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Author Topic: Sennheiser EW300 receiver strange problem.  (Read 3364 times)

Kevin Maxwell

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Sennheiser EW300 receiver strange problem.
« on: July 24, 2019, 01:05:31 pm »

Sennheiser EW300 receiver strange problem.

I am trying to setup a simple IEM system and have encountered a weird problem (a buzz) when trying to use the unbalanced ¼” output of some EW300 receivers and the XLR output at the same time when the XLR is going to the house system. If I unplug the XLR to the house and take just the ¼” output the signal is clean. The behavior (buzz or no buzz) is the same when the ¼” output is plugged into the XLR on the X32Rack (the IEM mixer) with proper adapters or just plugged into a battery powered headphone amp. I have tried every combination of wiring to the X32Rack from the ¼” connector. I have tried ground lifting the signal everywhere. After encountering this issue I unplugged everything from the X32Rack and was testing with just one receiver to try and narrow things down. 2 of the reviver didn’t exhibit the problem but those two don’t go directly from the XLR to the house system they go thru a processor in the rack and the out of that to the house system.

So I get a buzz on the ¼” output even when that output is connected to a battery powered headphone amp and the XLR is connected to the house. The XLR output always stays clean.

If this was for floor wedges and rock and roll I would say that the buzz would be lost in the noise floor but with IEMs this is not acceptable. 

The receivers and the X32Rack are in the same tall metal rack. If I use the XLR output connected to the house system I get a buzz only on the ¼” output. The XLR output stays clean. There are 9 receivers in this setup 7 are EW300 G3 one is a EW300 G2 and one is a EW100 G3. They get the power over the antennas from the Sennheiser antenna distro system. And those are AC/DC power supplies that aren’t grounded so a ground lift (for testing) there wouldn’t do any good. All of this (A/C power) is on the same breaker panel.

I still need to do more testing to see if I can figure out why this is happening. If I use an XLR Y cable and go from the Receiver to the X32Rack and the house system it is all clean. I am just not sure if using a hardwired split is the best way to do this. It would seem to be the easiest solution. I am also going to try a passive 8 channel transformer isolation rack mount unit so I am just using the one XLR output from the receivers.

BTW before doing all of this I asked Sennheiser tech support if this would work and they said it would. I spoke to tech support at Sennheiser this morning but we could come up with a reasonable solution.

Does anyone have any input?
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Pete Erskine

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Re: Sennheiser EW300 receiver strange problem.
« Reply #1 on: July 24, 2019, 01:31:11 pm »

Sennheiser EW300 receiver strange problem.

I am trying to setup a simple IEM system and have encountered a weird problem (a buzz) when trying to use the unbalanced ¼” output of some EW300 receivers and the XLR output at the same time when the XLR is going to the house system. If I unplug the XLR to the house and take just the ¼” output the signal is clean. The behavior (buzz or no buzz) is the same when the ¼” output is plugged into the XLR on the X32Rack (the IEM mixer) with proper adapters or just plugged into a battery powered headphone amp. I have tried every combination of wiring to the X32Rack from the ¼” connector. I have tried ground lifting the signal everywhere. After encountering this issue I unplugged everything from the X32Rack and was testing with just one receiver to try and narrow things down. 2 of the reviver didn’t exhibit the problem but those two don’t go directly from the XLR to the house system they go thru a processor in the rack and the out of that to the house system.

So I get a buzz on the ¼” output even when that output is connected to a battery powered headphone amp and the XLR is connected to the house. The XLR output always stays clean.

If this was for floor wedges and rock and roll I would say that the buzz would be lost in the noise floor but with IEMs this is not acceptable. 

The receivers and the X32Rack are in the same tall metal rack. If I use the XLR output connected to the house system I get a buzz only on the ¼” output. The XLR output stays clean. There are 9 receivers in this setup 7 are EW300 G3 one is a EW300 G2 and one is a EW100 G3. They get the power over the antennas from the Sennheiser antenna distro system. And those are AC/DC power supplies that aren’t grounded so a ground lift (for testing) there wouldn’t do any good. All of this (A/C power) is on the same breaker panel.

I still need to do more testing to see if I can figure out why this is happening. If I use an XLR Y cable and go from the Receiver to the X32Rack and the house system it is all clean. I am just not sure if using a hardwired split is the best way to do this. It would seem to be the easiest solution. I am also going to try a passive 8 channel transformer isolation rack mount unit so I am just using the one XLR output from the receivers.

BTW before doing all of this I asked Sennheiser tech support if this would work and they said it would. I spoke to tech support at Sennheiser this morning but we could come up with a reasonable solution.

Does anyone have any input?

Use an IL19 on the 1/4" out or any iso tran.
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Russell Ault

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Re: Sennheiser EW300 receiver strange problem.
« Reply #2 on: July 24, 2019, 04:13:41 pm »

[...] If I use an XLR Y cable and go from the Receiver to the X32Rack and the house system it is all clean. I am just not sure if using a hardwired split is the best way to do this. [...]

Sounds like the house system has some serious ground noise issues that are likely beyond your control, and by using both outputs you're coupling that noise into the signal chain on the unbalanced output. Especially since you can use a y-cable with no issues, I'd say that's your solution right there (and keep your grounds and your signals separate). Given what your tests have shown you, what concerns do you have about a hardwire split?

Transformers are great (especially if you plan to use this rig in other venues where you might run into other problems), but if it's a fairly captive application and the split works without transformers I'd be tempted to skip them for cost and weight reasons.

-Russ
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Kevin Maxwell

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Re: Sennheiser EW300 receiver strange problem.
« Reply #3 on: July 26, 2019, 11:00:46 pm »

Sounds like the house system has some serious ground noise issues that are likely beyond your control, and by using both outputs you're coupling that noise into the signal chain on the unbalanced output. Especially since you can use a y-cable with no issues, I'd say that's your solution right there (and keep your grounds and your signals separate). Given what your tests have shown you, what concerns do you have about a hardwire split?

Transformers are great (especially if you plan to use this rig in other venues where you might run into other problems), but if it's a fairly captive application and the split works without transformers I'd be tempted to skip them for cost and weight reasons.

-Russ

The weird thing is there is never any noise on the XLR. If it was a ground issue I would think it would show up in both places on the ¼” output and the XLR output.

Yesterday I made an 8 channel short XLR Y snake from two M-XLR to F-XLR short snakes. I will put that in next week. I don’t expect to have any problems with this since I already tested this hook up. I actually think this will be a better way to hook this all up.   
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Russell Ault

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Re: Sennheiser EW300 receiver strange problem.
« Reply #4 on: July 27, 2019, 01:05:55 am »

The weird thing is there is never any noise on the XLR. If it was a ground issue I would think it would show up in both places on the ¼” output and the XLR output.

Not necessarily; part of the point of balanced audio transmission (i.e. two signal legs that are at the same impedance relative to ground) is that it does a good job keeping ground noise out of the signal chain, while unbalanced audio transmission doesn't. It's one of the reasons why most live sound applications tend to try and avoid unbalanced connections wherever possible.

-Russ
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Ike Zimbel

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Re: Sennheiser EW300 receiver strange problem.
« Reply #5 on: August 01, 2019, 10:48:25 am »

Sennheiser EW300 receiver strange problem.

I am trying to setup a simple IEM system and have encountered a weird problem (a buzz) when trying to use the unbalanced ¼” output of some EW300 receivers and the XLR output at the same time when the XLR is going to the house system. If I unplug the XLR to the house and take just the ¼” output the signal is clean. The behavior (buzz or no buzz) is the same when the ¼” output is plugged into the XLR on the X32Rack (the IEM mixer) with proper adapters or just plugged into a battery powered headphone amp. I have tried every combination of wiring to the X32Rack from the ¼” connector. I have tried ground lifting the signal everywhere. After encountering this issue I unplugged everything from the X32Rack and was testing with just one receiver to try and narrow things down. 2 of the reviver didn’t exhibit the problem but those two don’t go directly from the XLR to the house system they go thru a processor in the rack and the out of that to the house system.

So I get a buzz on the ¼” output even when that output is connected to a battery powered headphone amp and the XLR is connected to the house. The XLR output always stays clean.

If this was for floor wedges and rock and roll I would say that the buzz would be lost in the noise floor but with IEMs this is not acceptable. 

The receivers and the X32Rack are in the same tall metal rack. If I use the XLR output connected to the house system I get a buzz only on the ¼” output. The XLR output stays clean. There are 9 receivers in this setup 7 are EW300 G3 one is a EW300 G2 and one is a EW100 G3. They get the power over the antennas from the Sennheiser antenna distro system. And those are AC/DC power supplies that aren’t grounded so a ground lift (for testing) there wouldn’t do any good. All of this (A/C power) is on the same breaker panel.

I still need to do more testing to see if I can figure out why this is happening. If I use an XLR Y cable and go from the Receiver to the X32Rack and the house system it is all clean. I am just not sure if using a hardwired split is the best way to do this. It would seem to be the easiest solution. I am also going to try a passive 8 channel transformer isolation rack mount unit so I am just using the one XLR output from the receivers.

BTW before doing all of this I asked Sennheiser tech support if this would work and they said it would. I spoke to tech support at Sennheiser this morning but we could come up with a reasonable solution.

Does anyone have any input?
Couple of things: First, since Henry appears to be otherwise occupied :o...the semantics police: With IEM's, the rack mount units are the transmitters ;)
Second, according to the the SR 300 IEM manual, the loop-through jacks are actually balanced and "buffered", meaning they have an active balancing circuit in line between the input jacks and the 1/4" output. SO, if you are using 1/4", TS (IOW "mono") plugs, you are un-balancing the output. Many less expensive active balancing circuits (and even an expensive one that I build...) are not happy with having having one leg shorted to 0v ("ground")
Have you tried all of this with TRS plugs? If not, try inserting the TS plug in part way, so the tip is actually engaging the ring contact in the jack. This avoids the short to 0v, but will result in your signal being reverse polarity and -6dB. IOW, NOT a solution, but just a quick test to see if the issue goes away.
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Kevin Maxwell

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Re: Sennheiser EW300 receiver strange problem.
« Reply #6 on: August 02, 2019, 09:34:42 am »

Couple of things: First, since Henry appears to be otherwise occupied :o...the semantics police: With IEM's, the rack mount units are the transmitters ;)
Second, according to the the SR 300 IEM manual, the loop-through jacks are actually balanced and "buffered", meaning they have an active balancing circuit in line between the input jacks and the 1/4" output. SO, if you are using 1/4", TS (IOW "mono") plugs, you are un-balancing the output. Many less expensive active balancing circuits (and even an expensive one that I build...) are not happy with having having one leg shorted to 0v ("ground")
Have you tried all of this with TRS plugs? If not, try inserting the TS plug in part way, so the tip is actually engaging the ring contact in the jack. This avoids the short to 0v, but will result in your signal being reverse polarity and -6dB. IOW, NOT a solution, but just a quick test to see if the issue goes away.

I am sorry; I just realized that I was making a lot of assumptions that the person reading this would understand some things that I didn’t make clear. I am sometimes not good at writing out what I am trying to get across.

I guess I confused things when I mentioned that this was for an IEM system. The IEM part of it (Shure PSM300s) has absolutely nothing to do with the buzz problem. The problem is entirely in the EW300 Sennheiser wireless mic receivers.

The weird thing is there is never any noise on the XLR outputs of the Sennheiser EW300 Receivers, no matter how I hook things up. If it was a ground issue I would think it would show up in both places on the ¼” output and the XLR output of the Sennheiser EW300 Receivers and be a hum not a buzz. Do you know why a device hums? Because it doesn’t know the words.

I made an 8 channel short XLR Y snake from two M-XLR to F-XLR short snakes. I put that in this week, it goes from the XLR output of the Sennheiser EW300 Receivers with one end of the Y cable going to the X33Rack (IEM mixer) and the other end going to the house system. I didn’t have any problems with this hardwired split.   
 
You said - “Have you tried all of this with TRS plugs? If not, try inserting the TS plug in part way, so the tip is actually engaging the ring contact in the jack. This avoids the short to 0v, but will result in your signal being reverse polarity and -6dB. IOW, NOT a solution, but just a quick test to see if the issue goes away.”
Regarding this now that I hope it is clear that I was talking about the Sennheiser EW300 Receivers. I talked to Sennheiser support and I clarified that the ¼” outputs are indeed unbalanced. Which shouldn’t have been a problem since I was only going about 2 feet with that part of the cabling. I did try using TRS plugs and it didn’t change anything.

Thank you for your help and bring to my attention the unclearness of my post.

Please forgive and grammatical and spelling errors. That should be my default tag line.

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Ike Zimbel

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Re: Sennheiser EW300 receiver strange problem.
« Reply #7 on: August 02, 2019, 11:51:50 am »

I am sorry; I just realized that I was making a lot of assumptions that the person reading this would understand some things that I didn’t make clear. I am sometimes not good at writing out what I am trying to get across.

I guess I confused things when I mentioned that this was for an IEM system. The IEM part of it (Shure PSM300s) has absolutely nothing to do with the buzz problem. The problem is entirely in the EW300 Sennheiser wireless mic receivers.

The weird thing is there is never any noise on the XLR outputs of the Sennheiser EW300 Receivers, no matter how I hook things up. If it was a ground issue I would think it would show up in both places on the ¼” output and the XLR output of the Sennheiser EW300 Receivers and be a hum not a buzz. Do you know why a device hums? Because it doesn’t know the words.

I made an 8 channel short XLR Y snake from two M-XLR to F-XLR short snakes. I put that in this week, it goes from the XLR output of the Sennheiser EW300 Receivers with one end of the Y cable going to the X33Rack (IEM mixer) and the other end going to the house system. I didn’t have any problems with this hardwired split.   
 
You said - “Have you tried all of this with TRS plugs? If not, try inserting the TS plug in part way, so the tip is actually engaging the ring contact in the jack. This avoids the short to 0v, but will result in your signal being reverse polarity and -6dB. IOW, NOT a solution, but just a quick test to see if the issue goes away.”
Regarding this now that I hope it is clear that I was talking about the Sennheiser EW300 Receivers. I talked to Sennheiser support and I clarified that the ¼” outputs are indeed unbalanced. Which shouldn’t have been a problem since I was only going about 2 feet with that part of the cabling. I did try using TRS plugs and it didn’t change anything.

Thank you for your help and bring to my attention the unclearness of my post.

Please forgive and grammatical and spelling errors. That should be my default tag line.
No problem. WRT the noise issue, you mentioned that it was present even when just checking through a battery powered amplifier. That says to me that the noise is being induced in that circuitry by something else in the rack. This could be rack lighting, either LED or fluorescent, some other RF emitting device like a router / wifi hub (or the switching power supply for any device in the rack). Or, I have seen Tempest 900 MHz intercom systems induce buzz in other devices when their Tx antenna was inside the rack.
In general, I define "Hum" as 60 Hz (or 50 Hz depending on what country you're in) and it's harmonics at 120 and 180 Hz (which can also be clues to different issues, for example 120 Hz is often a sign of failed filter capacitors in a power supply while 180 Hz is more likely being induced magnetically...ie; a proximity or shielding issue). "Buzz" I define as higher frequency noise and is more likely being radiated or induced and can be from things like RF signals in the air.
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Don Boomer

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Re: Sennheiser EW300 receiver strange problem.
« Reply #8 on: August 02, 2019, 02:03:37 pm »

Hey Kevin

Don’t lump “ground problems” and “ground loops” together. When you use unbalanced 1/4” connections you always have ground loops (if both pieces are connected to ac supplies). If your 1/4s are unbalanced (at either end) balanced TRS cables are no longer balanced.

The most simple answer if balanced outs work and unbalanced do not is you are getting ground loops. As suggested above, putting a transformer in the line would quickly confirm a ground loop issue.

Are your receivers and mixer connected to the same ac source?
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Mike Caldwell

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Re: Sennheiser EW300 receiver strange problem.
« Reply #9 on: August 03, 2019, 10:57:17 am »

Any possibility that something in the rack has an xlr connector
with pin 1 tied to the shell of the connector?

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Re: Sennheiser EW300 receiver strange problem.
« Reply #9 on: August 03, 2019, 10:57:17 am »


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