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How To Build An Audio Computer
Part 3- Power Supply and Case
More Power To Ya
One of the most important choices you will make in your new build will be deciding which power supply to purchase. The modern computer power supply is anything but simple. The power supply has the important task of providing clean DC voltage to the many power hungry components. It has to take a sometimes dirty or not well regulated AC wall voltage and send smooth DC voltages to the motherboard and other hardware. With each leap in computer performance there has been the need to increase the capabilities of the power supply. If it doesn’t do the job correctly the whole house of cards comes falling down.
Where does it come from?
AC or alternating current is what comes from your wall into your household appliances. AC power never stays in one place. It’s continually moving above and below what we call zero point or zero voltage.Think of a sine wave with a positive voltage on the top and a negative voltage on the bottom of zero point. This voltage fluctuates or cycles at a fairly set rate of either 50hz in the UK or 60hz in the United States. The main voltage from the power plant is in the thousands of volts AC and reduced at transformers along the way to more useable voltages.
If Thomas Edison would have had his way we would be using DC voltage from the power plant. He already had it in place in a few location in the states, but a genius by the name of Nikola Tesla developed a better way to use AC or alternating current power which was far superior for transferring power over long distances. The amount either above or below the zero point is the voltage. 115/120 volts in the USA and 230 volts in the UK or thereabouts. One of the challenges to a DAW power supply is to keep the outputs constant while the inputs move around slightly, for instance, I have measured anything from 110 to 127 volts here in the US depending on the location and the power demand. The same holds true for the UK. The voltage is dependent on the power grid and the load on it at any given time and might change at the same location. Power is generated from hydro, coal or nuclear plants and although the technology exists to automatically switch to different sources with demand however these changes aren’t always smooth transitions. A huge demand placed on one area may overload another area. Engineers are constantly monitoring the sectors of the grid to try and keep everything working well for end users.
Threats To A Power Supply
Some of the other factors that can potentially cause a problem for a DAW power supply are a sudden short in one of the transformers carrying power to your location. This usually results in a blown fuse on the power line. In extreme cases the transformer is blown to cinders by an internal short. In this case you might have an unexpected fireworks display on your street. When a large transformer blows up it can be a scary thing especially if you happen to be close by.
In most cases the line to your home opens the circuit and power is off until it can be restored. Notice I said “ in most cases”.
My job sometimes takes me to places where I work with high voltages. I’ll never forget one instance I encountered. A squirrel had ventured across the two main feeds on a transformer feeding power to a large building. This caused a direct short which blew the main building transformer safety fuse. When these blow it makes a really loud bang. Don’t ask about the squirrel. He had 13,500 volts pass through him.
Power surges and lightning strikes are probably the two most dangerous things for a DAW power supply. Sometimes there are “spikes” in the power supply or momentary voltage jumps that can go considerably above the typical voltage. Lightning strikes can affect your DAW even if they hit the line miles away. For both of these cases I highly recommend external power filtration and lightning protection. Most office supply stores carry several choices in these kinds of units or you can find them online. Anything is better than nothing when it comes to power surge protection. The better units will have battery backup so in the event of a catastrophic power failure your computer is on temporary life support or battery power until you can power it down and thus save a potential data loss. Another potential DAW killer is rapid power cycling. This places stress on components if the DAW is powered on and off rapidly.
If you have a supply voltage that is +/- 5% of typical , this is about the best you can do. Some things can’t be controlled. lightning can enter a window and come across the room to hit your DAW. Nothing is a 100% guarantee. I have seen lightning go down a chimney , come out the bottom , go across a room and hit a TV. Anything seems possible during a severe electrical storm. I have unplugged my DAW before a serious storm if I’m home at the time.
How does it work?
I’ll give a simple explanation and try to keep it short. A really simple explanation would be that the power supply takes one kind of voltage and turns it into another kind of voltage and changes/regulates the current/voltage. Since I want the reader to have a fairly comprehensive understanding of the individual parts that make a power supply work, I think we need at least a cursory overview of the internals of a computer power supply. This way you’ll know what’s going on to some extent.
The first thing that needs to happen is that the voltage needs to be reduced from the wall voltage to a much smaller voltage suitable for a computer. This is basically accomplished with a transformer. The transformer is an inductive device that uses two or more coils of wire wound together in close proximity to one another. The heavier coil is called the primary of the transformer and this takes the voltage directly from the wall. The lighter coil or coils are called the secondaries.The way it works is through inductance. The primary coil induces a voltage into the lighter coil or coils. This is usually aided by an iron core of some kind. Let’s take a simple and very common transformer used in both North America and in the UK. These are usually multi purpose and have multi taps so that you can switch it for either 115 volts or 230 volts on the primary winding.In the case of a multi country use transformer you would have a multi tap transformer primary coil . A common secondary winding voltage is 12 volts and maybe 50ma or milliamps current rating.
Applying 115 volts to the primary with give you 12 volts at the secondary. In the case of a computer power supply the secondary voltages will likely be of the multi tap variety, in other words there will be multiple secondary windings.You might have a few +5 volt taps a +3.3volt tap and a few +12 volt taps, all using the same primary winding. Some computer power supplies will have a switch on the back to select the voltage from your country. It is important to make sure you select the right one. Either 115 volts or 230 volts.
Smooth Out The Bumps
We have successfully reduced the voltage, now what happens? The voltage is still alternating current. We need to make it direct current or DC voltage to be compatible with a computer motherboard. This is accomplished with diodes and capacitors. A diode is an electronic component that only passes voltage and current in one direction. Through four of these diodes assembled in a square configuration in opposed relation to one another coming from the transformer secondary called a “diode bridge” we can get a rough kind of DC voltage .DC voltage has a more or less constant potential at + and – when compared to AC voltage which is constantly moving between + and – .
Once the voltage leaves the diode bridge it enters a series of capacitors. The capacitor is a device that can store and release electricity. The capacitor either stores or releases voltage depending on the voltage polarity across the two terminals. Once a voltage is stored it is held until the terminals meet a grounded condition. They filter the incoming voltage by storing and discharging in tandem running opposite one another hundreds of times a second. When the voltage is at a positive potential the negative side capacitors discharge, when the voltage is at a negative potential the positive bank of capacitors discharge thereby smoothing out the voltage. Resistors also play a huge part in the circuitry involved.
Since our intent is only to build a computer only a basic understanding is necessary. If you’re the type that really wants to get into repair you’ll find that many of the internal components in a power supply can be replaced. Repairs should only be attempted by qualified service personnel.
Are You Using Protection?
Most computer power supplies made today have an internal protection circuit that works by monitoring the voltage for problems. If the voltages aren’t correct at start up between 100 and 500ms into the start the power supply decides not to allow the computer to power up. This is great in a brown out situation since it can save the rest of your computer from attempting to run on a less than stellar voltage. In order to run the MOBO must see a POWER_GOOD or a POWER_OK command from the power supply. This signal must be continually present to the MOBO from the power supply. A low power condition or brownout causes this command to be lost and the power supply will not provide power to the MOBO. This results in a subsequent lockout or a reset.
This can also be caused by using a power supply that isn’t rated for the current demand of your peripherals. When building a computer it’s important to make sure the current rating is within the limits of the cpu/mobo configuration you intend to use. While it is true that most power supplies made in the 500w range are ok for a basic build, video cards and high current demands from the cpu can tip the scale in the wrong direction. Better to be safe and look at the requirements before deciding on a power supply.
I would discourage trying to salvage an older power supply, mainly because it’s already been in use and components will be closer to their life expectancy end. If it’s older it might not have the capacity. Things have changed a lot in the past ten years and what was once a great power supply could very well end up being anemic on a new system.
In many cases a power supply problem is misdiagnosed as a MOBO or other issue when it’s simply the power supply is failing or the input voltage isn’t correct and it’s telling the MOBO not to attempt a boot.. Poorly designed power supplies won’t have good protection circuitry.
Electronic components have quality and performance ratings. For instance resistors are made with +/- 2% tolerances, but others are rated for +/- 10%. If the engineer used all 10% resistors this means that at any given time there’s a 10% margin of error in performance.It might meet spec.s if the specs are loosely drawn up. A circuit made with all the cheapest components simply won’t have quite the quality and performance of a circuit made with better components. It might get you by, but don’t you want to do more than squeak by?
Dual or Single Rail ?
Dual rail power supplies have been advertised as superior and in most cases they are better than a single rail design. A rail is simply a tap from the power supply. In some power supplies all of the +12 volt power comes from only one feed. If you have multiple hard drives and fans all using +12 volts on only one small +12 volt feed there is a real possibility that you could draw too much current. Designers seen the need to add an additional tap or rail so that the system could use two independent +12 volt feeds. You could still potentially get into trouble if you overload one of the rails or if the power supply manufacturer simply took one basic rail and divided it into two without thought to increasing the current.
Since we are using the ATX form factor, all power supplies made to this specification will have the plugs already in place, there’s no decision to be made as to where a plug should go and this helps to assure that you won’t over load one rail over the other. All plugs are labeled and keyed. This makes these kinds of mistakes almost unheard of unless you start cutting into the wiring harness and adding things not intended to be on it.You can’t plug anything in backwards and you can’t plug plugs into the wrong places if you install the Power supply the way it was designed. The only possibility to get anything wrong might be in a few wires that power LEDs or light emitting diodes and case switch placement. Following the MOBO layout and the case design info will avoid these problems. Usually plugging one of these wires into the wrong terminal won’t result in any kind of a failure, but it might keep a function from working. Almost 100% of all power connections from the power supply are ready wired. You simply find the place it goes and plug it in.
Cooling and Sound Levels
Computer power supplies use negative pressure cooling by drawing air in the case over the components. Look for a power supply that is advertised to be relatively quiet for DAW use. If it specifically is advertised to be more quiet than the competition and lists sound db ratings all the better. They all make some noise. You can’t get away from that, however you can find some that you almost can’t hear. In a recording situation the noise is low enough that it won’t bleed into mics or become a problem when trying to mix on monitors.
There have been numerous changes to the requirements of power supplies over the last several years. More specifically the voltage requirements of new hardware as it came along. Designers have fallen in line with these requirements.
Typically dual inline memory modules or (DIMMS) use voltages in the range of + 1.8-1.5 . PCI Express uses 0.8 volts in some instances.
Since the rails of the power supply are commonly +3.3 , +5 and +12 volts. The motherboard uses additional voltage regulation to get to these lower voltages. This can be helpful info in a troubleshooting situation. Power supplies all have pin out voltages that can be checked with a meter by referencing the plug layout provided with the power supply. If you feel uncomfortable with a multimeter, you can alternately try a spare power supply if you have one on hand.
+12 volts is most commonly used to power cooling fans, disk drives. +3.3 volts is commonly used to supply power to the memory, PCIe cards, AGP ( Accelerated Graphics Processor) and other misc. chips. The same is true of the +5 volts. CPU voltage can be any of the three depending on the design and at what stage you measure it. Better power supplies will regulate the voltage to within 1-3%.
Some power supplies use negative voltages as well. I avoided this discussion because these are mostly legacy products and we are concerned here with a more recent build.
Parting Thoughts On Power Supplies
For best compatibility use ATX design and form factor power supplies with ATX MOBOs.
I recommend a power supply of at least 650-750 watts rating and upwards rating for any of the more recent motherboards and cpu’s.
Look for “quiet” in the description.
Just In Case
You don’t get much more utilitarian than a computer case, yet small companies have emerged because they came up with a better case design.
While it can be said that as a whole consumers aren’t nearly as concerned as home recordists when it comes to noise level there are obvious limits. No doubt anyone building a home theatre system or using a computer in any place where noise exceeding a certain level can be a detriment has wondered if there were alternatives.
Anyone who has ever built a computer with no real thought to sound levels and went for the bargain cooling fans and case has probably had second thoughts on that decision.
Most factory bought systems have made a great compromise between noise and cost. These things sit in offices under desks and some people notice noise more than others. Sales would likely be hurt if they didn’t make them fairly quiet. For these systems that’s ok, but we’re building something else. We want to keep the noise lor for a higher performance system. This means removing more heat and making less noise in doing it.
There are cases advertised to be noise reducing. I purchased such a case. These designs don’t deviate much from a standard cases. The main advantage to buying such a case is the use of sound insulation, quiet case fans, and designs that inhibit the propagation of sound from the case when compared to standard cases. I think it’s worth the investment to buy a quiet rated case and I’m happy with mine.
Other questions to ask when buying a case are, does it have plenty of space for all of my intended hard drives? Will it accommodate my chosen cooling system and still allow me to put the sides on? Don’t laugh, this is a real problem in some builds. Does the case make future service and the initial build easier? Does it include the wiring harnesses necessary? A good case will have an included wiring harness to help you join the mobo to the other hardware and have convenient chases to rout the wires in and through.The case I chose is great on all counts. If there were a drawback at all I would say it’s probably too big for my build. You could drive a Fiat into my case after the build.
One way that manufacturers cut costs is in using the thinnest gauge steel they can find that still does the job to make the case, or they use plastic.
To avoid problems I chose a case made of a heavier gauge steel. There are potential problems with cases of minimal or poor construction. A poorly made case can have sharp edges. A word of caution here, look for sharp edges when disassembling, assembling or working inside a case. Watch that you don’t rub against these edges. The better made cases have less of these kinds of problems.
Sound deadening cases have insulation usually mounted to interior surfaces not involved in supporting the hardware. It doesn’t look like much but it helps. Since most all sound emitted is of the high frequency variety it isn’t necessarily the size of the insulation that counts, but more importantly, if the case and insulation are tuned to the offending frequencies and help to dampen them.
Cases can be bought as a basic no frills unit or purchased with included power supplies and or fans. In my case there are a few fans and provision for a few more if necessary. Obviously this makes assembly easier if the case has as much already included as possible. Since I bought a case designed to be quiet it already had good quiet fans in it. I usually don’t recommend buying these combination cases because the hardware is usually inferior to something I might pick myself. I made a concession in buying a case with added fans because the company is reputable, the hardware used is reliable and I still picked my own power supply.
The way a case moves air inside and outside of the computer is very important. The best designs use negative pressure or they bring air into the front and remove it at the upper rear or the top. All other fans should work with this air movement, otherwise you may have fans fighting one another.If you mounted your cpu cooling fan pushing air to the front of the computer and the case fans are moving air from the front of the computer, efficiency is lost and all you’re doing inside the case is creating turbulence. The push pull method is best since fresh air is directly drawn in and removed. It is very easy to install the cpu cooler backwards. Older designs didn’t consider this concept and simply brought air into the cavity.
Inlet air is drawn in from the bottom and front of many case designs including mine. This is a great idea because it allows cooler air in from the bottom and warmer air to rise and be drawn out the back or top. Be sure to look for a case with a washable removable air filter at air inlet points. No filter means dust going into your case. The filters offered in many cases don’t trap all dust but they get much of it, certainly better than no filter at all. A well designed case should have feet on the bottom to get the case far enough off the floor that it allows sufficient air into the bottom for cooling.
Since we’re building an ATX system, look for an ATX case. All harnesses and access will be thoughtfully designed for your motherboard.
There are tower cases and rack mounted cases. This build uses an ATX tower case. If you have a recording studio with racks of gear and you have extra space you could opt for a rack mounted case.This is sometimes a good choice when space and accessibility are considerations. Keep in mind that surrounding equipment in the rack gives off heat and plan accordingly to avoid as much of the heat as possible. Stand alone tower builds can run cooler if they are located in a cool spot. Here is the next point, location. You should locate your computer away from heat vents and preferably in a place where there is regular air movement with at least 6” of clearance from air outlets in the case if possible.
Humidity above 90% can be bad for the internal DAW components. From my experience the opposite is usually true. Air in the computer space is less humid than normal. In the winter I need to humidify my space to keep the minimum 30-40% RH required to prevent nose bleeds, dry skin and stringed instruments from cracking. Computers are good at drying the air in a confined space. If you happen to live in the rainforests of Brazil, then your experiences will vary. If you live In Colorado, you might need to humidify year round. Anything less that 30% humidity just isn’t a fun space to work in.
It’s All About The Noise
There are two ways to combat computer noise, either reduce it at the source or reduce the effects of it. We have already covered the ways a good case helps to dampen noises inside the computer using insulation and quiet fans. There are some additional ways to reduce noise from outside a computer cabinet as well, but for now we’ll cover some ways to stop noise at the source.
Stopping Noise At The Source
Let’s start by addressing noise at the source. Since I used all solid state hard drives or SSD’s in my build I eliminated the noise so common in disk based hard drives. The power supply has a cooling fan in it which makes noise. I chose a power supply that has been proven to make less noise than some others. There’s a good chance that there are other designs out there even quieter than the one I chose.
My cpu cooling fan is one of the quietest there are. The manufacturer offers an additional fan that can be added for a push pull arrangement. The additional cooling gain was very small for the additional fan so I opted to keep it simple with only one cpu cooler. My cpu temperature never reaches anything near dangerous levels with one good fan on the cpu. You can’t go wrong here in choosing a good cooling fan. The health of your cpu rests on it. Most current mobos have a bios that will allow you to determine the rpm of the cooling fans to some extent. This capability will vary with manufacturer, but usually you can set the fans to run faster only when needed and slower at other times. This can be a great help in reducing fan related noise.
You can opt to use water cooling. I avoided water cooling in my build because water coolers have pumps that make noise albeit a small noise. They don’t completely eliminate noise. Secondly, you’re dealing with water. A leak, even a small one on your motherboard spells major disaster. A fan failure will simply signal an over temperature condition and likely shut your system down before it’s too late. If you choose water cooling be aware of the potential issues. I’m sure some will argue that water cooling is mostly trouble free, and you might have a great experience…or you may not. Water coolers are generally not as compact as fans. They locate the pump away from the cpu which means you need to mount it somewhere with water pipes coming from the cpu. Many cpu water coolers also use fans for the exchanger section. Since I wanted a functional design that wasn’t overly complex and had the most simple design possible I opted for air cooling.
The Video Card
I went against the grain on one item, the video card. I opted for slightly higher video performance which involved a video card with a fan. The fan is large for a video card fan. Large is good because this means it can run at less rpm and cool the same as a smaller fan running faster.. This translates to a quieter fan.The video card is rated to be one of the more quiet fan cooled video cards. If you want to eliminate all noise from this source entirely buy a video card with no fan cooling or use a motherboard/cpu with onboard video, but remember that if you opt to use onboard video and have a problem with it you’ll need to replace more than a video card.
When It’s All Said And Done
As you have seen, most noise involved in the computer is from the cooling and hard drives. Since we’re building a computer for recording we want it to be as quiet as possible. The only totally quiet computers are the ones that have sacrificed some level of performance, i.e. micro designs that don’t need as much cooling to function properly. One of those wouldn’t be enough computer for my studio, so some concessions were made, and as such my computer generates a very slight amount of noise, almost all computers do. So don’t expect a higher performance computer to be soundless. I think I’ve done pretty well in building a system for a small home recording studio. I’m happy with the db level. I can make recordings ( and I have) in the same space and pick up zero computer noise with a cardoid mic pickup pattern not pointed at the computer. Keep in mind that just because your ears hear sound, this doesn’t always mean the mic is picking it up. Try listening through headphones to see if you hear any noise.Chances are that in most mixes even a very small amount of noise won’t be heard or noticed depending on the sensitivity of your mic, gain levels and proximity.These can all usually be adjusted for best results.
If you’re recording the sound of pins dropping or flies having sex you may well want less noise. You have another option. Remove the computer from the space and relocate it in another space close by. If the only adjacent room is a bathroom you might be out of luck. Don’t discount basements. Relocation usually involves buying longer cables to reach and setting up the computer to be started up and shut down from the keyboard. You’ll also need to make a hole or holes in the wall ceiling or floor to run the cabling through.The shorter you can keep the cables the better everything will be. The external location should have good air temperatures and humidity levels.
You could opt to build a special soundproof box to keep the computer inside of, just be mindful of heat removal in that space.
In a situation that requires utmost quiet I usually resort to my small mini digital recorder and transfer the file to my computer. These can be great for making quiet recordings and many are capable to make excellent recordings.
For most cases the build in this write up will be sufficient, especially if you record a band. The only consideration then being that beer doesn’t get spilled inside the case or the drummer doesn’t cause the case to bounce around when he hits the bass drum. I regularly use mine for live acoustic recordings in the same space as the computer.
Next up Beginning The Build -Step One