I like that a lot. I'm going to start using those terms too.
Laptop sound noise
- Thread starterCorbettlight
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I like that a lot. I'm going to start using those terms too.
I think there's too much emphasis on having ground rods. Sure, they (or some equivalent) are required by code, and they may have value, but wouldn't it be better to ensure a proper grounding system that originates at the neutral-ground bond at the upstream transformer?
And how do you get a very low impedance with a ground rod when the earth isn't made of copper?
And how do you get a very low impedance with a ground rod when the earth isn't made of copper?
Yep. I don't see the copper rod working unless the surrounding soil has been treated electrolyticly and even then some locations and soil types make actual earth grounding impossible[1]. As far as I know there is no guarantee that there won't be a voltage differential between power utility ground and earth ground, I'm way out of bounds here as the only place we had that done (copper rod to some code) was manufacturing medical linear accelerators.
In control booth context there is, however, a probability that some venues will have a ground that likes to float regardless of how much engineering is thrown at it. I'd guess most facility engineers would know their site pretty well, the most likely problematic ones might be new where the contractor never bothered to check utility ground to earth ground (and or ignored the fact that a lot of construction workers were experiencing more shocks than normal). Codes vary from one locale to another so there are places where not much can be done (and not everyone will follow code anyway).
But I'm off on a tangent here (It's a writer thing?).
I'd like to that everyone for their comments and hope hijacking this thread did not step on to many toes. I'm very pleased to find that Antec provides a noise solution for towers and laptops (I did not find that out until last evening).
Unless we see posts to the contrary I'll assume Antec power supply upgrades are the preferred solution and will pass that information on.
Best Regards,
Richard V. Hale Jr.
[1] Its been a while but I think some power plant control rooms use really big isolation transformers which might provide an artificial ground in an extremely hostile environment. Also power plants relatively close to one another may have to run in phase or they will trash earth ground and loose power in the process. More useless stuff I'm not sure of but can be researched if anyone is interested.
TimmyP1955
Well-Known Member
llecount
Member
So what IS the answer to this problem then? I've tried PC-DI's, iso transformers, different cables, etc and I still cannot get rid of this noise. I can make it quieter, but it is still audible, and that is not acceptable. This is on a sound system in a meeting room. Laptops with 2 prong wall plugs do not have any problem, but laptops with 3 prong wall plugs are noisy as hell. A USB/Firewire solution is not practical for a room such as this.
Is there an affordable solution?
Is there an affordable solution?
Even something like Peavey :: USB-P USB Playback? It requires no drivers, although you do have to select it as your audio device.
Something like http://www.jensen-transformers.com/datashts/ci2mini.pdf should take care of ground loops, however the audio system in the meeting room probably can't tell unwanted noise from wanted signal so if the noise is inherent in the audio signal from the laptop then there is no easy way to address that other than perhaps trying to find an ungrounded power supply for the laptop or running off the battery.
In public forms we are constrained as to the message we convey.
Looking at other meeting room setups might tell you the practice at your locale (facilities and electrical engineering probably let it the laptops float).
I know its not the safest practice but I plead guilty to doing the same thing as the carpeting and pad are thick in our meeting room (on the second floor) providing a good deal of insulation. If the room had no carpet (concrete ground floor) then I'd at least lay down some rugs before using power amps.
Spilling a drink on a three to two prong adapter on a concrete floor is not good. Even with carpeting on top of concrete is little help if the drink has electrolytes (conducts electricity) in it. Maybe not allowing drinks in the room might mitigate the situation.
Sadly all the good solutions require investment. Upgrading to noiseless power supplies ($40 antec for all but a few newer laptops) would allow recharging of batteries during operation. They also could be swapped between machines that have just been charged with those running on a low battery.
Looking at other meeting room setups might tell you the practice at your locale (facilities and electrical engineering probably let it the laptops float).
I know its not the safest practice but I plead guilty to doing the same thing as the carpeting and pad are thick in our meeting room (on the second floor) providing a good deal of insulation. If the room had no carpet (concrete ground floor) then I'd at least lay down some rugs before using power amps.
Spilling a drink on a three to two prong adapter on a concrete floor is not good. Even with carpeting on top of concrete is little help if the drink has electrolytes (conducts electricity) in it. Maybe not allowing drinks in the room might mitigate the situation.
Sadly all the good solutions require investment. Upgrading to noiseless power supplies ($40 antec for all but a few newer laptops) would allow recharging of batteries during operation. They also could be swapped between machines that have just been charged with those running on a low battery.
I don't want to be rude about it, but...
You can't go and expect good audio quality from an onboard sound interface that costs under a dollar to make.
If you want decent sound, there are no free lunches in this world and you'll need to pay for a proper audio interface.
ANY solution that involves compromising safety grounding included by a manufacturer means YOU are PERSONALLY LIABLE for any injuries caused.
Just don't do it.
No show is ever worth a risk to people's wellbeing. EVER.
You can't go and expect good audio quality from an onboard sound interface that costs under a dollar to make.
If you want decent sound, there are no free lunches in this world and you'll need to pay for a proper audio interface.
ANY solution that involves compromising safety grounding included by a manufacturer means YOU are PERSONALLY LIABLE for any injuries caused.
Just don't do it.
No show is ever worth a risk to people's wellbeing. EVER.
There are two possible ways for the noise to occur. One is that the noise is produced in the sound circuitry of the laptop. It may simply be a case of power supply noise getting into the output. If that's the case, the only choices are to use an external sound device on the USB port, or use a different computer. The problem with a USB sound "card" is that the machine will have to have the proper drivers and settings.
The more likely possibility is that the noise is a ground loop and a good direct box or transfomer should do the job. The problem is that the quality of isolation of these products varies widely. Some use audio transformers with Faraday shields and some do not. Without the Faraday shield, there is capacitive coupling between the primary and secondary. Since the computer's switching supply makes a lot of high frequency dirt, it tends to pass through more easily than 60 Hz.
It's hard to know which manufacturers are cutting corners. Generally, the more expensive the product, the better the result, as they should have better transformers. This is why there are $40 interfaces and $300 interfaces that seemingly do the same thing. The Jensen products are top notch and I have had great results with them. Countryman also has an excellent reputation. I would stay away from Rolls and Behringer. Also, make sure that the DI or transformer is feeding balanced cabling and a true balanced input on your mixer.
The more likely possibility is that the noise is a ground loop and a good direct box or transfomer should do the job. The problem is that the quality of isolation of these products varies widely. Some use audio transformers with Faraday shields and some do not. Without the Faraday shield, there is capacitive coupling between the primary and secondary. Since the computer's switching supply makes a lot of high frequency dirt, it tends to pass through more easily than 60 Hz.
It's hard to know which manufacturers are cutting corners. Generally, the more expensive the product, the better the result, as they should have better transformers. This is why there are $40 interfaces and $300 interfaces that seemingly do the same thing. The Jensen products are top notch and I have had great results with them. Countryman also has an excellent reputation. I would stay away from Rolls and Behringer. Also, make sure that the DI or transformer is feeding balanced cabling and a true balanced input on your mixer.
NO and NO. I'm using the Behringer UCA202 from the laptop USB to the phono preamp input on an ancient stereo amp. The drivers are ROMed on the device (XP SP3). MS probably distributes it by default by now. There is absolutely no noise with this setup (admittedly far from perfect as it
is 16bit streaming audio. I have not run the 24bit tape/digital recording test).
I have no interest in Antec. The power supplies come with extremely high review recommendations. Call them up (or email) and ask them if you can return it if it is noisy. My understanding is that this would be a first ***AND*** everyone here would like to know about it.
I'm glad you have had good luck with the UCA202. I was thinking more of their direct boxes which haven't given me great performance and did not last long. In a meeting room situation, a USB device would require individual users to change their laptop sound settings. That is often beyond their capability. Plugging in an audio cable is about the all that can be expected.
You do realize that phono preamps apply RIAA equalization, which applies a 20 dB boost at 20 Hz., and a -20 dB roll-off at 20 kHz? The only thing a phono input is good for is connecting a turntable.
You do realize that phono preamps apply RIAA equalization, which applies a 20 dB boost at 20 Hz., and a -20 dB roll-off at 20 kHz? The only thing a phono input is good for is connecting a turntable.
I had a nice long reply but the machine ate it with a 404. Did not see the little "restore saved content" box, oh well... a few highlights:
Assuming a DAW class:
Cntl pnl/sounds and audio/audio/sound playback/Default device/UCA202
I did not want to drag curves into the thread. Its nice to get your input though, thanks.
The digital to analog signal is pre-eq'd with -6db 20hz and +6db 20Khz slope in itunes with the pivot point (0db) at 500hz (dinosaur school).
Those old pre-amps are lots of fun, all the rage with musicians (and some broadcasters) but mine is transistor. Second stage EQ is through a hardware ten-band amped up to about 70 watts rms and fed into a five way cross over custom hand built speaker box network (half JBL studio monitors).
Hardware EQ set at the familiar gentile S curve everyone should recognize, know and love.
A phono input is formally defined as an instrumentation amplifier which to understand requires at least one engineering book (I have a few around here somewhere). All I care about I cranking it up to about 70watts rms, near deafining spl with no noise or distortion when compared to the headphone headset.
Whats not to like about the $40 Antec solution ? That it does not work with newer proprietary lap tops is not relevant. Antec makes Tower supplies so duh, log in remotely, use the Tower as a real DAW Server. The laptop (or notebook) is just a display device.
Cheers !!!
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In the most recent scenario discussed here, it's a conference room or meeting hall, where we have no control over who is bringing in what computer. There may be no technical supervision. The solution has to be simple to untrained users and universal to any computer carried into the room. A solution that works fine in a controlled environment, like a theater control booth, studio, or home doesn't apply here.
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YIKES!!! Ushers at the bigger church venues (meeting halls) sometimes call this mob control. That would seem to only allow battery power.
Battery power is fine for the (executive) conference room and when batteries run low swap in another battery or if there are power outlets around the table plug in the $40 Antec and recharge without noise.
I'm looking for the problem here and cannot find one. Please educate me as I'm a life long student of the signal to noise ratio discipline. Thanks beforehand.
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That, is the problem. In one year at my high school, we've had everything from laptops running Windows 2000, to 2012 MacBook Airs, and everything in between. With people who just learned how to use PowerPoint for that event, to people who have years of experience. There is no way I could say (You just need to log in remotely, and connect to your computer, and then mine will actually supply the audio.
I guess my point is being missed here. There aren't too many situations where we can dictate to run on battery only, use only a certain brand of power supply, use a different computer, stand on your head and cough, to eliminate the noise problem. For example, how do we know the CEO giving the presentation hasn't just been using his laptop for three hours on the plane so the battery is run down? You can't just say "use the battery" so the audience doesn't have to endure a whine in the speakers.
As audio engineers, we try to find solutions to technical problems without making the system overly complicated, so it matches the skill level of the users, and meets the needs of the client. In this situation, the goal should be to build the audio system in such a way that it doesn't make noises no matter what computer combination is used. The way to do that is to use a good audio transformer to connect the computer to the mixer.
By the way, Chase hit the nail on the head here.
As audio engineers, we try to find solutions to technical problems without making the system overly complicated, so it matches the skill level of the users, and meets the needs of the client. In this situation, the goal should be to build the audio system in such a way that it doesn't make noises no matter what computer combination is used. The way to do that is to use a good audio transformer to connect the computer to the mixer.
By the way, Chase hit the nail on the head here.
!!! SPEC IT SO I CAN TEST IT !!! Yeah, Sr. Engineers and Scientists want to replicate the solution before giving any credit to the assertion (hypothesis).
BTW I crashed and burned badly with the "good audio transformer" solutions on ebay as the entire genre was yanked as (what I found anyway) they introduced more RF and EMI than they filtered out, not trying to be a pain in the backside just trying the ethereal solution that seems to keep slipping from my grasp.
The solution might be to put the "good audio transformer" inside a shielded well grounded box which would be fine.
I'm tossing in the towel because everything I touch turns to poo. But I would love to reproduce just about any solution anyone comes up with. In another life during the cold war a lot of work was done in 100% metal vaults known as "screen rooms" and EMP resistant devices known as tempest. Mentioned here because it has been
done before but at an astronomical cost.
All the Best,
Richard
Audio transformers aren't widely used, mass production items these days. Good ones are almost a lost art. They were widely used and understood back in the days of vacuum tube equipment, but not so much now. They are often overlooked because cheap ones create more problems than they solve. But, good ones can make the seemingly impossible work fine. Selecting an appropriate one on eBay is a total crapshoot. Specifications for inferior audio transformers are usually so incomplete that they are meaningless. Go check out the Jensen Transformers web site. There is plenty of information there, all based on good engineering and no hype. Bill Whitlock is legend in the audio community and he literally has written the book on audio transformers.
WELCOME TO JENSEN TRANSFORMERS, INC.
If you really want to delve into audio noise issues, engineer Neil Muncy coined the term "the pin-1 problem." He wrote some AES papers and gave a number of seminars about noise problems in audio interconnections that stood the audio industry on its head. Today, we have a lot of better audio equipment due to his efforts.
Pin 1 Problem
I'll give you just one, quick example of what transformers can do. My radio station has to feed broadcast quality audio several thousand feet between buildings. The buildings have different AC ground potiential. Using transformers, I can send the audio over exisiting (dry pair) telephone lines, and the results are 20 Hz to 20 kHz, S/N in the 80 dB range and distortion less than 0.1 %. It could not be done using copper cables without transformers. There simply isn't an active balanced input or output stage that would handle the high common-mode voltages between the two buildings.
WELCOME TO JENSEN TRANSFORMERS, INC.
If you really want to delve into audio noise issues, engineer Neil Muncy coined the term "the pin-1 problem." He wrote some AES papers and gave a number of seminars about noise problems in audio interconnections that stood the audio industry on its head. Today, we have a lot of better audio equipment due to his efforts.
Pin 1 Problem
I'll give you just one, quick example of what transformers can do. My radio station has to feed broadcast quality audio several thousand feet between buildings. The buildings have different AC ground potiential. Using transformers, I can send the audio over exisiting (dry pair) telephone lines, and the results are 20 Hz to 20 kHz, S/N in the 80 dB range and distortion less than 0.1 %. It could not be done using copper cables without transformers. There simply isn't an active balanced input or output stage that would handle the high common-mode voltages between the two buildings.
I love the citations referenced in the above post, always been a big fan of RLC circuitry, Inductive Coupling, Reflected Impedance and what a few discrete parts can do [1].
Nice. However spread spectrum hits 40Mhz using the same copper (my provider who I do not like **&*) and I'm to lazy to give you the spec but its in the management part of the router and partially implemented (about 256 bands if I recall). But this is irrelevant to the problem at hand (Laptop sound noise).
I'm still waiting for someone to post a spec for a solution (part number, circuit, whatever) superior to the Antec one.
I'm beginning to suspect there is no passive solution for cheap switching power supplies that act like RFI/EMI Transmitters. Sadly I wish there was a cheap old
school "audio transformer" with an op amp or digital circuit that would
work (SPICE2 simulation comes to mind [2]).
Sadly, by the time we come up with any CMRR audio transformer or modern noise cancellation technology it probably will be (A) Impossible for it to work in a digital world and (B) cost a lot more money than the solution already proposed (replace sucky power supplies or buy new systems with noiseless power supplies)
The best I can hope for is the niche created by Antec will spread in applicability and profitability such that major player's will jump in with both feet.
Sadly, here we have lots of wishful thinking, no solid test case (IEEE/IEC/NIST/NBS/etc.) to validate a solution if one were proposed even though
RLC circuits are well understood.[3]
As a society we have dumbed down to the point that when a working technical solution does exist there are social, physiological reasons why what obviously already works (DAWs in recording and stage performance) will, in the minds of some, just not cut it.
For Home Recording and Performer Wanna-bees (Me) Antec should benefit financially from their work (free market at work I'd propose).
Perhaps most others not. Regardless I love your effort and thought that you have given to this thread.
Best of Luck to everyone and Thanks...
Richard
Notes
[1] sengpielaudio.com/calculator-timeconstant.htm
[2] en.wikipedia.org/wiki/SPICE
[3] en.wikipedia.org/wiki/Transfer_function -- Potentially lots of useful filters mentioned which might be leveraged.
llecount
Member
EXACTLY! The systems in our rooms should just "work", no fiddling, no extra changes.. Just work as it should. If I was in the client's shoes, that is precisely what I would expect.
If there is no safe way of fixing this problem, then my only other solution I see would be to look in to a USB device.. But ONLY if it automatically installs itself on any modern version of Windows (XP-W7) or Mac OS. I've never looked to see if such a device exists.. If they are fairly inexpensive, I'd be willing to buy one and give it a try, just to see how it works in this situation. Though I'm afraid it'll just be another piece that would accidentally grow legs and walk off eventually.
