Tag Archives: Stereo

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

A little dab

In 2008, authors Karl Johan Åström and Richard M.Murray wrote about feedback: “Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.”

Now, that’s about as nerdy as one can get but their point is well taken. One must look at the whole.

Feedback is taking the outcome of a past event and, in the future, comparing it to one’s original expectations.

We have many different forms of feedback: from customers, friends, family, our own internal loops.

In circuits there’s also a great variety: loop, local, forward, negative, positive.

In my experience, in the world of stereo, the best use of feedback is to have it do as little as possible. In other words, we shouldn’t rely upon feedback to set our course. Rather, feedback should be the finishing touch.

This applies equally to personal and company feedback as well as circuits. We know that if an audio amplifier’s open-loop performance (operation without feedback) is good, then the addition of feedback generally makes things sound better. We also recognize that the opposite is true. Rely upon feedback for an amplifier’s stable operation and the audible results are not worth your time.

Like all things in life, a little dab’ll do ya’.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Card decks

When we enter this life we’re each dealt a hand of cards. Each hand has a different distribution of good ones and bad ones and it is up to us to make the most out of the hands we are dealt.

The same can be said for our HiFi systems and rooms. None are perfect. All are compromised.

How we handle our setups: emphasizing its strengths, shoring up its weaknesses, determines the outcome.

I have always been most impressed with the humblest of systems.

When those shine you know there’s a master card player behind them.

It is not a measure of how much great stereo stuff you have, it’s how effectively you have utilized what you do have.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Attributions

Knowing what attributes are important and why can be valuable.

For example, if we understand that AC voltage regulation is beneficial to our stereos performance, it behooves us to know why. Otherwise, we might take that info at face value and implement the wrong system. Case in point, there was a period of time when a few companies built long term voltage regulators that were purported to help sound quality—motorized variacs or multi-tap step/up down transformers. While these indeed regulated the voltage they sounded worse than not having them in the system.

That’s the problem with a thin understanding.

What this ignores is the deeper understanding of voltage regulation. In order to improve performance it must be dynamic (instantaneous).  And here’s where things can get confusing. With few exceptions, it doesn’t much matter whether a piece of audio equipment is being fed 115 volts or 120 volts. What does matter—the underlying area of importance—is the source impedance. The lower the better.

Dynamic regulation lowers source impedance while slow AVR (automatic voltage regulation) increases source impedance.

Both regulate but one helps while the other hurts.

But this isn’t a rant about lower source impedance. It is about attributions. We attribute better sound to voltage regulation, not because the ultimate voltage level matters, but because a specific type of voltage regulation has the secondary benefit of lower source impedance and it is lower source impedance that matters.

We attribute better sound to voltage regulation but it behooves us to dig a little deeper into why.

Without a deeper understanding of what that ultimately means, we might easily be led astray.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Saturday morning

Depending on where you are in the world this post will arrive at your doorstep on Saturday morning.

What a fine day to finally get off the old duff and fix up the stereo system. Yeah, I know, it’s probably a better day to kick back and roll some tunes on that system, but having just spent the last few Saturdays revamping and refreshing the PS Audio reference music system in Music Room II, I can tell you it is worth the effort.

For a few years now I’ve listened past some obvious sonic problems in Music Room II. Problems like high distortion at 100Hz from the EMIM midranges, and the lack of kick in the drums as a result of trying to make the EMIMs do more than they were really capable of doing. In short, as good as the IRS V system is, it isn’t without its faults: faults I and others have turned a blind ear to because…well…we could and we were lazy.

Speaker designer Chris Brunhaver and I had a come to Jesus moment over that system. Chris did his best to be gentle in pointing out how in the 100Hz to 300Hz region those EMIM planar drivers just cannot (and never could) produce the dynamics in music—especially pop music. And, when they did what they could there was distortion—like on the order of 10%. This never much bothered Arnie nor me when we were listening to classical and orchestral music since in that area there isn’t typically a lot of energy. And when it came to pop or rock music, mentally I have for years compensated for that deficiency. But now with so many producers, musicians, and rock/pop people relying upon that system for the ultimate standard reference, it was time to change.

Tomorrow I’ll tell you what we did and what happened as a result of it.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

MVP

When sports-minded people see the TLA MVP they naturally gravitate towards the acronym meaning Most Valuable Player. In our case, we’re going to refer to another definition, one used in product design, Minimum Viable Product.

Most stereo product designs start out with a MVP specification defining the least it must do. Designs are then generated to meet the MVP spec and then forwarded to the marketing department to see if anything more is needed to make it salable.

That’s certainly one way of designing products and, sadly, the most popular way.

Designers who are emotionally attached to their creations often assume a very different set of guidelines from which they design.

In this model, they dream big then titrate their grandiose dreams to something that fits into practical realities.

Two very different approaches.

The products resulting from these two design philosophies will likely perform differently as well.

Which would you choose?

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Defining personalities

We all like to imagine our products are completely neutral, transparent, and without sonic colorations.

Yet, we know that’s simply not true.

Like it or not (and I tend to like it) the designer’s essence, soul, tastes, and biases towards music are a part of the final product. Their tastes influence musical performance in the same way a recording or mix engineer’s decisions determine what’s going to get your stereo, foot tapping.

People, recordings, audio equipment, and even room furnishings imprint their personalities on the music we choose to listen to.

The challenge then is to make sure you like the personalities of what you choose to surround yourself with.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Linearity

The term linearity as it applies to amplification suggests a ruler-flat straight line. That is, for a given input voltage we expect a mathematical relationship with the output voltage that can be graphically expressed as a straight line.

So, for example, with an amplifier designed with a gain of 10, for 1 volt in, we expect exactly 10 volts out at every frequency. Easy peasy. Only, that isn’t what happens with amplifying elements.

Neither transistors nor vacuum tubes are natively linear with voltage or frequency, yet we expect them to perform as if they were.

Here’s a simple graph of input vs. output voltage of an amplifying element. Note how only part of its response is a straight line.

And this graph only covers voltage. A similar graph displaying input vs. output frequency is even worse.

What to do.

There are numerous ways designers have of overcoming a stereo device limitation. For instance, a transistor’s input vs. output is very non-linear at input levels below half a volt. So, imagine you’re trying to amplify the tiny output voltage of a phono cartridge—maybe 0.005 volts. Yikes! That’s so low the amplifying device wouldn’t even recognize it!

The answer to that problem is simple and straightforward. We pre-apply to the transistor a steady, small, “turn-on” voltage. Now, when we next add the tiny voltage from the phono cartridge, the transistor will add that voltage to the steady voltage and we get a linear output response we can count on. At the device output, we remove the steady “turn-on” voltage and, what’s leftover, is a perfect bigger version of the tiny phono cartridge output.

Bingo!

That process I just described is known in engineering circles as adding bias. And yes, you guessed it, the amount of that bias is categorized in familiar classes of operation like B, AB, and A. Remember? Class A or Class AB are well-known terms to audiophiles. They describe how much a device is constantly turned on with that steady turn-on voltage we will eventually throw away when we extract what we really want, the amplified output signal.

And, since today’s Saturday and we can write a longer post, how do we throw away that steady voltage? Well, in vacuum tube amplifiers and simple transistor amplifiers, we place a blocking capacitor. What it blocks is that unwanted turn-on voltage (DC) and what it lets pass is the desired amplified audio signal. The quality and construction of that blocking capacitor has an enormous impact on how the eventual sound we hear is. (Of course, there are other means of doing this, I use this simple example only for means of explanation).

But that covers only one aspect of what we must do to make a non-linear device like a vacuum tube or transistor perform the way we wish. Other tools in the belt include feedback, both local and global, and many tricks of the trade all in service of getting a non-linear device closer to the ideal of linear.

And yes, all that we do impacts sound quality.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

A place of honor

If you’re an important person invited to dinner, tradition suggests you be given the place of honor, perhaps the seat next to the host.

But places of honor aren’t reserved for just the dinner table.

In our home, the first thing you notice upon entering the living room is our beloved HiFi system.

You notice it because it occupies a place of honor, there for all to see, hear, and enjoy.

More than invited guests, our stereo HiFi systems are valued family members that contribute greatly to our well being.

They deserve a place of honor.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Audibility

We often ask ourselves what’s audible and what’s not.

We can say with some confidence 10% distortion is audible, but is 0.1%?

And, compared to what? Can we hear the difference between 0.1% THD and 0.0001% THD?

There comes a point in measurements where one must decide what matters and what does not. It probably doesn’t matter, for example, that one wheel of your car might be 1/10th of an inch different in diameter than another. On the other hand, 1/10th of an inch parts variability in a Swiss watch might be the difference between functioning and non-functioning.

From my perspective, once we hit THD and IM levels below 0.1% in a stereo product, the differences become more academic than audible.

And yet we hear major differences between differing topologies producing dramatically different levels of distortion.

What that suggests is simple. Beyond a certain point, the level of distortion becomes meaningless.

How those differing levels are achieved is where we find the bulk of sonic differences.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Finding your passion

Passion is a feeling of intense enthusiasm for something (or someone). Finding it isn’t always easy but, when you do, it’s great to hone in on the elements that really fan the flames.

If I look at myself I quickly identify two major passions: learning how things work and building solutions.

From as far back as I can remember, I had to know how everything worked: why the sky is blue, what are rainbows, how a button and a switch work, a synthesizer, a phono stage, a vacuum tube, a traffic light. When I interact with the physical world there’s not a lot around me I don’t understand.

Faced with a problem or presented with a challenge, I am inspired to build a solution. When I was unhappy with the sound of the first CD players from Magnavox I figured out how they worked, determined what I could and could not affect, and built one of the first outboard DACs to solve the problem. When I was unhappy with my stereo’s dynamics I added side-firing drivers activated by a log amplifier to extend the system’s dynamic range.

Not everything is understandable to me. Not everything is fixable to me.

That was never the point.

The point is to identify and then follow one’s passion even if it means failure.

What’s your passion?