The Imperfect Power Supply
This is an article about WHY audio and videophiles should care about power quality, but if you want the latest information about WHAT to buy please see
my new post here.
Every piece of electronic kit you own has a power supply. It is a bridge between a source of energy like the wall outlet or batteries, and the electronics which do the work.
You can think of your precious audio gear as having really two inputs. Music, and power. The music defines what the output should be, and the power makes it possible. If you think about the cables that attach to the equipment there are only 2 types of inputs: power cords and audio, so you probably already have some sort of idea that without both you get no sound. Here's a simplified diagram of how this works:
In the slide above, I've drawn potential paths for noise in red.
The power conditioner / power cord market is based these ideas:
- Incoming power is imperfect
- Power supplies are imperfect
- With higher quality of power you get better results
- Power surges damage equipment.
These items are undeniably true, but there is a huge amount of argument about how big a role each plays, and there is a large amount of variability in each. How bad is your incoming power? How robust is the power supply in your DAC, preamp, amp? There are other human issues you need to be aware of:
- Hearing and hearing memory is imperfect
- Snake oil salesmen are everywhere.
- The most expensive power conditioning gear can have diminishing or no returns at all.
- Surge protection may not matter to you if you have never lost gear from a lightning strike.
- You should balance your spending among gear, power, cables and room acoustics and their benefits.
So what are you budding audiophile on a budget to do? Here I present theory on how to achieve comfortably clean power, with a balanced budget approach. If you follow my advice, you can fully treat your gear to clean power from a budget of $180 to $800 quite effectively, and probably permanently. Spend about the same on room acoustics from
GIK Acoustics and you can stop thinking about tweaks.
Lightning Risk
Audiophiles have different feelings about whether or not they should put their precious gear on a surge protector or not. I feel like much of this may have to do with where you are and your past experience with surges, which are usually associated with lightning events. Fortunately there's a map for that. If you live on the west coast your risk of lightning damage is a lot less than if you live in Florida.
Choose your level of protection appropriately.
It is worth pointing out that while lightning accounts for significant power surges, accidents and equipment malfunctions inside and outside the home cause surges as well and these can occur everywhere. Some studies indicate that in terms of event counts, but not necessarily intensity, the majority of surges start inside a home instead of outside, and that over time these micro-surges take their toll on connected supplies.
Can you hear bad power?
As an apartment dweller, I always notice if my power conditioner is not in line, but it is not an obvious, immediate thing, it takes time and I wonder, "why am I unable to relax into this?" unless there's an active noise source nearby, which makes it obvious. If you ever feel like your system sounds better at night vs. the daytime, you probably also have suffered from bad power making its way into your music.
Direct Sources of Power Noise
In a perfect world, the incoming AC is a perfect 50 or 60 Hz sine wave (depending on where you live). That is, there would be no noise, and no distortion, and no matter what you attach, that power remains constant. The reality is that there are a lot of sources of noise which may be unavoidable and you want to keep outside your clean zone.
Listed in order of potential noise:
- Compact fluorescent lights
- Computer power supplies
- Old school wall dimmers
- Digital lighting adapters (think under counter, mood lights)
- Motors and compressors like refrigerators, air conditioners and elevators.
- Wall power adapters (wall warts)
- Class D amplifier power supplies
- DACs, streamers and televisions
It is important to note that in the first slide noise can flow both ways. That is, a digital device which is essentially running a microprocessor, can emit noise back into the AC line as well as be subject to it. That's why DAC's and streamers are listed.
Indirect Sources of Power Noise
Those sources listed above are all known causes of direct power line pollution. That is, they touch the power line and infect it. There are also indirect sources of AC noise such as :
- WiFi routers
- Wireless security devices
- Nearby transmitters and radio/TV stations
- Ethernet / HDMI and coaxial cables
- Cable TV boxes
- Game consoles
All of these can radiate noise which can infiltrate your power after a conditioner. This is why I recommend shielded cables along with a high value conditioner.
The Frugal, Dual Zone Approach
Here it is in a nutshell, and in order of importance:
- Use conditioners which work down to 3 kHz or lower
- Use a two zone approach, a "clean" and "dirty" zone. Keep noise emitting devices out of your clean zone or eliminate them altogether.
- Use inexpensive but shielded power cords like this one or consider building your own with parts from Parts Connexion. So we're talking anywhere from $40 to $100 per cord.
- Use a non-audiophile but still very good power strip for your networking, like the Trip Lite Isobar Ultra. If you life in a high risk area and want something to keep your streamers, switches and game stations healthy while reducing noise this is a very high end choice. It lacks the Furman's LiFT for noise reduction but also has a lower clamping voltage of 140V.
So, if you buy a
Furman Elite ($600) plus a couple of nice power cords, you've spent around $800.
If you need to go cheaper, 1 power strip ($180) plus a couple of shielded cords is around $290. Far far less expensive than some single boutique cables.
[Update September 2021: I've
updated my recommended products based on more data in a new blog post here. ]
Power Cords
Shielded power cords are rare, but not really exotic and vary in cost. Their main benefit is in keeping radiated noise (EMI/RFI) from re-entering the power stream after your nice conditioner has cleaned it all up. In addition, the added capacitance of the shield will further help drain anything that made it past the conditioner. Some audiophiles feel that shielded cables somehow make the sound less lively. That's not me. Go shielded or go home!
If you build your own, connect the ground (green) at both ends, shield at male end only.
Consider using shielded cables on your noise generating devices too! This will further reduce radiated noise.
Ultra Quiet Wall Adapters
If you use any sort of streamer or have a DAC which has an external power supply option I can highly recommend the iFi "wall warts." They run from about $50 to $99 each. I use one for my Mytek Brooklyn and another for my Raspberry Pi 4 which is my Roon streamer. Here are links:
- ifi iPower 5V 2.5A - Works on Pi 4 without high-drain accessories like drives.
- ifi iPower X 5V - 3A, next generation, $99. If you are at all worried about yoru Pi 4 get this one.
- ifi iPower 12V - Works on Mytek Brooklyn
- ifi iPower X 15V - Works on at least some Topping DACs, latest generation but $99
The latest generation has a little more current than the original, but for $50 more. I'm very happy with the bargain version.
The bad news: They still seem to put noise back into the AC, so keep them out of your clean zone.
Series Mode Conditioners
An oddity of most surge strips with filtering is they only start conditioning around 100 kHz, often called "EMI/RFI filtering." This has to do with their construction and what you are allowed by law and UL safety testing to use on an AC line. However, there is a radically different technology which gets around this and adds rock solid surge protection: Series mode surge suppression. By design these are low pass filters, which start filtering noise around 3 kHz. That's well within the audible noise range.
[ Update 6/2020 :
Series mode protection was originally created by
BrickWall and sold by
ZeroSurge, and licensed to SurgeX. Unfortunately claiming series mode protection does not mean a manufacturer is a licensee.
Please read the details of my discussion here.
To purchase an officially licensed series mode protector,
please follow this sponsor link. ]
Unfortunately for the audiophile community, these products command a premium and lack some features, like triggers, multiple banks, etc. we may want.
Among non true series mode conditioners, I've stuck with Furman as long as I can remember. Audio gear has sounded better when I use them, they are reasonably priced and have more home friendly features.
Furman as having the least expensive and most feature packed, which is why as a starter solution I strongly recommend
Furman PST-8 with LiFT and SMP as the best. The $180 power strip includes this and is also great add-on to fancier units. While it is a great unit it only has a single zone, so you want to keep noise sources outside of it if you use only one.
For around $600 you can get a
Furman Elite series conditioner which have multiple filter banks and more outlets. There are also devices like Shunyata and Chang which use kind of a similar approach as the series mode protection, but are not actually surge protectors. They do use coils, and multiple banks of coils, in their products, which is how they are the same. Not a bad approach but prices keep them out of this blog!
So from a price perspective, you may think: Maybe I should get 2 power strips for $300! Yep, you'd be right, it is a relatively cost effective solution to having a dirty and clean zone. There are two features you'd loose from the Elite line though:
- Power factor correction improves instantaneous current
- Remote turn on triggered outlets
Additional Approaches
The techniques listed above are very high value, low spend. However, they don't solve all issues. For instance:
- Whole house suppression is required as of the 2020 NEC since they can prevent house fires in addition to protecting your appliances. These clamp at 600V while surge strips like Furman and Trip Lite clamp at 188V and 140V respectively. It is recommended (by the NEC and the panel surge protection makers) to use these together with surge protector strips for your delicate devices.
- Too high or too low voltage are fixed by voltage regulators.
- DC on the AC line (causes mechanical hum) is fixed by eliminating the root cause (often a dimmer or digital powered light somewhere) or using a balanced power provider
- Ground loops are often better fixed by a ground lifter or Cable TV isolators
- Too much resistance in your AC line is best dealt with by fixing.
- If you have bad wiring, do consider an electrician. They can upgrade the cable, and fix bad connections to your panel. This can cause low voltage, voltage on the neutral and many other problems.
- If your voltage is consistently bad and the problem is NOT in your home, talk to the power company. I once lived in a new apartment in San Francisco and the voltage was consistently getting to 129 V. Building management spoke with the electrical company, and they did agree it was a touch high and eventually brought it down to a more reasonable 125V range. 129V was technically not out of spec, but they tried to shoot for 120-125V.
Tools
- To check if your outlet is wired correctly: AC Outlet Tester
- To test the voltage: I recommend this voltage and power meter. Since you aren't holding probes it's safer than a multi-meter and you can put it in line with say, your amp, to see if the voltage sags while you are playing music. This will give you a good indicator if you need more robust voltage regulation.
- To know how much noise you have, and how much you are removing, perhaps a PS Audio Noise Harvester will do the trick. It's flashing light will indicate how much noise you have, but at $100 it borders my frugality cut off.
The Weirdest Approach
One interesting approach which is also super-high maintenance is to use a lithium battery powered power generator like these from
Goal Zero. I say weird and high maintenance because they require you to commit to a daily ritual. Every night, you charge them, and then when you get home, you unplug them and turn on your stereo.
The advantage, of course, is that while they are discharging you are completely isolated from incoming AC wall problems. Compared to say a PS Audio or some other more expensive units they seem like very affordable devices but I'm sorry, but this is just too much for me. I strongly recommend a PS Audio Power Plant as a much less kinky way to approach absolute power goodness.
The Worst Approaches
Power as Tone
Power cords are for power. Don't use them as extravagant tone controls. If you need "tone controls" rely on room acoustics and .... tone controls! Far cheaper and more effective.
High Bandwidth Cables
Unfortunately some audiophiles get enamored of what I feel is exactly the wrong approach to noise and power. The last thing on earth I want is a very high bandwidth connection to the electrical panel, or the transformer. I want a pure 60 Hz signal, and no one else's noise. Creating a cable that works from 0Hz to 1 MHz like my interconnects is exactly what I don't want.
So, avoid high bandwidth, super high tech cables with exotic Litz or silver conductors. Don't plug in your gear straight into the wall, even amps. The Furman's are very high current devices and your gear is expensive. I feel sometimes people plug their amps into the wall because they accidentally polluted their clean power zone by putting all of their digital devices inside it, and so now we have the myth of amps needing a direct connection to the wall.
Super Expensive Cables
Before making any purchases, step back and think about the cost and benefit of each. Is 1% better worth $9,000 ? Don't let the idea of making yet another improvement blind you to the fact that the benefit is totally out of proportion to the cash being asked for. I recently read from an audiophile who spent $4,000 on power cables for a $3,000 speaker pair with built-in powered subs. Coincidentally, or perhaps exactly because, his speakers are among the worst speakers that regularly get positive reviews (and also post 1 or 2 page ads). Don't be this guy. If you find yourself convinced $3,000 cables are night and day, get a nice boom box and take up painting, your money is wasted.
Non certified surge protectors
If you need surge protection, make sure your device is rated to UL 1449. There are MANY power strips and conditioners which appear to be, but are not. Even if they claim to use series mode surge suppression it is important that you ask about this. Even whole house suppressors may not be rated. All the Furman devices which are "surge suppressors" are tested to UL 1449.
UL 1449 ensures that the entire device, as sold, has been tested. You find all sorts of things can go wrong at a couple of thousand volts, so this testing is important.
