Octave Jubilee Mono SE monoblock power amplifier

When I was a young man, blind dates were always laced with anxiety. (Proms were even worse. Once, when I arrived in a rented tux and my father's prized dress gloves, my date's father ordered me to take out the trash.)

More than half a century later, blind dates—now with review equipment—remain fraught. Sure, expectations and the frisson of unknowns heighten the experience, but if it isn't a good match, I'm stuck for the duration of our time together. If a component sounds so mediocre that I can't be sure what's on a recording, the review and my joy are compromised. When music's emotion and beauty remain locked within cascading successions of bits or tightening spirals of grooves, it feels as though once again I've been sent out into the cold.

I first discovered Octave's towering Jubilee Mono SE monoblock ($80,000/pair) at AXPONA 2022, in the listening room sponsored by Dynaudio of America. In that first encounter, I found the sound so disappointing that I hesitated to accept an offer to review it. When I later learned that this poor showing was related to an unfortunate—indeed tragic—event, I promised to return once the setup was complete. When I did return, the next day, the transformation was dramatic. That system delivered "captivating beauty ... with all the soundstage depth, air, and expanse one could hope for," I wrote in my AXPONA 2022 show report. "Beauty without bounds."

I promptly said yes to the review. Then, mere days after Dynaudio of America President Michael (Mike) Manousselis visited my home to help install the Mono SEs, I was off to Munich High End. There, I heard the monoblocks for a second time, with a different front end and loudspeakers. "Timbres sounded extremely natural and inviting on vocal and chamber music by Claude Debussy," I wrote in my May issue show report. "The sound [was] all that I could ask for. ... [C]olors and depiction of space were stellar." I was eager to return home, finish writing my show reports, and start listening to the Octaves.

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Octave's history and designs
Founder, owner, and designer Andreas Hofmann dates Octave's beginning to 1968, when his father, a specialist in transformers and high-frequency tube technology, founded a company to manufacture ultrasonic power transformers. Three years later, when Andreas was 14, he applied all he'd learned from his dad to building his first amplifiers. Five years later, after finishing school, he decided to go further. "I got in touch with the high-end scene, studied and listened to a lot of tube amplifiers, and decided to develop my own designs," he wrote. "I wanted to overcome some issues with the 'classic' tube scheme and increase user-friendliness and long-term reliability. I also wanted to develop power amplifiers that are uncritical in relation to the speaker."

Octave released its first model, the HP 500 tube preamp, in 1986. Over time, production expanded to include preamplifiers and integrated amplifiers. Octave has always produced all the components for its products in-house to ensure quality; that includes winding its own power supply, output, and step-up transformers. In 2021, while the COVID pandemic was raging and high-end sales were climbing, the company moved into newly constructed manufacturing and warehousing headquarters.

An in-person chat at Munich High End with Hofmann and Thomas Brieger, Octave's head of sales and marketing, revealed that the company's Jubilee Mono SE is a new design, based on a pentode push-pull system Hofmann designed 20 years ago.

"I wanted to optimize and find the limits of the pentode design," Hofmann said. "My concerns were not limited to power. I also focused on the naturalness, the clearness, the dynamics, and the stability of the amplifier against a complex load. The second-generation Octave SE, which uses multifeedback, represents a refinement of the push-pull technology. There is also a completely new output transformer with a better phase shift that improves the feedback and the total phase of the amplifier design. I also chose the KT120 over the original version's KT88 because it was reliable and good-sounding, and it enabled me to raise the output power to 350–400W into 4 ohms and maybe 300W into 8 ohms.

"From the beginning, I've done true pentode designs rather than ultralinear or triode. Ultralinear was developed in the 1960s as a means to rival solid state performance. Ultralinear may give you a little more output power and lower distortion, but in my opinion, it kills the tube. The tube is always overstretched, and lifetime is reduced. It is one of the reasons why the tubes sometimes blow out.

822oct.3

"In contrast, pentode technology conforms to the tube; it doesn't overstretch it. Pentode amplifiers also have completely different load characteristics. Ultralinear is very, very sensitive to the load; pentode is not so sensitive. ... Bob Carver once made a pentode design, but he stopped it. I may be the only one doing this type of pentode amplifiers now."

Hofmann claims that Octave's pentode designs have better phase stability and phase response, which is important for designs with negative feedback loops. He also believes that in pentode designs, feedback works better, amp stability is increased, and dynamic stability improves, as does the sound of mid and high frequencies.

"I don't use chokes or old-fashioned parts in the power supplies," he said. "I've developed very, very stable new optimized power supplies that are solid as a rock and have low distortion and very high-power capability. Many designers use chokes to tune the sound and make it warm. This can make the amp a little bit slow. I don't want this. I want the sound as natural and precise as possible; I don't want it too warm or too soft.

"Even without a choke, you don't hear hum noise. People always use chokes to get rid of the hum, but I get rid of it using other technologies. In my opinion, it's easy to design an amplifier that has no hum and has no noise. It's about the total: the wiring and the ground system. It took me a long time to optimize it."

Thanks to the Mono SE's special output transformer, which is optimized for push-pull, its output remains stable down to about 2 ohms. "The transformer has very high symmetry of both tube windings," Hofmann claimed. "Think of it as a symmetric tube input to an unbalanced speaker circuit. Phase shift is precisely controlled. Most people use output transformers with 4-, 8-, or 16-ohm taps. Because no speaker presents a stable load with average impedance, our output transformers have only one output winding that is optimized for average impedance, let's say from 3 to 12 ohms. This is why we say the Jubilee SE mono outputs 400W into 4 ohms, depending upon the power supply characteristics, and an average of 300W into 8 ohms. The amplifier remains stable from 3 to, let's say, 20 ohms. Nor does it oscillate with a low-impedance or high-impedance load. If demand gets too high, the amp's electronic protection circuit switches it off."

Octave's models use a mix of JJ and Russian tubes. Despite parts shortages and concern over future accessibility of tubes made in Russia (footnote 1), Octave's policy of stocking up at least a year's worth of parts has kept production constant.

Due to the ease of bias adjustment and the protection system, the company claims that tube rolling won't damage the amplifier. "If there's a lousy tube, the protection circuit goes on," Brieger said. "We have a solution that minimizes stress to tubes, capacitors, and resistors. When you switch on the unit from cold, we initially build up the voltage very slowly and keep it below the specification. This avoids blowing fuses and tripping circuit breakers during this critical time and greatly expands the lifetime of the components."

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"My designs are always a bit conservative; the amps don't get very warm," Hofmann added. "Because I don't overload the tube specs, I expect a tube lifetime of 5–8 or [even] 10 years. The unit turns on in three phases. When you [first] turn it [on], the current is limited to the mains and limited and regulated to the cold tube, so it comes slowly. After the tube is warmed up a little bit, we switch on the plate voltage to avoid stress in the cold tube. This extends the tube's lifetime. It takes 15 minutes to go from totally cold to getting the full sound.

"The amplifiers are bulletproof. My designs have extreme stability against load, because we know the stages inside, and we monitor the current and voltage. You can short-circuit the speaker or remove cabling, and it will make no difference. You can also switch our amplifiers on and off even if there's no speaker connected. Others say you should wait 7 or 8 minutes after you turn off a tube amplifier before you switch it on again, but because we perform startup and shutdown in a very controlled manner and follow the same procedure when we turn it on and off, you can turn it on and off without concern."

When I tried to talk about specific parts choices—for example, what internal wiring Hofmann uses—he replied, "I don't like to talk about this, because I don't want to get into these holy cow discussions that are endemic in the audiophile community over the capacitor being a silver foil capacitor or something else. Of course I listen to different wires and capacitors, but I don't want to make a philosophy out of it. Beyond the type of wire, the whole wiring system, distances, AC and DC connections, and the signal flow are of very high importance. Finding the best wiring schema can take a very long time. Thanks to the Audio Precision measuring system, we can analyze a lot inside an amplifier. But I can tell you that most of the critical small-signal connections are on a printed circuit board."

Brieger chimed in. "When you achieve the right angle and distance between the power supply and output transformer, specifications improve. After 40 years, Andreas can look at a PCB or inside a cabinet and immediately know how to place the parts and how to arrange them. It's not a secret that we use EPCOS capacitors, formerly made by Siemens.


Footnote 1: As noted in Julie Mullins's June Re-Tales column, Russian-made tubes used in Western hi-fi equipment—the Tung-Sol, Electro-Harmonix, EH Gold, Genalex, Gold Lion, Mullard, Svetlana, and Sovtek brands—are produced in a Russian factory by US-owned Electro-Harmonix.
COMPANY INFO
Octave Audio
US distributor: Dynaudio USA
500 Lindberg Ln.
Northbrook, IL 60062
(847) 730-3280
ARTICLE CONTENTS

COMMENTS
DougM's picture

I suggest that he's failed miserably in his quest to achieve "user-friendliness", unless said user is a hedge fund manager. This is just what we need, another review of a product that only a fraction of a percent of readers could possibly afford. I can't imagine how cowtowing to the extremely narrow group of audio elitists will increase readership and grow the magazine (and the hobby, to bring new young people in, with the current wealthy boomers all dying off quickly), but I guess you only care about catering to a few hundred filthy rich readers, and everyone else be damned, and don't matter to you. Great way to provide an example of inclusion in the hobby of audio.

rschryer's picture

"user-friendliness" has nothing to do with cash.

Jack L's picture

Hi

So I would consider "user-friendliness" means easy to handle, right?

Bias adjustment for each individual output tube at the back panel of the amp is already a pain for the users let alone different bias levels affecting the output power & the sound as well !!!

It is not that "user-friendly", correct ?

Jack L

johnnythunder1's picture

I enjoyed the review. If you don't like it and want to read stuff for the rank and file start your own blog. I don't own a house but I like reading Architectural Digest. Stereophile doesnt have a mandate to review things you can afford.

Jack L's picture

Hi

Please check the Stereophile home page showing a forum for budget
buyers:
"Budget Component Reviews - "under $1,000 or otherwise.."

Jack L

johnnythunder1's picture

of the other components Stereophile reviews. The majority of us buy things in the 5k range or more. You can certainly assemble a lovely and musical system for under 5k too but I want to read about more than beginning systems. Remember one important thing: this is not a public service. It is a consumer magazine that needs to sell advertising. There's a reason you see more ads on TV for deluxe cars instead of each manufacturers lowest priced model. Jeez. People want this to be a public service.

Jack L's picture

Hi

I wish Gordon Holt is still around to tell the reverse !

You still recall why he started up Stereophile 60 years ago? To provide consumer friendly service intead of advertisers showcase !

Jack L

PS: you already told us yr longtime experience in publishing here a while ago. So don't need to remind us here again. thanks

johnnythunder1's picture

chasing younger readers w a PAPER MAGAZINE is folly. Only us old folks subscribe to magazines. Skewing content for people under the age of 40 is a waste of effort. A magazine like this will be folded long before it changes its editorial direction in any way you would discern. Pick up Car and Driver or Vogue? are they reviewing the Nissan Versa or a Porsche? Is Vogue doing spreads on The Gap or on Saint Laurent?

mcrushing's picture

About a dozen power amps on the current recommended components list are under $5k. One is the Schiit Aegir, which Herb Went crazy over and put in CLASS A. That amp is like $800.

Stereophile has reviewed of almost every retail component I've ever bought - and most have been way, WAY under $5k. But also, I happen to LIKE reading about gear I'll likely never own. I come to this site for practical info, and to dream a little. That strikes me as making this publication pretty "user friendly."

Do people complain to Motor Trend when they review Ferraris? Or is this exclusively a hi-fi thing?

barfle's picture

While I don’t begrudge those who have more bucks than brains, I wonder just who actually buys these things. A year’s supply of tubes is what? 100? For that much money, you can hire an orchestra of some repute to play a private comcert.

DougM's picture

$80k for a seriously flawed design that produces excessively high levels of distortion, and exhibits extreme high frequency attenuation at lower speaker loads, and yet it's "Class A"? Your credibility is non-existant

JHL's picture

One generally checks the freely available ad copy, the specs, and the measured behaviors before plunking down $80k on much of anything, DugM, which in the case of this *tube* amplifier it seems that rolled-off 4 ohm speakers may be only conditionally recommended.

We call this pairing. Please advise if my credibility is thus somewhat greater than and not equal to non-existent.

I realize that when shopping for $80k amps one immediately rushes to the transformer-coupled tube amp aisle for candidates to power their *two* ohm speakers but maybe that compulsion could be revisited. As for simple distortion, at such time as you run a blinded distortion contest please put a flyer out in advance. Dates and times and so forth.

Actual sound while partnered with a compatible speaker may remain a controversial rationale among meter-readers but I'm not sure it has to be. I think maybe stuff could be used for listening but that's just me.

johnnythunder1's picture

Haven't we accepted this yet? Or do you want to be the Julian Hirsch of 2022? Listen to music not the THD. Not the punishing measurements into a 1 ohm load. Speaking of loads, your pompous negative postings bore most of us.

johnnythunder1's picture

Audio Science Review. Enjoy it with all the other skeptics who make fun of those of us that can hear differences in different cables.

David Harper's picture

that's exactly what I do.

johnnythunder1's picture

we like this. you like that. I don't post on that blog despite wanting to when I read the utter nonsense posted there. I prefer to listen to music w my ears and I don't need a lab bench to assist w me the listening. Read Consumer Reports and ASR and have a good chuckle with all the other science nerds that wouldn't know Mozart from from Moe Howard.

JHL's picture

Almost fifteen years ago Geddes reported on distortion and audibility. An excerpt from his remark on diyAudio.com:

Basically through an ellaborate test of some 25 college students we were able to show that THD and IMD are meaningless measurements of distortion as far as perception is concerned. Basically one cannot say that something does or does not sound good based on these measurements. .01% can sound outrageous in some cases and 25% can be inaudible in others. The numbers are meaningless.

This result has been confirmed by several sources and now virtually eveyone in the loudspeaker business is coming to the conclusion that making THD measurements is pointless. Floyd Toole believes that nonlinearties in loudspeakers is irrelavent as evidenced by the fact that his new book contains no discussion of this topic. Lorri Fincham recently remarked at ALMA that THD and IMD were completely meaningless as a judge of sound quality. My own presentation from ALMA (China) last year says the same thing and maybe goes even a bit further.

Basically distortion, as we are used to thinking about it, is completely incorrect.

https://www.diyaudio.com/community/threads/geddes-on-distortion-perception.121253/

Superior sound is the product of diligent work, not magical special insight in numbers. Like all things, true performance can't be boiled down to a handful of peripheral abstracts; there are precious few components that break some magic price-performance barrier. None whatsoever on the basis of design *for* meters.

Proponents of such biases haven't discovered magic - the rest of us had known and discarded simple static data's biasing influence on thinking decades ago. See the shabby lineage of Hirsch to Aczel to ASR. It's been done before and never has it delivered a superior musical system.

Meanwhile, despite those completely familiar presumptions and fallacies I'm unaware of any actual listeners driving by those internet addresses and heckling the data-biased. That would be supremely bad form, incorrect as they are.

It could be that where you think there's magic two hundred dollar product you are the product.

Jack L's picture

Hi

How come ? It did not fly in all in JA's lab report.

May I suggest this amp designer to study more about pentode/triode powerstage design ABC to build better tube amps, e.g
Radiotron Designer's Handbook: "Critical load resistance".

Quoted: "Pentodes are much more critical than triodes as regards the effect of variation from the optimum value of load resistance - this holds WITH OR withOUT feedback in both cases."

The above statement is just proven in JA's lab report !!!

Jack L

johnnythunder1's picture

which were some of the most unnatural sounding speakers I had ever heard. But they measured great! Flat as a slate! Many of Art Dudley's favorite components measured poorly but sounded great. I buy from dealers who put the emphasis on musicality not measurements. I listen w my ears and my heart not w a scope.

Jack L's picture

Hi

Me too. That's why I only go for triode tube amps, which measure much much worse than any solid state amps, yet sound soooo much better.

The difference is: I design/build/upgrde ALL my audios at home since day one decades back, thanks to my electrical engineering background without need to finance audio vendors !

Knowledge is the power to save & to enjoy !

Listening with own ears is believing

Jack L

zimmer74's picture

I also ran Celestion 600's for many years, and they were off-the-chart fabulous. No idea about the measurements, but also like JA, mine were driven by the huge Audio Research D-250 amplifier. Those speakers required serious power to wake up.

georgehifi's picture

I usually find those that "usually" say this, (not saying you) are not good with interpreting the banks of measurements that are given in Stereophile and other publications many cases. Those types usually cherish reading the "poetic license" type of review, like Absolute Sounds, that have no measurements.

If you think about it, you wouldn't go near a product that wasn't designed using tests/measurements firstly and then yes also listening by the designer.

If a reviewer is giving a "close to honest review" of a product, one can usually draw parallels to what is heard by him, against what is measured by J.A.

Cheers George

windansea's picture

I would have appreciated more comparison of this amp against some other big amps. Perhaps against an Audio Research also using KT120s.

This is my usual quibble when the component is at the upper end of the price range: more comparison to see if the price is justified.

Also, I like to the see the innards. I want to see the trannies and the wiring. Even if it's a PCB, I still want to see the guts.

Jack L's picture

H

Me too as audio amps design/build DIYer ! Obviously its schemetics as well.

I am really intersted to see the design of the differential balanced input of this $10,000 amps pair ! Tubes or solid state devices are used there ???????????

Listening is believing

Jack L

groig076's picture

Personally, I do enjoy reading about all this... stuff, especially the outrageously priced stuff that most can't even comprehend to own. At the same time I can't help my eyes rolling from time to time. It's a give-and-take. I've been reading Stereophile since I was very 'young' (the smaller book-type form) and it still manages to surprise me with every issue.

David Harper's picture

Obsolete technology overdesigned and overpriced. Like a $10K turntable.
A definetive high-end audio component; exotic, expensive, inefficient, and objectively inferior. But who am I to criticise. My friend still has a 1968 Plymouth Roadrunner in storage. A peice of junk by todays standards. But we both love it.

JHL's picture

...whether to justify boorishness with a reply.

Suffice to say that one of the automatic tells of the difference between drive-by benighteds is that they have this compulsion to show that, having no means to demonstrate their purportedly superior sound, they resort to insisting the other guy can't hear his.

It's the self-settling argument, assuming it rises to the level of argument. It's certainly never presented as one. Here the pedestrian Harper naturally resorts to a pedestrian false equivalence.

Heh. Capitulation accepted. "Your terms are acceptable".

David Harper's picture

Reread your post. Maybe two or three times. Then try to make objective sense of it. Make whatever revisions you think appropriate.Then try again.

JHL's picture

Contrasted against this journal's normalcy, with each remark the drive-by troll cannot but declare a refusal to technically understand fine audio, profess an innate inability to hear what it does, and aggressively advertise this habitual obtuseness to those who can.

For them it's not about sound. It's a boorish persistence at incivility or for them it wouldn't be so predictably attractive and repetitious. The rest of us just realize what powers it.

Jack L's picture

Hi

If tube amps belonged to some "obsolete technology", please tell us which technology YOU think is advant-gard in audio amp design ?????

I am all ears.

Listening is believing

Jack L

David Harper's picture

Is this a serious question? Are you twelve years old?

Jack L's picture

Hi

Harsh words could bring YOU nowhere, YOU talk like a kid, pal.

I am dead serious as you are challenging my intelligence !!!

FYI, I've been design/building/upgrading tube amps decades back as my leisure hobby to supplement my classical music enjoyment on vinyls. Tube sounds better than any solid state devices, IMO.

Now you are accusing the designers of these $100,000 Danish tube power amps were idiots because YOU think they are still using "obsolete technology" of tubes !!!!

So I requested YOU to substantaite your such BIG mouth allegation & you get mad because you apparently don't know what you are talkiog about & refuse to back down.

Vent your spreen somewhere else, pal !

Listening to quality tubes is believing

Jack L

PS: I am ready to discuss audio technology with you on tube or solid state amps any time !! 'Cause I learnt from studying, supplimented by my electrical engineering background.

MatthewT's picture

Or maybe wrapped to tightly if a two-sentence post is challenging your intellgience.

Jack L's picture

Hi

Three words, not even one sentence, can make you "very insecure" too - e.g when someone yells at you out of the blue : "YOU mother f..ker"

The issue is: do we NEED to insult a very hi-end amp manufacturer as such: using "obsolete technology" for its $100.000 tube power amps in a public venue? Unless if course, whoever makes such allegation is technically qualified to make such harsh statement.

That's why I request that whoever to stand up with its substantiation !

That whoever is soooo "insecure" as a child by firing me back like a spoiled kid ! Please behave in a public venue like here. Thanks.

Jack L

Anton's picture

If you are gonna bang on someone for repeating his experience in publishing, look in a mirror.

If I had a dime for every time you superciliously bloviated about how you build your own DIY stuff, I could buy this amp.

Jack L's picture

Hi

Then you should be thankful, right ?

Jack L

David Harper's picture

You're right. My post was uncalled for and insulting. My apologies. I should have made an argument about the obsolescence of vacuum tube tech.
I was just too lazy to do it.

Jack L's picture

Hi Dave.

You should apologize to the Danish tube amp manufacturer, not to me.
My role here is just to do the reminding.

Jack L

Ortofan's picture

... quite possibly employing avant-garde technology would be the NAD C 298.

https://www.stereophile.com/content/nad-c-298-power-amplifier

If you find the combination of "very high power with supremely low distortion" - as JA1 phrased it - unappealing, then the C 298 might not be to your taste. Likewise, if your power amplifier need not be "transparent, uncolored" - to quote KR.

"A" rated by Stereophile.
https://www.stereophile.com/content/recommended-components-2022-edition-two-channel-power-amplifiers

amplifierx's picture

Class D is not new.

http://diy.torrens.org/Sinclair/inside/Duncan.php

Ortofan's picture

... implemented by NAD are new.

Anton's picture

Kind of an exciting niche!

windansea's picture

I had a tube power amp with 8 EL34s in the past, supposedly a "matched set," but then one of the tubes blew, and I wish the amp had come with a spare tube or two.

For a fancy amp like this, if one tube blows, does the company suggest a whole matched set? Is it like tires, where replacing only one is not recommended (the mismatched tread means the car is more likely to lose control).

Relevant to the amp in this review, are matched tubes even more important in a differential circuit?

Jack L's picture

Hi

They are 2 entirely differnt designs serving totally different functions. Like left hand & right hand, shoud we compare which hand is "more important" ?? Both are important.

For yr EL34s power amp, I assume there should be bias adjustment of the power tubes. That said, if only one out of the 8 EL34 was down & no tube bias adjustment was available, don't worry about it. But make sure to replace it with tube of the SAME make. So RCA for RCA, JJ vs JJ. Try not to cross makes.

Whatever the minor "unmatched" difference of the new tube would be balanced out by the other 7 existing tubes.

Of course, if you can find a local radio shop with a tube tester, get the new EL34 with an exsiting older EL34 tested to ensure close enough spec. ie TRANSCONDUCTANCE !!!!

This how I match tubes - check the transconductance of the tubes with a tube tester. Be smart enough not to be ripped off by some tube vendors who charge you a premium for tube matching alone !

Jack L

windansea's picture

here's an amp that would have made for an interesting comparison against the Octave:

https://www.stereophile.com/content/audio-research-reference-160s-power-amplifier

shp's picture

From the designer...
"I wanted to overcome some issues with the 'classic' tube scheme and increase user-friendliness and long-term reliability. I also wanted to develop power amplifiers that are uncritical in relation to the speaker."

From John's test bench:
"I wouldn't recommend the Jubilee Mono's use with loudspeakers whose impedance drops below 4 ohms, however"

While the reviewer concluded "Class A" I'd hope that high distortion and speaker pickiness despite the objective would cost it a few points.

Jack L's picture

Hi

Apparently the amp designer failed it as per JA's lab report !

As quoted in my post above, The Radiotron Designer's Handbook stated clearly triodes are more adaptable to critical loudspeaker load deviation than pentodes with or without feedback.

Jack L

johnnythunder1's picture

talk about musicality. It's sad. "Ortofan" chimes in w one of his amplifier recommendations that he compares w the Octave that couldn't be more different in approach. Yes, a BMW and a Nissan Sentra will both get to the same destination traveling at the same speed but one is a completely different driving experience. Ditto w listening to amplifiers playing music and the ensuing listening experience. Who said one was paying for perfection w this amp? The measurements are what the designer wanted. He owns a successful business with a good reputation and the serial Know It Alls on this site have to shit on the measurements but not a word about how JVS loved how it played music.

Jack L's picture

Hi

Simply because the Danish power amps tagged for soooo much money.

Otherwise, we consumers would not "shit" on JA's lab pretty disappointing test result if these amps would tag for $10,000 or less instead.... with JVS Stereophile Class A component recommendation.

Consumers are much smarter nowadays ! They would know to differentiate sonic appraisal from sales pitch in light of its lab test result when big bucks are involved.

Jack L

Ortofan's picture

... avant-garde technology, in response to a post by Jack L.

As for a recommendation for a different tube amp, consider the McIntosh MC1502. A 2Ω output tap on the transformer (in addition to 4Ω and 8Ω taps) allows full power into low impedance loads. In their test of the electrically identical MC2152, Hi-Fi World found that the amp could output 220-240W into 2Ω, 4Ω or 8Ω. Frequency response was flat from 7Hz to 64kHz. The MC1502 sells for less than a quarter of the price of this Octave amp. JVS (and JA1) should evaluate it.

johnnythunder1's picture

for that. The McIntosh would NOT have lightish bass and that's a good thing.

ok's picture

..since all those things are mostly headed towards chinese market nowadays as chinese cheapo is mostly headed towards yours; why not happy then instead?

Jack L's picture

Hi

Hopefully not that soon, my friend. That said, quite a few brandname audios are already built in China as per Stereophile reviews, e.g. loudspeakers, etc etc.

That's what I qualify it as profiteering ! Business is to make money at the expense of we consumers.

FYI, I fixed quite a few made-in-China tube power amps using bigboy power tubes like 2A3 & 300B in the past. So I know well how good was Chinese quality control !

I don't mind use Chinese made audio electronics for dirt cheap prices without serious expectation. Again, money talks, right ?

Jack L

ok's picture

..some chi-fi either. They are decent sounding for their money and quality control has risen considerably over the years. It's the only kind of audio stuff that I usually buy based solely on measurements and looks. What could possibly go wrong?

georgehifi's picture

"So I know well how good Chinese quality control !
I don't mind use Chinese made audio electronics for dirt cheap prices without serious expectation. Again, money talks, right ?"

They are "ok" with solid state gear, but when it comes to output transformers for tube gear (the heart and soul of tube amps) they seem to get lost a bit. I've seen the bobbin windings in some of their output transformers, not beautifully layered and wound symmetrically,I call theirs scrambled, like it was hand wound by some kid rolling up a ball of wool for his mom.

Cheers George

Jack L's picture

Hi

In any transromers, the quality of the metal core that houses the primary & secondary windings are also critical due to its hysteresis & eddy current loses which should be maintained to the minimum.

For high power output transformers, steel of high silicon content (4.5% ++++) should be used for its E-core, but is not that readilly availble from steel mills in China for commercial use.

I have seen some brandname tube power amps got output transformers from Japan for their high gause & H-H saturation line density. Much much nore pricey than Chinese built irons, but better sound qualtiy.

Jack L

Jason Victor Serinus's picture

Oh my goodness. I took a number of days off from checking the Stereophile site, and all of a sudden I discover folks fighting over my review.

I thought these monoblocks sounded wonderful. Their one weakness, on my speakers—insufficient bass—is borne out by JA1's measurements. My Class A recommendation is, of course, dependent on pairing them with speakers that don't dip below 4 ohms.

One of you mentioned the Audio Research M160s. My system has changed in significant ways since I reviewed them, but their sound at the time was quite dissimilar from the sound of the Octave Jubilee Mono SE monoblocks. Check the review.

As for biasing, it is as simple as can be. Hey, I take my shoes off every time I enter the house, and have to tie them multiple times a day. I also need to take leashes on and off the dogs. I need to pick up the poop of three terriers at least twice a day. I need to wash my hands before and after eating. It all takes time. So what? If you have enough time to post over and over, you certainly have time to bias amplifiers every once in a while.

When I entered Jeff Joseph's wonderful sounding room at the Pacific Audio Fest and discovered that he was powering his speakers with Doshi monoblocks (which I also reviewed), I asked what bias level he had chosen. When Jeff told me that while Nick Doshi had sent the monoblocks with bias instructions and a screwdriver, he hadn't checked to see if they needed readjustment, I asked for the screwdriver , lay on my belly on the floor, and checked the bias. Two of the eight tubes needed adjustment. Done. It was simple. As simple as adjusting the bias on these monoblocks. Except that with these (big) babies, I didn't have to bend over or lie on the floor.

Here's hoping everyone has time to listen to some great music in the days ahead.

jason

Jack L's picture

Hi

Bass performance;

So how come you did not mention this critical "insufficient-bass" weakness of this very expensive amp in yr review above & mentioned only here NOW ?

Instead you commented "On its own, the bass sounded timbrally right and snappingly complete." on streaming 'Strauss's Also Sprach Zarathustra', an acid test for sub-bass response. This would give us the impression its exellent bass performance.

So which of tbe yr above statements is valid then ?

In fact, the same music on LP (DGG label, performed by Boston Symphony Orchestra conducted by William Stenberg) is one of my test LPs for deep sub-bass. I know too well.

Listening is believing

Jack L

Jason Victor Serinus's picture

Bass was tight and convincing but not quite equal in impact to that elicited from my challenging Alexia 2s by the solid state D'Agostino Progression M550s, which pump out 1100Wpc into 4 ohms.
...
Besides lacking the ultimate in bass oomph on my speakers, everything was in place, perfect and delectable.
...
No, the low bass on Yello's "Electrified II" from Toy (24/48 MQA, Universal/Tidal) and Strauss's Also Sprach Zarathustra (from the album cited above) wasn't as room-shaking as with some solid state powerhouses that have entered my system. But I'd never have missed it if I hadn't heard fuller bass with other amplification. On its own, the bass sounded timbrally right and snappingly complete.
...
Having heard what it can produce with speakers more easily driven than mine, I have no doubt thatmost music lovers will find its bass convincingly complete and natural, its midrange marvelously full and smooth, and its highs heavenly.

Jack L's picture

Hi

Sorry, "those who have eyes' can not read one single word of yr straight-forward comment: "Their one weakness, on my speakers, insufficient bass" in your review. We only read it just now instead of in yr review. So who is playing games here ?

From consumer viewpoint, even those rich & willing would think twice or more to spend such big bucks to acquire any amp with "insufficient bass".

No need any "solid state power houses" to deliver "room-shaking" low-bass.

FYI, on playing my sub-bass tester LP: "Also Sprach Zarathustra", my design/built 5W+5W 6-triode power amp + 3x100W subs (L, R, L+R) virtually shake up my 700sqft basement audio den with its powerful 20Hz opening bars & following sharp & forceful kettle drum beats. No sweat !

Play smart is the name of the game !

Listening is believing

Jack L

georgehifi's picture

At this $80K price, amps should be able to drive nearly anything.
Even speakers with EPDR (Equivalent Peak Dissipation Resistance) measurements down to 2ohms which many are these days.
As many are only quoted down to 4ohms normal impedance measurements, but EPDR measurements of the same speaker will take them to 2ohms and even 1ohm loading and that's nearly always in the bass, making this amp, **** itself into that loading

Cheers George

JHL's picture

...to tube amps to drive 2 ohms. Still. That's not a function of cost but of amplifier type.

Jack L's picture

Hi

There is no such "normal" impedance specfied for any loudspeakers.

Do you mean "nominal" impedance ?!! "Nominal" impedance is a pretty vague terminology indicating some 'minimum' values of the loudspeakers ever changing impedance vs its frequency response.

Depending the measured impedance values vs its frequency spectrum, 4 ohm may mean at certain frequencies its impedance drop down to as low as 4 ohms. But for other frequenceis it could go up to 20 ohms etc etc. So the impedance of any loudspeakers swing up & down like a roller coaster.

Take my duly upgraded KEF 2-way standspeakers for example. After replacing the factory mylar dome tweeter (which rang like hell) with the Danish SEAS soft-fabric dome tweeter (now sounds sooo much better) 2 decades back, Both tweeters shared the same x-over frequency.

I measured the impedance of the upgraded verson.
12ohm @ 50Hz, 25ohm @ 1KHz, 12ohm @ 2.5KHz(our ear most sensitive frequency), 17ohm @ 10KHz & 13ohm @ 20KHz.

So I would take the norminal impedance of my upgraded KEF: 12ohms !
Or any suggestion ?

Listening is believing

Jack L

dumbo's picture

I'm having a hard time swallowing the idea that someone would spend almost $100K on amplifiers that measure as poorly as these do.

The Freq Resp chart looks atrocious and the distortion figures are already hitting 1% at a fraction of the advertised power output. And this is supposed to sound great?

If this were a $3K or less set of Mono-blocks I could appreciate the effort achieved by the creator given a good price/performance ratio but for $100K I expect near perfection across the board (SQ & Measurements).

I think Stereophile needs to implement a weight scale for reviews. In the simplest form there could be two categories; one for experienced SQ by the reviewer and the second being how it performs on the test bench. So 50/50 each category.

To make the "A" List of Recommended Components a device needs to achieve a score of at least X to make the cut. Otherwise, it gets kicked down to Rating B or less depending on the total it had.

David Harper's picture

Assinine audiophoole idiocy. No one with any brains
would buy this amp.

Union Square New Yorker's picture

Save your Stereophiles, one benefit of reviewing crazy expensive gear is that if you fall in love with a piece, in 3-5 years it will be 40-80% less used.

But I am sticking with ARC, CJ and VTL Made in USA.

rashirey's picture

Love the reviews in Stereophile , audiophiles tend to be very passionate about their preferences. I prefer to tweak my equipment and I enjoy the sonic results of a tube preamp with a solid state power amp with decent specs, however , listening to music to is a subjective and personal experience and lab results alone rarely reveal the totality of that experience

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