We find power supplies in our tiny cube-shaped iPhone charges, laptop power bricks, and in every wall wart. They help convert mains AC (120V) into usable DC power (12V) for our sensitive electronics.
Power is just power, isn’t it?Unfortunately, not all power supplies are made equal.
There are primarily two types of power supplies: switch-mode (SMPS) and linear (LPS). The general tradeoffs are noted below.
Switch-mode vs Linear Power Supply
Small footprint – doesn’t use huge transformers
Susceptible to radio frequency interference (RFI). Requires shielding.
Susceptible to electromagnetic interference (EMI). Requires filtering.
Produces high-frequency noise – Could backwash back into AC mains.
Greater ripple voltage
Slower transient response
Potential reliability issues
Not as susceptible to EMI and RFI
Much quicker transient response
Better isolation from mains
Low efficiency – Sometimes less than half of SMPS
Gets hot – requires heatsinks
Due to cost and size, the majority of power supplies you’ll see are switch-mode. Taking a look at the low-noise benefits of an LPS, you’ll expect to get better sound from an LPS.
This doesn’t mean you can’t get great performance from an SMPS. In fact, some manufacturers have found an LPS to be noisier than SMPS. I also reviewed the SOtM sPS-500 (a highly filtered SMPS) which faired very well against the UpTone Audio LPS-1.
Check out this power supply comparison, along with the Paul Hynes SR7 here.
I’ll be installing this linear power supply into an Oppo UDP-203 Blu-ray player very soon. This should elevate Roon playback through the Oppo.
So What’s Inside a Linear Power Supply?
The layout of an LPS is deceptively simple:
AC Mains –> Transformer –> Rectifier –> Filter Capacitor –> Linear regulator –> DC Mains
Obviously different topologies will have different requirements but this is the general layout of an LPS.
Let’s break down each piece.
The job of the transformer is to step up or down the AC voltage via electromagnetic induction. The ratio of windings determines the voltage difference. For example, if we wanted to step 120V down to 5V, there will be 24 more copper windings on the primary than the secondary (24:1).
There are many types of transformers (E-core, HF, etc). LPS for audio components typically use toroidal transformers. They’re more expensive and bulkier but have the following benefits:
fewer stray magnetic fields
Transformers are rated for VA (volt-ampere). With purely resistive loads, this value translates to watts. So 500VA = 500 watts. The maximum output current is the VA rating divided by the desired output voltages.
A larger VA rating also means a larger core and a higher impedance. As far as LPS design for audio, it’s generally preferred to have separate mains transformers for each output (rather than having secondaries wound on a larger transformer). Of course, this adds bulk and incurs a much higher cost.
Some transformers could be arranged in a balanced configuration, which will require more windings and a larger core. This design should reduce noise even further.
The rectifier could take the form of four discrete diodes or a GBU bridge rectifier (or a more powerful bridge). Its job is to take the AC signal from the transformer and convert it into DC.
It does this by forcing the signal to go in the “positive” direction – essentially the absolute value of the AC signal. As expected, this DC isn’t a straight line on an oscilloscope but rather pulses or ripples. In this state, the power isn’t quite usable just yet.
Also, diodes have a forward voltage drop (typically 0.7V) so there will also be a lower voltage at the output of the rectifier.
Voltage ripple is dependent upon capacitance, AC frequency, peak voltage, and load current. In order to smooth out those ripples from the rectifier, a filter capacitor is used. Since it temporarily maintains a charge, it helps to keep the voltage across a load more constant. The higher the capacitance, the greater the voltage and the longer the duration of the charge. Ideally, you would want to use an “infinite” capacitor to get a perfectly straight line on the o-scope – but they don’t exist.
The common types of capacitors used for LPS:
Electrolytic – The e-cap is the most common type of capacitor.
Wet – cheaper but not as reliable
Solid – better performance and reliability but expensive.
have lower voltage limits but store large amounts of power.
more robust and deliver charge much quicker than batteries.
Some designs will add decoupling capacitors before the rectifier to reduce mains noise.
At this point, the voltage is unregulated. The output voltage could still vary due to the demands of the load, capacitance, and the input voltage across the transformer. This is fine for non-critical applications but rarely acceptable in audio components where these voltage ripples could be problematic. We want the output voltage to be constant regardless of these fluctuations.
That’s the job of the voltage regulator.
Through a feedback network, voltage dividers, NPN bipolar transistors – a voltage regulator tries its best to maintain a certain voltage level. Regardless of temperature, load demand, etc. They come in set voltages (12V, 5V, etc) or could be adjustable. They typically require more voltage at the input than the voltage required at the output.
Some of the most popular, 3-pin, off-the-shelf voltage regulators (typically in TO-220 packaging):
LM78XX (where XX is usually the voltage)
LT1085 – An improved 317
For audio, these regulator characteristics are most important:
Low noise – lower low-level signal interference
Quick transient response
Quick settling time
Low output impedance (10 milli-ohms or better)
Wide operating bandwidth – to deal with RFI and allows better control of load current fluctuations at higher frequencies (e.g., from DACs). These MHz current pulses will test the speed of the regulator and may add noise at the supply output.
SOtM sPS-500 and Paul Hynes SR4
Now that you have a better understanding of how an LPS works – what does this mean for sound?
A speaker provides tone, impact, shine, and texture. A DAC will give you a foundation of resolution, transparency, and air.
A better power supply will reward you with:
A lower noise floor
Tighter outlines and a more fleshed out sound
A much smoother, refined, and gradational sound
A more natural soundstage in both size and atmosphere
After breaking down and rebuilding multiple systems, I’ve found one can’t achieve a truly “lifelike” sound without a better power supply at every part of the chain. There isn’t a piece of audio gear that won’t benefit from a better power supply. I even have one powering my modem and router to improve Tidal and Spotify streams. Unfortunately, most audio products (DACs, amplifiers, servers) will require a custom solution.
In essence, a better power supply will sonically “align” the complex analog and digital signal into something that’s properly outlined and shaped. This alignment is responsible for the tighter lines and an overall more insightful listening experience. Without a proper power supply, there are “gaps” and “jumps” in the sound.
Simply put: Music is less artificial, less rough, and more live.
Mr. Audio Bacon himself. An open-minded electrical engineer and software developer by trade. I have an obsession with the enjoyment of all things media - specifically in the realm of music and film. So much heart and soul (and money) go into the creation of this artistry. My aim is to find out which products get me closer to what the musicians and directors intended.
a bridge rectifier actually converts the AC Sine wave to either all positive pulses or in few cases negative pulses. The filter capacitor smooths out these pulses by storing voltage to smooth out the hills into a smooth road. The capacitor will always provide a slightly lower DC than the peaks of the AC.
Hey, have your herd about Linn Switch mode PS, they are expensive and among the best out there
Keces OUT OF TAIWAN is offering a lot of LPS AT AN AFFORDABLE PRICE
Paul Hynes power supplies are the very best. I’m glad you mentioned him. His PSUs are in a class of their own and they are worth every penny.
Anyone know how to get ahold of Paul? I have been trying firstname.lastname@example.org since mid Dec…..I would like to buy an SR-4!
The new Clones Audio PowerStation is great!
Very musical yet not too expensive.
And availability is much more stable than Paul Hayne.
This guy doesn’t think so: https://benchmarkmedia.com/blogs/application_notes/152143111-audio-myth-switching-power-supplies-are-noisy
What do people think?
I generate my audiophile power source by jerking off at exactly a 50hz sine wave I can totally hear the difference
How would a better power supply to the router help? That makes no sense to me? At that point the streaming music is still digital, so as long as the bits get though, what’s the difference? Isn’t the DAC the first point, where power supply would make any difference?
It’s not really a matter of digital or not, but what impacts the analog side of things. From my listening tests, the quality of power has a substantial impact on the sound. Whether it’s better or worse is up to the listener.
If I understand correctly, you are advocating for improving the power supply of your router, which is a DIGITAL standalone device in your network, connected to your streaming device/computer (digitally), which then is connected to your sound system (through analog or digital).
If I understood correctly, this is the dumbest shit I ever heard and is exactly why audiophiles get made fun of so much.
I however hope I didn’t understand correctly.
You understood correctly. 🙂
Power supply of Your router can’t affect your sound. How would it happen?
Try powering your router with a battery and hear the difference.
I hear you, you have to have a good system to hear or see the difference a good PS does and Batteries are even better!
What type of bridge rectifier do we use south of the equator?
Thanks for explaining how a transformer would need 24 more copper windings to step 12V down to 5V. I am trying to learn more about electricity. I’d like to be able to handle small electrical problems in my home in order to save money in the future.
I, indeed, heard major improvements when I hooked up diy linear supplies to my mini fanless PC music server and NAS. Unfortunately the damned HEAT blew me away! So, my next move will be large off-board heatsinks, using angled aluminum pieces to make the connections. BUT, I also saw a solution used by Meiyan and GZLOZONE (a couple of Chinese cheapies) where the regulators are bolted directly to the big heatsinks that make up the sides of the case, and are wired back to the board. Does this sound feasible for a DIYer? What would be the challenges?
This site seemed like a good find until i went to the “power supply sound review” linked above and saw various cult esoterica like 3000 buck power cable. Honestly if it makes DC power and it doesn’t have noise … it makes DC power and doesn’t have noise and … that is all there is to it. There is no “special DC voltage” that costs more money. There are capacitors and responsiveness but mostly the thing you power up has all that in hand.
I build power supplies as an enthusiast and I like some of my designs better than others but mostly its about having enough current, stable voltage … and I can clean noise out with really cheap methods that I’m sure you get ripped off for when you buy these things in a sexy box.