Tag Archives: Power Amplifier

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.

Can work either way..

Subwoofer connections

For more than three decades I have strongly advocated the high-level connection of subwoofers—where we connect the output of the power amplifier to the input of the subwoofer.

What amazes me is that still to this day, that viewpoint is considered radical.

The vast majority of subwoofer manufacturers would have you connecting their subwoofers through low-level inputs as supplied by your preamplifier. Their reasoning is simple. The output of a preamplifier is cleaner and more direct than what happens after a power amplifier has processed it.

My good friend, John Hunter of REL subs is one of the few subwoofer manufacturers agreeing with me.

And here’s the thing. The majority of subwoofer manufacturers are correct. There’s no argument that the output of the preamplifier is cleaner, purer, and more direct than the output of a power amplifier.

So why the debate?

Because they are missing the point. Subwoofers should not stand out in the system. The whole point of a subwoofer is to augment the performance of the main loudspeakers. We don’t want to hear the subwoofer. We want to pretend as if it were a perfect appendage to the main speakers. To make that happen we need to do whatever we can to get closer to matching the sound of the main speakers—a perfect pairing.

We want the characteristics of the power amp to color the output of our subwoofer in an effort to more closely integrate it.

Hope that helps.

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.

The home stretch

In yesterday’s post, we learned that our homes present an impedance of about 1Ω to our stereo equipment. This matters, as you can imagine, because when we try and drive a 4Ω speaker with a power source with that high of an impedance we get power line modulation.

Put another way, we make things worse for any audio equipment plugged into our power lines.

Adding an active power amplifier like that found in a Power Plant will improve that situation by an easy factor of 100. And, 100 times better performance is a welcome thing to most of us.

But now we have an opportunity to make things even better.

If we only use the impedance lowering amplifier for that single purpose we lose the opportunity for a couple of major improvements: voltage regulation and waveform correction.

Our incoming powerlines suffer from all sorts of maladies including fluctuating voltage, waveform distortion (called flat topping), and powerline modulation from equipment in our own home.

Simply lowering the impedance in the line doesn’t solve any of these problems.

That’s where we take the next step in the magic of a Power Plant, we feed the input of our impedance lowering amplifier with a perfect sine wave (instead of the raw incoming power).

Now, we have lowered impedance by a factor of 100 and fixed the waveform and restored the missing energy from a flat-topped sine wave.

Life is good, but we still haven’t tackled the last wish on our list, increasing the size of the power supply capacitors inside our equipment.

How to make the caps in your equipment’s power supply bigger is tomorrow.

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.

The free lunch counter

In yesterday’s post, we learned that to effectively lower impedance we need to add energy.

That’s what a power amplifier does and what a passive power conditioner cannot do.

In fact, a passive power conditioner (one without an active power amplifier inside) makes things worse. It raises impedance.

Wrong direction.

To get the most out of our stereo systems we need to figure out a way to stop restricting the power they need by actively lowering impedance.

Good things come at a price.

If we want to lower impedance we either move our home next to the power generating facility or add an amplifier to actively lower impedance.

Here’s why.

The average home wiring chain presents an impedance of between 1Ω and 0.5Ω depending on the wire gauge within the home and the distance from the utility pole.

14 gauge wire, which is the standard our homes are wired with, has a resistance of about 2.5Ω per 1,000 feet. The thicker wire feeding our homes has about 10X less resistance. So, we’re going to assume a combination that gets us to an average of about 1Ω.

1Ω is a lot of resistance for our power to have to struggle its way through. As our main power amplifier tries to drive those 4Ω (or lower) speakers, it’s struggling to suck needed power through a restrictive 1Ω pipe.

What happens if we add an impedance lowering amplifier between the high impedance power line and our musical power amp?

Voila! Now, instead of 1Ω of restricted access to power, our musical amp can enjoy 100, or even 1,000 times lower impedance feeding it.

Our story continues tomorrow.

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.

Shortening wire length

In yesterday’s post, we posed the question of what might happen if we were to lower or even eliminate the impedance inherent in the AC power wires feeding our home.

The answer is simple. Dramatically better sound.

Something we all want!

But, how best to eliminate or significantly lower the impedance of hundreds (often thousands) of feet of connecting power cables shared by our neighbors?

Traditionally, lowering impedance inherent in wire can be handled in two ways: shortening its length and/or increasing its thickness.

Increasing wire thickness from the standard of 14 gauge copper, which is about 0.06″ thick, to something ridiculously heavier like 0 gauge wire, which is nearly ten times the thickness (times 3 conductors), would help but wouldn’t solve it. Only thickening and shortening the wire to mere feet would get the total impedance where we would want it, to perhaps 0.01Ω or lower.

The problems with taking these steps would be one of practicality (or the lack thereof). Let’s start with thickening the wire. 3-conductor 0 gauge wire is about 1.5″ thick and weighs in at about 1.5 lbs per foot. That’s going to be a bear to install in the walls (never mind the impracticality of typing that wire into an AC receptacle). But, let’s say we managed all that copper. We still need to shorten it to mere feet. To do that we’d have to move our home next to a noisy, stinky, coal-fired power generating station.

We might get some spousal pushback.

Fortunately, there is an alternative. A power amplifier.

Let’s back up a moment.

If you want to power a pair of loudspeakers you won’t get very far connecting the output of your preamplifier to them. Preamps can’t drive speakers because their output impedance is too high.

To lower a preamplifiers output impedance you need to add energy, something a power amplifier is very good at.

Power amplifiers have high input impedance and low output impedance.

Does this sound like something that might interest us in our quest to reduce the impedance of the power line from high to low?

Methinks, maybe.

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.

I’d be willing to bet that for every audio designer that thinks high end audio amplification design like Paul, there are an equal amount that think otherwise. As far as an amp breaking a sweat, my experience with certain types of solid state amps is that they sound their best when breaking a sweat.

Careful on the input

One of the ways we designers make good sounding audio amplifiers is to lightly limit the input frequency while at the same time extending its high-frequency response.

That’s something that might seem counterintuitive but it works.

For example, at the input of a power amplifier, I like to form a light low pass filter of around 30kHz but within the amplifier’s circuitry, extend its bandwidth to as high as is practical—hopefully somewhere close to 100kHz.

This combination of limiting what the amp has to deal with while making sure what does come in is easily handled makes for a wonderfully open and easy presentation of music.

I like to think of it as a car with more power than it needs, and then a light foot on the accelerator pedal.

Easy in so the amp never breaks a sweat.

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.

The problem with evaluations

What do you call the lowest-performing student graduating medical school?

A doctor.

In any field, the range from good to great is all over the map. Graduation degrees, specifications, and even reviews only tell us so much.

A power amplifier meeting all the basic requirements of distortion, frequency response, and power output does not—can not—sound the same as a different design with identical specifications.

It’s why we interview our medical providers.

It’s why we read the first chapter of a best seller before committing to the whole.

It’s why we listen to our amplifiers.

Specs, degrees, and reviews are fine for clearing away the cruft of the unworthy.

The rest is up to you.

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.

Our first integrated

I just received my second CoViD shot last night and so find myself on shaky ground at the moment but wanted to make sure I didn’t miss a day of a post.

I was just ruminating on the steps leading up to our first integrated amplifier, the Elite.

When Stan and I had built our fledgling company to the point where we hired our first two employees, Lowell and Jeff, we were building two products: our phono stage and its companion Linear Control Center. The LCC was not a whole lot more than a volume and balance control, an input, and a gain selector.

From a circuit perspective, there was a 10X stereo preamp inside that offered 20dB of gain the user could choose to run the signal through or not. Passive or active preamplifier.

As Jeff and Lowell did their best to keep up with customer orders, Stan and I worked on our new power amplifier to be called the Model One. The power amp’s circuitry was not a whole lot more than the LCC’s gain stage with a pre-driver, driver, and output transistors. The Model One was capable of 70 watts per channel into 8Ω.

Because we didn’t want to “color” the sound of our new amplifier while it was in development, we chose not to use the LCC as a volume control. We wanted the signal path as free of circuitry as possible so that we would be tuning only the amplifier and not the combination of LCC and amplifier.

But we still had to control the volume of the turntable/phono stage.

Stan grabbed a power drill off the shelf and without saying a word proceeded to punch a hole in the amp’s front panel, then from inside the amplifier popped in a potentiometer, and added a knob.

Voila! The first PS Audio integrated amplifier.

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.

Cross breeding

Purity is appreciated when it comes to purpose, water, and immorality. It’s not so great when it comes to a power amplifier’s architecture, where hybrids rule.

For many years, amplifier manufacturers were determined to keep their designs pure: 100% solid-state, all vacuum tubes, nothing but FETs, class D from input to output. Over time we’ve come to grips with why this commitment to design purity is not such a great idea.

Power amplifiers are misnamed and therein lies the problem.

On the surface, they seem simple enough: little signal in, big and powerful signal out.

What’s missing is the recognition that inside a power amplifier we have two completely distinct systems each with very different amplification duties: voltage and power.

The input voltage gain stage takes a small voltage and amplifies it into a big voltage. From beginning to end there is only voltage and no power. If you were to take the output of a power amplifier’s first stage and attempt to drive a loudspeaker you’d be met with silence.

To produce watts we need the second system, the actual power amplifier (where it got its name).

The fact that each of these two stereo systems has such very different functions should be clue enough to understand why a purebred power amplifier’s a bad idea.

The smart designer recognizes the difference between the two systems and applies the best technologies for the job: vacuum tubes and FETs are much better at delivering voltage while bipolars, power MOSFETS, and Class D stages are best at delivering power.

Purity benefits us most when we apply it to where it matters.

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.

Hard to imagine

When Stereophile reviewer Michael Fremer writes “on electric bass… the M1200 is a monster”, he’s not alone. More and more emails daily come across my screen extolling the virtues of the M1200’s bass.

How can it be that one flat measuring power amplifier can sound remarkably more powerful in one area than another?

Flat is flat, right?

Not so fast. Let’s have a closer look at the M1200’s measurements. 10Hz – 20KHz +/- 0.5dB

A measurement of 10Hz – 20KHz +/- 0.5dB says a lot if you look closely (and know what you’re looking for). What’s first apparent is its ruler flat performance within the range of human hearing.

But a deeper look shows something else: the amp is down at 10Hz by only 1/2dB. This is important because it means that an octave higher the amp is perfectly flat. Ruler flat response within the audible band is critical for removing phase shift. Turns out the ear is very sensitive to phase shift and the way to keep the phase from shifting is to start any measurable roll off well below the limits of human hearing.

You see, most power amplifiers will have specs that are more like -3dB at 10Hz (-3dB is important because it’s believed that’s where the ear perceives a level change). Fine that the point we first perceive a level change is below the ear’s frequency limits but what’s not mentioned is the phase shift. To be -3dB at 10Hz means you’re 1/2dB down point is well up into the audible range of bass—and we get phase shift.

When phase shift happens in the audible frequency range it will convince the ear the bass sounds wimpy.

And one more point.

A monster amp like the M1200 not only has no phase shift in the audible bass regions, it also has the power and reserves to effortlessly deliver that phase free note without any change in character.

Measurements aren’t always clear and simple.

The story behind the measurements matter.

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.

Some well deserved marketing from Paul today, heaping praise on PS Audio’s new power amplifier, their Stellar M1000 monoblock power amplifiers. I’ve not heard them, but a lot of power for their size and very efficient, using a Class D output stage.  One reason they probably sound good is due to their use it of B&O’s ICE power modules, which I think sound a lot better than the more typically used Class D Hypex modules.

And the hits just….

…keep on coming. In the January issue of the UK’s HiFi News, our killer M1200 monoblock combo received another stellar review (pun intended).

“The latter track positively erupted, the amplifiers creating a searing midband with Matt Heafy’s sinewy guitar tone brought to the fore, and drums again hitting with the speed and aggression of a champion boxer.”

Reviewer Mark Craven goes on to write:

“This slender monoblock amp is not solely devoted to room-shaking power. It has that capability, but appreciation of its punch comes with an appreciation of its grace. The sound is a confluence of steel and silk – fast, rhythmic and able to respond astutely to the shifting dynamics of music. A smooth treble lifts it high above the realms of the rough-and-ready, and there’s an energetic delivery of the midband. But the star attraction – the one that gets your blood pumping right away – is its exceptional bass handling.

To check my Bluesound Vault 2i was behaving itself, I fired up, at random, Chris Rea’s ‘Daytona’ [The Road To Hell; Tidal Master]. After no more than a second I had stopped worrying about my network connection and started focusing on the music. This gentle, mid-tempo homage to a Ferrari race car (complete with tires squealing over the outro…) arrived with a slippery, fluid and authentic bass sound that I wasn’t prepared for, the kind that has you wondering why you haven’t always done your listening through 600W monoblock amplifiers.”

If you’d like to read the entire article, you can download a copy by clicking here.