Buzzing sound from L1®

Portable PA
1

Hi everyone,

DJ Ron wrote to me about a buzzing sound he is getting with his setup. With his permission, I am moving our conversation here. I am hoping that with more eyes looking at the problem we can solve it together.

quote:
Originally posted by DJ Ron:
Hello ST; its been a while since we last talked. What causes a buzzing sound almost like ground loop hum from the T-1. I have high quality cables and I still get noise. The cables are not excessively long, nor do they run over power wires. I use Hosa Shielded cables that run from the T-1 to the powerstand (L-1 Model II). I tried changing the gain several different ways and I still get buzz from the tower. In fact, my towers make noise with no connections to them connected straight to a power conditioner. Any ideas what could be causing this. Here is a picture of my setup minus the T-1.

Thanks Ron

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quote:
Originally posted by DJ Ron:
Here is a second pic
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quote:
Originally posted by ST:
Hi Ron,

Does the buzz change if you disconnect (unplug) the laptop power supply?

A few scenarios to try:
  • unplug the power supply from the laptop
  • remove the power supply from the shared power source
  • disconnect the laptop from the signal chain


Please let me know what you hear.


quote:
Originally posted by DJ Ron:
Yes, it still does it. I am starting to believe its generating from the L-1 powerstand. It makes a hissing/buzz sound with nothing plugged into it which is odd. it's not very loud but it is present and you can hear it if you sit down next to it. My Classic PAS when I had it was whisper quiet with nothing plugged into it. But what are the odds of me getting two bad L-1 powerstands, I doubt it seriously but possible. The laptop is running on battery power bypassing the three prong ground which I know causes some noise.


quote:
Originally posted by ST:
Okay, I guess we've eliminated the laptop power supply.

What if you remove the power conditioner and plug the Power Stands directly into the wall?

Do get the noise in different locations?


quote:
Originally posted by DJ Ron:
Yes, I still get noise when I plug the powerstand directly into the wall with no power conditioner or power strip. This is also with nothing plugged into the stand just the speakers and powerstand, there is still noise. It should be whisper quiet with nothing connected to it.


quote:
Originally posted by ST:
Just trying to eliminate environment as a factor.

quote:
Do get the noise in different locations?


quote:
Originally posted by DJ Ron:
Hello ST; this is really strange but some how the noise is now gone. I got a new T-1 yesterday and hooked it up, absolutely no noise, whisper quiet. If I connect one L-1 with 4B1s and a packlite to my mixer and not using my laptop, I get buzz and I am using a high quality mixer (Denon DN-X1500s). When I connect the T-1 as the manual suggest making the connections, there is no noise at all. I am using the same cables so this makes no sense. The first time I reported this noice problem it was with and without the laptop so I know it wasn't the laptop causing the noise problem plus it's hooked up from the usb ports on the laptop to the Denon Players directly which have internal sound cards on each player (Denon DN-HS5500). I am not using a power conditioner with this setup but I do have a high quality 8 outlet power strip surge protector with all of my electrical connections running into it. What do you think?



quote:
Originally posted by ST:
Hi DJ Ron,

I'd really like to get this out into a public discussion so that we can get more eyes looking at this.

Is that okay with you?


quote:
Originally posted by DJ Ron:
sure


quote:
Originally posted by DJ Ron:
I think the topic should be renamed to buzzing sound from L-1 since that is where it is coming from or shall I say where it was coming from. I am going to hook up the second L-1 now to see if it makes noise like it was before.


To All: Can you help?

Thanks!
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Ok, here are my connections:
From Denon DN-X1500S Mixer Balanced Master Out (Right) XLR to ¼ TRS Stereo in Line 4/5 on the T-1
Supplied Cat-5 cable connected from T-1 to L-1 Model II Tone Match Port.
(2)B1 bass modules are connected to the L-1 Power stand
(2)B1 bass modules are connected to A-1 Packlite and connected to L-1 Power stand Bass Out ¼ TRS stereo cable; let’s call this the main system.
All gains are turned to zero and the System is powered up. The T-1 is powered up last and the volume on the L-1 is placed at 12 O’clock position and the T-1 Volume is placed at 12 o”clock position. I can barely hear any audible hissing sound which is good. I turn up the mixer volume after loading a song with my Denon DN-HS5500 media player /controller and the music plays crystal clear with no distortion at all.
Here is where the problem starts; I connect the second L-1 Model II (lets call this the remote setup), 4 B1 bass modules and A-1 Packlight. Plug the ¼ TRS stereo cable into the L-1 power stand and run the other end to the Master Out of the T-1. The gain is turned all the way down on the second L-1 and the power is turned on along with the power for the A-1 Packlight. I match the gain on the power stand to 12 o’clock and the hissing sound is extremely loud. The Left side is a lot louder than the right I turned the gain on the power stand down on the right side to about the third notch to even out the high frequency on each tower. I am sure I am doing something wrong adjusting my second (remote) setup on the T-1.

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Another issue, the bass is also out of phase. I used only one side and the bass is strong and when I hook up the second set to the other L-1 Model II the bass is out of phase and is reduce dramatically, reminder, this is with the subs stacked either two by two or four high. If I disconnect the T-1 and just hook up my L-1 (model IIs) directly to my mixer the sound is balanced and so is the bass response.

6

Where’s your cell phone located in all these tests?

Wild shot but worth the ask.

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Cap; I found out at my first setup that cell phones and PDAs cause all kinds of noise but that is not the issue here. At this point the loud hissing sound is coming from the second setup. The one the T-1 is hard wired to is quiet. If I reverse the setup and connect the T-1 to the side that makes the noise and use the other side as the slave, it too makes noise and the hard wired side is quiet.

8

This is a puzzle…

quote:
…I got a new T-1 yesterday and hooked it up, absolutely no noise, whisper quiet. If I connect one L-1 with 4B1s and a packlite to my mixer and not using my laptop, I get buzz and I am using a high quality mixer (Denon DN-X1500s). When I connect the T-1 as the manual suggest making the connections, there is no noise at all…

First questions … to clarify …

1) When you connect the T1, are you using the digitial (Ethernet-style) cable or the analog output of the T1 with a separate power supply?

2) Is the mixer disconnected when the T1 is connected?

Speculating-1: With just the T1 connected, and no inputs on the T1, can you turn up the Master on the T1 and ‘recreate’ the noise? (I’m wondering if the digital input is acting as if the “trim” is way up when no cable is plugged in – even though there is no actual “trim” for the digital input.)

Speculating-2: If the T1 is analog connected, again, can you recreate the noise by turning up the Master (with no inputs on the T1… and try it with all the channel knobs fully ‘off’ as well as fully ‘on’).

If neither of these T1-related experiments cause the same kind of noise you get with the mixer connected directly to the (analog only, of course), then I’m really suspicious of the grounding.

Another experiment would be – if the T1 connection is ‘quiet’ – to then connect the mixer output to the T1 (e.g.: channel 4) and see if it remains quiet. If not, then it seems to me that there is most likely a grounding issue amongst all the equipment.

Does simply replacing the ‘shared power’ device (power strip) change anything? (You’d think these relatively simple ‘power strip’ devices wouldn’t cause such problems – but they can. I’ve had just one outlet fail in a simple surge protector; weird.)
(Edited to reflect having truly read all the notes above! Frown Roll Eyes )

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DJ Ron: Okay, boss.

My L1 experiences with loud hissing (Classic and Model 1) is when the trim controls on channel 1 and/or 2 are cranked up all the way.

On two separate reported occasions, that hiss was loud although the trims were zeroed. In both cases, the anomaly was cured by setting all the dials on the wired remote to 12 o’clock (default), plugging it in, turning on the power stand, then off, and remove the wired remote. I know. That’s weird, shouldn’t happen, doesn’t make sense, but it worked.

Is there a reset on the T1? Have you gone ahead and performed the T1 updates again just for drill?

I’m throwing darts here, Ron, knowing how frustrating chasing these electronic ghosts can be. Good luck with it.

10

Hi, DJ Ron … I didn’t see this note when I was creating my previous post above. Now I understand more of your setup.

quote:
Originally posted by DJ Ron:
…At this point the loud hissing sound is coming from the second setup. The one the T-1 is hard wired to is quiet. If I reverse the setup and connect the T-1 to the side that makes the noise and use the other side as the slave, it too makes noise and the hard wired side is quiet.
By ‘hard wired’, I see (now!) from an earlier post that you mean the T1 connection via the “EtherCon” cable … and that you are not using a separate T1 power supply.

It seems to me, then, that the problem is related to an analog output of the T1 and the “other” L1.

I evidently glossed over your setup in a previous post… let me deal with those items …
quote:
…The T-1 is powered up last and the volume on the L-1 is placed at 12 O’clock position and the T-1 Volume is placed at 12 o”clock position. I can barely hear any audible hissing sound which is good. I turn up the mixer volume after loading a song with my Denon DN-HS5500 media player /controller and the music plays crystal clear with no distortion at all…
There is no “volume” on the Model II powerstand. That ‘knob’ is the “trim” for the analog input only. If you turn it all the way down, you should either hear no change – or even a slight reduction in the hissing.

Now, regarding the ‘remote’ system:
quote:
…Plug the ¼ TRS stereo cable into the L-1 power stand and run the other end to the Master Out of the T-1.
You do realize that you are thus running a “Dual Mono” setup?

Have you tried a “mono” TS cable … or at least a different brand of TRS (which is actually just being used as a ‘balanced’ mono cable, in this situation)?

By the way, the “Dual Mono” may explain why the bass seems to be ‘out of phase’.

quote:
… I match the gain on the power stand to 12 o’clock and the hissing sound is extremely loud. The Left side is a lot louder than the right I turned the gain on the power stand down on the right side to about the third notch to even out the high frequency on each tower.
First of all, it is perfectly normal … expected … that you have the “trim” on the ‘remote’ L1 (Model II) only 1/4 to 1/3 of the way up. I would suggest that you start with the L1 Trim knob all the way down, then – when the volume from the primary L1 is “right”, bring up the Trim gradually on the ‘remote’ L1 until it matches in volume (you’ll have to walk back and forth between them to really judge this “equality of volume” with any accuracy).

If you are not truly running that 2nd L1 as a ‘remote’ system (one more than 15-20’ away from the primary L1), then you may want to configure the T1 for “stereo” output by using both the Master and Aux outputs. There are notes in the Wiki for doing that here (with diagrams). This requires using two separate T1 channels, not the single 4/5 channel (which is really just one channel with two input connections).

As noted above, also, re-confirm that the two L1’s are truly on to same power source.