Gramophone Dreams #68: Lab12 Mighty power amplifier & Pre1 preamplifier

In my realm, the most sophisticated, intelligent, difficult thing anyone can do is create something mysterious. It could be a poem, a photo, a movie, a song, a symphony, or a piece of painted wood. What's most important is the mystery—and that experiencing the mysterious creation inspires in the observer a desire to probe its hidden realms, to somehow figure it out. Human cultures are founded on mysteries: Mysteries incite art, inspire science, and facilitate dreaming.

To me, mystery and beauty are synonymous. Consequently, I have steered my years so that I am always engaged in a search for, or a study of, the mysterious. And nothing—not books, nor museums, nor seas, nor forests, nor even my day job as a flâneur—has captured more of my mystery-seeking and -studying time than listening to recorded music in my studio.

I've spent 50 years developing my current viewpoint about audio system engineering, a set of beliefs about how sound systems work (and should work) and which engineering strategies result in the probing, high-engagement sound I seek. Historically, I've favored directly heated triodes powering large horns, or, alternatively, paper-cone drivers with powerful magnets on open baffles, or, less esoterically, class-A solid state amplifiers powering electrostatic, ribbon, or planar-magnetic dipoles.

Unfortunately, all but the smallest of those speaker types are too big for my apartment. Fortunately, my listening room works perfectly with small nearfield monitors such as my current references, the Falcon Gold Badge LS3/5a and the Genelec G Three. The Genelecs provide the cleanest window I know for examining line-level source components. And, during my 30+ years of almost continuous use, different versions of the LS3/5a have proven themselves worthy of being powered by the finest tubed and solid state amplifiers, low power or high. Who would have guessed an 83dB-sensitive, dome-and-cone, sealed-box loudspeaker could thrive on 8W from a single 300B tube? Or sound an equal but different kind of wonderful with 300W from Parasound's A 21+? No loudspeaker I know shows me the nature of the components behind it with more clarity and certainty than the Gold Badge Falcons.

When differences collide
This month, my Falcons are being powered by a matte-black amplifier with recording-studio looks and round meters called the Mighty. The Mighty is a relatively small (12.6" × 6.7" × 11.4") stereo amplifier that weighs just 20lb and is specified to output 10Wpc into 8 ohms. It is designed and manufactured in Greece by a company called Lab12 and costs just $2290 with tubes.

All last month, my system was anchored by Parasound's monolithic A 21+ stereo amplifier, which I enjoy with the Falcons because its high-bias class-A/AB power layers copious amounts of well-ordered detail into an exceptionally deep soundspace.

When I switched to the 10W Mighty, those deep-space illusions closed forward some, but now the detailed insides of these shallower spaces were illuminated by a steady, beguiling light that rendered voices and instruments with a shimmering, Technicolor presence that in comparison made the A 21+ seem a bit stoic and gray. Both amplifiers recovered large quantities of recorded information, but the Mighty's detail was presented with a measure of eye-popping Webb-telescope dazzle.

1222granny.tub1

It's Mighty simple
The Mighty is a simple, well-proportioned, small amplifier that uses solid state rectifiers and two tubes per channel: a 6N1P dual triode, which is a plug-in replacement for the 6DJ8, ECC88, or 6922 although it consumes more heater current; and a Russia-made Electro-Harmonix EL34 power tube operating at fixed bias (as opposed to self- or cathode-biased). According to the Mighty's manual, users may substitute 6550 or KT88 tubes.

In an email, Stratos Vichos, Lab 12's managing director, explained that the Mighty is a beneficiary of Lab12's "Separate Rails, Separate Grounds" technology (SRSG), which means "We keep high current circuits totally independent from signal circuits. That means we use one star-grounding array for the high current returns and another star-grounding array for signal returns. They meet at only one specific point."

Vichos explained that the Mighty benefits from another Lab12 technology, Fine Symmetry Design (FSD), which he described as a PCB-layout strategy in which "we take care about the technical symmetry of the two channels," with the modest goal of keeping the two signal traces equal in length and the less-modest goal of "keeping the capacitance and inductance of both paths equal." Implementing FSD involves labor-intensive parts matching and tube matching. I suspect that, like loudspeaker matching, the effort pays off with noticeably sharper image focus, more specific soundstage mapping, and superior transparency.

(Later in this essay, I outline my long-held misgivings about Ultralinear operation of pentodes and conclude that the Mighty somehow avoided typical UL sound. Something tells me that Lab12's FSD "technology" may have played a part in that.)

Two small, unmarked switches between the Mighty's power tubes and output transformers allow users to switch between Ultralinear (UL) and triode modes of operation.

Stratos Vichos says the Mighty is rated at 10W, but the "EL34 in single-ended triode mode can provide about 8–9W depending on tube. Then 10%–15% more power can be achieved using Ultralinear operation. Optionally, you add another 10% to 15% more power with 6550 tubes."

1222granny.bactub

On its secondary, the Mighty's output transformer has separate taps for driving 8 or 4 ohm speakers. And Vichos swears "no feedback is applied." Inputs are unbalanced (via RCA connectors), with a stated sensitivity of 600mV in triode mode and 400mV in Ultralinear mode to achieve full output power. The warranty is 5 years, one year on tubes.

Those meters I mentioned? They're "mostly visual, adding to the retro-modern style of the Mighty," Vichos said. "This is not a studio device." The meters are functional, though, showing "a [Volt-Amps] measurement of an interstage point between driver and power stage. It perfectly corresponds to the output, and you can estimate the soft beginning of 'tube clipping' on red areas of the meter."

1222granny.Bowie-Cello-Symphonic-Blackstar

Listening
Starting with the first recording I played, Maya Beiser and Evan Ziporyn's Bowie Cello Symphonic: Blackstar (24/48 FLAC, Islandia Music/Qobuz), the Mighty found one way after another to mess with my head, sound better than I thought it should, and make me reconsider five decades of carefully cultivated engineering biases.

Familiar songs, like "When I Lay My Burden Down," performed by Turner Junior Johnson on The Land Where the Blues Began – The Alan Lomax Collection (44.1 MQA, Rounder/Qobuz), came through with the unexpected vibey feeling of an electrified soundspace, within which I was forced to notice the Mighty's unusually corporeal presentation of instrumental and vocal textures. Besides this surprising physicality, the Lab12 Mighty, operating in Ultralinear mode, made violin and acoustic guitar harmonics shimmer and linger seductively in the air.

Before I began these auditions, I was sure that generic pentodes like the EL34, though cheaper to buy and easier to drive than power triodes like a 211 or 300B, are generally good-sounding but never great-sounding: bleacher-seat tickets to the SET experience. That was bias #1.

I was also confident that when connected as triodes (screen grid wired to plate and suppressor grid tied to cathode), pentodes sound pure and nice but not starkly clear like real triodes.

I know pentodes generate distinct distortion spectra when wired as pentodes, triodes, and in that triode-pentode blend we call Ultralinear (aka UL), where the tube's screen grid is connected to a separate, intermediate tap on the output transformer's primary. This connection allows a portion of the tube's output voltage to energize its screen grid—a form of local feedback.

Consequently, each of these operational modes sounds different. I've always appreciated the vivid energy, transparency, and sharp raw detail of pure pentode—likewise the radiant beauty of triode-connected pentodes—but I always felt there was something impure, something compressed and blurred about the sound of Ultralinear. That was bias #2.

Similarly, while I was building my own mostly directly heated triode amps, I felt that a fixed bias, in which a negative voltage is applied to a tube's control grid, sounded crisper, cleaner, and more immediate than cathode bias, which is simply a resistor of a certain value inserted between a tube's cathode and ground. I never used fixed bias because I thought it presented recorded energy with a stiff, slightly brittle viscosity that sounded more electronic and less natural than self-bias, which I thought presented recordings with a lower magnitude of internal friction. That was amplifier-design bias #3.

Listening to records with Lab12's Mighty showed me that I was wrong about the focus factor of UL and about the viscosity of fixed bias. The Mighty played waltzes and reggae with Leica-lens focus and a thinner-than-water flow that let me believe that the sounds I was hearing were coming from instruments and humans with dense bodies—that pianos and sopranos stood solidly on floors near microphones. In UL, the Mighty came across as taut, focused, fast (flow and transient-wise), and über-transparent. Suddenly, I am listening to my favorite blues song ever, "When I Lay My Burden Down," and digging it more than ever—with pentodes! In Ultralinear! And fixed bias!


Footnote 1: Lab12, K. Varnali 57A, Metamorfosi, 144 52 Athens, Greece. Tel: + 30 2102845173. Email: contact@lab12.gr. Web: lab12.gr. US importer: Fidelis Distribution, 460 Amherst St., Nashua, NH 03063. Tel: (603) 880-4434. Email: sales@fidelisdistribution.com. Website: fidelisdistribution.com
ARTICLE CONTENTS

COMMENTS
Glotz's picture

Thank you!

Great review and the comparisons to your recent review hammers home the importance of the LAB12 gear. I need to audition these for sure! Love to see preconceptions smashed! We're all better for it.

Jonti's picture

You crack me up, Herb. :)

NY State of Mind's picture

Hey Herb,
Great review as always and I love your music selections too!
I can't seem to get the above referenced track to play in MQA using Audirvana, the DAC indicates only regular 16/44.1 on my system.
How did you get this album to play in MQA?
Thanks and keep up the great work!

Herb Reichert's picture

it was no burden — it's on Tidal via Roon

but that song's so good it would knock you down coming out a broken clock radio

h

NY State of Mind's picture

Ah, got it, so the MQA version is only available on Tidal and not Qobuz as mentioned in the piece?

tenorman's picture

Another beautifully written review Herb . Thank you for mentioning the magnificent voice of Fischer Dieskau. In his prime he was surely the greatest interpreter of German Lieder - irreplaceable. Lucky you to be raised in a household that played Mahler, Schubert Lieder etc.

Jack L's picture

Hi

For my design-built Class A SET preamp & power amps, I always use "fixed bias" topology - They sound better musically. No "bias" to me.

That said, not all fixed bias circuitry sound equally superb. I used only certain type of rechargeable batteries (seried-up) for grid biasing of all the triode driver & triode-strapped pentodes in my home-brewed SET.

My ears love the sound of fixed bias with batteries way way over AC -to-DC fixed bias used in most most, if not all, brandname SETs & Push-pull power amps, like the famous vintage Dynaco ST-70 UL PP power amps.

I also used same type rechargeable batteries for fix-biasing my phonostage vintage Telefunken ECC83s - musically superb sounding.

Listening to battery fixed bias is believing

Jack L

Jack L's picture

Hi

Yes, I never liked the sound of my vintage Dynaco ST-70 UL power amps when they were donated to me 2 decades back - totally unacceptable to my ears. It was resurrected from its sonic hell to
2nd heaven after my thorough upgrade including replacing its factory composite electrolytic filter cap in its HV power supply with brandnew AC motor-run oil capacitors.

Pretty musically pleasant with my upgraded ST-70 UL - fast, clean, transparent, detailed & pretty open sounding.

YET, when it now sounds even much better like further raised up to 4th sonic heaven when I converted the EL-34s to triode, triode-UL PP switchable. I always keep it on triode mode which sounds soo much better than its orginal UL mode.

Listening to triode is believing.

Jack L's picture

Hi

I second your above statement, BUT, it is not your bias - it is a sonic fact to discerned ears, including yours truly.

NO, repeat, NO other model tubes can match up the ELEGANT musicality of WE300B, not even 2A3 or the more powerful 211 & the like triodes, period, IMO. EL-34 ? not even remotely close musically, IMO ! This is tube design physics !

Again, I can describe the sonic beauty of WE300B :
"Like a Cinderella spinning in her ballet dancing shoes vs an old bag dragging her feet"

Listening is believing

Jack L

Indydan's picture

Hey Jack L. do you like talking to yourself? Nobody seems to be listening...

Jack L's picture

Hi

No, I am talking to YOU as well as the editors etc, just to name a few. So you listened & just opened your big mouth to respond, right?

Jack L

Indydan's picture

Big mouth, me? Really? I am not the one who litters these articles with nonsense posts all day long.

You seem to think you have a special relationship with the editors. That is both funny and sad...

Keep it up Jackie Poo!

Jack L's picture

Hi

Really? Show me which are the posts "nonsense posts all day long" ????
YOU, BIGmouth SourGrape !!!!!!!!

I challenge YOU hereby to post something decent here instead of shooting in the dark, SourGrape !

YOU BIGMOUTH is soooo naive to think the editors here have chosen to turn a blind eye to my posts ???? Use your head, kid !

Don't YOU litter the space here again with your utter nonsense !

Jack L

Indydan's picture

Hey Jackie poo, relax or you will wet your panties.

Glotz's picture

The moral of the story is Herb challenged his biases and found that LAB12 gear not only broke those biases, but provided new benchmarks in his listening experiences. That was important to him- and me.

It reminds us that our new auditions of gear should be done with open-minds, not old convictions of what is 'best'.

Things have changed!

Jack L's picture

Hi

I indeed agree to the "moral of the story" of Herb you just mentioned. Honestly, you know him much better than I know him.

But LIVE perfomrance I always use as the yardstick of gauging home audio has NEVER 'changed' for me at least.

Jack L

Glotz's picture

I do value your deep knowledge, Jack.

Thank you.

Jack L's picture

Hi

Thanks. Your profound humanity insight serves heartfelt complement to me.

Honestly, being an engineering guy with true intention to help out whoever not so fluent in audio, I know I might have overdone it by offending whoever unconciously. A rough diamond I might be ?!!

I hereby offer my sincere apology to whoever I have offended !

I wish we did not have to fight bitterly before arriving some mutual understanding just now.

Please feel free to ask me anything about audio to hopefully improve your music enjoyment. I am all eyes & ears for your goodself.

Keep up your great humanity insight ! Frankly, this is my weakness.

Jack L

Glotz's picture

And many blessings to you, Jack.

Jack L's picture

Hi Glotz

May God bless your goodself & your family folks in many years to come !

Yours truly Jack

Jack L's picture

Hi

What can be more "natural & unaffected line level preamp" than no line preamp ??

We got to know what harmonic-rich music likes & dislikes ! It dislikes fighting its way through electronics to reach its destination.

That's why live acoustical music is so emjoyable to music lovers. Music goes straight to our ears !!!

So to spend $2,300 or even up to $4,500 for a "most natural & UNaffected" tube line preamp ? Just for a volume control with undue harmonic, intermodulation & phase distortions & noise as bonus ??

Yes, I am a cheapskate who would never spend a penny for redundancy. Yet I've spent big bucks in high fashions for my wife & my quality lifestyle.

Like it or not, any line level ACTIVE preamp is an absolute redundancy, IMO.

The myth of acquiring an active line leveo preamp is to ensure the power amps pumping out enough power to drive the loudspeakers !

Again, any programme sources, like CD/DVD players, DAC, etc digital media, phono preamps, tape deck, tuner & the like analogue media already provide adequate output voltage/current for any power amps to deliver their rated maximum power. So should we still need/want to spend big bucks to aquire an active line level preamp ????

A PASSIVE line level "preamp" with volume control/input selector is what we neeed which is musically & technically "most natural & unaffected" device for much much much less money !

Money bring happiness, musically ?

Let me kill the myth of the need of an active line level preamp.

I just did a sound pressure level measurement with my digial sound level meter set up at my ears level at my sweet audition spot which is 11ft from each of my front loudspeaker front panel.

Music source: Tchaikovsky Piano Concerto No. 1 from one of my reference CD (2006 recoreding). My no-name DVD player hooked up to my no-name DAC (24bit192KHz) then to my line input of my home-brewed phono-line preamp, with passive direct bypass mode on. It means my DAC drives virtually direct my home-brewed 5W+5W tube SET.

The performance was (is always) enjoyable. With the volume control set only at 12 o'clock midway (50%), From solo instrument measured below 50dBC (max & fast response) to sky-is-the-limit climax (being passive) 90dBC. I can hear the micro details of the pianist's fingers hitting the keyboard & the rich harmonic decay of the foot pedal. So entire performance was so OPEN & AIRY & spatial abundant.

Please tell me your nusical experience of any ACTIVE line premps, price irrespective that bring you back soooo close to the original performance enjoyment.

Listening is believing

Jack L

Jack L's picture

Hi

YES, star-groundings should be used for audio amps as a matter of course for nowadays grid power vs old timer audio installation with multi-point groundings decades back.

The question is: how & where to plant an effective "one point" grounding to the metal enclosure chasis ?

An effective single-point grounding device, comprising solidstate rectifiers, UHV capacitor & resistor, enchored at one specific point of the amp metal enclosure chasis serves 3 crucial functions:

(1) to reduce circulating ground loop currents to minimize 50/60Hz hum noise induced to the audio amps.

(2) to drain away RFI/EMI noises emitted from surrounding digital gears. WiFi & home electrical appliances.

(3) to provide a free flow of large FAULT currents away from the audio circuitry installation to external safty grid earth via the metal chasis.

The (3) function is crucial to prevent electrocution in case of major HV short circuits or meltdown due to, say, power transformation failure or power tubes meltdown etc etc. FYI, 300B is pretty 'meltown" vulnerable !

Safty first, I always installed effective on-chasis one-point grounding device to handle the above 3 electrical issues for my amps installations.

The crucial question: any brandname amplifiers ever got such life-saving grounding devices installed ???? I am not sure any audio designers know enough electricity faults to prevent it from occurring in their amps ??????

Otherwise, Good luck audio consumers !

Jack L

Rothwea's picture

An insightful review Herb. I've recently auditioned three Lab 12 components and all of them contradicted my preconceptions and sounded better than I thought they should.

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