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Pass Laboratories XA200.8 pure Class A monoblock amplifiers Review, Part 1

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Why review the XA200.8

Two years ago, I made a decision that changed my audiophile life. I went to a big box home improvement store where I spied some furniture dollies, and a chill ran down my spine. I was ill prepared should I review some big, immensely heavy amplifiers, ones well past 100 pounds. But if I had some sturdy stands with casters, I could manage to move such amplifiers around and avoid strain on my back. The thought was especially pertinent as I build a lot of systems. My methodology in reviewing is not to wait for a predetermined period of time for a new component placed into a system to settle, or burn in, but rather to get right at it, and I build as many systems as I can over the review period to find out how the component interacts with other gear. I feel this is a superior means of assessing audio equipment versus waiting for something magical to happen. I will learn much more about a component by using it in five systems than I would by playing it for weeks and perhaps making one or two changes to the system.

Because of my methodology, I move all components and speakers regularly. I build new systems every few weeks, and many more discrete systems having slighter changes. It has amounted to hundreds of rigs over the past 13 years. To maintain that pace, I move amplifiers in and out of the system several times during the review period. I needed a way to handle beefy amps efficiently, much the way I determined to put casters on the Vapor Audio Joule White Speakers because they are quite heavy and would be a PITA to move regularly in and out of the listening room. That decision was serendipitous, as the speaker benefited from the approximately 2” lift in soundstage that was conferred by the addition of casters, bringing the speaker’s sound closer to the large towers I have used. In addition, I did not elevate the speakers evenly, but slightly raised the back of the speaker higher to tilt forward the front baffle, thus bringing the top module’s alignment closer to ear level, a maneuver that influences the intensity of midrange and treble relative to the bass output and improves the coherence of the speaker.

The furniture dollies were quite long, made of unpainted 1×4” hardwood, but they had solid, sizable casters. I must have presaged this review, because two years before I used them, I bought, cut down to size, painted and stored those “amp stands.” This is the review for which ambition was rewarded! I was originally going to do a review of the XA30.8, which, were I to move it about the room, is a manageable 88 pounds, but as we shall see destiny demanded that these homemade stands be put into service! As a point of fact, I do not believe in luck (and neither do gambling interests). I do believe the saying, “Luck is when preparedness meets opportunity.”

For those readers who are disgusted by the idea that I am reviewing Pass Laboratories’ largest XA Series Class A monoblocks on furniture casters, please feel free to contain your disdain. The rest of us, who understand that an amp’s sound is no more harmed by placement on cinder blocks or furniture dollies versus a $10K audiophile stand, are managing quite nicely. My informal testing over the years has shown funky furniture to be of little consequence to amps compared to what happens with the power and signal path. Besides, I know things about industry insiders (read manufacturers) who place components in the most bizarre ways but do not publicize it; by their actions they pay little attention to the foundation upon which their gear sits.

Another thing you should not expect me to discuss, much less endorse, is the controversial phenomenon of “burn in.” When I say it is controversial, I do not mean to challenge the idea that capacitors age, or that speaker drivers can have measurable differences over time. I am saying that the hand wringing about how long to burn in an audio component is a waste of time. I will not digress at length here, but feel free to read my Audio Blast: Thou Shalt Not Overemphasize Burn In, in which I put it to test and found it entirely lacking in merit. Few things in audio have failed my Law of Efficacy as spectacularly as burn in. If you feel that I cannot judge a Pass Labs amp without 100-200 hours of burn in time, please keep your excoriating comments to yourself, because I am not inclined to respond to you if you wish to make a stink about it. Now, to those who are more interested in a variety of systems being built to assess this amplifier’s performance, let’s proceed.

How did making homemade amp stands change my life? I wish I was not getting wussy, but at 57 I’m starting to think a lot more about the oversized stuff I’m hauling, first down, then up the basement stairs to and from the listening room. Weight of a component has become a variable I pay more attention to than ever before. I am reminded of Karl, a member of our church and a natural athlete with whom I played basketball for a number of years. When Karl was about 55, he pulled back from participation in the church basketball league. I ribbed him a lot about it, as I was 45 at the time and thought I would push on past that point. Humility comes with age, as does soreness! Four years ago, two years before Karl, my joints and general health dictated that I also quit. Humbled, I admitted to him that I could feel in my bones why his decision was made.

Just as I relish large speakers for their dominant sound, I still enjoy the incomparable headroom of an amplifier with classic design, and that usually means a lot of weight. Nevertheless, I spent the past two years relishing the diminutive First Watt J2 amplifiers. While purposing them for more suitable speakers in the review, I harbored the hope that two would be just enough to handle my beloved Kingsound King III electrostatic speakers. I revealed in my review of the J2 that I preferred it holistically to the beefier XA160.5 and the mighty X600.5 monos. Yet, the J2 did struggle with the King III. I had to push the amps to their limit, and every so often the circuit protection would activate, shutting a unit down. Thanks to First Watt’s robust quality, similar to Pass Labs amps, it never skipped a beat. A brief cooling period and cycling of the power unfailingly brought it back. I wonder if that point may be absent from the J2 review, as with time I pushed it more to its limits in an effort to achieve higher listening levels and better dynamics with the King III. Lately, my goal was to sneak in an article on the new .8 series, perhaps the XA30.8, to retain the tenderness and get a smidgen more power.

I have two members of the Pass Labs team to thank that this is not a review of the XA30.8.  At AXPONA 2018, I opined to Pass Labs President, Desmond Harrington, that I was in search of a bit more power, but without giving up the sweetness of the J2. Knowing my experience with the .5, he said the .8 series was different from the .5 Series, and that I likely would enjoy it much. He encouraged me to tackle the XA160.8, and I concurred. After all, I had some amp stands waiting in the basement. I would wait for the next set of XA160.8 to be made. When the appointed time came to check in on the progress and establish a delivery time, I was in conversation with another Pass Labs employee, Kent English, who said that the set of XA160.8 were slated to be sent to RMAF and would not be readily available. However, he noted, there was a set of XA200.8 monos boxed up with nowhere immediate to go. I balked – after all, they weigh 157 pounds each! He had some great stories to tell me, including how he had to move these amps up a flight of stairs alone and did so by walking them up the stairs, lifting them end over end. He said, “We’ll figure something out. There’s always a way…” I would like to publicly thank these men, as by their encouragement they have made me a most happy reviewer! Meaning no slighting of the XA30.8 or the XA160.8, I am glad that these amps are in my room!

I sound like such a wimp, especially since I still do an hour of cardio or weights six days a week. The big reason I am leery of heavy amps is that I have heard horror stories of guys my age and older screwing up their backs. I do not want to wrench my back and have troubles forevermore. You can’t blame me for such caution, as I know firefighters, mechanics, steamfitters—people who handled heavy stuff —whose backs are shot. I do not wish to be among them, especially from voluntary involvement with mongo amps. But Kent was right, I found a way, which I will explain shortly.

 

Hot topic

One potential challenge in ownership of such a hot build as the XA200.8 is the operating temperature, which is significant. I recall reading about enthusiasts with Class A amps who rotate them into the system as seasonal heating and cooling demands changed. I can understand the impulse; my room is very energy efficient. The truth is not stretched to say it is built like a vault for acoustic purposes, and is so solid that it only needs 1 supply vent and one return vent. It holds the air so completely that in the heat of summer I keep a polar fleece in the room to take the chill off the air that comes from the AC, and in the deepwinter I go down to the room in shorts and T-shirt, even if it is -20 degrees outside! In that environment, when the XA200.8 are on for 1.5 hours with the door shut, the room becomes toasty. My simple solution is to manage the air temperature by opening the door to the room, which allows the cooler basement air to filter in, allowing for longer listening sessions. Years ago, I used to chafe at the idea of listening with the door of the room open, but now, in an empty nest home, quiet is the norm. With age some things are no longer critical. If the XA200.8 demands room conditioning to hear it, the door stays open and I can listen as long as I wish.

Weight and heat are everyday realities that impinge on the audiophile’s idealism. The first thing I thought about when Kent prompted me to take the XA200.8 for review were those homemade amp stands with casters! Preparation came back to bless me in this review, especially since the XA200.8 has allowed me to push the envelope on system configuration in a way that has not occurred previously. Perhaps you, too, will overcome some shyness to lay hands on these brutal beauties.

 

Installation

Oh, what travails I have when reviewing (thanks for listening; you are a true friend)! Having unburdened myself, I will explain how I received and installed these amps practically by myself. I’m not supposed to have done this all alone, but Kent encouraged me to not be overwhelmed, as he had to find clever ways of moving the amps himself when help wasn’t available. If he could do it, then I would as well —after all, I have both a hand truck and a furniture dolly!

The thoroughly defensively packaged XA200.8 weighs the better part of 200 pounds, and thus they arrived unscathed from shipping. As with other heavy objects that are on the edge of my capability to move down the steps alone, I have my wife assist by steadying it at each step. She is well aware that were I to stumble it would likely crush her; what a trooper! There is no higher token of true love to an audiophile, but that a wife lay down her life for his listening enjoyment! A bungee cord tight around the thick cardboard outer box was sufficient to keep it pressed to the hand truck.

Once downstairs I kept the lettering on the side of the box upright, presuming that it would orient the amps correctly for removal by opening them up and turning the box over to release the amp. That presumption proved correct, and soon enough the amps were free. Moving them into the listening room required the hand truck, and this time I employed a trick that Kent shared with me. I placed two equally thick paperback books (I did not know paperback Bibles exist! –Pub.) toward the edges of the floor of the hand truck, creating a sizable gap between them. The thick protruding .5” thick ring of the amp’s faceplate meter sat between the protective books as I moved the amp face down on the hand truck, bottom to the outside —perfect! Make sure you have rubber padding on the front of the hand truck when doing such maneuvers or you risk marring the item you are moving. Adding to the elation, when I approached the positioned amp stands, I maneuvered the front thick rubber footers at the bottom of the hand truck directly onto the amp stands. In a slow-motion balancing act, I lowered the amps onto the stands, causing the stands to snap to attention, standing nearly vertical with the footers on the bottom wooden cross member. The large, non-slip footers gripped well enough that they held the amps in place as they were lowered onto the stands. The immense weight on the front casters caused them to sink into the thick Berber carpeting and underlay such that they held their position as the amps and the back of the stands were lowered together. The process was so smooth and relatively easy that I paused for a moment to admire the result, for all the variables lined up perfectly to make it painless. No strained back during this installation! Kent would have been proud of me!

 

Straightforward

Thankfully, Pass Labs and First Watt amps are among the most user-friendly devices in high end audio to operate, likely a factor in their popularity. Their complexity is internal, their simplicity in use makes ownership a snap, and their reliability is well documented. They are so robust that they can handle mishaps, such as a dead short, that would ruin many other amps.

The .8 series, like the .5 series, retains the clean, industrial façade and fearsome heat sink fins of classic high bias amps. I appreciate the large meter with the powder blue illumination, and although it is not a great departure from the former, I find the front more appealing than the .5 Series. The arguments online about the meters on Pass Labs products provide mild entertainment. If you want to see much ado about nothing, observe audiophiles bickering about meters. The meter on the XA200.8, according to the Owner’s Manual, “…reflects the bias current through the output stage.” For those worried that the meter does not sit in the correct position, the Manual explains that for the X series the wand sits around 10 o’clock, while in the XA series the wand sits around 12 o’clock. My prideful self considers my audio system flawless, because in the first half hour of use the wand migrates from 1:00 to high noon, and it never budges from there.

The consistency of the needle’s pointing northward is so reliable that it reminds me of Quartz Lock indicators on old receivers. When it comes to performance, I prefer a wan Pass wand to a vigorous needle of most brands. That is especially so given the rock-solid reliability of Pass products. A while back, perhaps two or three years ago, I was told confidentially of a different brand’s amplifier that looks like jewelry and sports an obnoxiously large, fancy meter with green illumination— it needed repair three times. You don’t hear of things like that happening to Pass and First Watt products. The most upscale gauge in the world will not redeem an amp that needs repair three times. Knowing the types of glitches that can happen to even high-profile manufacturers, I appreciate the motionless Pass Labs meter for what resides behind it!

 

Advancements over the .05 Series

If you want to see technological advancement in a seemingly negligible feature, then consider the binding posts of the XA200.8, which have a “wing” style protrusion for easier turning and a pressure release system. Similar to the snap of a car’s fuel tank to indicate that the cap has been closed fully, the binding posts, when cinched down, click and thereby release pressure on the assembly. The spade remains tightly cinched. With as much wrangling of wiring as I did during this review, the posts never loosened a smidgen. They score high marks for visibility and ergonomic efficiency.

There is a thorough discussion of the more formidable improvements in the .8 Series in the download “Point 8 Owner’s Manual” at the Pass Labs website. Here I share salient segments of that discussion. In brief summary, the following improvements are realized in the .8 Series, including larger hardware biased, “more deeply into the Class A operating region.” That means large Class A bias values and, “a higher level of single-ended Class A bias current applied to the output stage.” Consequently, the smaller models have more output devices, and necessarily larger heat sinks.

The “front end circuit” for each amp is unique, versus one shared front-end circuit for all .5 Series amps, as stated: “Each amplifier in the X.8 series has an individual characteristic depending on the number of devices, heat sinking, supply voltage and push-pull versus single-ended bias currents. The output stages of each model have individual transfer curves and it’s their favorite feedback figures which must be complemented by the front ends… The result is a front end with high stability, low distortion and noise. It has a very high input and is DC coupled. There are no compensation capacitors – in fact there are no capacitors in the amplifier circuit except across the shunt bias regulators and (obviously) the power supply. “

Finally, regarding the power supply, the smaller amps have one third more storage capacitance. All .8 models still use very large Plitron toroidal transformers, and have new On/Off switching and high current delay, allowing conformance with the stand-by draw of 1 Watt. The front-end circuits have larger power supply decoupling, “This coupled with interleaved layout techniques has reduced the output noise of the amplifiers by another 10 dB. The range between peak output and average noise floor is greater than 130 dB.”

Even in the vault-like room, the noise level of the XA200.8 through even higher efficiency speakers is to my ear nonexistent. Note that 130dB is in the range of Class D amps! The only time I heard a peep from these monoblock amps was sometimes, when warming up or cooling, a tine of the heatsink fins might ping once or twice, but not continuously. The quietness set the stage for music played at a moderately high listening level to explode from the coveted “black background”— an exciting experience!

 

Speaking of development: differential design

The owner of a new piece of equipment should carefully read the Owner’s Manual. How many audiophiles do you think follow that advice? Scan the following paragraphs from the XA200.8 Owner’s Manual and see if you can spot an unusual characteristic of the .8 Series design:

“You can hook this amplifier up to any normal loudspeaker without danger of damage. Note, however that both the (+) Red output connection and the (-) Black output connection are live. There is no ground reference at the speaker terminals. The black (-) speaker terminal must never be treated as ground.

This can be important when you are hooking up active sub-woofers to the output of the amp – if you need a signal ground connection then use the white ground terminal provided on the rear panel.”

Did you spot the unusual design feature? Both the Red output and the Black output connection are live; there is no ground at any of the speaker terminals. To the person who hooks up speakers in traditional configurations this would likely be a non-issue, but for the person who is tempted to try alternative wiring configurations, such activity could be disastrous.

Back when I was using a pair of the First Watt J2, Nelson Pass gave me a bit of help to boost performance with the Kingsound King III electrostatic speaker, a lot of speaker for the lower powered amps to handle. He suggested that I join the outputs on each of the J2 amps: “About the J2’s as mono, while the two channels share the supply, you want to keep in mind that Class A circuits like these draw pretty constant power, so technically there is very little difference between running the two channels versus just one. What you might find interesting with the electrostatics is running them in mono by paralleling the two channels, literally connecting the outputs together red-red, black-black and driving both inputs with the same signal.  This will give you twice the current, which is often appreciated at the top end of electrostats where the impedance drops.

The XA200.8 looks like a conventional Class A amplifier, and it has two pairs of outputs, so upon first glance I thought of paralleling the two channels as I did with the First Watt J2 Stereo Amplifier. Thankfully, in conversation with Pass Labs I asked about it and was given a warning not to do so. In other words, after four reviews of Pass amplifiers, I had become lazy and thought I was fully informed on their operation. Obviously not; the incident was a reminder of the onus being on the user to know the Owner’s Manual.

 

Never “bridge” a differential amp’s outputs

When I learned that the XA200.8 is a “differential” amplifier, I inquired of Pass Labs to provide explanation. Desmond explained succinctly, allowing a quick glance at the topology, “… the amp is effectively bridged inside. So, both terminals are hot (+/-), not unlike balanced cables. The advantages are distortion and noise cancelling, and more voltage swing.”

In the event that you glossed over the above section, do NOT try using both sets of outputs to power one pair of speaker posts with the XA200.8, or with any amplifier employing a dual differential design! You cannot safely sum channels with such an amp!

Nelson further explicated advantages of the design:

“The X and XA amplifiers would be referred to as balanced, as they have both differential inputs and outputs and amplify the signal as balanced, however they are set up so as to accept a single-ended input by simply treating ground as if it was the ‘-‘ balanced input.

There are numerous advantages.  First off, the two balanced halves see the same noise and fluctuations of the supply, and to the extent that the channels are matched, most of any issues caused by this appear the same at the output terminals and thus are not seen by the loudspeaker.

Second, any distortions which are asymmetric will also tend to be cancelled at the output. The feedback loops, if any, can concentrate on the symmetric distortion components.

Third, common mode input noise from the source and environment can be rejected at the balanced input.

Fourth, the high frequency slew rate is doubled, as each side of the amplifier only needs to deliver half of it.

Fifth, the voltages that can be delivered is doubled, so for a given supply voltage you can get 4 times the power. Very helpful when dealing with high power amplifiers and parts which are very high quality but limited in terms of reliability at high voltage.

The downside?  More hardware and cost. Also, black output terminal is not grounded.”

As a result of the enlightening discussion of the features and advantages of a balanced differential design, I feel vindicated for all the years of procuring stereo amps that could be bridged, and preferring to run them that way, as they sounded better when bridged. I also conclude that the differential design is a primary reason why the XA200.8 distances itself from the other amps discussed below.

 

A tale of two Camrys

Which segues flawlessly to a discussion of automobiles. The 2019 Toyota Camry LE that I drive is my fourth; I started with a dirty gold one, moved to white, then sand, and now a silver vehicle. I am starting to panic that they will run out of colors before I die. They were all outfitted with the same aftermarket features, namely pin striping, mud guards, auto-dimming rear view mirror, body side molding (to protect against door dings), and aftermarket wheels. I have used the same number of Pass family products over the 12 years as Camry LE vehicles.

The most fundamental difference between the 2014 Camry LE that my wife now drives and the 2019 Camry LE that I drive could be described as a shift, or two, away from comfort in the seat and responsiveness in the drivetrain to the opposite in the newer vehicle. The engine and drivetrain of the two vehicles are distinctly different. They are both 4-cylinder, but the 2014 is a 6-speed and the 2019 has an 8-speed transmission. Whenever I get in the older car and merge onto the adjacent highway the car lunges forward like I am exiting the pits at a racetrack. It is unintentional; it takes a few moments to adjust the need for much less foot pressure on the accelerator. The 2019 requires much more foot depression on the accelerator to wind up the transmission in the lower gears to get the vehicle moving, but once in gear for longer travel I appreciate the potential 46mpg versus mid-30mpg.

Pass Labs has traveled a different road than Toyota, as the models of amps through the years have become more subtle, more comfortable, more elegant. The “ride” of the Pass Labs amplifier is decidedly more upscale now than 12 years ago. The X600.5 and even the XA160.5 both were “sporty” in that they would appeal to younger ears itching to hear resolution over tonal suppleness. Now, with the advent of the .8 Series, the lagging tonal richness has been addressed in a convincing manner.

 

Copy editor: Dan Rubin

Read Part 2

 

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