Exclusive interview with Nelson Pass

How it all started and when it was the first time you would considering entering the high-end audio industry?

In college, another guy and I formed a little loudspeaker company and cranked out a few 3 way speakers with a 12” woofer, 5 inch Peerless midrange and Peerless tweeter.  Not long afterwards I went to work for ESS, arriving a couple weeks before they met Oskar Heil.  I left ESS about two years later and with Rene Besne (later also Joe Sammut) formed Threshold, where we built amplifiers for 17 years.

Please tell us about your role in Pass Labs and more about your First Watt venture?

I left Threshold to its new owners and management in 1991 to form Pass Labs, and initially I did many of the jobs with the help of a few people.  As the company grew, I hired more people and acquired additional business partners for technical and management.  By the late 90's I could afford to primarily devote myself to creative work, which has been my role for the last 20 years or so.

Twenty years ago I also created First Watt as the creative outlet for design work that did not fit Pass Labs market.  In some cases, First Watt served as a test bed for ideas that later were used by Pass Labs.  First Watt amplifiers are all low power output, Class A and interesting simple circuits, many of which other companies would be afraid to try. 

First Watt doesn't need to make a profit, but it does anyway.  It literally started out as a little “kitchen table company”, but over the years it grew until I couldn't keep up with it, so I recently turned the manufacturing over to Pass Labs.

Do you consider yourself an audiophile?

Yes, and proud of it. :)

Who were your inspirations (and perhaps still are)? 

Long list, but near the top are Stanley Kubrick and Roger Corman.

Would you say that one's love for music reflects in his creations-amplifiers? 

You would have to love music to want to do this, and certainly you could not subjectively judge product without it.

What would you say sets apart your products compared to the competition?

Some companies are completely grounded in objective measurements, and some only care about the subjective listening experience.  We place a strong emphasis on both.

No mystifying? Just honest and clever engineering? 

I think we are good at electronic design and understanding what objective elements are important to audio.  Also, we are good listeners.  It's actually a lot of work, and it usually takes about a year to get a new design out the door.

What would you say, that is the ultimate goal of any high-end audio designer?

Rich and Famous?  Free to design what you like and not have a boss?  All the toys you think you need?

How about yours?

I seem to have achieved those goals, so I am just trying to stay creative and have some fun.

The first watt is the most important watt?

I think the saying was “Who wants an amplifier that is good at 1000 watts if it sounds like crap at 1 watt?”
I believe that one of the important characteristics of a good sounding amplifier is that the distortion decreases with decreasing output, that is to say monotonic.  This is also a characteristic of Class A amplifiers.

Also, people don't usually realize how little power they are often listening to.  I keep an oscilloscope handy on my system, and I have fun showing people how loud things can be at 1 watt.  I don't usually need high power for good sound.

Is the Class A the Holy Grail?

Good Sound is the Holy Grail.  Class A makes it easier to achieve.

What about AB Class?

Not as easy for good sound, but practical.

What is your take on the Class D, that is highly push forward in past decade? 

Class D is cheap and efficient, and is already beginning to dominate the consumer audio amplifier industry.  That's fine with me - I have no plans to make switching amplifiers.

Is the balanced topology a must for achieving the best sound? 

No.  It depends on what kind of best sound you are trying to get and sometimes on the power levels that you need.  Pass Lab amplifiers have a balanced topology for the most part, and First Watt is mostly single-ended.

What kind of speakers are "good enough" to show the real potential of the amplifiers?

Everybody's choice is different.  At PL we have a standard which is Tannoy 15” coaxial drivers from the 1960's mounted up in upside down Jensen Imperial enclosures with a custom crossover that my partner Joe Sammut spent about 10 years on.  We have three pair, one pair at my home/lab at Sea Ranch where I work.

These speakers are not the best sounding you could have, but they are very revealing of the character of amplifiers, and they are a good tool for that.  You will see this in studios, where the monitors are not necessarily “audiophile grade” but where they are used for specific purposes in the process of making the recording.

How important are the built in parts?

Some parts are extremely important.  Sometimes not so much.  For me the most important parts are the Fet transistors that carry the signal.  Their character dominates the performance over the passive components such as resistors, capacitors, wire and such.

What about using the "exotic" parts?

The Toshiba Fets we use in our front ends would be considered exotic at this point.  Toshiba discontinued them years ago, and they are so valued for performance that their street price has gone up by 60 times.  Fortunately, we bought a lot of them, and we still use them exclusively for production.

We have the occasional exotic part, but it has to improve the performance to justify the expense.  Among the exotic parts are the SIT devices in some of my First Watt designs.

Can you tell us more about your SIT amplifiers? How do they differ from you other designs?

Static Induction Transistors were Jfet transistors invented in Japan in the 50's which behave much like a Triode.  This is an interesting feature, as the other Fets have by comparison, Pentode characteristics.  By choosing the appropriate working load-line for the device, you can get very low distortion because you cancel the non-linearity of the Gate-to-Source character versus the Drain-to-Source and minimize distortion.  They are sonically similar to Triodes but don't require heaters or output transformers.

Unfortunately, power SITs are very expensive and hard to get.  About seven years ago I had the opportunity to have some custom Silicon Carbide devices made by Semisouth [now out of business], and that resulted in the models SIT-1, SIT-2, more recently the SIT-3 from First Watt.

THD importance?

Everything is important.

But THD is a helpful metric, especially if we look at the details of the distortion - amplitudes of the various orders of harmonic and their phase.

Also, IM distortion is very important and is often the bigger problem.  Still, it reflects the same characteristic that creates THD, so there's no mystery to it.

Talking about first, second... order harmonics can quickly ignite a flammable discussions. Kindly elaborate your stance?

People can hear distortion, and the different harmonic orders are perceived to different degrees.  It is pretty much accepted that 2nd and 3rd are the least objectionable, and that higher orders are more trouble.  This is fairly old information, going back at least to Hiraga.

In our work with SIT character over the last 8 years we came to the conclusion that the phase of 2nd harmonic had a distinctive effect in blind listening tests, and so we have designed around that in the SIT amplifiers, even to the point of having an adjustment knob that allowed varying the load-line for the SIT for positive phase 2nd, nulled 2nd, and negative phase 2nd. 

Measurements vs listening?

There is no versus.  Both are important to us.  Even if we designed purely by ear we would need measurements to assure that products conform to the sound of the original product.

In practice, we adjust, measure and listen.  Over and over.  Sometimes the tests are blind, often they are not - we just listen.  It takes a long time.

How do you know when to stop with the designing and go into actual production? 

For upgrades to existing models, we let the improvements accumulate until there is enough to justify a model upgrade.

For new product, it takes more than a year from initial design work to product delivery, but we still have the time we need - on average we upgrade a design every 8 to 10 years (the X amplifier models have been out for 24 years).  After a year or so of R&D we usually have a pretty good picture of what we've got, and there is a pilot run to shake it out before release.

After all that, it's not hard to know when the product is done.

How important is the preamplifier is the high-end audio setup?

Pretty important, although you want to know that our preamps are designed by Wayne Colburn, a long-time business partner stretching back to Threshold.

Personally, I prefer quite neutral, good measuring preamps, but then my primary use is evaluating power amplifiers....

Passive vs active preamplifier?

If the system doesn't need the gain or features of a regular preamp, then it's a good approach.  My experience is that like everything else, it is best to try them out in a system before making a decision.

Do you voice your electronics?

Adjust the circuit against a particular sound?  With the exception of the SIT-1 and SIT-2, we tend to be subtle about it.  As an example, we want low distortion, but we also want the harmonic content to follow a pattern of harmonics declining with order.  Sometimes a compromise needs to be reached, but we still try to arrange that harmonic pattern within the context of low distortion numbers.

How important is the power supply?

Gotta have it.  We need lots of constant quiet power.  Without it, noise and distortion spoil all the effort we put into the audio circuits.  Crappy power supply?
Might has well have a crappy circuit then...

Classical music or studio recorded music. What kind of music would you say is the ultimate test for ultra high-end components and system? 

Both are.  Example would be thinking about 2nd harmonic of an amplifier.  Makes simple material sound great much of the time.  Not so much with complex symphonic music.  Different customers have different needs, depending on a lot of factors, including what they listen to.  We try to have different products that cover these needs.

Where is the fine line between, resolution, transparency and musicality? 

If I knew, then I probably still wouldn't tell. ;)

What have changed over the years with the product designing?

More of my time is dedicated to R&D, which generally gets my afternoons. Much of the equipment is better, but I still use my first good voltmeter (HP 3435A) and my old Audio Precision System 1 with Windows 98. :)

Are the contemporary electronic parts really that better, than those of the past?

There are a few examples of really great older parts, but on the whole I am happy working with new designs, particularly for transistors.  By a number of metrics they tend to get better, although many are not designed with audio in mind and are not very suitable.

Korg's Nutube is certainly interesting. What's your take on it?

It is certainly interesting.  I currently have a DIY product out which uses it, but we understand that like the examples of SIT-1 and SIT-2, they are not for everyone.  If you are an audiophile who chooses tube pre-amps to sweeten up the sound of your power amp, then these would be candidates.

The classical questions. Solid state vs tubes? 

For me, solid state.  That is where I live.

Does form follow function with all of your product designs?

Yes, I think so.  I don't mind a nice faceplate, but really I'm a cheap guy who doesn't want to spend money on something that isn't part of the performance.

I was once criticized for a comment made that my circuit board layouts look just like the schematic.  Having some service repair background, I like the actual circuit to look like the schematic — it just makes life easier.

What is the reference for you when designing the products? 

Earlier I mentioned the Tannoy loudspeakers.  I have a D1 DAC from the earlier days of Pass Labs, and I often use a B1 for the gain control.  Digital sources for the DAC are various.  XP-25 for the phono preamp, and a variety of phono cartridges including Dynavector, Grado and D&S optical.  Several turntables including the Basis 5200 and modified Technics SP10 and SL1200.

Who would you say typical Pass Labs customers are? 
Most of them are dedicated audiophiles.  They like performance and reliability.

What about First Watt? 

Also dedicated audiophiles, maybe even more so, since the FW products are not nearly as convenient or attractive.

How close can one get with digital reproduction in comparing to analog in your opinion? 

Like analog, digital can be very good.  If you look at the numbers it often looks better.  Like many audiophiles I appreciate vinyl for its sonic charms and the pleasant physical involvement it demands.  I am happy to forgive it its shortcomings.

I like to think that serious audiophiles are more than intelligent when spending the money. How do you see this? 

I like to think that also.  But like any other endeavor, there are also people who like to spend more, where the rule of diminishing returns applies.

Would you say that high quality is more affordable today or you have to pay premium price for best quality sound? 

You can buy many fine products at reasonable prices.  I purchased a pair of the Andrew Jones-designed Pioneer SP-FS52 loudspeakers the other day.  They were inexpensive and quite good.

Of course, you can also save a lot of money if you build your own stuff, and that is the source of much satisfaction to DIYers.

There is the hi-fi, high-end and ultra high-end. What is the difference in your opinion? 

Price, for one.  Usually ultra has more fashion styling, and appeals to art more.

How important are the room acoustics to achieve state of the reproduction?

Very important.  Very difficult.  Fortunately, not my particular problem.

Is it possible to achieve the real live drama and illusion with high end audio system?

Sometimes.  Not as often as I would like.  Even with great playback systems, there is not that much source material that does it.

How do you see the state of the present high-end society? 

Looks OK to me.  I'd like to see even more DIYers.

Any last thoughts for our readers? 

This is the most number of questions I have ever been asked.  I think you got it all. :)