Paul's Posts — 20 October 2012
By Paul McGowan
Our Hi Fi systems depend on power to operate and the power they need is DC – yet we feed them AC. Most of us are familiar with battery powered stereo products as they were all the rage for quite some time, but interest in them fizzled out and we plug our equipment into the AC wall socket instead.
If what came out of our wall socket was DC (battery voltage) then we would never need to convert AC to DC to make music. But imagine for a moment that DC was coming from your wall; what would the voltage be? 12 volts to run all your computers and mobile equipment? Fine, but you can’t then have enough voltage to run a power amp. Power amps need at least 100 volts DC and many bigger amps need 150 volts DC. AC is the only practical way to get different voltages to equipment in the home.
So AC it is but what kind of AC? Remember a few posts back I suggested that if you were to flip a battery around quickly going from + to – again and again, 60 times a second, you’d have AC? Well that simple explanation was correct but would make for horrible AC for our stereo systems. Flipping the battery like that would make a square wave. On, off, on, off. Looks like this:
If you put this into your stereo system it would sound awful. You’d hear a huge buzzing noise and be very unhappy. The buzzing noise happens because there are faster changes from + to – than 60 times a second and our power supplies aren’t equipped to handle these faster changes so they get added to the music we hear.
Instead what we want is a sine wave. A sine wave is the same thing you see in the picture of the square wave only with all the faster changes removed. A sine wave looks like this:
Notice how it is very gently curving up and down? That’s what our power supplies in our stereo systems want.
Just to make sure we all understand this very important fact, here is a picture showing a sine wave and a square wave laid on top of each other to make the point.
Notice how the two are the “same” but different shapes? The difference is important to understand because when we convert the AC to DC to make music, one works better than the other. So shape matters.
How did this sine wave come to be and why is everything we listen to in audio based on receiving this nice, gentle waveform? Was it because of some super smart guy like Tesla invented the sine wave with purpose in mind?
No, actually it was the other way around. The nature of how AC is generated creates the sine wave and our technological society adapted everything to it including our stereo systems. Sine waves weren’t invented, they are a result of a process.
Tomorrow I’ll explain how and the importance of the sine wave to making music.
Forward to a friend and help us engage more readers
Related Articles
Share
About Author
(2) Readers Comments
Leave a Reply
You must be logged in to post a comment.
Recent Comments
- What’s all the fuss about? (1)
sbrinck: Paul The Munich audio show was the bomb !! I am extremely envious ! If you ever decide to quit your day...
- Treat the cause or the symptoms? (13)
Paul McGowan: Yes the apertures are located in the 1/8 space corners so they should be as effective as possible....
Soundminded: I’m quite curious and I must admit somewhat skeptical about how effective these frequency tuned bass...
Paul McGowan: Aging memory Mark. I wrote what I remembered and then went back and actually measured it.
The Q...Soundminded: Paul, on April 27 you posted “The main listening room at PS Audio is approximately 16 feet wide...
oliver T. Finch: Simple. Treat the cause and there won’t be any symptoms.Regards.
- Get that mole! (5)
Paul McGowan: You’re certainly correct and I’ll do my best to give a full report.
Paul McGowan: Thanks! Glad you’re enjoying.
petewilson: As suggested above, it’s a Good Idea to fix the cause(s). But, in general with real-world rooms,...
Soundminded: In response to the question about treating the cause or the symptom in medicine it’s my...
jb4: Thank you for very interesting posts and video’s. I totally agree with your approach, cure the cause,...
- The best way to organize music files and folders (3)
countessouroboros: I realize this post is a bit old now, but for future viewers I feel I need to point out that...
- Jelly rolls (3)
oliver T. Finch: Excellent posts. I look forward to them everyday. Very informative too.I am being convinced more...
Paul McGowan: Oh my goodness yes, depending on the capacitor type the inductance is certainly an issue – for...
coppy: Great articles, Paul, Thanks. And thanks also to all those knowledgeable folks who add their comments as...
- If you have to ask ….. (1)
demeter: “…You cannot hear 1Hz – but you can hear 20Hz and you can feel 16Hz and even...
- Capacitors (1)
Bassman23: It’s been a very long time since I earned my Third Class broadcasting license. Thanks for the...
- Direct coupling (3)
Paul McGowan: The 20 year period between 1973 and 1993 peaking in the early 80′s
oliver T. Finch: What is the second golden era of audio? This a new term to me. Regards.
Soundminded: The purpose of capacitors in the signal path in amplifiers and preamplifiers is to allow independent...
- Gas pedals and plucks (9)
Soundminded: Yes as I pointed out in another thread some time ago the sound of the string itself is barely audible...
Paul McGowan: Sorry, I didn’t mean to suggest “more energy” in a literal sense – I guess...
Soundminded: If you could get more energy out than you put in without an external power supply or built in stored...
Paul McGowan: I’d have to agree with Mark on this one – it really depends on whose hands to instrument...
Paul McGowan: You are absolutely correct about resonance build up – just think about how a whistle or a pipe...
- Ringing (3)
Soundminded: I don’t agree. One way to measure frequency response is one frequency at a time. The input and...
Paul McGowan: Well, correct me if I am wrong but those frequency response peaks won’t occur without...
Soundminded: “We don’t see this added energy in typical audio measurements such as THD and IM because these...
- Just pluck it! (1)
Soundminded: Bowing a string is just like plucking it many times a second. As the taught rosined horsehair on the...
- Music loving animals (5)
Mike48: Our late cat listened with me often. I always thought he enjoyed the music, and he especially seemed to...
Monty
I’m new to these articles, and I’m really loving them. I hope this doesn’t seem patronizing, because it’s not at all meant to be. It’s like a father figure explaining how a complicated thing works (electricity), and how it relates to one of my primary interests (music). Fascinating.
I’ve already relayed several of these stories to my wife and kids (despite the occasional eye rolls.).
Thanks, Paul, for all the great insight.
Paul McGowan
Thanks Monty that means a lot to me and I appreciate it. The posts have morphed over time and it’s hard to know what people want or like – but I do love helping folks understand how things work – I probably enjoy that more than anything.
I give a 1 hour class to our sales folks each Thursday on helping them understand the basics so they can better communicate with our customers. There’s a lot to know in our industry.