Tag Archives: preamplifier

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.

Fast and slow

After 50 years of working with audio gear, it’s easy for me to forget not everyone knows the basics. I’ll do my best to help remedy that.

A few days ago we got into fuses, a subject that helped me realize not everyone knows there are two basic types. Fast and slow.

A fast fuse saves circuitry. A slow fuse saves lives.

First, let’s talk fast blo fuses. You don’t see these a lot anymore. They are typically used in the DC “rails” (the power supplies) that feed circuitry. They need to be quick because they are there to stop the voltage feeding circuitry before something bad happens to that circuitry. Their most common use is to protect power transistors in the output of a power amplifier. Where small signal circuitry like that of a preamplifier doesn’t have enough “juice” behind it to cause damage to the silicon, a power amplifier surely does. The fuse must die faster than the transistor it is protecting.

A fast blo fuse is basically a whisker-thin wire inside a glass (or ceramic) enclosure. Here’s a picture of one.

Fuses are designed into the power supplies that feed the output transistors of amplifiers. They are chosen by their rating of how much power they can pass before the little wire inside heats up and vaporizes—thus breaking the connection to the power supply.

Most amplifiers don’t have these because there are now more modern means of providing the quick shut off (other solid state devices).

A slow blo fuse has the same characteristic as the fast blo, meaning it too is chosen by the maximum amount of current (power) that is allowed to pass through it. The difference is time.

When we first plug in a product to the AC wall socket, or flick on the power switch, a surge of power flows into the unit. Perhaps you’ve noticed the room lights dimming on first turn on of a power hungry something. This inrush of current (power) needed to fill empty power supply capacitors (or start a motor or heater) is only for a brief moment. Thus, what we want is a fuse that will tolerate that momentary inrush of power until the device settles down.

That’s why it’s called a slow blo. Here’s a picture of one:

Instead of the whisker-thin wire of the fast blo, we now have what looks kind of like a spring. Pass enough current for long enough through the spring and it too heats up and vaporizes.

Slow blo fuses are found at the very input of products. Before the power supply. They exist to make sure that your product doesn’t light on fire, or that the wires in your home don’t light on fire.

Of course, modern homes are doubly protected. An electromechanical version of the venerable fuse is required for safety. It is called a circuit breaker.

Hope that helps.

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

Technocrats and artists

When a design engineer tackles a new product there are a myriad of options available to them.

Take for example a preamplifier. Here the designer must choose the type of amplification topology: single ended or balanced, differential input or single gain device, direct coupled or capacitor, solid state or vacuum tube or hybrid. And once chosen there’s another bushel full of choices to be made, each resulting in a very different sound.

Or take the challenges presented to a loudspeaker designer. Number and types of drivers, open baffle, closed baffle, dipole, bipole, monopole.

Once the direction is chosen, there comes a divergence of workflow depending on whether the design engineer leans towards being a technocrat or an artist.

The technocrat worships the god of technology while the artist’s muse leans more toward serving their emotional side.

An analytical approach versus one more centered around the emotional side.

Mr. Spock vs. Picasso.

Our own philosophies at PS Audio have always been centered somewhere closer to middle ground.

Norman Rockwell.

As a consumer, you’ll want to decide which products on offer appeal more to your analytical or emotional side.

The fruits born of the labors of technocrats and artists sound very different indeed.

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 don’t use EQ the way Paul describes below, however I do use EQ on my home made Altec 604 GPA loudspeakers. Although I only use them in the band centered around 2k, it helps makes a great speaker sound even better. My EQ’s, which are UREI 539’s, only cut level, not add and this is actually the right way to do it!

Eq limitations

Equalization is the act of increasing or decreasing the amplitude (loudness) of specific ranges of frequencies.

The most common form of EQ was once the ubiquitous bass and treble controls found on consumer audio equipment. These knobs or sliders allowed one to reduce or increase the amounts of both frequency ranges. (in my experience they were almost always cranked up on high).

Today, a few brave souls are using EQ to help adjust low frequencies anomalies in the room—mostly with the addition of a low cost easy to use DSP product like the MiniDSP. For $100 this device can take the analog output from your preamplifier and be used to feed a separate bass amplifier in a bi-amped system. Once inserted between the preamplifier and woofer amplifier, a simple and intuitive user interface can be used to adjust the bass response of your woofer.

Any loudspeaker with separate binding posts for woofer and tweeter can enjoy the benefits of biamping and EQ control using this simple setup.

While I wouldn’t recommend trying this for anything other than a woofer, it can be helpful in smoothing out the peaks and bumps caused by room modes and standing waves.

While peaks and bumps are easy to eliminate fixing the dips and valleys caused by the room are almost always impossible to fix. That’s because the loss of bass frequencies in a room are caused by cancellation (just as peaks and bumps are caused by addition). And unfortunately, regardless of how much more loudness you pump into the system at those frequencies, the cancellations just keep doing their thing.

So, should you go down this EQ road, just be mindful the most valuable improvement you can hope for is the reduction of peak and boom, not the pickup of missing bass.

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.

Impedance differences

If you double the input impedance of your power amplifier from, say, 30kΩ to 60kΩ you’re not going to hear a difference.

Yet, double the input impedance of your phono amplifier and you’ll hear a change.

What’s different between the two?

In the first case of the preamp feeding the amplifier, we won’t hear any difference because nothing in this chain affects frequency. The amp’s input impedance must be high enough to not load down the preamp, but aside from that, not much else matters.

That’s not true when it comes to a device such as a phono cartridge. Here the small coil generating the voltage feeding the phono preamplifier is part of what we refer to as a tank circuit—a tuned inductive network where the frequency response is a function of impedance and capacitance.

Think of it like a filter where the resulting output is dependent on the values of the elements that make up the network: coil, cap, resistor.

It is natural to assume that if the impedance setting of one element within our system matters, then it stands to reason all must.

Hopefully, it helps to have a short little explanation like this to set the record straight.

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 price of scarcity

When something desirable is scarce its value increases.

It’s the old supply and demand theory we learned about in school. If more people want something than there is an available supply, the price adjusts upward.

Think of a vinyl album where only so many copies were pressed. Or, consider that only 58 pairs of IRSV speakers were ever made.

Scarcity can even apply to simpler things. Terri and I were skinning a bushel of our homegrown tomatoes last night. We turned those beauties into a delicious tomato sauce we’re going to freeze and sparingly consume over the winter months. No one else on the planet has the same tomato sauce as do we.

Thankfully, much of what we as audiophiles value with respect to new equipment isn’t scarce. You can grab a copy of a production DAC, integrated amplifier, or preamplifier without much worry about bickering over price. That’s not quite as true with vintage equipment.

What we can say about scarcity is that for most of us, the collection of hand-picked equipment, cables, room treatment, and careful placement is unique in all the world. Your stereo system in your room sounds different than mine because of the environment and the choices made to create that system.

What kind of price would you assign to your hand-built creation?

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.

Mechanical vs. solid state

When we need to switch inputs on an analog preamplifier we use a switch. The kind of switch we use affects stereo sound quality.

For years we had only mechanical switches from which to choose. Standard switch contacts in those days were nickel or tin-plated while the more expensive and better-sounding styles were either silver or gold.

These worked great and sounded excellent, but they had a problem. They were nearly impossible to remote control.

The customer’s desire to control their systems from their easy chairs drove us designers to replace mechanical switches with electromechanical relays. Relays were available with the same contact materials though because they weren’t self wiping (like mechanical rotary switches), their slap and connect operations produced a slight degradation in sound quality.

Relays are expensive and cumbersome.

Along came silicon switching. Low cost, quiet, reliable, and without the problems of contact degradation. Sonically, they fell into third place, but not too far behind relays.

Engineering is always a matter of compromise. We give up one thing and in exchange get something else.

In most of PS Audio’s PerfectWave series of analog audio products, we rely upon a combination of electromechanical and electronic switching.

Common sense, practical, excellent performance.

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.

Systems

Each of us produces a liter of mucus per day. Snot, actually, and we use it to keep our esophageal system working smoothly. And here’s the thing, despite the fact that’s a lot of snot, unless there’s a problem we never notice it.

And that’s the way most systems work, seamlessly and in the background until something goes wrong or we yearn to make something better.

It’s the fringes we notice, not the main system.

It is good and proper we focus our time and energy getting our core audio systems functioning properly, but it’s almost never what we think about.

I have for many years been a proponent of stepping back from the pieces in my system I interact with like the transport, preamplifier, or streaming interface, and pay homage to my silent partners that make it all happen: the AC power, amplifier, audio cables, and rack system.

Central systems are easy to ignore until something goes wrong or we wake up to the fact we can make improvements that 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.

Who’s on first?

Making a decision as to which model of loudspeaker, amplifier, phono stage, or preamplifier can be daunting. There are more brands than one can count and, within those brands, many models.

In the days of dealers, we relied upon their curation skills to narrow the field. The only problem with that model is that most times big dealers carried not what they believed you needed most (after all, how could they?) but what worked best for them.

Fortunately, that wasn’t the norm in our small high-end industry. The dealers we loved and honored were those that stocked what they loved and eschewed brands and products that didn’t meet their standards. Those were the good guys in our industry. Personal pride and a love of audio drove their interests and formed their opinions.

Sadly, many of those heroes are gone. (Lyric HiFi recently announced the closing of its New York City store)

Despite the shrinking number of honest and heartfelt curators, it is still possible to cut through the cruft to narrow down the field to a few choices.

That happens through trust. Trust built through a magazine, an advisor, a reviewer, a manufacturer, or a friend.

Who’s-on-first gets less confusing when we’re working with people we trust.