Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Most loudspeakers have crossovers.  I am hard pressed to think of a full range loudspeaker that doesn’t.  I know they exist, but …..

The crossover is a filter network that makes sure the tweeter and woofer (and midrange) play only what they are supposed to play.  But you can imagine that any time you have such a filter, crossing over to different speaker drivers, you’re going to get “non-perfect” reproduction.  They are a necessary compromise.

Yesterday I heard a full range loudspeaker sans crossover.  Nothing.  Nada.  And listening to music that reaches the lowest depths of bass to the highest tweets a speaker can make, without any interruption of a crossover was a real treat.

What’s the name of this loudspeaker?  The Audeze LCD-X, the subject of Andrew Benjamin’s latest thoughts we published a few days ago.

But wait!  These are not loudspeakers, they are headphones!  Technicalities, technicalities.  Yes, they are headphones, but they are speakers as well.  And when my friend Arnie Nudell invited me over to hear just how remarkable these “loudspeakers” are, he wasn’t kidding.  What I noticed immediately was the lack of a crossover.  I didn’t intend to hear that but after listening to speakers with crossovers for much of my life, hearing one without – and yet with full frequency response – was a real slap in the face.

No, I am not yet buying into the headphone thing yet.  Getting closer, but I still appreciate listening in the room.

But I have a new appreciation for the possible.

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Taking things for granted

Over the weekend our kitchen sink backed up.  Of course I tried everything I could think of, from pouring gallons of Drano to buying a pathetic 25 foot snake at Home Depot.  In the end a call to the plumber solved it.  But without that sink life changed immediately.  It reminds me how much we take things for granted.

And one of those things some of us take for granted is our media.  A friend burned a collection of great demo materials for me on a CD.  I use that CD nearly every day without even giving it a second thought.  Then a funny thing happened.  I had reason to burn another couple of copies of this disc, one for another friend and the other for Music Room Two.  I burned both on a Mobile Fidelity gold CD and didn’t think much of it.  Then I grabbed the new copy and made sure it would play properly.  Wow.

The difference between the original and the new copy was not subtle.  So now I have taken the original, which I took for granted for months, and replaced it with the new copy.

Should I do the same for the hundreds of CDs in my collection?  Or should I continue to also take them for granted?

This obsession of mine for perfection drives me up a wall sometimes.  There’s no freaking way I am going to take the time to replace all my media.Mobile Fidelity,Music,disc,

Until the sink backs up again, I’ll just continue to take them for granted.

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Our story wraps up

Today memory is cheap.  Back in the 1990′s it was expensive.

The Digital Lens we were designing back then had a whopping half a megabyte of memory.  That memory required two large IC’s to house it.   For comparison, today’s version of the Digital Lens, which we place into our Transport, is 250 mB, 500 times greater than the original.

Half a megabyte was just enough to handle all the data a standard CD player could give us and allow enough space to rebuild the data and reclock it out of the memory with no jitter.  But there was a problem.  It is the same problem faced by every digital audio designer today, the power supply.

The digital audio data coming out of the CD player was jittered.  This means that the precise bits of musical data weren’t so precise and were varying back and forth in time.  Every pulse of data that comes into a product affects the power supply of that product.  In other words, the jitter we wanted to eliminate had gotten into the device and polluted the power supply with jitter.  That pollution would contaminate the perfect output we worked so hard to achieve.  So despite our best efforts at eliminating jitter, we were reintroducing it back into the output.  Bummer.

But we had a plan.  We would use two power supplies: one for the input and memory, the other for a separate output and clock, and we would place both on separate PC boards and connect them with light.  Yup, remember our discussion on TOSLINK?  If we used something similar and optically connected the input board to the output board we could effectively decouple the two so the jitter pollution would not enter into our digital audio stream.

It worked.  It was not perfect.  But it worked.  We sold several thousand Genesis Digital Lenses and even after all this time, it’s hard to find a Digital Lens on the used market, so effective they were.

Now you know the story and the design challenges we faced bringing the world’s first RAM buffered jitter reduction product to the world of high-end audio.

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Not a pretty feature

Thanks for all the great feedback on our new video series on Jitter.  Click the link to our YouTube channel so you can view what you want.  We’ll be adding a new video or two on the subject of digital audio and jitter each week, so hopefully we can all share a lot of what’s interesting to you.  Ted Smith is a fascinating fellow and just sitting down to chat with him is a real treat.  Ted’s been working with us for a couple of years now.  He was involved with the Mark II upgrade to the PWD and you’ll see more of the results of this collaboration soon enough.  Wink, wink.

Continuing our story of the Digital Lens RAM buffer product, introduced in the mid 1990′s, Arnie Nudell and I decided to break from loudspeakers and jump into the fray with a new product concept, the Digital Lens; a RAM based digital rebuilding instrument (kind of like a Power Plant of digital audio).  Before the Lens was introduced there were jitter reduction devices aplenty, but none like what we were contemplating.

To build a “perfect” jitter reduction device we would have to accept the incoming data from a CD player, strip the clock from its data, store the data in a memory and then recombine that data with a new, low jitter clock.  Sounds simple enough but when we went to mechanize it we discovered a problem: the CD players were all running relatively out of time from an accurate clock.  From the CD designer’s perspective this mattered not because in a digital audio system, the CD player becomes the master timekeeper in the system.  That’s right, whatever is feeding your DAC has control over the timing, the jitter, the pacing.  It has control of everything and the DAC is just a slave.  So CD player designers didn’t really care if they were a bit slower or faster than what’s considered accurate because the DAC didn’t know any better.  But the Digital Lens did know better.

What was surprising to us was the amount of variability and to what products the timing error applied to.  CD players that were in the many thousands of dollars were some of the worst, while cheap CD players and transports were close, but still off.  To make matters worse, none of the players were consistently off in terms of timing.  They would speed up, then slow down, all within the course of playing a single CD.  There was simply no standard these players were following.  Our prototype Digital Lens had a precisely timed, expensive reference clock that was accurate to many parts per million.  CD players were all over the map.

So the first challenge we faced building a practical RAM buffer reclocking circuit was measuring the error of the CD players.  Why was this important?  Because if the player was slower than our master reference clock, we’d have to tell the RAM buffer inside the Lens to fill up before it started delivering the data to the DAC.  And if the CD player was too fast, we’d want to deliver the data immediately but assign enough RAM space to we wouldn’t have an overflow problem.  This was not trivial stuff and during the course of a single CD play, the players could vary from too fast to too slow.  We’d have to measure that difference and assign the buffer to respond accordingly.

The first result of our designing a measurement system for speed error quickly turned into a new feature on the soon-to-be product: a PPM error readout on the front panel (we couldn’t resist).  Yup, once we had to figure out how far off each player was from the reference, we wanted to immediately display the error for customers to see.  This was actually our chief engineer’s idea, Bob Stadtherr, who gently suggests things like “you know, we could display the errors if we wanted to ……”  That’s about all it takes to ring my bell and so it becomes a feature.

The errors were measured in PPM (Parts Per Million).  This was a great idea and helped sell Digital Lenses, only there was a problem.  Remember I told you that the more expensive players had worse errors than the lower cost ones?  Just imagine the flack we got from owners of $20K transports who had timing errors worse than a $500 CD player.  They couldn’t believe what they were seeing.

It wasn’t pretty.

Next up, trying to get the data out to the DAC without any jitter.




Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Why jitter matters

As we progress through our story of the world’s first high-end audio jitter storage tank, the Digital Lens, introduced in the mid 1990′s, I thought you might enjoy watching a few videos on the subject to help you get versed in Why Jitter Matters and The Audible Effects of Jitter.  Click on either of those links and you’ll be brought to our YouTube Channel page.  There, PS Audio’s consulting digital audio expert, Ted Smith, shares with us some insights into jitter and why it matters and how it sounds.  I promise you’ll enjoy his talks.  I’ll be publishing more of these videos on our YouTube Channel as time allows.

Today, enjoy the videos.  Tomorrow, we’ll pickup where we left off.  I spent all day preparing these videos and as it’s Sunday, Terri’s got a list of Honey Do’s for me to complete.

Enjoy.

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Progress on the new amp

We’re right in the middle of our discussion on jitter and how, in 1994, we built a product called the Digital Lens that reduced jitter of anything we plugged into it to almost nothing.  We’ll continue this tomorrow as I wanted to give my readers an update on the new power amplifier.

As many will recall we have been working on a new power amplifier for some time now.  In fact, way too long.  The amp was supposed to come out in January but we halted the project because it didn’t sound right.  The top end of the amplifier was somewhat missing and there was a scrunched up quality to the sound.  Nothing we wanted to have out there as a product.

These things happen because we design products on paper first, based on our best experience and guesses as to what’s going to work.  Then we prototype that circuit up on a PC board and listen and tweak the results.  That’s a long process and many times we get it right.  Sometimes we don’t.  This time we didn’t.  So we scrapped the PCB and started over with a clean slate.

The overwhelming desire is to create a world-class power amplifier that is about as open and musical as it can be.  To do this we decided to really move in a different direction than we’ve done in the past: a zero negative feedback loop.  Now, typically in a power amplifier, if you have no negative feedback from input to output you suffer from poor control over the loudspeakers because your output impedance is relatively high.  But if you break up the power amplifier into sections, as we have with this design, then you can have your cake and eat it to.  This new design breaks up the power amp into two completely separate and isolated sections: the power output stage and the analog input stage.  Both have separate power supplies, both are designed entirely differently.  This design topology of breaking the amp into two distinctly separate sections is nothing new: we first introduced the idea to high-end audio nearly a decade ago in the Classic 250.  But today’s design is quite unique for a number of reasons.

I will get more into depth on this topology and the reasons for it, but let this short note bring you up to date on what we’re doing.  A redesign of the analog input stage, from what it was to this new design seems to have solved most of the issues I was hearing and to my ears is a revelation.  The input stage is now a high voltage, class A, all MOSFET design with zero feedback.

So far I have only compared it to our last efforts.  It blows away what we had and music is coming forth from the Infinity IRS as never before.  The next step is to gather a collection of other manufacturer’s power amplifiers to compare those to what we have.  That’ll tell the true tale.

But from a music standpoint, the standpoint that really matters, I think we have something extraordinary; a device that lets the instruments sound like themselves, where music sounds like music.  In the end, what else matters?

If you want to see a picture of the new PCB of the input stage, you can go to our Instagram page http://instagram.com/psaudio1 .  If you click on the follow button on Instagram, I’ll be posting more pictures this weekend of the amp, our DSD sessions in the listening room and other fun things…

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Why rubidium clocks are a myth.

In yesterday’s post Storage Tanks we concluded that if the reduction of jitter was our goal, as it should be in digital audio, we would not be happy with a Band Aid, like those found in the majority of the early de-jittering boxes of the 1990′s.  The reasons were pretty clear: using a “regulator” to lower jitter worked, but not as well as we wanted.  Those regulators were PLL’s (Phase Locked Loops) which are essentially a fancy low pass filter.  I know this is more technical than we want, so suffice it to say, these primitive filters reduced large amounts of jitter above a certain point, but like any filter they didn’t remove everything we don’t want.

As in our water analogy, what we really wanted was a storage tank or buffer, placed between the CD player’s digital output and the input to our DAC.  But to be more specific, what we REALLY wanted was a new, jitter free signal.  The only way to get that from a digital audio signal that is already full of jitter is to throw away the clock that is causing all this jitter and provide a new one that hasn’t any.

Remember that jitter is our audio data arriving at the wrong time.  But who’s keeping track of the time?  Well, our clock of course.  Just like the train conductor looking at his watch to keep the trains on time, the term “on time” is relevant only to some sort of reference time keeping device.  And this happens to be called a clock.  The clock isn’t really a clock as you might think of.  Clocks we are familiar with keep a record of passing time with their seconds, minutes and hour hands or displays.  But a digital audio clock doesn’t care what the actual time is.  Our audio clocks care only about the pace and keeping that pace constant.  Like a clock that only shows seconds, not minutes or hours.

You’ve read about DACS that use fancy rubidium based clocks?  These are essentially atomic clocks that are uber accurate.  But their level of accuracy is meaningless in digital audio.  And don’t let anyone tell you differently.  A rubidium clock’s accuracy is long term, meaning the time it is keeping will be the same a year from now.  But for audio purposes we could care less.  Our aural memories aren’t going to know if the clock rate is slightly faster or slower over a long period of time, probably not even over a minute or two, let alone a year or a decade.  The reason DACS using rubidium or expensive clocks sound so much better isn’t the increased long-term accuracy, but most likely because of the care their engineers lavished on them in terms of wiring, shielding, power supplies and so on.  What I can tell you for sure is there’s nothing magical about their long term accuracy when it comes to audio.

But pacing is important.  No, let me say that a different way.  Pacing of the clock, from one clock cycle to the next, is CRITICAL to sound.

So what we want in our digital reduction box we’re building is a perfectly accurate clock that keeps its pace the same for minutes at a time.  And we want a clock that is unaffected by any external factors like the power it is using to run and the signal coming into the box the clock lives in.  This is the clock we’re looking for.  And once we have this clock working perfectly, we’d like to use it to send out our audio data to the DAC.  But we discover there’s a problem.

The audio data being sent to us by the CD player is not only full of jitter (short term timing problems), but it also has relatively long term speed problems.  The data and the clock of our CD player runs slow and then fast relative to our expectations.  In fact, that data runs so much slower and faster than our perfect clock that it is impossible to synchronize the two without messing up our perfect clock’s performance.  So while we really don’t care about the long term speed problems when it comes to listening, we do care when we try and synchronize one clock to another.

When we had this problem with our water system we went to a storage tank to buffer the incoming water speed differences.  Now we’re going to use that same technique with our audio data once we strip out its clock and throw it away.

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Storage Tanks

In yesterday’s post Jittered, we used a water flow analogy to further our understanding of jitter and how to make it go away.  You’ll remember that jitter is all about timing and making sure that the digital audio bits arrive on schedule without any slow downs or speed ups to their progress.   What you hope for is the source equipment that’s sending out the digital audio hasn’t any jitter, but that’s a lot to hope for.  Certainly a lot to hope for back in the mid 1990′s.  At that time the CD player was relatively new and the only source of digital audio.  These early machines had a lot of jitter.

In our quest for better sound from digital audio we knew the high levels of jitter had to be reduced or eliminated.  But how?  We couldn’t actually start from scratch building a CD player at that time, like we can now, so our only two choices were to reduce jitter at the DAC’s input or place something between the CD player and the DAC.  And the latter is what came about as a new class of product called Jitter Boxes.  There were a bunch of them and they all worked pretty much the same way.  With a regulator of sorts.

For the record, the first de-jitter device was designed by our friend and engineer Doug Goldberg (who also invented our MultiWave for Power Plants).   Goldberg’s first de-jitter device, The DTI (Digital Transmission Interface), was designed for Audio Alchemy owned by our friend Mark Schifter.  This was circa 1990.  It decoded S/PDIF, reclocked the data with a series of shift registers and two crystals (44/48).  The DTI Pro, a later product from Audio Alchemy, added a DSP that did inerpolation and dither as well.

If you’ll recall our water plant analogy we had an uneven flow of water from our stream.  Let’s relate that to the CD player outputting faster and slower bits of music.  We could smooth out the irregular flow of bits by placing a regulator directly in the path of those bits.  In water terms a regulator restricts some of the incoming flow to produce a somewhat steadier output: faster water can’t get through quickly and slow moving water is let through without restriction, thus the flow is steadier.  In electronic terms our regulator is called a PLL (Phase Locked Loop) which does pretty much the same thing.  Neither fix the problem of uneven flow, but both help.  Band Aids to be sure, but if you’re bleeding, a Band Aid is a welcome thing to have.  So too is a jitter reducer.

I have never been big on Band Aids or partially correcting problems when it’s possible to actually fix it perfectly.  Just not my style.  I am not alone.  Let’s go back to our water plant manager, faced with the problem of uneven flow.  His predecessor has installed flow regulators on every home and they helped, but customers still have problems.  Our new manager finds those problems unacceptable and aims to fix them once and for all.  He builds a water storage tank.

Our mythical engineer has figured out the only way to eliminate flow (timing) problems in the water supply is to have a large reserve tank full of water.  During high demand and low supply periods, the tank has enough reserve in it to supply what’s needed and acts as a buffer.  During high supply and low demand, the tank stores the excess and also acts as a buffer.  And buffer is the key word here.

If only there was an easy way to add a storage tank to our digital audio stream, we could simply buffer the faster and slower bit rates and output a constant, jitter free stream of bits that would help our DAC sound its best.  In 1995 there were no easy solutions to this problem but it was possible to build what we wanted.

Just not easy.

Asheville’s Home Theater and Audio specialist presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

Jittered

Probably time to cut back on the coffee.  But if your jitter problems relate to your digital audio system then there’s hope.

Jitter is all about timing.  Digital audio depends heavily on an accurate clock.  That clock meters out precise intervals, like a musical metronome, and the quality of your music depends greatly on its accuracy.

It’s 2014 and some of us are just getting comfortable with the idea of jitter and its effects.  But the general high-end audio populace first became infatuated with the subject way back in the prehistoric mid 1990′s.  Heck, it wasn’t even in this century.

In those long-gone days analog was still king, digital an up and coming wanna be.  Things have changed in the new century.  Even diehard analog devotees have to give some forms of proper digital audio its due, but back then everything was an uphill battle.  To be honest, those of us interested in digital in the 90′s were tolerant of its weaknesses, and there were certainly plenty of those.  But the pioneering spirit was alive and well in us because we could hear the potential, and there was a lot of potential.

There were three distinct groups of thought on the subject of digital audio quality.  First, and foremost, you had the ‘flat earth’ society proclaiming there could be no audible differences since ‘bits are bits’ and they could prove that all the digits arrived safely; therefore all digital audio must sound the same.  Next you had the ‘I believe everything’ society proclaiming sonic differences were lurking around every corner; therefore nothing in digital audio sounded the same.  And somewhere in the middle you had a group of dedicated engineering folks who accepted a more middle ground and found themselves determined to get answers.  Count us among the third group.

Because we could hear digital differences, yet intellectually accepted the fact that bits are bits, we knew the answer must lie in missing information.  We simply weren’t seeing the whole picture.  This is fairly common, when your senses detect something your mind can’t logically accept.  The answer isn’t to jump up and down and deny what your senses are telling you, rather it’s time to try and figure out what’s missing.  And one of the missing elements was the timing of those ‘perfect’ bits.  But how does timing affect the sound quality of digital audio bits?

Just imagine, for a moment, that you’re a water quality engineer and in charge of your city’s water supply.  The challenge is to deliver a steady stream of water to all your customers.  Problem is, the supply of that water isn’t steady because it comes from a stream that runs faster and slower depending on the temperature of the day.  So what would you do?  Perhaps the best idea would be to place a small regulator at each home to slow down the maximum any customer could access the water.  That would certainly even out the flow, eh?  But what happens when the weather gets really cold and there’s simply not enough water to go around?

Tomorrow’s post will dig a little deeper into the problem.  Not of water, but of bit timing.

Re-posted with permission by Cane Creek AV, Inc.

Asheville Home Theater and Audio presents Cane Creek AV and Paul McGowan – PS Audio, Intl.

The Noise Monkey

In yesterday’s post about oiling up the snakes I touched on the idea that marketing can sometimes get in the way of people’s acceptance of a particular technology.  Yet without market-speak, products would sit on the shelf as dull and uninteresting to customers.  The best product names seem to be a blend between forming a mental image of a product’s function vs. not making an outrageous product claim.

To yesterday’s example, the Noise Harvester makes a mental picture of harvesting noise; and that’s what it does.  If we’d have called it the Noise Killer that might imply its ability to remove ALL the noise, which it doesn’t have.  Or maybe we should have made it a cutsie name like the Noise Monkey (gag me).

Then there’s the much more reserved method of product naming like the old Mark Levinson line: the 30.5 as an example.  It says nothing about the product or its function.  It could be a designation for motor oil or salad dressing.  But applied with enough advertising it kind of works in a reserved sort of way.  It certainly isn’t a friendly name, but then the Mark Levinson line was never intended to be friendly; just expensive.

I don’t know about other designers, but in our case, we choose the name after we design the product.  So internally it has a name we call it in engineering but that name rarely ever gets out into the public sphere.

One such product of years ago is the Genesis Digital Lens, designed and built in 1995 by Bob Stadtherr and I.  When that project started it was simply called the RAM buffer.  Not a great market-speak name, but certainly described well what it did.  After we figured out a simple RAM based FIFO (First in, First Out) wouldn’t work, we had to add intelligence to the device.  It then became known as the Smart Buffer; an equally bad name for going to market.

I thought it might be fun to dredge up the project and tell a bit of a story of how it got started, what we were trying to do and how it finally got named.

See you tomorrow.