I Broke My Arm!

Exercise
by Mike Clements

Riding Tiger Mtn on Sat 5/12 with a friend, a wet slimy tree root suddenly torqued my front wheel around and I hit the ground hard, banged up but all body parts still firmly attached. I continued riding, but every bump triggered sharp pain in my left shoulder, so we got off the trail and rode out along the (less bumpy) gravel fire road. That meant climbing back up to the summit again before we could go back down. The good news: we got a tough cardio workout with 4,000′ of climbing in 15 miles. The bad news: got some x-rays on Mon 5/14 and found out my left humerus is fractured. I can still ride but will stick to the machines in the gym for a few weeks.

The break is a crack at the upper end of the humerus where the ball-shaped top end tapers to the straight part of the bone. The doc says it will probably heal on its own, but there’s some chance the shoulder muscles might pull it out of alignment, in which case it will require surgery to realign the bone.

I’m getting another x-ray soon to see which way this is going.

4 years later… I don’t know why I didn’t put up the pictures. They’re quite interesting, showing how fast bones can knit and heal. Bone injuries can heal faster than ligaments. In 13 days the bone had closed and knitted the crack, though it took several more weeks to fully heal.

Day 2 – cracked

Day 13 – crack is closed and knitted!

Velocity: Orbital vs. Escape

Flying, Math
by Mike Clements

While thinking about escape velocity recently, I wondered why orbital velocity wasn’t the same as escape velocity. The intuition was: consider an object in a circular orbit around the Earth at speed v. If the object speeds up just a smidge, then its centrifugal force increases, which pulls it slightly further away from Earth, where gravity is weaker, so it goes even further away, etc. It seems like a positive feedback chain reaction, the object getting progressively further away from E. That would imply that orbital velocity equals escape velocity, because if you go even a smidge faster, you’ll eventually escape orbit.

However, I worked out the equations and escape velocity is not equal to orbital velocity, but it’s about 41% faster (actually, square root of 2 faster). Upon further thought, I realized my earlier intuition missed a key point: as the object moving slightly faster goes further from Earth, its trajectory flattens out. When its trajectory is a circle, the force of Earth’s gravity is perpendicular to its motion, so it does not affect the object’s speed. But when the object’s trajectory flattens out, it’s no longer a circle, so Earth’s gravitational pull is no longer perpendicular to its motion. Some small portion of Earth’s gravitational pull is slowing it down! Then, of course, pulls it forward speeding it up as it comes around the other side of the ellipse.

So when the object speeds up a smidge, its orbit becomes elliptical. It has to go significantly faster than that to escape from Earth. In fact, about 41% faster since the difference is the square root of 2.

This also means orbits are stable: if the velocity changes a bit the shape of the orbit changes, but it stays in orbit. If escape velocity equaled orbital velocity, orbits would be unstable: the slightest bump would send it out into space or spiraling inward.

When the math contradicts intuition, it leads to re-thinking which can deepen one’s intuitive understanding.

Escape Velocity

Flying, Math, Tech
by Mike Clements

Escape Velocity is commonly described as the minimum speed an object must reach to escape the Earth (or other celestial body) into space. But this definition is ambiguous and can be misleading.

You can escape the Earth at walking speed, if you could walk straight up; you don’t need anywhere near escape velocity. Imagine a rocket launch; in the first few seconds just as it starts to move, it’s going up at walking speed. Theoretically, it could throttle back the engines to maintain that slight upward speed all the way into space, so long as it didn’t run out of fuel or become unstable. A space elevator could also leave Earth at mundane speeds.

The key to this ambiguity is escape velocity applies to a free body, an object that is passively moving according to the laws of physics, having no thrust of its own. In other words, if a rocket achieves escape velocity, it could at that point turn off its engines and it would still escape the Earth. Intuitively it seems the higher the altitude, the slower the escape velocity. This turns out to be correct.

Escape velocity is easy to understand and derive mathematically with some creative thinking. Imagine 2 objects in space (a big one and a much smaller one, like the Earth and a stone) surrounded by vacuum, no other objects. So there is no friction and no other bodies exerting gravitational pull. Suppose the stone is at rest relative to the Earth and almost infinitely far away. The gravitational pull is effectively zero. Imagine the stone precariously balanced just on the outer rim of Earth’s gravity well. Then you nudge the stone just a smidge toward the Earth, so it crosses that rim and the Earth starts pulling on it (and vice versa). It starts out slow, but accelerates toward the Earth incrementally faster and faster.

Eventually, when the stone reaches the Earth it will be moving very fast. Escape velocity is the speed it is going just before it smashes into the Earth. Or if it misses the Earth, it’s the speed at its point of closest approach. More correctly and completely, the stone is always traveling at escape velocity at every moment along its path. The escape velocity for that distance from the Earth, is the speed at which the stone is moving when it’s that far away.

Note: the bold face statement above is the nut of this explanation. When you grok its fullness, you grok the fullness of escape velocity.

That’s because of conservation of energy. When the stone was at the rim of Earth’s gravity well, it had a lot of potential energy. At the point of closest approach, all that potential energy has been converted into kinetic energy. Assuming no atmosphere, no losses, the two energies are equal. So as the stone speeds past the Earth, slowing down due to the same gravitational pull that sucked it in, that kinetic energy is converted back into potential energy. So it must reach the exact same distance away when it peters out and eventually stops.

The direction of motion is irrelevant to escape velocity. Normally this seems counterintuitive, but understanding escape velocity with our theoretical example, you can easily see why direction doesn’t matter. At that point of closest approach, it doesn’t matter what direction the stone is moving relative to the Earth. It could be nearly straight up (can’t be exactly straight up, or it wouldn’t have missed), or nearly horizontal. If it’s going horizontal, it has to travel further to escape, but being horizontal, gravity isn’t pulling it as hard. These conflicting factors are equal and cancel each other. All that matters is the altitude (distance of closest approach), because the speed depends only how much energy it’s gained from Earth’s gravity field.

If, at that point of closest approach, the stone were moving any slower, then it would have less kinetic energy, and it will not go as far away. That means it won’t make it to the rim of Earth’s gravity well, so it will still be inside the well, reverse direction and eventually come back to Earth. So escape velocity is the minimum speed a free body can have, and escape the Earth.

Of course, in the real world direction does matter. The Earth has an atmosphere that creates a lot of friction and energy loss at high speeds. If you go straight up, you’re in the atmosphere for a shorter time, less energy loss. If you go horizontal, you’re in the atmosphere longer and will lose more energy.

Here is the mathematical derivation:

escapeVelocity

Gun Culture: NYT Op-Ed

Politics
by Mike Clements

Today the NYT published an Op-Ed by David Joy. I enjoyed reading it and share some of his observations. About 3/4 of the way through he suggests an AR-15 is somehow different from other rifles in the store, saying, “the idea of owning a rifle designed for engaging human targets out to 600 meters just never interested me.” He asks a friend why he owns an AR-15 and is unsatisfied with his friend’s response. Here is mine.

First, David’s belief that the AR-15 is somehow different from other rifles in the store, is not justified by the facts.  The AR-15 is a semi-automatic .223 caliber rifle. It is less powerful than most common .30 caliber rifles, like the Savage .308 David uses to hunt deer. These more powerful semi-auto rifles are just as accurate, often have longer range and are commonly used for sport, hunting and self defense.

Second, David mis-characterizes the AR-15 when he describes it as “a rifle designed for engaging human targets out to 600 meters”. For engaging human targets out to 600 meters, look at what military snipers use. They use a rifle that is more powerful, more accurate, and has longer range than an AR-15. This rifle is the M-24, which is a .30 caliber bolt action Remington Model 700 with a 5 round capacity, the same kind of rifle your Grandpa carried through woods, still carried by thousands of hunters across the USA. Later, Army snipers switched to the M2010, which is another .30 caliber bolt action rifle with a 5 round magazine.

In short, according to the US Army, a rifle like David’s Savage .308 is more effective than an AR-15 at “engaging human targets out to 600 meters”. But that’s not a fair comparison; the Army doesn’t even use the AR-15.

People who don’t know much about guns believe, incorrectly, that the AR-15 is a military rifle. They believe this primarily for cosmetic reasons. Instead of steel and wood, it is black with lots of plastic and resembles the M-16 that US soldiers carry. Yet it is unusual to see an experienced gun owner like David make this mistake. The military M-16 is not an AR-15. The M-16 can fire in full automatic mode (a machine gun) which has been strictly regulated since 1934. The AR-15 fires one bullet each time you pull the trigger.

So when David says, “My friends see no difference between the guns I own and their ARs,” this should come as no surprise. The only material difference is magazine capacity.

To David’s final point, there are several good reasons to oppose an assault-weapons ban.

  1. The term “assault weapon” is pure fiction. They’re not machine guns; those have already been virtually banned since 1934. The guns named as “assault weapons” are based mainly on cosmetic features; they’re not functionally different from common sporting and hunting rifles.
  2. The AR-15 magazine holds 30 rounds. This is more than most other rifles in common use and makes it the only functional difference between the AR-15 and these other rifles. It is worth debating whether restricting such high capacity magazines might reduce crime or improve public safety. Yet our country has already had this debate, and more; see below.
  3. The Federal Govt banned “assault weapons” for 10 years, from 1994 to 2004. This included a ban on magazines in any firearm holding more than 10 rounds. Serious academics (such as the National Academy of Sciences) and the Dept. of Justice comprehensively studied the law and found it had no effect on crime, accidents, suicide or public safety.

In short, an assault weapons ban has already been tried, studied, and found to be ineffective. And the reason why is obvious: true “assault weapons” — machine guns — are already banned and have been since 1934.

Note: I don’t own an AR-15 simply because I find other guns to be more useful for sport, hunting or self defense. However, having used one, I don’t believe there is anything about it that makes it more dangerous than other rifles in common use today. I don’t see the AR-15 as a sign of a rift in gun attitudes or culture. The gun owners I know are responsible citizens, whatever kind of rifles they prefer.

Back to the HD-580 – For a While

Audio
by Mike Clements

My Audeze LCD-2 fell off my desk at work and got pranged so they’re going back to Audeze for repair and, incidentally, upgrade to the 2016 drivers. My home pair has  these drivers and they are a subtle improvement over the 2014.

In the meantime, I’m listening to my trusty old HD-580s. Original 18 year old drivers, though I’ve replaced the headband and ear pads, and the cable, a few times over the years. They’re clean and play, fit and look like new.

First impression: these HD-580s are nice headphones! Smooth mids, nice timbres, well balanced. They really were the very first audiophile headphone, SOTA for 1999, a whole different league apart from Grados and the like. But compared to the LCD-2:

  • The low bass is rolled off
  • The bass is not as tight
  • The mids are a tad boxy, not as open sounding
  • The high treble is rolled off

Overall, they sound a tad muffled and slow compared to the LCD-2. Conversely, the LCD-2 has:

  • Wider bandwidth: deeper bass, higher treble
  • Better detail & articulation throughout the range

One advantage the HD-580 has over the LCD-2 is comfort. The HD-580 are lighter and breathe better. That better breathing is due to having velour earpads instead of leather, which is more comfortable but it doesn’t seal as well which likely contributes to the bass attenuation.

Another advantage of the HD-580 is their midrange linearity. The LCD-2 has a response bump in the mids (600-1200) and a dip in treble (3-4 kHz). If you don’t have EQ to correct this, the HD-580 can actually be better than the LCD-2.

A gentle parametric EQ helps widen the HD-580’s apparent bandwidth:

  • +6 low shelf @ 100 Hz, Q=0.67

I’m enjoying this trip down memory lane. I listened to these same HD-580s during most of the 10,000 hours I put into Octane Software back in the day. They sound nice, but I will be happy to get my Audeze back.

Audio History

Audio
by Mike Clements

I loved music and was fascinated with audio electronics since I was a little kid. Later I became interested in the physics of sound.

I bought my first audio component in the 1980s in college, a Harman Kardon integrated amplifier. It was simple and cheap, had no tuner, only 40 WPC output, but it did have a phono amp (MM only) and decent gain stage. To find good speakers, my friend Shawn and I visited the local audio store and listened to several different speakers (Klipsch, Polk, and a few others) with a variety of music. We both liked the Polk 10Bs best. They had the smoothest least colored sound for my limited budget. My musical taste at the time was about half classical, half rock.

Back in those days digital audio and headphones were not an audiophile option. Good headphones simply didn’t exist and digital audio was so new, consumer CD players were expensive and tended to have poor reproduction of high frequencies and transient response. Because of this, there were no good cheap paths to high quality sound, like we have today.

I didn’t have a turntable, they were too expensive. But I did get a good CD player, an Onkyo DX-530 which was one of the first CD players to use oversampling, which improved the high frequency and transient response by enabling more gradual slope Nyquist filters.

This little system lasted me through college with many hours of satisfying listening. Then, my junior year in college, the local audio store went out of business and I got their used demo pair of Polk SDA-2 speakers. This was a big upgrade from the 10Bs, and the price was so good it was almost an even trade when I sold the 10Bs.

After graduating from college I was ready for a decent turntable. I visited the local audio store and auditioned a couple of different turntables & cartridges for several hours, picking a Thorens TD-318 MK II with an Ortofon MC-3 high output MC. That was in 1991. That HK integrated amp only had a low-gain MM phono amp, and my budget didn’t allow for a low ouput MC. The high output MC was a little on the bright side, but it had the smoothest, least colored sound compared to the MMs.

This little system lasted me for several years, until around 1995 I got a new job and promotion and my budget was ready for an upgrade. I auditioned a couple of different power amps and pre amps at the local audio store and ended up taking home an Adcom 5800 power amp with a Rotel RC-990BX pre amp, which had a dual-stage phono amp, so I could now try low output MC phono cartridges. And I had enough power to fully drive those Polk SDA-2 speakers.

At this time, digital was improving but to my ears, good vinyl still had more natural sounding high frequencies and transient response. But only good vinyl – like heavy 280-220 gram pressings, half-speed masters, etc. I started collecting MoFi half-speed masters, Cheskys, Audioquest, Telefunken, Wilson Audio, Classic, Water Lily, and other audiophile vinyl. I didn’t have the budget for much, so I carefully selected and treasured each new addition to the collection.

In the late 90s I replaced my Onkyo DX-530 with a Rega Planet CD player. I read so many good things about it, I thought it must be great. I never really got into this CD player, I think the old Onkyo was actually better. The Rega had a distinct sound that grabbed one’s attention at first. But upon further listening it was to my ears, congested and the high frequencies were all wrong. I ended up selling the Rega about a year later. It was so popular, it was easy to sell. I replaced it with a Rotel RCD-1070. Nothing special, but a solid well engineered good sounding player.

Fast forward a few years to 2000, when I sold my first startup (Octane software) and was ready for another audio upgrade. I already had reference quality amplification so this time it was the speakers. I visited the local audio store with my best albums and spent all day listening to every fine speaker system they had. I also did a bunch of research in audiophile channels. I ended up picking Magnepan 3.6/R speakers, as they had the most natural, linear, uncolored midrange and treble of any speaker I listened to. The Adcom 5800 had plenty of power with enough refined clarity to make these excellent speakers really sing.

About a year later I designed and built my own ladder stepped attenuator to replace the preamp. This added a level of clarity and transparency to the system — no active preamp is cleaner than a single metal film resistor in the signal path! And I learned a little about analog audio circuits, grounding and soldering. Now I didn’t have a phono amp anymore. I did a bunch of research and picked up a DACT CT100, which is an excellent reference quality flexible phono amp, but just a circuit card. I designed and built a power supply for it (dual 12V batteries), with a small chassis, cabling & grounding & connectors. I was delighted with the sound, a noticeable upgrade from the Rotel pre amp’s phono amp, which was quite good to begin with.

This new level of transparency revealed the limitations of the Rotel CD player so I looked for alternatives, knowing that DACs were constantly improving. I ended up with another Onkyo, a DX-7555. It had a more refined sound with more natural midrange voicing.

After we moved from Orcas Island to Seattle my listening room changed. I used test tones, microphones and measurements to tune my new audio room. I built floor-to-ceiling height 22″ diameter tube traps for the rear corners, RPG acoustic foam 4 layers thick strategically located on the wall behind the listener, careful room and speaker arrangement, and ended up with a great sounding room that was within 4 dB of flat from 40 Hz to 20 kHz. It wasn’t perfect though. There was a small rise in the mids around 1 kHz, likely inherent to the Mag 3.6 speakers, and the lowest bass octave was from 6 to 12 dB down. Notwithstanding these limitations, it was a great sounding room.

I kept this system for about 10 years, from 2005 to around 2015. Then I replaced the ladder stepped attenuator with an Oppo HA-1 DAC, using the digital outputs from my source components. And I got a Behringer DEQ 2496 and used its pure digital parametric EQ to tame the 1 kHz bump and lift the bottom bass octave. This put the in-room system response within 3 dB of flat from 30 Hz to 20 kHz, which is comparable to a good recording studio. The sound is fantastically natural: detailed yet smooth and not bright, bass is deep, yet controlled and fast, natural voicing through the mids with seamless transition to high frequencies.

Finally, in Jan 2018 I sold my turntable, vinyl, and related analog equipment. I just wasn’t using it anymore, since I had all those recordings on digital, and the sound quality of digital had improved so much, while great LPs do sound great, I no longer felt that they sounded any better than great digital.

Mike’s Best Vinyl LP Records

Audio
by Mike Clements

UPDATE: Mar 2018: These are all sold!

As I’m liquidating my vinyl and playback equipment, I’ve sorted through all my LPs and found about 100 of them to be half-speed masters, heavy vinyl, 45 RPM single sided, Japanese Press, Mobile Fidelity, Chesky, Wilson Audio, Telefunken limited edition pressings, or other such. Many are out of print, all are in mint condition – no scratches, cleaned with the Nitty Gritty 2.5FI, played only on properly aligned high end equipment.

I’ve got a few hundred more LPs not shown in this list, many of which are nice, but they’re standard quality. I’ll probably sell them in bulk for $1 each somewhere.

Here’s the list of my best LPs. Items already sold are highlighted in RED: lpListHighQuality-1712

Vinyl LP Cleaning Solution Recipe

Audio
by Mike Clements

I covered this topic about 10 years ago, offering a recipe for fluid to clean vinyl LPs. I still use that recipe in my Nitty Gritty; here’s a summary and a few more tips.

It has 3 ingredients, one of which is optional:

  • Distilled Water
  • Isopropyl Alcohol
  • Wetting Agent (optional)

Most wetting agents are soaps which contain fragrances and other non-essential ingredients that you don’t want polluting your record cleaning fluid. I’ve stopped using the wetting agent and it still works just fine. If you use a wetting agent, all it takes is a couple of drops for a small batch.

Alcohol is a solvent that may degrade the seals of record cleaning machines. To avoid damaging the machine, keep the alcohol below 20%. That seems to be a conservatively safe level, and it doesn’t take much alcohol to do the job so adding more won’t necessarily get records any cleaner.

Two kinds of isopropyl alcohol are commonly available: 70% and 91%.

  • Recommended: Conservative formula (< 20% alcohol)
    • With 70%: 1 part alcohol to 3 parts water = 17.5% alcohol
    • With 91%: 1 part alcohol to 4 parts water = 18.2% alcohol
  • Aggressive formula (< 25% alcohol)
    • With 70%: 1 part alcohol to 2 parts water = 23.3% alcohol
    • With 91%: 1 part alcohol to 3 parts water = 22.8% alcohol

As for cost (as of Jan 2018):

You can buy 91% isopropyl for about $3.50 per quart, and distilled water for about $1 per gallon. That makes 1.25 gallons of fluid for about $5. Nitty Gritty charges about $80 for 1 gallon of their solution, which is for all practical purposes the same thing.

Updating Celestron Telescope Firmware

Tech
by Mike Clements

Here’s how I update the firmware in my Celestron 6SE telescope from my Ubuntu Linux system. There’s another nice guide here, but it didn’t work on my computer until I figured out the trick below of changing the port name.

Kudos to Celestron for writing the software in Java so it can run on any computer, Windows, Mac or Linux!

My scope has a phone-type connector to the handset and came with a cable that is a 9-pin serial on the other end. Plug this cable into your computer’s serial port and into the bottom of the handset. While the scope is off, hold down the handset Celestron & Menu buttons while turning it on. The handset will say Boot Loader Serial or something like that to indicate it’s in firmware update mode.

Now, find the Linux device file for your serial port by entering this command: dmesg | grep tty

My output looks like this; yours may be different:

[    0.000000] console [tty0] enabled
[    0.671956] 00:06: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A

On my computer, the serial port is /dev/ttyS0

Check this device file’s permissions and ensure you can read & write it. Typically you need to be in the dialout group, or just chmod the device file to 666 to open it to anyone.

Follow Celestron’s instructions to download the CFM software from their web site. You’ll get a file named something like CFM.jar. Once installed, go to its directory and run it with Java: java -jar CFM.jar

When it starts it will tell you it can’t find the serial port. Select Options|Connections from the menu. In the dialog that appears, you’ll notice it says COM4 (or something similar) as the serial port name. Replace this with ttyS0 (or whatever your port’s name is, from above).

Now click Seek Devices from the app main screen and it will find your telescope. Click the main screen Update button and CFM will find and download the latest firmware for your scope and install it.

Audio: Balanced and Unbalanced

Audio, Tech
by Mike Clements

The term “balanced” is somewhat ambiguous when it comes to audio. Definitions:

Balanced: means conductors have equal impedance to ground.
Differential: means 2 complementary voltage signals, where complementary means that at every instant in time their voltages are opposites of each other.

Generally speaking, you can have either one without the other. But in audio, they are almost always used together. Thus in the realm of audio, the term “balanced” usually means both differentially signalled and balanced.

Unbalanced Audio

Most audio gear (at least consumer gear) is unbalanced. The musical signal or waveform is a voltage. And a voltage is a potential difference between 2 points – we can’t talk about the voltage at a single point. So the musical signal is carried by 2 wires, + and –. The voltage that represents the musical signal is carried on the + wire, and swings back and forth positive and negative relative to the – wire. The – wire does not carry a signal; its voltage doesn’t change; it is ground.

What exactly do we mean by ground? At least 2 different things! Signal ground is the 0 voltage or “neutral” against which the + wire is compared. Chassis or frame ground is the 0 voltage or “neutral”against which the device power (115 or 230 V) is measured. With standard unbalanced audio, signal and frame ground are the same thing.

The potential problem with standard unbalanced audio is that the – terminal isn’t always an unchanging “zero” or “neutral”. It can pick up a varying voltage. In an ideal system this never  happens, but in the real world it does. When this happens, it creates noise because the “music” is the difference between + and –, so any variation on the – terminal changes the musical signal.

How can the – wire pick up a spurious voltage? Imagine a source device (like a CD player) plugged into a different power outlet than the headphone amp. Different power outlets in your house may have slightly different voltage levels on their – terminal, and may have small (a few ohms) of impedance between them. This can cause a small current flow through the ground wire. When that happens, that ground current can appear on the – wire. If that ground current is alternating (for example at 60 Hz, the frequency of our AC power), then this 60 Hz tone (and additional harmonics) is added to the music. We hear “hum”.

Balanced Audio

A balanced system eliminates this problem by adding an extra wire: each channel is carried by 3 wires. Signal +, signal –, and ground. Put differently, balanced separates signal ground from frame ground. In a balanced audio system, the musical signal is the difference between the + and – wires. So, if there is a ground current like above, it travels on the separate ground wire and doesn’t affect the signal.

As the musical signal is the difference between the + and – wire, we have some options how to use the – wire:

  1. Could be a flat “zero” or “neutral”. The – wire doesn’t carry any signal, but only serves as a neutral reference for the voltage on the + wire, much like unbalanced audio.
  2. Could carry an inverted mirror image of the + wire. It’s a varying voltage that is the opposite of the + wire at every moment in time.

Most balanced audio systems use option (2) above, which leads to a discussion about differential signalling.

Differential Signalling

Below is a graph of what an standard unbalanced (single ended) audio signal looks like. The Y axis is volts, the X axis is time. The red line is the + wire, the black horizontal line is the – wire. The + wire carries the musical signal, the – wire is ground. This is sometimes called “single-ended” because only one wire carries the musical signal.

audioSignal-unbalanced

Below is what the same audio signal looks like when balanced (signalled differentially). The red line is the + signal, the blue line is the – signal. Here, neither wire carries frame ground. Each wire carries the same signal, but they have reverse polarity (inverted amplitude). The difference between them is a signal having twice the amplitude of either alone. At every instant in time, the voltage sum of the + and – wires is zero, so the overall cable (containing both + and – wires insulated from each other) has a net field of zero, which makes it immune to interference. Put differently, any external electrical field interference affects both wires the same, so it doesn’t change the difference between them.

audioSignal-balanced

This gives balanced audio 3 advantages

  1. S/N ratio is 6 dB higher (twice the voltage = 6 dB)
  2. Immunity from common interference
  3. Immunity from grounding issues and loops

Balanced audio was designed for microphones, which have low level signals carried on long wires. In this application, noise isolation is important and you need all the S/N you can get. Consumer audio analog line levels are in the range of 1-2 Volts, about 1,000 times or 60 dB stronger than microphones. And cable runs tend to be shorter.

Thus, balanced audio doesn’t make much difference in most consumer audio applications (if your house is wired properly). It’s a superior engineering design, but it doesn’t necessarily make any audible difference especially in top notch gear that already has S/N ratios over 100 dB. It’s nice to have, but I would not choose one piece of equipment over another, for this feature alone. Sound quality comes first, balanced vs. single ended is a secondary concern. All else equal, balanced is better. But all else is not always equal, and some single ended amps are better than some balanced amps.