Manley Mahi mono power amps

Manley Mahi head photo
Manley Mahi head photo

ReMusic Spark AwardThe late David Manley can be legitimately considered as the originator of the tube audio equipment revival, during and after the decade 1980-90, which was dominated by the tyranny of the digital/solid state duo. His work came from his great experience in designing tube devices, in working in studios and in recording. He started his activity in South Africa, then he moved to England and finally to the United States where he found the right environment to develop and spread his ideas.


Since the first VTL prototype in 1981, he was always very prolific and his products were of top quality and designing variability. Around every existing vacuum tube, there is an audio circuit made by Mr. Manley. The tube is polyhedral, you can use the anode instead of the cathode and vice versa, you can earth the grid using the cathode as input and ten other variable choices. A Manley device is never the outcome of maniacal measurements and doctrinal technical terms. This because the measure can be a great support but never the primary source for a good sound. You can get an authoritative sound only if you focus the designing action on the strict relationship between the art of recording and the playback. If you have never been in a recording studio, if you do not have any listening experience, what idea can you have of the sound quality? The takes made using analogue consoles and microphones have greater audiophile value than the engineering value of the digital sets.


The ministers of the digital would have hammered all the existing tubes if individual like Manley had not organized, luckily in good company, the Fronde of “resisting, resisting, and resisting”. He succeeded and we will always be grateful. The fifth wife of David, EveAnna, had been able to perpetrate the company tradition, as she has an adequate background. Her father, Al Dauray, was President of Ampeg, manufacturer of tube amplifiers for guitar and bass used by many rock stars in the 60’s and 70’s, like Johnny Cash and the Rolling Stones, and today still appreciated worldwide.


From his undisputed leadership and commitment with the thermionic apparatus, David got the appellative "The Manley Tube Queen". Furthermore, he played the sax and owned thousands of records. This means that he condensed in himself all the fundamentals required to dominate the art of manufacturing and reproducing a sound. In the last two decades of EveAnna’s management the production has been aiming to studio equipment, like equalizers, compressors, microphones, preamplifiers, mixers, all rigorously with tubes, and also refined tube home audio apparatus among which I want to mention the wonderful Steelhead phono stage. You can see EveAnna’s enthusiasm in all the videos on-line, while she introduces a new piece of her production, a creature to be proud of, disregarding the genre.


You can see her motherhood also in the Manley Mahi monoblocks, object of this review. The word that comes into my mind is “mini”. They are small and light, manageable and easy to place. Mini are also the transformers and the tubes: four EL84 power tubes on each monoblock. This pentode is known for its musicality and sweetness, but there is something more here. The tube equipment counts also an input 12AT7 triode and a 6414 NOS driver, as interface between the input and the output stage. The thinness is only apparent. The chassis is solid and reliable, as well as the RCA input and the ends for the loudspeakers, two strong WBT put vertically on the top, behind the transformers. These last ones are custom homemade following the requirements of the circuital design. In our case, the output transformer is optimized for a load of five ohms. The Manley brand dominates everything, included the output tubes, on top of which the logo is printed and illuminated when the amps are on, giving that wonderful retro aspect that all the tube enthusiasts do love.


The switch is on the back, coupled with the IEC socket, close to the transformer and the power capacitors, hence far from any interferences with the input stage. Everything is effective and handy. Instead of the feet, every block has four small cylindrical columns on each corner of the chassis, whose top is spiky so to get a better isolation from the positioning surface. A show of symmetry and solutions at the service of simplicity, operability and adaptability.


The company provides a tester. What’s for? Close to every output tube are two holes: one to insert the positive tip of the measurer, the other to reach the check trimmer of the Bias. The negative tip has to be inserted in another hole, placed in the front, where the mass contact is available. What you have to do is switching on the power amp, disconnecting it to the system, putting the tester in DC mode, scale 2 V, inserting the tips as described and fixing clockwise the value of each tube at 250 mV. The higher the level of the Bias, the shorter is the duration of the tube, while at a lower level the distortions would increase. On the front side are two small switches: the right one is to commutate from ultra-linear mode to triode, the left one to choose between three kind of feedbacks: 3 dB (MIN), 6 dB (STD) or 10 dB (MAX). By combining the two switches, we have six possibilities of configuration and six power levels, from 14 W, in triode with minimum feedback, up to 41 W, in ultra-linear with maximum feedback. Besides, the input sensitiveness follows the variability so to allow several matches with a preamplifier.


In order to compensate the output differences coming from the six combinations, the circuit is designed to give an increase of the input sensitiveness whit a low power setting and vice versa. The effect is getting the maximum control on the overall gain, avoiding saturations and distortions. Choosing a different configuration instead of another can affect the tone, the three-dimensionality and the dynamics, but it does not prevent to choose how to assemble a system following your tastes.


Important suggestion: burn-in the Manley monoblocks for at least one week. Like all the tube amplifiers, ours emit a light puff in the loudspeakers, but it is more like a breath of life.

After the burn-in, you have to play two records at least to get full performances. My first test is with a Music First Audio passive preamp and then with my Audio Tekne TP8301 MKIII. Same loudspeakers: a pair of modified Klipsch Heresy I of 1972. In both cases, the outcome has been excellent, in ultra-linear mode and maximum feedback first and then in triode mode and minimum feedback. In triode mode the sounds were sweeter and delicate, the vocal and instrumental plots more consistent.


By keeping the feedback at 3 dB the sound images are rightly projected in the room, while at 10 dB the music seems to retreat and becomes aggressive and brilliant in the high notes, with a terrific midrange in terms of personality and substance. I have spent days trying different configurations but, at the end, I have never being able to individuate which one was the best. But, maybe, the best does not exist. I think that the nature of the project is just this one: a pair of universal power amps, for all seasons, all tastes, all ears. Certainly, with the Audio Tekne the Mahi took wing: from good amplifiers to classy devices. Consequently, all the timbric/dynamic differences of the different setting have become negligible.


The resolution is well defined, without any harshness. The soundstage has widen the boundaries of each one dimension, balancing the back and front depth and rounding itself softly in the corners of the room. The sound and space-temporary microcells have emerged and increased the micro-dynamics. The music has gained a great presence by materializing the musicians. With small jazz bands or camera quartets/quintets, the triode option offers the top of the musical accuracy. Still the sound is always full and strong without losing naturalness. The ultra-linear choice with the big orchestras is amazing. The bass drums and the timpani go very low, with a remarkable acoustic intensity. The voices are on the entire arch of the tone expressions, from falsetto to baritone, always well placeable in any contest, from studio to stage, from church to concert hall.


I find the apotheosis with the Overture 1812, Op. 49 by Tchaikovsky, performed by the London Symphony Orchestra directed by André Previn on 5th and 6th May 1972 at the Kingsway Hall in London, Hi-Q Records Supercuts, 2010. The opera has a great historical and nationalist value since it represents the retreat of Napoleon’s troops defeated in 1812 by the Russian army. The themes are: God Preserve Thy People, the Marseillaise that symbolizes the invader, and a traditional motif from Novgorod. The Overture ends with an aura of glory and the victory celebrated with the Russian anthem.


The composition was performed in 1882, for the consecration of the Cathedral of Christ the Savior in Moscow. I can assure that the recorded cannon shots explode in the room with a terrifying punch. No matter whether clangorous or delicate, music is never compressed or boxed, but airy without defined limits. It flows fresh and liquid like a source and wraps the listener without assailing him. I cannot resist playing some rock with the Mahi in ultra-linear mode and the feedback at 10 dB. The signal becomes dirty, sweaty, and irreverent. It is the first time that Marquee Moon by Television, Elektra/Asylum Records, 1977, is so authentic and charged-up.


Forty minutes where the composing energy of Tom Verlaine and Richard Lloyd explodes in a perfect combination between the abrasive electricity and the intellectual essence of the New Yorker rock wave of the late 70s. Same sensation with the Talking Heads in the double live Rome Concert 1980, Vinyl Passion Records, DMM Cutting, 2010. An irresistible Psycho Killer with incisive guitars and insistent rhythms. Two amazing groups, two amazing records. Two amazing amplifiers.


The Manley Mahi monoblocks are unexpected. I have tested them for one month living an amusing and fulfilling listening experience. The infinity of technical solutions they offer, are a continuous stimulus to experiment and are suitable for all. The sound parameters to measure the quality of a device here are great indeed.


I appreciate tone, macro and micro-dynamics, image, acoustic scene, three-dimensionality, manufacturing and design. With a curriculum like this, they deserve a Spark in the Dark.



Official technical specifications

Input Tube: 1 x 12AT7EH large plate Electro-Harmonix Russian

Driver Tube: 1 x 6414 JAN NOS GE or Raytheon branded

Output Tubes: 8 x EL84 Ships with Russian NOS EL84M (aka 6Pi14Pi-EB) We are out of Ei 6BQ5.

Output Tube Quiescent Standing Current: 25mA

Set Bias for 250mVDC measured across each 10 ohm cathode resistor

Input Impedance: 110 kohm

Negative Feedback: MIN= 3dB; STD=6dB; MAX=10dB of global NFB


  • FB MIN: 30.7 dB 32.1 dB
  • FB STD: 28.5 dB 29.1 dB
  • FB MAX: 26.1 dB 27.1 dB

Input Sensitivity for Maximum Output Power - defined as input voltage required in order to produce maximum power output reaching 1.5% THD at 1KHz: TRIODE/UL

  • FB MIN: 175mV 155mV
  • FB STD: 312mV 340mV
  • FB MAX: 480mV 566mV

Input Sensitivity for 1W into 8 ohms: 61mV 53mV

Maximum Output Power - defined as power output reaching 1.5% THD at 1KHz into 5 ohms: TRIODE UL

  • FB MIN: 18W 20W
  • FB STD: 27W 42W
  • FB MAX: 28W 46W

into 8 ohms: TRIODE UL

  • FB MIN: 14W 24W
  • FB STD: 24W 40W
  • FB MAX: 25W 41W

Signal to Noise Ratio Ref. 1W: Typically 82 dB A-WGT 20-20K

Noise Floor: Typically 150µV = -74dBu A-WGT

Noise Floor: Typically 650µV = -62dBu unweighted

Will Scratch Your Floor: Use pennies under pointed feet to avoid marring cabinetry. Try quarters if you are in upper tax brackets. The bargain performer would be nickels. Paper currency does not function as well. Euro coins work 1.54 times better. Concrete pavers or wooden chopping blocks serve fine for amplifier platforms.

Dynamic Range: 83dB

THD+Noise at 5W: less than 0.15%

Frequency Response at full power UL mode w/MAX NFB: 20 Hz to 20 kHz FLAT

Frequency Response at 5W into 5 ohms: 10 Hz to 30 kHz FLAT, -3.75dB at 100KHz

Recommended Speaker Load: Optimized for 5 ohms

Output Impedance: TRIODE / UL

  • FB MIN: 2.43 ohms TRIODE; 3.10 ohms UL
  • FB STD: 1.47 ohms TRIODE; 1.67 ohms UL
  • FB MAX: 0.90 ohms TRIODE; 0.95 ohms UL

Damping Factor: TRIODE / UL

  • FB MIN: 3.29 TRIODE; 2.58 UL
  • FB STD: 5.45 TRIODE; 4.78 UL
  • FB MAX: 8.90 TRIODE; 8.43 UL

Power Consumption (idle): 102 Watts (0.85A at 120VAC)

Maximum Power Consumption (at Full Power): 168 Watts (1.4A at 120VAC)

Operating Mains Voltage: Factory set for 100V, 120V or 220-240VAC operation for original destination country's mains voltage.

Operating Mains Voltage: changeable with power transformer re-wiring and fuse value change.

Mains Voltage Frequency: 50 ~ 60 Hz

Fuse type and ratings at 117 VAC operation: MAINS fuse 3 Amp 3AG slow-blow use glass body Littlefuse Series 239

Fuse type and ratings at 230 VAC operation: MAINS fuse 1.6 Amp 3AG slow-blow use glass body Littlefuse Series 239

B+ Fuse: MDA 400 mA SLO-BLO Ceramic Time-Delay fuse

Badge Illumination: Units produced before 3/2003 use 8V, 0.3A "Fuse-Lamp" 1/4" X 1 1/4" - Serial numbers after MAHI036 use LED illumination which probably won't burn out

Dimensions: 11" deep x 10" wide x 5" tall

Shipping weight each: 18 pounds


Official Italian dealer: to the Tempio Esoterico website

Official current price in Italy: 5,900.00 EUR

Associated equipment: to Giuseppe "MinGius" Trotto's system


Selector for standard or ultra-linear mode
Selector for standard or ultra-linear mode
Giuseppe Trotto’s listening room
Giuseppe Trotto’s listening room
Bias adjustament
Bias adjustament
EveAnna Manley’signature
EveAnna Manley’signature
Selector for the level of counter-reaction
Selector for the level of counter-reaction
ReMusic visits Manley in Chino, California, USA
ReMusic visits Manley in Chino, California, USA
ReMusic visits Manley in Chino, California, USA
ReMusic visits Manley in Chino, California, USA
Mahi monoblocks production line
Mahi monoblocks production line
EveAnna describes the production line
EveAnna describes the production line
The main area of the Manley production line
The main area of the Manley production line
Manley’s homemade transformers
Manley’s homemade transformers
by Giuseppe
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