Balanced Audio Technology REX 500 power amplifier

There was a period in the 1970s when many pop ballads that should have had understated arrangements instead turned grandiose and even maudlin. Take Gilbert O'Sullivan's sensational single "Nothing Rhymed" (a track that went deep for a pop hit, referencing famine, duty, and morality). Soon after the start, O'Sullivan's piano is overshadowed by a loud, saccharine string section.

Another example is "Lotte," German singer Stephan Sulke's portrayal of a dying love affair. The devastatingly wistful chanson is burdened by a mawkish orchestral track—the equivalent of glitterbombing an Edward Hopper painting.

Contrast this with Roberta Flack's definitive version of Ewan MacColl's "The First Time Ever I Saw Your Face." Apart from Flack's voice and her emotional delivery, the gently strummed guitar and quiet piano do all the heavy lifting. An unhurried double bass and a couple of minimally bowed string instruments leave swaths of negative space, helping to give her interpretation its hushed, reverent character.

I reflected on all this after spending several months with Balanced Audio Technology's REX 500 solid state power amplifier ($25,000), which has more in common with the Roberta Flack track than with the bombast of "Nothing Rhymed." I don't mean to say that the REX's sonics are understated—that might imply shyness, and it definitely isn't a shy-sounding product, but it's a far cry from the amplifier equivalent of O'Sullivan's bombast. But enough about this for now: more after you've met the amplifier in question.

Attack of the forklift
You'll need help moving and unboxing this beast, which is deeper (23.5") than it is wide (19") and weighs a grueling 140lb. I experienced its bulk and weight more than once because the first time I received the REX 500, it had to go back for repair. What seemed at first like an inconsequential tear in the shipping box was, upon closer scrutiny, the likely result of a forklift blade punching through the cardboard and ramming the REX's right side. The bend in the casework looked like it was part of the swooping design of the flanks, and the damage to the heatsink was invisible except when the top cover was removed. What was easily noticed was a loud hum from the speakers. Hours of troubleshooting got me nowhere. The buzz was impervious to different outlets, power conditioners, interconnects, power cables, and assorted sources. It did go away when I substituted either my Krell or Anthem amplifiers. At that point, I knew that the REX needed a bench check, so back it went to the Wilmington, Delaware, BAT cave.

The company determined that a hard impact had dislodged one of the SuperPak capacitors and broken some solder joints. (The build quality of the REX 500—all aluminum except for a thick steel bottom plate that supports the supersized transformers—is sterling (footnote 1), but in a deathmatch with a carelessly driven 9000lb forklift, it lost.)

About 10 days later, I took possession of a replacement Rex 500. Other than my poor back, after that, all was well.

Visually, the REX means business. Forty-eight heatsink fins adorn each side, hidden behind the fascia when you view it straight-on. The front of the amplifier is almost but not perfectly symmetrical: On the left edge is a 1"-wide vertical billeted-aluminum strip, mounted at about a 20° angle toward the rear, milled to read "Rex 500" with a swoopy, vaguely art deco–style R. Positioned in the middle of the front plate is a springy, narrow, 2"-tall power switch. The blue LED just to its right, slightly off-center, has a simple function: It merely indicates whether the power is off or on—it doesn't flash during the roughly eight-second turn-on sequence or turn red when the protection circuit kicks in. Protruding from the back panel is a curved metal handle that's intended to assist in lifting the REX—but it's not enough by itself. BAT advises using a rope or cloth sling tied around the front so that two people can lift the REX from the box and move it into place.

Also on the back, you'll find loudspeaker binding posts, a pair of XLR inputs, and two each—one per channel—IEC connectors and fuse holders.

BAT makes a point of avoiding fuses inside its amplifiers: "The best-sounding fuse is no fuse at all," the company says. BAT's auto-protection circuit does away with the need to replace internal fuses. The absence of internal fuses has the secondary benefit of allowing the REX to handle higher currents without crippling the circuit's operation.

Those fuse holders you see? They're in line with the AC, to protect the whole amplifier from external power surges. Why two? Because the REX 500 has separate left and right power cords and power transformers.

Speaking of protection circuits, if your speaker cables are terminated with spade lugs, as my AudioQuest Thunderbird Zeros are, I'd advise caution. The posts are close enough together that large spades are only separated by a millimeter or two. Once, with the amp turned on and everything connected, I decided to tidy up the speaker cables a bit. As I moved the first one, its positive and negative lugs torqued around the binding post stem ... and touched.

The only anomaly I experienced during my time with the REX involved the auto-protection circuit, which kicked in seemingly at random three or four times over a few months. The puzzled BAT team asked if it shared the AC line with another piece of equipment with a large power draw, such as a refrigerator. It didn't. In fact, my listening room has a dedicated line for audio, with a pair of 20A circuits. Perhaps, we speculated, intermittent voltage drops or surges caused the cutouts.

Then again, since I began using the new room more than a year ago, no other straight-to-the-wall amplifier seemed affected by voltage irregularities.

None of this is worth obsessing over considering that the BAT's better-safe-than-sorry protection circuit activated infrequently and that getting the amp back to normal was always a quick affair (footnote 2).

To preamp or not to preamp
Because my equipment console is only 15" deep—about 8" too short for the REX—I used an impressively beefy Finite Elemente Pagode HD-10 amplifier stand, centered on the floor between the speakers. Atop the amplifier, separated from it by a 4"-tall Townshend Seismic Podium that allowed for good separation, I placed the REX's preamplifier brethren, the tubed VK-90. BAT had sent the VK-90 along with the REX 500 in the expectation that it would prove an ideal pairing.

I decided to evaluate the amp in three ways. First, I went without a preamp, using the volume control of my main source, an Aurender A20 digital transport and server. Then I listened to the REX with the Aurender connected via the line stage of my Benchmark HPA4. Finally, I pressed the VK-90 into service, again using the A20 as a source.

While I did indeed prefer the sound with the BAT preamp in the chain by a small margin, I spent the least amount of time with that combination because I wanted to home in on the sonics of the REX without the wild card the VK-90 presented.

BAT co-founder Steve Bednarski told me he's keen on listening with a preamp in the system. I asked him why: What's the downside to feeding a power amp the output stage of a DAC or other digital source? "A well-designed active line stage will provide greater current delivery from its output stage than almost any source omponent," Bednarski emailed back. "Current delivery gives a sense of liveliness and joie de vivre to the reproduction of music. For instance, a CD player that uses an op-amp–based output stage will provide weak current delivery. When such an output stage is connected directly to an amplifier, the music can sound flat and uninvolving." (footnote 3)

Bednarski wanted me to experience the REX with a tubed line stage like the VK-90 because he feels that combining a valve preamp with a solid state amplifier can better flesh out colors and textures. This regard for tubes goes back to the company's very beginning, in 1995. For almost three decades, BAT has built high-end valve and solid state components, the latter culminating (for now) with the REX 500, BAT's flagship power amp.

Footnote 1: Damage aside, removing the top cover reveals this to be a very handsome amplifier on the inside—at least as attractive as its outside. That assumes, though, that it hasn't been rammed by a forklift.

Footnote 2: I swear that right as I was typing that sentence, the amp's protection circuit kicked in. An all-day storm is raging outside, with 65mph coastal winds that tax my state's antediluvian power grid.

Footnote 3: There are other arguments in favor of using an active preamplifier. For one of the more convincing, see the post by Benchmark Media's John Siau at application_notes/benchmarks-256-step-relay-controlled-attenuator. Scroll down and start reading at the subhead, "The 'Fully Passive' Myth."—Jim Austin

Balanced Audio Technology
1300 First State Blvd., Suite A
DE 19804
(302) 999-8855

David Harper's picture

25K for a stereo amp. One can only wonder how delusional audiophiles have become. Not all of them of course. Only a very small minority that have more money than brains. But we now live in a post-factual world. Ever since the 2020 election we no longer have any commonly agreed upon understanding of truth.

MatthewT's picture

Same crap, different day.

supamark's picture

Just because you can't hear the difference between amps doesn't mean others cannot. I'm sure you don't believe sommaliers can do their thing with wine either, because to believe otherwise would induce cognitive dissonance. It's the same frickin' skill, just different senses.

I'm sorry your hearing isn't very good, but you don't seem to understand that your experience is not the same as others' experiences. Also, your posts are pretty one note, maybe try some other notes in the key or even change keys to liven things up a bit.

On topic of the amp, not for me but I get what they're trying to do - make a tubey sounding solid state amp. There's a market for that because tubes are a pain in the butt but have a pleasing sound to a lot of folks, so I'm sure they'll sell many of these amps. And $25k for a 140lb amp... ain't exactly out of line - BAT's COGS is probably around $6-7k for the amp.

georgehifi's picture

Steve Bednarski told me: "A well-designed active line stage will provide greater current delivery from its output stage than almost any source component. Current delivery gives a sense of liveliness and joie de vivre to the reproduction of music. For instance, a CD player that uses an op-amp–based output stage will provide weak current delivery"

That drawing a long bow when the input impedance of the poweramp is 215kohm!!!! All that's need is voltage output from the source.
(Any source with less than 1kohm output impedance and volume control if it goes loud enough will be better than any preamp into that 215k input impedance)
Sounds to me he just wants to sell you an preamp also!!

Cheers George

supamark's picture

have more than one source, a simple passive 1 in/1 out volume control like yours is completely useless for people with more than one source. Also, active preamps are less sensitive to the output impedence of source components than a passive volume control. All that and a balance control too! Then you have interesting innovations, like from the late Charlie Hanson of Ayre that use the volume control on the input instead of the output. I'd love to hear their TOTL preamp but I can't imagine it's $20k better than my Pass XP-22 *for my tastes*.

Different strokes for different folks yo.

pbarach's picture

It is pointless to complain every time someone reviews an expensive component. Will the complaints stop manufacturers from making expensive stuff? Not as long as enough people buy it. So please direct your complaints at the people who use their wealth to buy such items (not that they care about your opinions).

Nirodha352's picture

Agreed. It is also the “blame feeling” I get from whiners. Grown ups can decide for themselves how to spend their money. If I forsake holidays to save up for some expensive gear, it’s up to me.

Glotz's picture

Comment about the product directly or the technology. If not, it shows one doesn't know shit about any of this.

Just because you can't see people owning this for their love of audio and music, please don't feel free to complain. It only shows ignorance.

georgehifi's picture

supamark: "have more than one source, a simple passive 1 in/1 out volume control like yours is completely useless for people with more than one source."

There are many passive pre-amps on the market if your source has no volume control that have multiple inputs, that in this case with 215kohm input impedance of this amp will still sound far better than an any active preamp will.
Cheers George

Don't believe me? Remember what Nelson Pass said:
Tell him he's wrong also.

jpan99's picture

Thank you for that. I use a passive pre into Pass mono blocks. A change that took my system to a whole different level. Incredible. Love it so much.

georgehifi's picture

Yep just like Nelson said, some just like the added colourations/distortions of an active preamp in the system, even when it's not needed. (like he said it's a psychological thing of the volume control being up at 2/3 level with a passive instead of 1/3 with an active.)
If the input/output impedances are in a good matched state when a passive is used and you have enough output level there's no need for an added active gain stage to be in there.
But sometimes you need extra gain because the source is too low in output level voltage or the power amp has low gain, and you cant get up to the loudness you need, that's when you have to use an active preamp with extra gain, but that also comes with added colourations and distortions.

Cheers George

Glotz's picture

Several components that do not add to the "colourations and distortions". I've heard many.

Many ways to skin an audiophile.

supamark's picture

And your quote doesn't make your point like you think, he's talking about other mfg's designs. I can't see him letting Wayne design a preamp that "throws away" gain, and my experience owning a XP-22 is that it's really f'ing good and a bargain at $10k. Hell, Nelson has stated that the XP-30/2 preamps are intentionally designed to directly drive a loudspeaker (over 30V output). Pass Labs, by Nelson's description, has a weird and unconventional design/listening process. And an amp that uses 1,000 JFETs lol.

Maybe take your own advice and... listen.

georgehifi's picture

supamark: "Nelson doesn't design preamps"

Really!! of cause he does, he's a businessman and needs to make money, and he makes them also to drive the a couple of amp models he's designed that have that have little or no gain and very low 2kohm input impedances.

supamark: "Maybe take your own advice and... listen."

I think you should take your own advice

supamark's picture

It is a fact that Nelson Pass only designs power amplifiers for Pass Labs and FirstWatt. Wayne Colburn has been doing his small signal work for *decades*. Wayne is very very good at what he does, which is why his preamps are significantly more successful than your piddly passive volume knob.

georgehifi's picture


cognoscente's picture

Indeed, this is 3 times the price of a very, very good power amplifier, and one more than you will ever need. So more than 15k on this power amplifier is pointless and therefore a pure rip off. This no longer has anything to do with simply enjoying music. And yet many "audiophiles" (they're not) continue to pay these kinds of prices. Fodder for psychiatrists, not for music lovers. But I'm fighting a Don Quixote battle here.

I've been referring to this for a while now as "the last throes of the audio industry just before it collapses" because (almost) anyone under 40/50 has no interest in good audio. And most of the money is with the 70+ people, who will soon all be dead or demented. So let's get their money now it's still possible (the industry thinks).

teched58's picture

...where I have to explain to my adult kids that after I go, if they want to use the turntables they will need to one day change the needle.

"Change the needle? I didn't know you had to do that!"

supamark's picture

Look at the pro audio industry, there are tons of young people entering the engineering and production side because they care about good sound. Not a great time to be a brick and mortar recording studio, but it hasn't been for like 30+ years. For "high-end" audio to survive, it literally only needs like 0.1% of the general population or fewer (8 million+ people worldwide) to care about sound to be very successful. I mean, there were maybe 10 or 15 of us in my high school who cared about good home audio (early Gen X), so don't try to pretend that it's always, or really ever, been anything but niche.

As the Silent and Boomer generations age and die, their money will enable their children to buy high end gear (or a house, etc). Millenials are the largest generation currently and their parents are only now beginning to pass on.

Glotz's picture

And your own ignorance.


a.wayne's picture

The VK500 was and will always be an 8ohm load only type amplifier for best sonics , so its size and cost flatters to deceive if purchased to drive low Z SOTA type loudspeakers and yes an active Pre amplifier does Bring drive and dynamics as well as level matching to the table..


JohnnyThunder2.0's picture

JA reviews Parasounds that are roughly the same price and everyone is blowing kisses at him. Yes it is a lot of money (but this is a luxury goods market pals) and yes I can't afford it (my amp cost me $4k) but we've seen so many amps that cost way more reviewed in these pages. The Linn Monoblocks that were just reviewed are infinitely pricier and everyone knows Linn stuff is marked up at least 50% from an equivalent product (and I am not saying their stuff is bad, just expensive as you're paying for marketing, industrial design and lots of R&D and UK wages.)

supamark's picture

The high cost of boutique type products comes in part due to the fact they are *not* mass produced so they have to recoup R&D, marketing, salaries, etc (aka COGS) in larger chunks per unit sold to stay in business.

You also advertantly make excellent points.

DaveinSM's picture

I agree, and $25k for a 140 lb kilowatt solid state amp is not out of line with Pass Labs products like your XP22 (that’s a nice preamp, and one that seems to offer a lot of value for a fair price, even if it isn’t inexpensive).

In a world of $500k speakers and six figure phono preamps and turntables, some people would even call these “mid fi”. Whatever. I’ll take 99% of the way to state of the art for 10% the cost of entry any day.

georgehifi's picture

supamark: "than your piddly passive volume knob"

Your blind statements above and in comments of other equipment "measurement tests", prove that you have very limited knowledge of Ohm's/Kirchoff's or any other laws of electronics, and also with no knowledge of the output/input impedance matching of audio.
Even though Nelson Pass has told you here also.
Yet you still argue blindly that you need an active preamp with more gain in a system no matter what the case.

supamark's picture

Don't f'ing call me stupid, you're here to promote your single input passive volume knob and pretend to be a real EE. Saying I don't understand the relationship between impedence, voltage, and current is as stupid as saying you don't understand the importantance of breathing to being alive. I've watched in schadenfreud when real EE's have corrected your misunderstanding of various electronic principles. Or a biochemist (me), as I'm about to do:

From your product page, "your source (ie CD Player, Streaming Device, DAC etc) must have enough output (measured in ohms)..." Dude, that should read, "low enough output impedence (in Ohms)." Anyone who's taken an electronics course knows that "enough output" is measured in either voltage or current (or their product, Watts), not impedence. Who doesn't know Ohm's law again? lol. You also conflated capacitance and impedence when talking about appropriate interconnects, "and preferably low impedance (less than 100pf per foot)". The impedence for interconnects is inconsequential compared to the in/output impedence of the electronics, you meant capacitance (or should have). It's pF, not pf - Farad is capitalized. So is Ohm.

It's a dimmer switch for an LED that lights a photoresistor in a box to control volume. Not the worst idea, I'll give ya that but you should really correct your website's errors in terminology. Did you get the idea from opto-compressors (love 'em), guitar amp tremelo, or somewhere else?

The reality is you're just a blowhard who has a belief based not on evidence but faith that a passive pre-amp *must* be better than an active one. Kinda like how every EE said you could not make a parametric equalizer with continuously variable Q until George Massenburg proved them stupid by doing it in 1971, presenting the paper at Spring 1972 AES - AES means Audio Engineering Society fyi. Variable Q was the final piece in the fully parametric equalizer puzzle.

Give me a cogent description of entropy, showing real understanding, and I'll stop thinking you're ignorant. Regurgitating Bolzmann's S = k log W equation or invoking "the arrow of time" doesn't count. If you cannot, I will provide one in a later post.

Not sure why you brought up Kirchhoff's circuit laws since I've never gotten into the nitty gritty of circuit design here (or anywhere)... unless you were for some reason talking about one of the other laws named after him.

Oh, and you always seem to neglect how varying the input resistance seen by a source can change the sound with a passive volume control. I can hear it with a headphone amp I have that has one and a slightly too low input impedence. It's a bit of a color box. Your product page literally specs the range of impedences you can connect to for that very reason.

Finally, for the love of the diety of your choice, say something new besides "proper square wave" on every non-class D amp test, and "a passive volume control would be better" all the damn time. Your setlist is stale, get a new schtick because currently you're just repetitive and exhausting.

georgehifi's picture

Like I said, take it up with NP, I'm sure he'll get a kick out of you.

Glotz's picture

George pretends he his his own god a bit too much.

georgehifi's picture
Glotz's picture

I still enjoy your rants.

michelesurdi's picture

looks like bat should stick to midfi

ok's picture

hi-end audio would be long dead.

Glotz's picture

Like at all.

There were 10,000 people at AXPONA this year in Chicago. ALL of them were there purely for stereo! Young people, too.

Sales and revenue are the greatest they have ever been.

ok's picture

..I'm grateful to the asians for keeping our hobby alive and kicking, although their greedy demands are the main reason for the skyrocketing prices which fuel an increasing frustration west side. Anyway budget hardware has never been better: a decent smartphone with good headphones puts to shame any hifi system of yore; why on earth should youngsters invest their precious in expensive home-fi? I know practically no one under, say, 40 something interested in ever buying hi-end gear and, mind you, I know hundreds of them. I, on the other hand, have been in this hobby since my early teens and certainly not alone back in the 80s.

Glotz's picture

A lot generalizations here.. most of which are not true.

Headphones and phones lead to other things, like friends.. lol.. and homes and later a hifi. And you don't need to be rich to own much of it.

Axpona also proves you wrong. 10000 people and there were plenty young there. The older guys with your attitude are the problem. Too much negativity. Build up a digital front end to them if you are a teacher or audiophile. Your phone as a source sucks balls.

You're forgetting about Europe and their growth, as well as here. More companies are being created all the time. And the old ones still flourish... VPI, Benchmark, PS Audio.. many more.

And why on earth should youngsters (great word, btw) spend money?? Because they have it now! The IT people have more spendable money than they ever have! $50k for a car is nothing for them, really.

Why else would they be buying $5000 headphones? Their priorities are almost correct... they need to get rid of naysayers like you and listen to other music lovers that actually aren't bitter about this hobby!

Owning high end budget equipment is as doable with home audio as it is with personal audio! Just have some patience when it comes to owning like a frigging BAT reference amp!

But, I guarantee you that 75% of IT pros could afford MOST of this gear in Stereophile! $25k on a solid system for the home is not a lot to invest in.

Many will spend that in traveling in a few years or luxuries for their home, like a friggin kitchen. Priorities...

ok's picture's all my fault. But now I see the light: positive thinking. Thanks for the tip!

DaveinSM's picture

This is, frankly, a stupid comment.

“Greedy demands” get a supplier nowhere in a free market in which plenty of buyers have no problem with the prices.

Then, in the next breath, you state how “budget hardware has never been better”.

Where do you think that stuff is being made?

Get yourself together, man. SMH

ok's picture

did not understand a single word of what I said nor have you the slightest idea of how modern hi-and audio market actually works. You could politely ask for clarification, but no. So keep the "stupidity" comment all for yourself.

DaveinSM's picture

He said it much more nicely, but most of what you wrote is simply not true.

I work in the electronics industry, BTW, and have more experience with suppliers than you will ever know.

There is a world of reality out there, and you are wholly unfamiliar with it.

Glotz's picture

To explain one's position, the market, audio, without being rude.

It's taken me a long time too... lol.

Well, the key to simply not use direct insults when a better understanding / explanation of the issue will suffice.

I guess that's a bit of wisdom, despite our increasingly impersonal lives?

And not so obviously- bringing the conversation back where it needs to be- to the article above.

I value every one of we posters making pointed comments to the subject at hand or even one-offs that bring levity or an alternate perspective to the discussion.

Taking a bit more time to be succinct or explicit is worth it.

georgehifi's picture

As intimated they did make their "fame" with tube amps, especially their 6C33C amps which sound "close" in bass control to SS, but still had that "euphonic 2HD sound" in the mids and highs compared to solid state.
Now they are trying to make their solid state amps sound like the 6C33C amps because tubes are expensive dinosaurs now, and the Chinese tubes just don't cut the mustard like the Russian ones did, and the output transformer is also high cost item if interleaved and made well.
So next best thing for them (business wise) for a certain sector of the market, is to make a SS amp (with local feedback) sound "like" tube. Nothing wrong with that as there are many speakers that scream at you if no "euphonics" are introduced to shut/smooth them up.

Cheers George

supamark's picture

2/3 Laws of Thermodynamics involve entropy directly, and the other (1st Law) indirectly - if you could create/destroy energy from/into nothing it would affect entropy. Hell, the "Zeroth Law" is a reformulation of the 3rd Law but without entropy.

One amusing way to think of entropy is that the universe is lazy, because it prefers everything to be in its lowest stable energy state (3rd Law). Everything (literally) chill, and relaxed. Paradoxically it isn't possible - entropy prevents anything from reaching absolute zero, aka 0 Kelvin, though *negative* temps (in Kelvin) are possible, and very very hot.

What does that mean, lowest energy state? Well any time atoms are combined into molecules, for example, energy must be input to make the reaction happen. O2 + H2 + heat gives you H2O and a lot of heat (bang! goes the Zeppelin). That release of heat is the system's entropy going up as the O2 and H2 reach a lower stable energy state as water. This is all covered from a different POV in enthalpy, which is not the same as entropy. Also, water is one of the weirdest substances in the universe. Seriously.

For endothermic (heat absorbing) reactions it's sort of the opposite - the entropy of the molecule decreases, but the entropy of the universe must increase by at least slightly more. The Laws cannot be broken and the entropy of a closed system cannot decrease (2nd Law, and origin of the "arrow of time" because the universe is considered a closed system). This also means perfect efficiency is not possible. Not even for class D amps.

Equilibrium in a system (like a living organism) is when it finds its lowest energy point. (back to the 3rd Law). If that system *is* a living oranism, it is no longer living if it's at equilibrium. Constant energy inputs (like food and sunshine) are required to keep the system out of equilibrium. The universe reaching equilibrium is commonly called the heat death of the universe as all energy will be evenly distributed throughout the universe. This is the end result of the 3rd Law, depending on the actual Hubble constant of course.

Entropy can also be thought of as order/disorder and the universe tends to and ordered chaos. Drop a glass and it shatters - a little kinetic energy and it's more stable. More stable? Yes, drop the pieces again from the same height and few will break and most will stay the same. More stable. As the pieces get smaller, they get harder to reduce because they're approaching their lowest stable energy state and are more uniform. Mathematically they have fewer state options: S = k ln W, where W is the possible number of states in a crystal (quartz is the crystal form of SiO2 glass). FYI, ln 1 = 0. W never = 1. Upon the heat death of the universe, it will be orderly (everything very close in temp to 0 Kelvin), and chaotic as everything will be randomly distributed.

I could go on for pages because entropy is such a huge and important topic/concept and I've only scratched the surface in/re thermodynamics. I won't, because we all have lives. That is why none of the above, in part or whole, fully explains entropy. That's what the hell of physical chemistry is for.

tl/dr: Take P-Chem.