The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
Eliminating hiss per a wireless boom setup? Dynamic Microphones
Old 1 week ago
  #1
Here for the gear
 

Thread Starter
Eliminating hiss per a wireless boom setup?

Hey everyone,

Here's the scoop. I'm having a terrible time trying eliminate really bad hiss (a truly unacceptable noise floor) per a wireless boom setup that I’m assembling. What I have right now theoretically should work, but the hiss renders the sound capture totally unusable. Maybe it’s a simple fix that just involves adding an inline RF filter somewhere?

The signal chain is as following:

Audio Technica AT4053b (boom for indoor voice) ***OR*** Audio Technica AT875b (short shotgun for outdoors) ---(8” XLR patch cable)--->
Sennheiser MZA14 48 (supplies +48V phantom power to either mic) ---(8” XLR patch cable)--->
Sennheiser EW100 G3 wireless microphone XLR transmitter —(WIRELESS CONNECTION)--->
Sennheiser EW100 G3 wireless receiver —(3.5” headphone jack to XLR)--->
Sony FS7 (line in)

Again, what I hear is clearly a hiss and not a hum or a rumble.
There is is no AC power involved in the system, let alone an earth ground anywhere.
In some cases, I can attenuate the hiss by holding the MZA14 and the EW100 transmitter boxes differently (I guess I’m the ground in that case?).
But then, once I have the noise quieted a bit, sometimes I hear music in the background - which sounds like pop music that you wouldn’t typically hear on AM radio these days.
When I let go, or change the position, the hiss comes back in full force.

Per the Sennheiser EW100, I have played with the squelch, sensitivity, changing channels, and even dropping the preamps on the FS7. No luck.
Again, it seems to have something to do with there not being an earth ground involved.

Per testing individual components in order to rule things out, the signal is totally quiet when:

* Either mic is directly connected to the FS7 just via a simple XLR cable (with +48V provided by the FS7
* Either mic is directly connected to the FS7 via an XLR cable and just the MZA14 (with +48V provided by the MZA14)
* The EW100 system is used without the MZA14 in the chain (such as with an MD46 mic that doesn’t require +48V or an EW100 G3 wireless lav transmitter)

Per my research, I thought a “ground lift” (eliminating ground pin 1) might eliminate the hiss - but that seems to be for ground loop issues - meaning hums and not hisses. I haven't tried it, but I'm guessing it won't work.

Any thoughts? Thanks in advance!

- Seth
Old 1 week ago
  #2
Gear Nut
 

Just thinking out loud: play with the sensitivity setting on the transmitter. The variable seems to be the mic/transmitter pair.
Old 1 week ago
  #3
Here for the gear
 

Thread Starter
Thanks! I definitely adjusted the sensitivity on the transmitter, and that didn't help.

Basically, the mic/transmitter pairs work perfectly and is totally quiet - as long as the Sennheiser MZA14 isn't in the chain to provide +48V to the mic.
To give you an idea, if I use a Sennheiser MD46 (which doesn't require phantom power and hence the MZA14), it's dead silent.

My gut says that the MZA14 is behaving like an amplifier when connected to the EW100, but that makes no sense as the MZA14 is dead quiet when used directly with a mic and the FS7.
Old 1 week ago
  #4
Lives for gear
Make sure you are modulating the TX sufficiently
Radio links are never as quiet as cable
Listen to the RX and increase the gain on the TX until you hear it pump on speech and then back off a little
There is gain on the MZA and the EW 100, get that structure right
Enable the 80 Hz filter and select various gains to the TX to fully modulate
Send tone if you can and look on a meter, the MZA will give more level than the electret lavaliere
Old 1 week ago
  #5
Lives for gear
 
Bruce Watson's Avatar
 

Quote:
Originally Posted by Thoomp View Post
The signal chain is as following:

Audio Technica AT4053b (boom for indoor voice) ***OR*** Audio Technica AT875b (short shotgun for outdoors) ---(8” XLR patch cable)--->
Sennheiser MZA14 48 (supplies +48V phantom power to either mic) ---(8” XLR patch cable)--->
Sennheiser EW100 G3 wireless microphone XLR transmitter —(WIRELESS CONNECTION)--->
Sennheiser EW100 G3 wireless receiver —(3.5” headphone jack to XLR)--->
Sony FS7 (line in)
And there's your problem. You are using a microphone level device on a line level input, which is making you crank the amps on the FS7, which is where your noise is coming from.

Use the G3 as the microphone that it is, use mic level in on your FS7, and try again. Proper gain staging (letting the Sennheiser receiver do most of the amplification, so you can turn the Sony pretty far down) will set you free.

No reason to believe me when you can spend 10 minutes testing and prove it to yourself. Try it and see.
Old 1 week ago
  #6
Lives for gear
 
jwh1192's Avatar
Quote:
Originally Posted by Bruce Watson View Post
And there's your problem. You are using a microphone level device on a line level input, which is making you crank the amps on the FS7, which is where your noise is coming from.

Use the G3 as the microphone that it is, use mic level in on your FS7, and try again. Proper gain staging (letting the Sennheiser receiver do most of the amplification, so you can turn the Sony pretty far down) will set you free.

No reason to believe me when you can spend 10 minutes testing and prove it to yourself. Try it and see.
or does the G3 output Line Level ??? if not, do as advised here and try mic level input on FS7 - if there is one that will not add more Hiss !!!
Old 1 week ago
  #7
RPC
Gear Maniac
 

My guess is that the step-up converter in the MZA14 is causing RFI in the transmitter. Things to try:
1) Get the boxes further apart, at least as an experiment. What happens to the hiss if you place, say, 5m of cable between them (and move them 5m apart)?
2) Try a clamp-on ferrite bead on the cable between the MZA14 and the transmitter.

(This is free advice and worth every penny!)
Old 1 week ago
  #8
Lives for gear
 
tourtelot's Avatar
Yes. A chance that the Sennheiser power supply is picking up RF from the transmitter. Wear one on each hip and see if it's better.

Also, as others have said, the gain structure of the rig needs to be correct. There should be no line level anywhere in the transmitter end (worn on the boomman) and maybe the receiver needs to come out at mic level if it's the line level gain stage in the receiver that makes it suspect to being noisy. Let the gain stage in your mixer do the work. Cabling on the transmitter end needs to be impeccable. Only the best wire in the whole system, mic to antenna.

I used a Lectro high-power transmitter and a Denecke power supply velcro'd together for years that worked perfectly, so there is a way to do it. Also be aware that if your boomman is wearing a wireless return, Comtek or Letro IFB or the like, the transmitter for the mic may be getting into that as well. That pack should be worn on the hip opposite the transmitter for sure.

Good luck with your trouble-shooting.

D.
Old 1 week ago
  #9
Lives for gear
I used the MZA 14 into Microns for many years and it worked very well and gave excellent P48 , pads and low frequency attenuation
Old 1 week ago
  #10
Gear Nut
 

Senn G3s are ok, but not the quietest wireless sets out there. If your budget would allow, rent something else, Lectro, Zax, Audio Ltd.
Old 4 days ago
  #11
Here for the gear
 

Thread Starter
Thanks for the updates so far, everyone! I’ve been away for the past week and away from my gear; I’ll do some more testing now that I’m back. Here’s the update:

*********************

Here’s an update after a bunch of testing this afternoon, which will hopefully help rule things out. It looks like I have two separate problems here:


(1) RF SPRAY FROM THE SKP100 TRANSMITTER?: Check out this link to a picture of my setup, that I posted over at CreativeCow:

https://images.creativecow.net/324225/img_1084.jpg

When I hold the SKP100 just like this, with my three fingers fully wrapped around the XLR connection and with the palm around the body of the SKP100 transmitter, almost all the noise goes away. Can I put something in there (ferrite RF chokes?) to shut down what may be RF Spray?

I’ve pulled the mics themselves out of the equation; the noise happens regardless of whether a mic is connected to the chain. Stripped down, it happens when the MZA14 is directly connected to the SKP100.


(2) FM RADIO INTERFERENCE: Once I hold the grip that way, most of the noise is gone. But in certain circumstances I’m now picking up variably slight broadcast radio noise. What’s weird is that I am in fact picking up FM (not AM) signals. At its worst, the sound is a couple of FM stations playing all at once. The clearest of the radio station signals is WBMX 104.1 FM, which is a powerful FM radio station (21,000 watts) broadcasting from the Prudential Tower exactly two miles away.

By the way, as far as cable quality goes, I’m planning to return the brand new 8” one (shiny cable ends) to Amazon -- but neither cable seems to do anything to significantly solve the main hiss problem. I think the coiled black cable (Pearstone, with Neutrik ends) picks up less of the lower FM signal, but there’s higher handling noise when the coil moves around – so I’ll likely have to replace both cables for this application.

Again, you’ll get no argument from me per getting the levels right. But this is something where the hiss is as loud as the sound input…and not subtle background hiss like you’d get from an inexpensive pre-amp. Just figured I’d clarify, as I have played with getting the correct levels and it was of no use.



Thanks again in advance - and for all the advice so far. I really appreciate it!
Old 4 days ago
  #12
Lives for gear
Are you going into TX unbalanced?
Old 4 days ago
  #13
Here for the gear
 

Thread Starter
@rolo46 - As only a single XLR cable connects the MZA14 to the SKP100 (the transmitter), I'm assuming that it is balanced. Although the issue exists even when a mic is attached, that connection is also made via an XLR cable. So again - it appears that everything is balanced up until the transmitter.
Old 4 days ago
  #14
Lives for gear
Are you going in at line or dynamic mic level, the supplied electret will be low level and unbalanced
Old 4 days ago
  #15
Here for the gear
 

Thread Starter
@rolo46 - The SKP100 Tx side of things appears balanced (where the problem is) but is definitely unbalanced on the Rx side going into the FS7 (which has 3 options: Line / Mic / Mic +48V). From what I've read, the correct setting on the FS7 for the Rx side would be "Mic" in this case. But again, this whole issue is happening on the Tx side; it works a treat when the Tx is a different unit (i.e, the SK100 with a lav).


BTW - Someone said on a different forum that they have the same exact problem. They're getting acceptable (albeit not perfect results) by putting a transformer in between the MZA14 and the SKP100. Any thoughts on this?
Old 4 days ago
  #16
Here for the gear
 

Thread Starter
I'm tentatively optimistic here! With a test of effectively disconnecting Pin 1 (by jumping the Pin 2 and Pin 3 pairs respectively -- but not Pin 1) between the MZA14 and the SKP100, I think I created a ground lift - which has quieted things down. As the mic works, the +48 phantom power is in fact being passed through.

Would a solution of using a transformer instead of a ground lift do the same thing here? Would that be a quieter solution than a ground lift?

Assuming I just go pick up a ground lift (as a permanent solution to the first problem here), I now need to get rid of the rest of the hiss and FM signals that I'm picking up. Any thoughts? What's the next step?
Old 3 days ago
  #17
Lives for gear
 
jwh1192's Avatar
Quote:
Originally Posted by Thoomp View Post
I'm tentatively optimistic here! With a test of effectively disconnecting Pin 1 (by jumping the Pin 2 and Pin 3 pairs respectively -- but not Pin 1) between the MZA14 and the SKP100, I think I created a ground lift - which has quieted things down. As the mic works, the +48 phantom power is in fact being passed through.

Would a solution of using a transformer instead of a ground lift do the same thing here? Would that be a quieter solution than a ground lift?

Assuming I just go pick up a ground lift (as a permanent solution to the first problem here), I now need to get rid of the rest of the hiss and FM signals that I'm picking up. Any thoughts? What's the next step?
may i ask .. what happens if you have a Dynamic Mic plugged into the SKP100 ?? do you still have the same issues ?? not just a Lav but something like an SM58 ..

and too bad you do not have the SKP300 (has 48volt power from what i read)

and you isolated the Camera out of the equation - using a Field Mixer or some or mixer of some sort ???
Old 3 days ago
  #18
Here for the gear
 

Thread Starter
@jwh1192 - I've never had a problem with a dynamic mic with the SKP100 - as I've used it with an MD46 for years with no issue or hiss.

It's only when the MZA14 (which supplies +48V power) is in the equation, which I'm guessing is amplifying the RFI from the SPK100 via the Pin 1 connection.

And I would really love an SKP300 - but it's over $500 and unavailable used...and I'm already in over my head having spent so much on the AT4053b. Camera seems to be just fine, although I'll be testing with a mixer next. I happened to have the SKP100 in our kit already...so I my hope has been to just make use with what we already have on-hand.
Old 3 days ago
  #19
Lives for gear
 
jwh1192's Avatar
Quote:
Originally Posted by Thoomp View Post
@jwh1192 - I've never had a problem with a dynamic mic with the SKP100 - as I've used it with an MD46 for years with no issue or hiss.

It's only when the MZA14 (which supplies +48V power) is in the equation, which I'm guessing is amplifying the RFI from the SPK100 via the Pin 1 connection.

And I would really love an SKP300 - but it's over $500 and unavailable used...and I'm already in over my head having spent so much on the AT4053b. Camera seems to be just fine, although I'll be testing with a mixer next. I happened to have the SKP100 in our kit already...so I my hope has been to just make use with what we already have on-hand.
ok, do you have another Box that can provide 48volts ?? i have several Countryman ones here .. but they only put out 18volts for my EWM lavs .. what voltage can your microphone take ??

and the PS i use is the PSC - the older model that deos 48v, and 12T power ..

if you get really stuck and want to try one of these we can work out some shipping so you can try them .. if you have nothing as an Alternative in your World of friends and Bostonian Mixers .. !! happy to help a fellow mixer !!
Old 3 days ago
  #20
Here for the gear
 

Thread Starter
@jwh1192 - Thank you so much! I have an old Mackie 1202 that I'm going to bust out and see if that helps. Although the AT875r can take up to +48V, the AT4053b requires a full +48V. I'll keep you posted, to say the least.
Old 3 days ago
  #21
Lives for gear
 
jwh1192's Avatar
Quote:
Originally Posted by Thoomp View Post
@jwh1192 - Thank you so much! I have an old Mackie 1202 that I'm going to bust out and see if that helps. Although the AT875r can take up to +48V, the AT4053b requires a full +48V. I'll keep you posted, to say the least.
ok .. and i would try the Mackie Powering the 4053b before the Transmitter .. if this is what you are thinking too .. might isolate the portable PS ..

has the PS ever been dropped, might have a broken cold solder joint inside !!!
Old 3 days ago
  #22
Lives for gear
Have you disconnected the phantom power to the lav this may be causing an issue
Old 3 days ago
  #23
Here for the gear
 

Thread Starter
@jwh1192 - Basically, I'd swap out the Mackie for the MSA14, at that location. I'm guessing it has been dropped before; I opened it up but things look intact. I tried tightening down the four screws inside; not much of a help; no clear solder joints broken anywhere.

@rolo46 - Not sure what you mean, as no lavs are used in this particular setup.
Old 3 days ago
  #24
Lives for gear
You are going in on a mic level to the TX this will have electret phantom on it
Is there a pin config for dynamic or line?
Old 3 days ago
  #25
Here for the gear
 

Thread Starter
@rolo46 - I don't know; I'll have to check on that. Thanks!
Old 2 days ago
  #26
Lives for gear
 
jwh1192's Avatar
Quote:
Originally Posted by Rolo 46 View Post
You are going in on a mic level to the TX this will have electret phantom on it
Is there a pin config for dynamic or line?
hi Rolo, https://en-us.sennheiser.com/plug-on...one-skp-100-g3

i do not see anything regarding Electret Power on this model, let me know if i missed something .. i think it was solely meant for Dynamic Mics for ENG handheld mics only ...

UPDATE: the SKP300 has 48v ..
Old 2 days ago
  #27
Here for the gear
 

Thread Starter
Interesting, Rolo. BTW - I'd kill for an SKP300 but it's way way way out of my budget and am just trying to make do with what I have. Again, I got the MZA14 very inexpensively and I figured that it would easily provide +48V.
Mentioned Products
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump