Tag Archives: PS Audio

Asheville Home Theater presents Paul McGowan – PS Audio, Intl.

We got close.  Really close.  The technician finished stuffing the new input stage, our chief engineer Bob Stadtherr brought it up and tested it, he and I spent a fun afternoon tweaking the square wave response and then 5pm rolled around.  5pm Friday December 21st.  The last day of work for a week for many folks at PS Audio.  Now I have to wait another week till the holidays are over before we connect the input stage of the amp to the amp module and listen to it.  I too am heading out this morning to spend a week with my family.  I am bummed about having to wait a week and impatient with the holidays getting in the way of listening to my new amp.  Where’s my lump of coal?

In the meantime let me tell you about tweaking the square wave response and a little more about this stage.  Round about 4pm Terri walked into the lab where Bob and I were huddled around the scope stroking ourselves over the beauty of the square wave of the new amplifier input.  We beamed with pride.  ”Check that out!”  Said I to Terri.

You know that look people give you when they think you’ve slipped a cog?

“Seriously?  Really?  You two nerds are admiring that thing on the scope and want to know what I think?”  No, we probably didn’t want to know what Terri thought.  Bless her heart.

There’s nothing like a good square wave response on an input stage.  I know this sounds funny because we don’t listen to square waves, but in fact square waves tell us a great deal about how a circuit is going to sound.  Not everything, mind you, but a lot.

A square wave is a collection of sine waves.  There’s a fundamental sine wave, the main one at the frequency you set, and then declining higher frequency sine waves that fill in the edges.  Over the years, as a designer, you look at a lot of these to see how your amplifier is doing.  You tell a lot by how it looks at the beginning and the end of the square wave. Here’s a picture I borrowed from a Stereophile review.

Overshoot

It isn’t important what this product is that the image is taken from.  Could be anything.  Let’s focus instead on how the example looks at the beginning of the square wave.  See the little “tit” or rise at the beginning?  The little sharp edge?  This will tend to sound a little bright when you have this rise.  You see this type of imperfection when you use feedback.  You can see it in other situations as well, but when it’s a result of feedback, there are sonic consequences.

I am sure the technocrats will howl over this, but I am simply sharing with you some years of experience.  If this tack-sharp blip is present in an amplification stage with GNFB (global negative feedback), almost invariably the amp will have a hard or slightly bright sound indicative of that type of topology.  Yes, a designer can add a capacitor to smooth out the little tit, but that in itself will not help the sound, only the way this looks on the scope.  If the tit is present because of feedback, lowering or eliminating the feedback is one surefire way to get better sound.  It’s also possible to fix the open loop circuit (no GNFB) such that when you close the loop (add back GNFB), the tits aren’t present.  But that’s fodder for another discussion.

This is the kind of stuff you find out over years of looking at scopes and listening to the sound of circuits.

Now take a look at this square wave.

good one

See how nice, rounded and gentle this looks?  Compare it to the other one.  If you see this type of response on your scope and it’s the output of a simple circuit with or without GNFB the audible results will be far nicer sounding (e.g. musical).

This is the stuff we nerds get excited over at work.  Is it any wonder I am antsy about listening to the new circuit?

Standby

Have you ever noticed that most “power” buttons on equipment front panels don’t actually turn the power on or off?  In fact, most of them are really standby buttons, turning the front panel lights off and keeping the unit in standby.  One of the main reasons is to keep enough of the circuitry on so the remote control works.  If you turn off the power, the remote does nothing.

Years ago all products had hard power switches and buttons on their front panels.  But not PS Audio.  We were one of the very first companies to build this standby feature into our products.  And this was way before anyone had remote controls.  Some may remember that remote controls during the 1970′s were very crude devices and used mainly for televisions.  I remember our first remote, you had to mash down hard on each command key to make it work.  The force was needed because the remote was actually generating an ultra high frequency sound that the TV would listen for.

No, we didn’t add our unique standby feature to accommodate remote controls.  We did it to make sure our products sounded better, in spite of our customers.

When we originally produced our first product, the stand alone phono preamplifier, there were zero controls on it.  No power switch, no load resistors, nothing.  Nada.  You plugged the box into the wall and powered it up and left it on.  There were two reasons for this decision: we wanted to make sure someone didn’t turn the power off when the device was connected to a live system, causing a huge and potentially speaker damaging thump.  But the main reason was sound.  We had discovered early on that audio equipment needed to break in and always sounded better if it had been on for some time.  A cold phono preamp sounded considerably worse than one on for several days.  This seemed obvious to us.  That many customers wanted to ability to turn it off seemed simply wrong headed.

Our products were one of the very first in the industry to come with a money back guarantee.  Remember, this was 1973 and no hi fi equipment I know of had any such guarantee.  It was a bold move and one we prospered by, even to this day.  Of the thousands of phono preamps we shipped perhaps 10 or 20 were ever returned to us for a refund.  One such return was from a man who was upset because when he connected the phono preamplifier to his system, his speaker seemed to disappear.  He could no longer close his eyes and point out the left and right channels; so distinct they were before our product was introduced.  He demanded his money back.  We happily refunded it, thrilled that our hard work at making speakers disappear paid off.

But he had cut the cord of his returned unit and inserted a small in-line power switch.  This was rather odd and we took the time to call him and ask why.

“I can’t stand to see the light on all the time.”  Asked if his hatred of the light was about power usage he replied no, he just couldn’t bear to see that damn light on.  At night, everything in his system was turned off.  That’s the way he liked it.  He wasn’t alone.  This was a common complaint amongst our customers and they demanded relief.  We, on the other hand, couldn’t bear the idea of people routinely turning their system’s power off each night, only to have it sound cold and uninvolving on power up.

I am sure you can see where this is going.  From that day forward every PS Audio product, except our power amplifiers, had a button on the front panel labeled “Power” on/off.  But that button did not turn off the power.  It muted the outputs of the device and shut off all the front panel lights.  To keep us happy, the power remained on, the unit always ready for great sound.

In later models we felt a bit guilty calling it a “power” button so we changed it to “Input” and one of the selections was “Off” which did exactly the same thing.

We never had a complaint and we had a lot of customers amazed how our units always sounded perfect even when they were “cold”.

We just smiled and said “thanks”.

Paul McGowan – PS Audio, Intl.