| Author | Message | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 122 Registered: 6-2002 |
So here I am with a home recording setup of an Edirol FA-101 firewire interface at a powerful laptop, connecting my DS-5R directly to the FA-101 (for now). Here is the problem: It seems like the bare fact that I plug the DS-5R to the power socket does amplify the hissing that presumably comes from the hard drive within the laptop. The problem does not occour when I only connect a passive instrument (i.e. a Fender Strat) to the FA-101. Unfortunately I cannot run my doubleneck without the DS-5R as the bass does not consider battery power. I assume the hissing problem has to do with using the same power circuit. However, I don't seem to have two seperate power circuits available at my current location (I am on the road away from my own place). Is there a device that helps me isolating the power plug of my Alembic from the rest of the recording setup? Or am I even looking at a totally different problem here? In the perfect world I would also like to use my F-1X and SF-2 with the setup, but I don't dare to connect them yet without the current problem fixed. Any help is highly appreciated! Thanks a lot! Hartmut | |||
| byoung
Member Username: byoung Post Number: 52 Registered: 12-2004 |
My experience has been that ground loops usually show up as hum (60Hz), not hiss. If you really think that power could be a consideration, have you tried plugging your DS-5 in to a power conditioner? An uninterruptible power supply (UPS) might help. Brad | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 123 Registered: 6-2002 |
Thanks for your reply, Brad! As I am located Germany I am not entirely familiar with the term "power conditioner" although it seems like I expected something like this could be my solution. Can you describe what the conditioner exactly is and does so I can look out for it here in Germany? The hiss that occurs is really that high frequency sound the hard drive makes, amplified by a ton of dBs, which is gone when I unplug from the power any of the Alembic devices. Hartmut | |||
| keith_h
Junior Username: keith_h Post Number: 46 Registered: 2-2005 |
A power conditioner will even out voltage fluctuations, filter power line noise and provide voltage spike protection. Here in the states, with 120V A/C, dirty power and voltage fluctuations are not uncommon and are known to introduce noise. This is why many people use a power conditioner for their rig. A well built UPS will also perform power conditioning in addition to its UPS duties. Searching the net I saw some complaints about the FA-101 picking up noise while the laptop battery recharges. Maybe it would be good to better define the term hiss. When I hear hiss I think of the "ssss" sound. When I hear a hard drive searching or being accessed I would say it is more of a chirping sound. A whine is similar to the sound a camera flash makes while it is charging or an electric motor makes as it starts up. If the sound can be better defined it might help with suggestions. Maybe attaching an MP3 so we could hear it. Is it possible that the pickups on the bass are picking up the noise and injecting it into the recording. I know that I have to be carefull how close I get to electrical appliances with my active basses. My passive basses/guitars seem less susceptible to external electrical noise and interference. Keith | |||
| byoung
Member Username: byoung Post Number: 53 Registered: 12-2004 |
Hartmut, You might also try running the laptop on battery (no AC), and turn down the brightness on the LCD all the way. You might be experiencing Van Eck-style* radiation (your bass, power supply, or cabling might be picking it up). I have an IBM laptop that can't get within 10 feet (3M) of a radio without putting static in the signal. Also, try moving your bass as far away from the laptop as possible, or introduce shielding (happen to have any lead lying around? =)). Would you say that the sound is like white noise (television set tuned to a dead channel), or like a high pitched whine? Most of the older hard drives I've heard (before those fancy fluid drive bearings, etc.) have what I'd call a wheeee noise. Of course I have worked with some hard drives that sounded like rock crushers and machine guns, but that's another story altogether. As far as power conditioners, here's a link to a power conditioner: http://www.furmansound.com/products/international/ac-210e.php If you google for power conditioner, you'll find many-- they're very popular in home theatre and home audio. Brad * Van Eck: http://www.disappearing-inc.com/V/vaneckphreaking.html | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 124 Registered: 6-2002 |
Thanks guys! That is a lot of useful information. Keith, here is the mp3:
It gives you a clue why people aren't allowed to use computers or cd-players on airplanes during take-offs and landings.  I just plugged some notes so you can compare them to the volume of the noise. However, running the laptop on battery did in fact help as expected. A little of the noise remained but moving the bass away 3 feet did indeed help. Moving away did not help while the power cord was connected though. The drawback of running the laptop on battery is that I would like to use it on its docking station to have some more connections (USB, firewire etc.) available. Obviously the docking station does not run on battery and needs the power plug. So, would the power conditioner help even in my case? Thanks everyone! Hartmut | |||
| davehouck
Moderator Username: davehouck Post Number: 1686 Registered: 5-2002 |
The bass sounds nice! | |||
| adriaan
Senior Member Username: adriaan Post Number: 546 Registered: 6-2002 |
Did you check if it makes a change if you move the power cord for the laptop away from the other power cords? Cords can act as communicating antennas, especially when they run in close parallel, so if one is sending out 'dirt' the other one can pick it up - there's little or no shielding in power cords. So increase the distance between the cords, and try to make them run not in parallel. | |||
| keith_h
Junior Username: keith_h Post Number: 48 Registered: 2-2005 |
Harmut, Nice sounding bass. After listening to the file I noticed that the sound is pulsing at a constant interval. My loose calculation is somewhere around 84 cycles per minute. It would take a longer segment to get a firm number. The fact that you still hear it when running on battery implies to me the power chord is acting as an antena and not the cause. It is something within the lap top itself that is generating the interference. One thing that might be causing the problem is your monitor or display. I base this on 85hz, which is close to my calculation, being a valid refresh rate for some monitors. Can you change the refresh rate and determine if the noise changes? To expand further on Adriaan's suggestion try not to cross any power chords or signal cables. If they must cross then try to ensure they cross at 90 degree angles to minimize cross talk. How far apart can you move the FA-101 and the DS-5R from the PC and each other? For testing I would try to get each of then as far apart from each other as possible. I left the hardware side of engineering many years ago so I am not sure what other things in a PC could cause the 84hz interference. From my past experience EMF problems are usually harder to isolate than resolve. However resolve does not imply inexpensive. I do suspect though, that there is someone here that might be able to help take the diagnosis further. Keith (Message edited by keith_h on May 09, 2005) | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 125 Registered: 6-2002 |
Interesting info everyone! I will try out a few things in the next days and let you know in case I didn't succeed. I found someone who can lend me a device that may be similar to your power conditioner. I will also check out all the other options. Good point on the display, it never occurred to me that it might not be the hard drive. Of course the credit for the nice sounding bass goes to Ron and his great people. I can't even wait to add the F-1X and the SF-2 - as soon as the noise issue is resolved... Hartmut | |||
| byoung
Member Username: byoung Post Number: 56 Registered: 12-2004 |
Hartmut, You might also try turning the LCD on your laptop off. Most laptops have an option like this, since it conserves power. It may sill be entirely the LCD, since most laptops will dim the brightness when on battery. This would cause the tone to decrease. That doesn't necessarily excuse the AC adapter, which I suspect is contributing. Does the hiss change at all as you do things on your laptop? E.g.: when you move windows around, can you "hear it" in the audio signal? Does it change tone when the processor is working hard? Can you get the fans in the laptop to switch to "high", and does this make a difference? Brad | |||
| mica
Moderator Username: mica Post Number: 2416 Registered: 6-2000 |
Here's a good article my dad wrote up about ground loops, you may find this useful, Hartmut! In the old days we had equipment without the safety ground connection to the chassis, and the signal cables provided the only ground path. This is still the best approach except that it provides no safety if there is a fault in the equipment that would put mains voltages on the chassis. So we have to think differently and minimize the effect of the ground loop. Just having a ground loop doesn't ensure that you will have hum, the hum is caused by magnetic coupling into the ground loop. Let's look at where the ground loop is being formed. We have two mains cables going to either a wall outlet or to a plug strip. The safety ground wires are connected together at this point. The mains cables go to separate pieces of equipment. We make the ground loop when we connect a signal cable between the two pieces of equipment, thus creating a continuous connection around a "loop". A varying magnetic field can now induce a current into this loop, and create a voltage drop across the wires that form the loop. Even though the two pieces of equipment are grounded thru the signal cable shield and simultaneously grounded to each other thru the safety ground wires in the mains cables, in the presence of a varying magnetic field, the ground potentials at different points in the loop are different. To understand why you don't hear the hum when no instrument is connected, consider that the center signal wire of the cable between the amplifier input and the power supply doesn't connect to anything at the power supply end. If that wire weren't shielded, then we could induce noise into the center wire by electrostatic (or capacitive) coupling, and we would often describe the resulting noise as "buzz" since electrostatic coupling more readily couples high frequency components. The shield of the cable (and the metal boxes of both the amplifier and power supply) acts as a Faraday cage and shunts any potential electrostatic noise to the ground (or earth) and prevents this type of interference from being heard. The fact that the system is quiet with the instument disconnected assures us that the electrostatic shielding is performing properly. Even though we still have the magnetic coupling generating voltages in the shields, it has no means of being sampled since the center wire is not terminated. When the instrument is plugged in we now have a means of listening to the magneticly induced noise (which is stronger at the fundamental frequency of the mains generator) so we percieve it as a "hum" sound. So how do we keep our safety grounds and minimize the hum? It might be easiest to first consider what we would do if we wanted to build a circuit to find a source of magnetic fields. We would take our “loop” and maximize the area and move the loop until it surrounds the source of the varying magnetic field. Our actual cable to the guitar is of no help to us in maximizing the hum since the signal conductors take exactly the same path as the outer shield and the area enclosed by this portion of the loop is zero. Thus you won't be able to move the guitar and its cable around to make a difference in the amplitude of the hum. So where is the area of the loop? It's that area between the mains conductors and the signal cable between the amplifier and the power supply, but also includes the metal chassis themselves. So what we want to do is to minimize the area by using a short signal cable, and by dressing the two mains cables, or even twisting them. In some cases this may be sufficient to make the hum acceptably low. Unfortunately, one of the hard things is that the source of the magnetic hum field is the power transformer inside the amplifier which is also part of the conductor path that makes the loop. So the entire loop is something like: one safety ground connection at one of the mains connectors, thru that power cable to the bolt on the chassis of the amplifier, thru that chassis metal and if the input jack is grounded to the chassis, to the input jack serrated washer that cuts thru paint, then thru the jumper cable to the power supply, whichwhere the jack is grounded to the chassis, then up thru the cable to the instrument, thru the selector switch in standby, and back down thru the cable and to a bolt thru the chassis that connects to the safety ground terminal on the mains connector, thru the mains cable, and to the same safety ground connection we started from. So we can minimize some of the path, but other parts you'd have to smash by driving a truck over the chassis and bend them to minimize them and the equipment wouldn't work after you did that! So let's go back again to the concept of how to maximize the hum. And realize that if we make a coil out of the jumper wire between the amplifier and the power supply, say about 6 inches in diameter, then we can move the coil around and generate a larger or smaller ground loop current by positioning it closer or farther from the power transformer. Also, if we invert the coil by turning it over (or the same thing if we take the coil apart and wind it in the opposite direction), then the polarity of the signal that is picked up is reversed. So we can by trial an error, determine the winding direction to generate a signal polarity that is opposite that in the loop portion that we can't do anything about. And then position the coil or adjust its area by changing it from a circle to a narrow loop which changes the area which in turn changes the amplitude. If we can set the loop just right we can generate a current that is equal in amplitude to the one we can't do anything about, with the opposite polarity, and the hum is cancelled out. Quite frequently, the use of a short jumper and dressing the mains cables to follow the same path, and using a power strip so the mains connectors are side-by-side will make the hum sufficiently low. If that isn't effective, then building the loop as described above can work after a period of tedious trials to determine the number of turns and the area to be enclosed as well as the position that will generate the right "hum bucking" voltage to exactly cancel. Note also that sometimes instead of making the coil with the signal jumper, you can make it with one of the mains cables and position it under the amplifier chassis. The principle is simple, but since our eyes can't see magnetic fields, then we're blindly trying things. But understanding the fundamental nature of the problem helps us in our blindness. (Message edited by mica on May 10, 2005) | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 126 Registered: 6-2002 |
Thanks a lot, Mica! Apart from my problem it is also an extremely interesting article on the hum canceller concept! Brad, you are so right! Moving things around on the screen in fact does make sounds. There are "blip" sounds when I minimize and maximize a window and even a scratching noise is there when I move a window around. The blip sounds really sound like R2-D2 or some cheap video game sound, very awkward to hear this as a "noise" sound. I haven't had a chance to try the power conditioner yet but I was moving things away from each other. So far no matter what I tried, the noise would remain unaltered unless the laptop would be disconnected from the power plug. However, with the laptop on battery, moving away the components from each other did almost cancel out all noise. I plugged the bass equipment to a different wall outlet (although the same circuit, I am sure) which was an improvement in itself. Also moving away the audio interface from the computer helped. It helped best while the interface was not connected to the laptop through firewire, which isn't of much use of course except for plain listening to the bass via headphones. As I said, all this success would only work when the laptop is not connected to the power outlet. There are still some more options I haven't tried yet and I will let you know how they will come along. Thanks to everyone so far! On to the next tests... Hartmut | |||
| davehouck
Moderator Username: davehouck Post Number: 1691 Registered: 5-2002 |
Thanks Mica!! This is another one of those things that I would never have thought of, but when read, it makes a lot of sense. I have once again learned something new in the Alembic club! And I had already figured that smashing the amp with a truck was probably not going to work. | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 127 Registered: 6-2002 |
Now, here is an interesting one: Switching the LCD off erases the noise. Right, we almost expected that. But changing brightness works like a CVQ on some of the lower hum (which I almost overheard before), changing the frequency of the hum with every step. The punch line: The hum totally disappears when the LCD is set to its HIGHEST brightness setting. Unfortunately the pulsating hiss is not affected and does still remain. | |||
| byoung
Member Username: byoung Post Number: 58 Registered: 12-2004 |
Hartmut, I don't think that you have a ground loop; I think the LCD on your laptop is the culprit. Try turning the LCD off-- all the laptops I've owned will turn off the screen if you close the lid, but you may wish to double check the power settings in the control panel-- some laptops will suspend when the lid is closed, and that wouldn't help. Basically, start the recorder, and then turn off the LCD. I suspect that the noise will go away, even if plugged in. What I think causes it is the ballasts for the cold cathode tubes that backlight the LCD. I don't think that there is much you can do other than isolation and shielding: Isolation: Isolate the AC mains by physically separating them. In the US (residential), we have two 120V buses in the power system, 180 degrees out of phase, and putting them on different buses might help if you can figure out which bus is connected where in your house. That may not help, since they share the same grounded connector. The grounding (neutral) connectors are on different buses, but are tied to the grounding connector at the ground point (all buildings in the US have a single ground point). Of course, you have 230V @ 50Hz, and I'm not sure if you have separate buses in your panel or not. Oddly enough, Germany hasn't adopted the US electrical code (I'm kidding!). Shielding: You could try to cook up a faraday cage (look up "faraday cage" or "tempest shielding" on Google-- these are both related to Van Eck Phreaking, which I referenced earlier). You may need to figure out a way to ground the cage; this is something to talk to an electrician about, since you can be injured or killed by hooking things up to your electrical system. In short, turn off the LCD while recording. I can almost guarantee that will fix, or at least markedly improve, your issue. Especially since you can hear windows moving and whatnot. Brad | |||
| byoung
Member Username: byoung Post Number: 59 Registered: 12-2004 |
Okay, The LCD is a partial culprit-- but there is still the pulsing hiss. Hmm. It sounds like a fan motor to me. I'm not sure why it pulsates. I think that you can isolate whether the fans are the culprit by seeing if the sound changes tone when the fan speed changes. Most (if not all) laptops I've owned have multiple fan speeds, and may or may not be controllable in software. The one reliable method of getting them to run at theie top setting is getting the processor HOT. Run something that will use every CPU cycle in the machine (plug into the mains) like a benchmarking tool or advanced 3D game (Unreal 2). Run it hot for a while (with the fans on full), and then try your recording again, with the laptop on full brightness. Compare the tones-- if it is higher pitched while the fans are full speed, then that is your culprit. It might be Wi-Fi, if you have it. Try disabling it. It operates at 2.4GHz (802.11g/b) or 5 GHz (802.11a). If the tone remains constant, then it might be the hard drive or the processor. Brad | |||
| adriaan
Senior Member Username: adriaan Post Number: 547 Registered: 6-2002 |
The hum disappears when the brightness is set at the maximum - sounds like the brightness control is actually a dimmer of some sort. The type of thing that manufacturers select on grounds of the lowest price possible. Definitely try to turn off the LCD. Laptops usually have a function key combination to toggle between LCD or LCD+CRT or CRT, and it should work even without a CRT connected. | |||
| byoung
Member Username: byoung Post Number: 60 Registered: 12-2004 |
Adriaan, The dimmer (probably Pulse Width Modulated) is causing some of the RF interference, so either all off or all on (not dimmed) should be fine. The next question is whether the fans, power brick, CPU, Wi-Fi, hard drive or something else are causing the remaining interference. Brad | |||
| haddimudd
Intermediate Member Username: haddimudd Post Number: 128 Registered: 6-2002 |
The fan is usually not running while the noise is audible, but even in times when the fan is running the noise does not change. I didn't have time to check the other components yet. To me it kind of makes sense to believe that the pulsating is in connection with the display frequency as Keith already indicated, although I haven't found time to check this either. |
hisHissDemo.mp3