Hephaestus Audio

When I stop and think – imagine – the most fantastic images come to mind.  I know I’m getting the smallest sliver of a glimpse inside of my subconscious and my conscious mind is futilely attempting to make sense of it in the terms it understands: vision, hearing, etc.  This process is so amazing that I’ve never been able to convey it very well, although I’ve no doubt that other designers have a similar experience.  Most likely even more so.

That’s the first step.  Thinking.  Imagining.  However, for others to benefit from this process it is necessary next to do something.  A former professor of mine, Carl Pavarini, once said “Ideas are worth their weight in gold.”  After the class full of engineers enthusiastically agreed, Dr. Pavarini then posed the question “How much does an idea weigh?”  Ouch.  It’s a tough pill to swallow, but it’s painfully true.  You must do something – whether your medium is paint, words, code, or solder.

I’m not sure what’s more incredible: the fact that I have the great joy of experiencing these creative visions or the fact that so many others have as well!  The following quotes provide terse insight to the inner workings of great minds.  These are the thoughts of the giants on whose shoulders we have all stood.  The best innovators distinguish themselves by not fearing to stand at such a great height.

“I do not think there is any thrill that can go through the human heart like that felt by the inventor as he sees some creation of the brain unfolding to success… such emotions make a man forget food, sleep, friends, love, everything.” — Nikola Tesla

“But I think Steve’s [Jobs] main contribution besides just the pure leadership is his passion for excellence. He’s a perfectionist. Good enough isn’t good enough. And also his creative spirit. You know he really, really wants to do something great.” — Andy Hertzfeld

“People take the longest possible paths, digress to numerous dead ends, and make all kinds of mistakes. Then historians come along and write summaries of this messy, nonlinear process and make it appear like a simple, straight line.” — Dean Kamen

“An essential aspect of creativity is not being afraid to fail.” — Edwin Land

“One of the unfortunate things about our education system is that we do not teach students how to avail themselves of their subconscious capabilities.” — Bill Lear

“One always has to remember these days where the garbage pail is, because it’s so easy to make sounds, and to put sounds together into something that appears to be music, but it’s just as hard as it always was to make good music.” — Robert Moog

“With all the knowledge and skill acquired in thousands of flights in the last ten years, I would hardly think today of making my first flight on a strange machine in a twenty-seven mile wind, even if I knew that the machine had already been flown and was safe.” — Orville Wright

“Knowing is not understanding. There is a great difference between knowing and understanding: you can know a lot about something and not really understand it.” — Charles Kettering

“Opportunity is missed by most people because it is dressed in overalls and looks like work.” — Thomas Edison

“The real secret of success is enthusiasm.” — Walter Chrysler

“What is it that I like so much about the house you’re building for me, Howard?”

“A house can have integrity, just as a person,” said Roark, “and just as seldom.”

“In what way?”

“Well, look at it.  Every piece of it is there because the house needs it – and for no other reason.  You see it here from the inside.  The rooms in which you live made the shape.  The relation of masses was determined by the space within.  The ornament was determined by the method of construction, an emphasis on the principle that makes it stand.  You can see each stress, each support that meets it.  Your own eyes go through a structural process when you look at the house, you can follow each step, you see it rise, you know what made it and why it stands.  But you’ve seen buildings with columns that support nothing, with purposeless cornices, with pilasters, mouldings, false arches, false windows.  You’ve seen buildings that look as if they contained a single large hall, they have solid columns and single, solid windows six floors high.  But you enter and find six stories inside.  Or buildings that contain a single hall, but with the facade cut up into floor lines, band courses, tiers of windows.  Do you understand the difference?  Your house is made by its own needs.  Those others are made by the need to impress.  The determining motive of your house is in the house.  The determining motive of the other is in the audience.”

This is the way Howard Roark, the main character of Ayn Rand’s The Fountainhead, describes the house he has designed for friend and supporter Austen Heller.  This novel is rare in its accurate illustration of the way many creative types feel about design – whether architecture, art, or amplifiers.  Non-functional ornamentation can provide transient beauty, but lasting beauty comes only from functionality.  Some of the most beautiful designs in the world are beautiful for two simple reasons:

1) The design serves a purpose better than other designs
2) The embodiment of the design is a function of the purpose

The human body is the best example I am aware of.

Anybody ever notice how “amplifier kits” sound the way that “beer kits” taste?

I recently took up homebrewing and, not knowing any better, I smiled as the nice LHBS man filled up my arms with “beer kit” paraphernalia.  I read the instructions carefully, bottled it up happily, and waited patiently for EIGHT weeks as it aged to “perfection”.  For any of you who have tried a beer kit, you are probably aware that “perfection” is a term to be applied loosely…

After dumping out bottle after bottle of icky beer, I was motivated to try making some beer from scratch.  This took lots of research that involves terms particular to beer making such as “degrees Plato”, “brix”, “original gravity”, “final gravity”, “wort” (pronounced “wert”), etc.  Make no mistake that I still made plenty of errors as I learned the ropes of making beer from scratch, but with a little tenacity I finally made something pretty good.  Please see the recipe below.

This whole experience bears an uncanny resemblance to “amplifier kits”.  This is where you take somebody’s amplifier controller and simply add the right ingredients – output stage, output filter, and power supply are typical – to build a complete amplifier.  It all sounds so simple, like the beer kit, and great results are promised, but these amplifier kits never quite manage to live up to it…

After throwing out the amplifier kit (i.e. “dumping the bad beer”) some are motivated to do research to figure out what is needed to make an amplifier from scratch.  There are many terms particular to amplifier design such as “dead time”, “slew rate”, “THD”, “EMI”, etc.  There are plenty of errors still in store for the would-be amplifier designer, but again with some tenacity it is possible to develop an amplifier that will shame any amplifier kit out there.

“Dry Ice Ale” Recipe

• 6 lbs Briess 2-row malted barley
• 2 oz Glacier hop pellets (added during boil)
• 2 oz Cascade hop pellets (added to secondary)
• 11g Nottingham ale yeast, proofed
• Bring 5 gal water to 160F (fill pot with water night before)
• Add grain and steep 30 min stirring occasionally
• Remove grain and bring to boil (this is a no-sparge process)
• Boil 30 min while adding 2 oz Glacier hops continuously
• Put in ice water bath and stir gently for 20 min
• Pitch proofed yeast and pour into primary
• Fill airlock with water and let ferment 1 week
• Transfer to secondary, add 2 oz Cascade hops
• Fill airlock with water and let sit 2 weeks
• Transfer to bottling bucket and add 1/3 cup sugar
• Fill bottles and let carbonate 1 week
• Put in cellar and let rest 4 weeks
• Serve at cellar temperature and enjoy!

“We aren’t making the best products just because some customer suggested them to us, or even assured us of big orders, but because we have a passion to bring some art, in which we have a large personal investment, to the pinnacle of perfection.” – Barrie Gilbert 

This quote comes from Ch. 18, “It Starts with Tomorrow”, of The Art and Science of Analog Circuit Design.  If you love analog circuits, then this book should be placed right next to your copy of The Art of Electronics, if it isn’t there already.  Please refer to this IEEE article, “The Gears of Genius“, for more on this amazing designer.

There is a section of this chapter that deserves a brief summary – a bit of pseudohistory entitled “History through Dark Glasses”:

“…the first step to a successful product is thorough market research,” reads a young Thomas Edison in his new copy of “Yours is the Market: How to Find Out What People Really Need and Thereby Become Rich and Famous” by Harvard professor Yucan Sellum.  It is essential, says professor Sellum, to listen to the “Voice of the Customer” (VOC).  Young Mr. Edison now goes door-to-door to conduct the needed market research asking if his potential customers see any possible improvements in the way they light their homes.

Door 99

“First, if you can invent a stronger, brighter gas mantle, people will beat a path to your door.  Those durned things are always breaking!  And second, if you can invent a way that causes leaking gas pipes to be self-healing, you’ll quickly find yourself off these streets.”

Door 100

“Now, if you find a way to make our oil-lamps burn twice as bright and and twice as long from one filling, that would be something you could sell.”

Edison returns to his lab, dejected.  He has adhered to professor Sellum’s advice that he must conduct his marketing research “in such a way that…one only elicits those facts which the customer freely wishes to impart to the researcher.”  “Too bad nobody ever asked me if I had any ideas of my own,” sighs Edison as he gazes at his new tungsten lamp powered by a generator spinning in the basement…he then writes:

“Trip Report, 18th November, 1878.  Spent all day doing a VOC in Menlo.  Spoke with 100 people re lighting improvements; got good info. from 83….Action Item: Write Product Development Proposal re Improvements to Gas Mantles and Oil-Lamp Wicks.  Do before Monday exec. council mtng.  Call KJ to consider weaknesses in present methods of mnfng mantles.”

After your masterpiece is created you must listen carefully to your customers and adapt quickly.  However, for that first critical, tenuous, and beautiful spark, you must listen only to the inner dynamo that drives you to create that which has never before existed.

Remember writing essays in school?  Unless you are of a very different sort than I, this consisted of adding useless filler words, excessive punctuation, generous font sizes, and plenty of spacing and indentation – all in an effort to reach the required minimum length.  The end result was judged by many parameters – including reaching the minimum length and conciseness.  These two goals seem mutually exclusive to me.  If the desired end result is a 1½ page essay, perhaps the english instructor could lead the class through this exercise that starts with a 3 page essay:
 

• Write a 3 page essay on high-end audio
• Round 1: eliminate 25% of word count and reread
• Round 2: eliminate 25% of new word count and reread
• Round 3: eliminate 25% of new word count and reread
• Submit essay with original word count reduced by 50% 

Maybe some instructors do this and if so, congrats!  These lucky students will go on to write emails, papers, blogs, maybe even books, that will require far less of the readers valuable time for the same quantity of information and entertainment.  This is a great approach for writing, but why stop there?  It can even be applied to electronics design!  For example, the electronics instructor could lead the class through this exercise to reduce the number of components used in a design by 25%:
 

• Design a 100W switching audio amplifier
• Round 1: eliminate 10% of component count and retest
• Round 2: eliminate 10% of new component count and retest
• Round 3: eliminate 10% of new component count and retest
• Submit design with original component count reduced by 25%

Of course this technique should not be limited to a classroom setting.  We can and should do this all the time.  With the written language it leads to concise, informative and enjoyable documents.  With audio electronics it leads to simple, elegant and enjoyable designs!

Although there are many different types of connectors available, and there is sometimes mixing and matching on a given product, the two groups shown below are representative of audiophile and professional connector sets: 

Audiophile

• RCA input
• Binding post output
• IEC mains

The RCA input is very common, but unfortunately it is single-ended.  This does not in general offer the same degree of noise rejection as a balanced input.  Five-way binding post outputs are great for their versatility, plus there are versions available that offer very low contact resistance (e.g. the excellent connectors from WBT).  The IEC mains connector is convenient and available everywhere, but does not give the same performance as newer offerings. 

Professional

• XLR input
• Speakon output
• PowerCon mains 

The XLR input is balanced and there are very good gold-plated versions available.  The Speakon output is rated for high current, but is not quite as versatile as five-way binding posts.  The PowerCon mains connector offers about one-third of the contact resistance of an IEC mains connector.  An advantage of these professional connectors is a locking mechanism that allows for robust installations.

One of the biggest issues with a professional connector set is that the specialty cable market has not yet embraced them.  This serves as a major deterrent to those who already own, or may wish to purchase, specialized audio cables.  I hope to see this deficiency remedied soon so that audiophiles may begin to enjoy the benefits of these high performance connectors.

There is much confusion over amplifier power ratings.  There are two primary things to be aware of: what type of measurement a given rating represents and what this means as far as one’s listening experience.  The former is fairly objective while the later is very subjective.

Continuous RMS

This is the most rigorous of the power measurements, although even in this category there are a few “flavors”.  For example, what is “continuous”?  Ten seconds or ten years?  Also, is this at one frequency (e.g. 1kHz), the full audio bandwidth (e.g. 20Hz-20kHz), or the full bandwidth of the amplifier (e.g. 5Hz-100kHz)?

The next question is how appropriate this measurement is for an audio amplifier.  It is probably very appropriate for a precision programmable ac power supply, but I’m not sure how many people listen to continuous full-amplitude sine waves.  Some may feel better knowing their amplifier will be well within its limits with audio material, but as far as actual audio quality, there isn’t much benefit.

Burst Power

Like with continuous RMS there are a few ways of interpreting this measurement.  Is this the peak power of a continuous sine wave, in which case it is double the continuous RMS value, or does this represent the maximum instantaneous power, in which case it is a function of the power supply rail voltage at idle and the lowest allowable load impedance?

There is some merit to this sort of measurement, but the burst interval should be of a reasonable length.  A 20mS burst test is common with very high power amplifiers, such as those from Powersoft or Lab.Gruppen.  Measurement of actual program material indicates that a 200mS interval may be more appropriate – please refer to this AES paper.  Given a reasonable burst interval, this test is probably the most useful for amplifiers intended to reproduce audio material.  Please note that this burst power measurement may be given as either “peak” or “RMS”, with the former having twice the value of the latter.

EIAJ

This is a measurement of the saturated square wave power of the amplifier and is common with consumer and car audio products.  It tends to give an inflated power rating, which is no doubt why it is popular with low-quality audio products.

This test may be useful for giving a feel of what an amplifier is capable of when severely overdriven, but is not really appropriate for high-quality audio products.

This article shows the measured crest factor of some representative pieces of music.  The conclusion is that, for a “typical” home audio setup, peak power in excess of 500 Watts may be required for an average power level of only a few Watts, if the goal is clean (i.e. unclipped) audio.

Note that heavily compressed audio has much lower crest factor (i.e. headroom) requirements.  However, the average listening level is typically much higher, so the peak power requirements are still comparable.

“Beauty is truth, truth beauty, – that is all ye know on earth, and all ye need to know.” – John Keats

A former co-worker of mine, Alexey Astanovitskiy, told me what his father had told him with regard to electronics design: “If it looks beautiful, then it will work beautiful.”  He was a very gifted designer and I have sought to emulate his example ever since.

This beauty in design goes beyond that which the customer is intended to see (i.e. the outside of the product) – it is in every aspect of the design, right down to the layout of the PCB.  Take off the cover and look inside (please unplug the unit, allow some time for the capacitors to discharge and don’t touch anything).  Was the layout put together last minute with little attention paid to aesthetics and the difficulties of switching design?  Was the designer involved with this critical part of the design, or was it simply handed off to a layout person to “finish it up”?  Gaps like this in execution can turn an excellent design into a marginal product.

It is the little details that make a big difference.  The ones that nobody may ever be consciously aware of.  However, audiophiles do have an interesting habit of noticing these “little details”.

Total Harmonic Distortion (THD) is the standard measurement for the accuracy of audio equipment, particularly audio amplifiers.  Unfortunately, it is a poor metric for audio amplifiers for one simple reason: they are intended to be listened to.  If the amplifier were intended to drive a precision actuator for an industrial process, for example, then perhaps THD would be a good metric, along with bandwidth, slew rate, settling time, etc.

Lower-order harmonic distortion tends to be perceived much more favorably than higher-order harmonic distortion (the ear naturally generates low-order harmonic distortion).  This leads one immediately to at least consider a harmonically weighted distortion metric.  In fact, such a metric was proposed as early as 1937 by the Recording Manufacturers’ Association of America, however such metrics have seen little, if any, practical application.  No doubt this is due in part to the many different choices for harmonic weighting functions, frequency dependent factors, etc. – there are no such choices with THD.

Fairly recently a metric has been proposed that seems to have very good correlation with subjective impression.  This is the “GedLee Metric” by Earl Geddes and Lidia Lee of GedLee LLC.  Here are the first and second parts of the relevant AES papers.  There is a tremendous amount of momentum to overcome for a metric such as this to ever gain traction in the audio industry.  Especially resistant will be any manufacturers that stand to have their specifications suffer by it.  For example, low THD linear amplifiers that have made use of large amounts of global feedback, with little attention given to the linearity of the open-loop transfer function, may look poor in the light of this new metric.