Hephaestus Audio

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.

Most audiophiles agree that there is a certain “break in period” required for audio gear to start sounding right. Most non-audiophiles will agree that this is the case for something like a loudspeaker, where there is a measureable change in the driver parameters after loosening up a bit, but tend to regard break in phenomena in audio electronics with great skepticism. Most audiophiles point to the usual suspects: resistors, capacitors, and magnetics. This is a good start, but there is a bit more to it.

There is a great exhibit at the Exploratorium in San Francisco. It consists of a basketball, a hoop, and a pair of funky glasses that skew your vision to one side. You start by making a few shots without the glasses - no big deal, the hoop is fairly close. Next you put on the glasses and every shot now goes off to one side - a very strange sensation! However, after several shots you notice that each shot gets a little better as your brain starts to slowly adapt to this new “reality”.

Much like the illusion given by the funky glasses in the basketball exhibit, every piece of audio equipment is nothing more than part of an ”illusion engine”. Since the musical reproduction we are creating is an illusion, our brain must learn how to perceive it correctly for the illusion to work at all. This is a significant part of the break in period for audio gear - we are breaking in, right along with the equipment!

Every piece of audio gear has errors, regardless of typical ”perfect sound forever” claims. Some errors are easier for your brain to adapt to than others. A longer break in period may in part be the result of errors that require a bit more “training”. Note that the amount of training needed is also a function of the individual. Some listeners may readily forgive certain types of error (e.g. dynamic compression), while being hypersensitive to other types of error (e.g. poor imaging).

Okay. Uncle!

We tried to eliminate the requisite blue LED on the front of the HMA-1000 to avoid distraction in a dark home theater environment, but we can see we’re outvoted. A quick search through your favorite audiophile publication will yield scores and scores of products with a virtual ”Lite-Brite” set of blue LEDs on the front panel. We’ve decided to succumb quickly to the inevitable, rather than die a lingering non-blue death.

We’ve upgraded the HMA-1000 kilowatt switching amplifier to the BLU-500 half-kilowatt switching amplifier. The reduced output power is due to the high power draw of the new Industrial Blue LED Array™ on the front panel. The build and audio quality had to be reduced as well to hit the same price point, but we think the sacrifice is well worth it. Our customers tend to agree, as illustrated in the following cherry picked testimonials:

“The sound is crap. Everything I look at outside of my home theater has an orange tint now for Christ’s sake! They tell me it’s because of ‘complementary colors’. Whatever. Anyway, the only redeeming thing about the BLU-500 is that my complexion has never looked this good! I believe more salons should carry this product.”

Corky Saint Claire, Elko NV

“The build quality of the BLU-500 is marginal. Wire nut outputs? Honestly. The audio is poor as well with what I can only describe as random ’chicken-like’ sounds. But the bright blue LEDs are just plain beautiful! This is true art and not the Jackson Pollock kind either. I really can’t stop looking at it, despite the warnings and all.”

Bubba Diablo, Fargo MN

Here is a happy pair of customers enjoying a favorite movie in their unique high-end home theater, all while basking in the soft glow of the BLU-500:

Although not technically a laser, the Industrial Blue LED Arrayâ„¢ can cause injury with repeated brief glances. Therefore, all units ship with the following placard, to be displayed prominently within 25 feet:

We truly believe that moving from the HMA-1000 to the BLU-500 will be a big win for both Hephaestus Audio and the audiophile community. The American architect Louis Sullivan once said, “form ever follows function”, but here at Hephaestus Audio we like to say, “form ever follows finance”, especially if there’s some serious money to be had!

P.S. April Fools!

ABX testing is a form of audio testing where two components (A and B) are carefully matched with respect to level, some means is included to at will switch between the two during the course of a musical passage, and the listener is completely unaware of which is which (X). This is the “de facto” standard for serious audio testing. It is an excellent approach in principle, however there is a serious flaw: it only allows for the detection of gross differences due to the relatively brief samples involved.

The Heisenberg Uncertainty Principle in its most common form states that:

Where is the uncertainty in position, is the uncertainty in momentum, and is Plank’s constant divided by .

There is another form that gives the same relationship for energy and time:

Where is the uncertainty in energy and is the uncertainty in time.

What does this have to do with ABX testing you may ask? Well, nothing actually, as the principle does not apply to the macroscopic world due to the extremely small value of Plank’s constant. However, it provides insight to the issue of ABX testing. I propose that there is a similar relationship between the perceived difference and the listening interval. Let’s denote this as follows:

Where is the uncertainty of the listener as to whether a difference exists or not, is the interval during which the listener compares the two components, and is is a listener-dependent constant (i.e. it is larger for “tin ears” and smaller for “golden ears”).

The bottom line is that a given listener will be able to detect finer and finer differences between two components over time. This means you really have to “live” with a component for some time to appreciate the subtle differences between it and another component. Unfortunately, it is very difficult to be objective with a long term test such as this, but I have no doubt that somebody will ultimately figure out a way of doing it.

Hephaestus Audio continues to grow! I am very happy to share these press releases and web ads for the HMA-1000:

From Mr. Srajan Ebaen’s 6moons:

http://www.6moons.com/news/news.html

From Mr. Matej Isak’s Mono & Stereo:

http://www.monoandstereo.com/2009/03/hephaestus-audio-hma-1000-kilowatt.html

From Mr. Clement Perry’s Stereo Times:

http://www.stereotimes.com/speak031709.shtml

From Mr. Steven Rochlin’s Enjoy the Music:

http://www.enjoythemusic.com/news/0409/

Linearity is the exception rather than the norm. We live in a very nonlinear world - for example, it is now known that a sinusoidally driven resistor/diode/inductor combination can exhibit chaotic behavior! Please refer to this excellent SPS Report.

One of the simplest equations that demonstrates this nonlinear behavior - this chaos - is the “Discrete Logistic Equation” or the “Logistic Map“. Mathematically, it is given by:

This is typically used as a simple model of population growth with finite resources (i.e. food). represents the population at the next time step, based on that at the previous time step where with “growth rate” where . A plot of the logistic map with respect to growth rate is given below for the interval :

Using MATLAB, more sophisticated visualization is possible that may give greater insight into what is happening to the population dynamics as the growth parameter is varied. For example, how the periodic regions return to chaos via a period-doubling bifurcation. Shown below is the interval :

One lesson to take from all this with respect to audio electronics is that simplicity is best! If a resistor/diode/inductor can result in chaos, then what can the circuitry in an overly complicated amplifier do? Not only in electronics is simplicity the best, for example in Strunk and White’s The Elements of Style there is the simple mantra: “Omit needless words!” Vastly different disciplines - same guiding principle.

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.

There are some amazing parallels between color theory and music. The color wheel is a basic tool from color theory that shows the relationship between the colors of the rainbow. Colors directly across from each other are called complementary colors and tend to give the most striking contrast.

These colors may be combined using various color schemes - each giving its own sort of “feel”. If each of these colors is now associated with a note from the chromatic scale, then it turns out that the way a color scheme is perceived is very similar to the way the associated note combination is perceived.

Yellow → C
Yellow-orange → C#/Db
Orange → D
Red-orange → D#/Eb
Red → E
Red-violet → F
Violet → F#/Gb
Blue-violet → G
Blue → G#/Ab
Blue-green → A
Green → A#/Bb
Yellow-green → B

This “mapping” is somewhat arbitrary and could be shifted, provided the order is maintained. Is C a “yellow” note? I don’t know, but perhaps somebody who experiences synesthesia would have a preference. Here are some examples of color combinations and the associated note combinations:

Monochromatic / single note

A single color or a single note is generally uninteresting (unless you really just love that color/note).

Analagous / dyad

An analagous color scheme uses two nearby colors on the color wheel. It is much more interesting that a monochromatic color sheme. A dyad consists of two notes, again this gives much more interest than a single note.

Complementary / tritone

A complementary color scheme is very striking and gets your attention. It is good for adding interest, but a little goes a long way. In music, the tritone is the most dissonant of intervals and is used sparingly to create tension.

Split complementary / chord

Rather than using the color directly across on the color wheel, a color on either side is used. This creates a pleasing combination without the stark contrast of the complementary color scheme. Similarly, a musical chord creates interest, potentially even more than a dyad, while not being as dissonant as the tritone.