPII and I’m noticing a bit more hiss than my Lectro has. It’s not horrible but it is significantly louder than my Lectro SMV on the pole. I know Lectrosonics uses noise reduction but even with the smart NR off the zaxcom is noticibly noisier.

 

Again, not horrible, but I’m curious if what I’m hearing is normal. This is the first time I’m using Zaxcom anything and I may just not be used to the sound yet. I’d love to hear from some Zaxcom users. Thanks!

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What you are hearing is the noise floor of the system. Companded FM wireless like Lectro hides the noise floor with the compander and then further reduces it with noise reduction software. The result of Zaxcom is a lower distortion transmission with a more open sound. The transmitter has a downward expander that can be activated if you want to lower the noise floor but very few find it necessary.

 

The TRX743 noise floor would be lower by 6 dB and still provide all the other benefits of the Zaxcom system. I would also recommend the ZMT Phantom II. Using a separate 48V supply does not yield the best results as the ZMT3 can not shut down its LAV power supply and is a unbalanced input by design. The ZMT phantom II is a true balanced input and also works with LAVs

 

Glenn

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im going to bet that Richards post suggesting to put an XLR on and get the transmitter away from the mic removes the hiss.
so, a few questions.

what mic are you using and what suspension?

i had problems with my mics until i cut the connection between pin 1 of the XLR and the shell of the suspension - i was using Cinela mounts.

whilst that flies against what everyone knows should be a good thing to prevent noise, it pretty much eliminated most hiss i would be hearing.
taping the antenna to the boom pole also worked, but not to the same extent.

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3 hours ago, r.paterson said:

As a test Put the zax and ump11 to the bottom.of pole or  extend from mic a few metrers and see if hiss disappears, if it does the mic is picking up am modulation from the zax..

Thanks, just tried it but the hiss is the same as far as I can tell.

 

52 minutes ago, rich said:

what mic are you using and what suspension?

I’ve used a CMIT and a 416. Same relative level of noise. 416 has higher output so It’s covering it up a bit better. I’ve tried a rycote invision 7(I think?) with a couple different cables (with and without an EMC connector and ground was not tied to shell in any of them) and a cinela. Same.

 

I can still hear the hiss even with no mic plugged in. Could it be from the Ambient supply? I had Trew make the cables specifically how the diagram says to.

 

 

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From my experience, this UMP II + TRXLA2 pair just doesn't work. UMP II picks up a RFI from the transmitter quite badly. I don't know if Ambient has sorted out as mine is a quite an earlier model (there aren't a belt clip on mine). I you want to use a 48V phantom power supply, the only one that worked for me is French distributor Areitec's Pico 48, but I think it is now discontinued. Circuit designer has integrated a very small sized Lundahl's transformer in it which is known to be very transparent and efficiently cut any noises.

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Thanks everybody for the responses. I compared the ZMT3 to a ZMT phantom at a local rental house and the ZMT phantom had a little less noise, so I’m thinking that the Ambient phantom supply is adding to it.

 

I would like to clarify that what I’m hearing is self noise and not a whine. I tried the ZMT with a Denecke phantom power supply and got a real nasty whine. Totally different from what I’m hearing.

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Thanks for the video!

 

Earlier this week I went by Audio Department in Burbank to test the ZMT3/ambient against the ZMT phantom. While the Ambient solution was a little noisier, I was still surprised by the noise floor of the Phantom, still higher than I expecteded. I’d be really interested to hear how noisy the 742/743 is from anyone who has used it.

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The TRX743 has a 6dB better noise floor than ZMT. If lowest noise is the deciding factor TRX743 is the best choice as it also has never clip eliminating limiter distortion.  ZMT phantom 2 has many advantages but smallest size and lowest power consumption limit other specifications a bit. 

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  • 1 year later...
On 11/20/2018 at 5:41 AM, Trey LaCroix said:

Thanks everybody for the responses. I compared the ZMT3 to a ZMT phantom at a local rental house and the ZMT phantom had a little less noise, so I’m thinking that the Ambient phantom supply is adding to it.

 

I would like to clarify that what I’m hearing is self noise and not a whine. I tried the ZMT with a Denecke phantom power supply and got a real nasty whine. Totally different from what I’m hearing.

 

Hi Trey

Did you manage to find out what was causing the hiss?

I am currently testing a ZMT Phamton 2 and even with no cable connected the hiss is really loud.

Are you using the transmitter's expansion to combat this?

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1 hour ago, julian said:

 

Hi Trey

Did you manage to find out what was causing the hiss?

I am currently testing a ZMT Phamton 2 and even with no cable connected the hiss is really loud.

Are you using the transmitter's expansion to combat this?

Unfortunately, I did not. I learned to live with it and haven’t received a single complaint from post. It’s annoying but the small size and weight still outweighs the hiss.

 

I don’t mess with the expander.

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  • 2 years later...

Hey there, 

 

because of the back problems of my boomer, I got some used ZMT3 Phantom for the most lightweight solution. Coming from Lectro HMs, the Zax-hiss is very noticeable.

Since there is already this topic, I want to ask, what solutions you found eventually...?

 

I´m using a Mini-Cmit running on 12V into a QRX 235. The ZMT is sitting in a Soundguys-solution ZMT-Bracket, Antenna facing down to the pole.

Should I try different expander settings or is it rather important to get a proper, perfectly shielded XLR-cable?

The hiss is changing when I touch the antenna or the cable. Also the exact cable run seems to be crucial somehow.

 

So what to do?

It all reminds me on the journey I had with my A10 on a boom. Is it the normal digital hiss you can't take coming from Lectro with NR?

A little help or thoughts would be very much appreciated. Thanks a lot!

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23 hours ago, TimMey said:

Hey there, 

 

because of the back problems of my boomer, I got some used ZMT3 Phantom for the most lightweight solution. Coming from Lectro HMs, the Zax-hiss is very noticeable.

Since there is already this topic, I want to ask, what solutions you found eventually...?

 

I´m using a Mini-Cmit running on 12V into a QRX 235. The ZMT is sitting in a Soundguys-solution ZMT-Bracket, Antenna facing down to the pole.

Should I try different expander settings or is it rather important to get a proper, perfectly shielded XLR-cable?

The hiss is changing when I touch the antenna or the cable. Also the exact cable run seems to be crucial somehow.

 

So what to do?

It all reminds me on the journey I had with my A10 on a boom. Is it the normal digital hiss you can't take coming from Lectro with NR?

A little help or thoughts would be very much appreciated. Thanks a lot!

Why are you running your mini cmit on 12v and not 48v phantom?

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2 hours ago, Wandering Ear said:

Why are you running your mini cmit on 12v and not 48v phantom?

Because it can handle 12V and it's better runtime, so why not.

But I realized, that the hiss is a little bit less on 48V, so 48V it is (though I don't understand why that's a difference).

I also changed Tx-Power down to 25mW and put on the expander to get some results I can live with...

But there must be a better solution.

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On 4/23/2023 at 2:33 PM, TimMey said:

Because it can handle 12V and it's better runtime, so why not.

But I realized, that the hiss is a little bit less on 48V, so 48V it is (though I don't understand why that's a difference).

I also changed Tx-Power down to 25mW and put on the expander to get some results I can live with...

But there must be a better solution.

I've had good success with the sound devices a-filter. Haven't used it with zaxcom but works great with other digital transmitters.

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On 4/23/2023 at 11:33 AM, TimMey said:

Because it can handle 12V and it's better runtime, so why not.

But I realized, that the hiss is a little bit less on 48V, so 48V it is (though I don't understand why that's a difference).

I also changed Tx-Power down to 25mW and put on the expander to get some results I can live with...

But there must be a better solution.

Lower noise floor on 48v is why I asked.

Also worth double checking that the cable you are using properly grounds the shield of the lemo connector.   I think extra noise can be induced if the connector shell is not grounded to pin 1.

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