The 47 Laboratory 4706 Gaincard S Dual Mono Integrated Amplifier

The 47 Laboratory 4706 Gaincard S Dual Mono Integrated Amplifier


Constantine Soo

8 November 2002


4706 Gaincard Specifications:
Output power: no internal power source
Input impedance: 22k (unbalanced only)
Attenuators: 12-steps for each channel, output on and off switches for each channel
Dimensions: 170 mm W x 40 mm H x100 mm D
Price: $1,500 (plus $1,800 for one regular 4700 Power Humpty)

4700 Power Humpty “S” Specifications:
Application: Power supply for Gaincard, PiTracer & Gemini Progression 
Power Output: 50 W, 8 Ohm (25 W with regular Power Humpty) 
Dimensions: 130 mm W x 195 mm D
Weight: 20 pounds
Price: $2,500

Total System Cost: $4,000 (one Power Humpty “S”), $6,500 (two Power Humpty “S” in dual-mono power supply)

USA Distributor
Sakura Systems
2 Rocky Mountain Road
Jefferson, MA 01522
Telephone: 508-829-3426

As the Gaincard was the primary amplification in my earlier reviews ofELAC 518Loth-X BS1 and Linn Ikemi, I encourage readers to examine my findings in those pages for a broader perspective, and I shall attempt to refine my opinions on the Gaincard in these pages.

The Gaincard Preliminaries

The main body of the $3,300 47 Laboratory 4706 Integrated Amplifier “Gaincard” is of such diminutive proportion that it will invoke as much wonderment as well as puzzlement from all onlookers. Yet, in spite of its unworldly smallness, the Gaincard is meant to be 47 Laboratory’s prime amplification device, complementing its own $25,000 PiTracer CD Transport, the pride of Mr. Junji Kimura, the company’s proprietor and designer. For readers who are interested in the company background, please refer to my commentary.

In compliance with his design philosophy of “Only The Simplest Can Accommodate The Most Complex,” Mr. Kimura finalized on a version of the Gaincard by framing two miniature monaural input/out modules together via a front and rear rail bar. A unique and genuine dual mono design, each module sports a rotary gain control, a power switch, a single RCA input and one pair of screw-down speaker terminals. The terminals are designed to accept light spade terminations only, negating the banana termination. 47 Lab also offers the $700 RCA-only 4707 six-input “Input Chooser” to supplement the Gaincard in a system with multiple sources.

Via a pair of meter-long umbilical cords, the isolated Gaincard draws power from a 25 Wpc or 50 Wpc version of the 20 pound, outboard custom cylindrical 2-channel power supply unit named Power Humpty, and Power Humpty S. The PH has no power switch and remains powered on once plugged in. As long as the PH continues to supply power, turning off the Gaincard will only disengage power output, and the chassis will remain warm to the touch until the umbilical cords are pulled. Readers can add a second PH of the same output to facilitate dual mono operations. 47 Laboratory’s exclusive U.S. importer, Mr. Yoshi Segoshi of Sakura Systems, sent me a Gaincard with two of the more powerful, 50 Wpc PH S for dual mono amplification.

The Gaincard Perspective

In addition to the 3 reviewed pieces mentioned at the top, four other speakers were also rotated for pairing with the Gaincard S. In order of efficiency, they were the 104 dB/8 Ohm Klipschorn, the 94 dB/8 Ohm bi-wired Audio Note AN/E SEC Silver, the 90 dB/6 Ohm Genesis VI and the 82 dB/8 Ohm bi-wired Celestion SL700. The Audio Note M3 preamplifier provided the crucial additional gain for the Gaincard when bi-wiring the 89 dB/4 Ohm ELAC 518. 

Five pairs of interconnects were rotated with the Gaincard, including the 1.5-meter Virtual Dynamics Nite, my Granite Audio #470, the Audio Note AN-V, the Aural Symphonics AS-One and the Kimber PBJ. Speaker cables were my Cardas Quadlink 5C, Virtual Dynamics’ top-of-the-line “Nite Series” and my Tara Labs Phase II TFA Return. Other fine speaker cables, such as the Audio Note AN-La, AN-SPx and my Van den Hul MCD-352 have banana terminations at the amplifier end and were therefore unfortunately excluded from this review.

The Gaincard’s dual-mono channel separation was among the most discrete and elaborate in implementation I have seen. The resultant midrange was extremely resolute in rendition of instrumental and vocal energy, with tremendous upward extension clarity most appreciable with the voices of acoustic instruments. Switching digital sources between my 47 Lab Flatfish/Progression and the Linn Ikemi exhibited the absence of intrinsic subjectivity from within the Gaincard. 

Playing the CDs “The Famous Sound of Three Blind Mice” [TBM-XR-9001], the Gaincard’s discernment of Dame Ayako Hosokawa’s vocal on the “Bridge Over Troubled Water” between the two digital front ends was revelatory. While the singing voice from the 47 Lab’s was meticulous and yet energetic, it was rich in tone and smooth in texture when compared to the Linn. In “Face to Face” [JVC VDJ-1198] from fusion jazz trumpeter Tiger Okoshi, the 47 Lab Flatfish/Progression deciphering of the Tiger trumpet produced tremendous harmonic sophistication with a most immaculate polish, very fitting for the necessary conveyance of the trumpet’s sheen. In retrospect, the Gaincard allowed the Linn Ikemi’s formidable ability of spatiality to blossom, giving rise to enormous spatial cues on the locale and body of the brass solo. 

Certainly, JVC’s exclusive Extended Definition CD (XRCD) 20-bit K2 Super Coding process on both CDs played an integral role in the playback excellence. In particular, the ELAC 518’s JET tweeter revealed the Gaincard’s top-end delicacy most beautifully.

While speaker efficiency was of paramount importance in consideration of the Gaincard’s limited current capacity, the result was every bit as breathtaking, as long it was driving speakers with impedance nearing 8 Ohms, such as the 104 dB Klipschorn or the 82 dB Celestion SL700.

For instance, via the Celestion SL700, the Gaincard’s renditions of “A Night on Bald Mountain” from The Stokowski Sound [Telarc CD-80129], and “Don Juan” from Karajan Gold [DG 439 016-2 or BMG D 134748], revealed its solid-state vigor with potent transients that were crafted with precision. Seemingly insurmountable mass of tonalities were mobilized with an unbelievable agility from the little 47 Lab, lending the music liveliness from the fast transients, and in doing so, portrayed the strings and brass cunningly with sophisticated textures. While the Klipschorn represented a perfect load for the Gaincard, I was surprised by its success with the otherwise inefficient 82 dB Celestion SL700 in the combo’s creation of lofty dynamics as well as lingering subtleties.

Timbral definition on featured instruments was highly acute, whether it was projecting a piano solo from 33 Variations on a Waltz by Anton Diabelli [DG 289 459 645-2], or a highlight on a flute amidst a lively full orchestra on James Galway Plays Khachaturian [RCA RCD1-7010], with image stability to boast. In the case of the James Galway CD, there were well-delineated contrasts between the soloist and the accompanying orchestra.

On Gaincard’s Idiosyncrasies

The Gaincard is extremely functionality-derived, and unusually idiosyncratic in operation. Its 12-step attenuation occasionally incapacitated optimal volume control when used in conjunction with a high output source such as Audio Note’s DAC One 1x Signature. The output differences between steps became too great. DAC’s with average output, such as the Progression DAC, represent a far better match, facilitating finer volume settings. 

The minimalist execution of the Gaincard also represented a regular regimen for me in connecting and disconnecting interconnects and speaker cables to the rear panel. Its screw-down speaker terminals were utterly difficult to use, as it would not accept banana terminations. 

Because of the singular RCA provision, the act of attaching interconnects capsized the diminutive Gaincard frequently for its lack of mass, and the pulling forces of inserted, sizable interconnects and speaker cables alike on its rear panel constantly lifted and displaced the unit. Despite the fact that the unsightly uplifted Gaincard performed without detriment, I stabilized it with a 5-pound dumbbell initially, a measure that quickly became inadequate when more substantial cables were used, such as the Virtual Dynamics’. Although the Gaincard could fit more comfortably into a home than its full-size American cousins, I was stricken by the realization of nowadays’ preamplifiers’ necessity to have considerable dimensions and weight to form a universal compatibility with many of the fantastic but massive cables. I am open to different suggestions for stabilizing the Gaincard rather than using my unsightly dumbbell. 

47 Lab sent me their OTA cable that is meant for use with the Gaincard, ameliorating the capsizing abnormality. Adhering to Mr. Kimura’s ideal, the OTA is a single strand of 0.4 mm oxygen-free copper wire named “Stratos”, housed in a transparent plastic tubing which is devoid of complex constructions and networks, rendering the body extremely light and flexible. The OTA is intended to be used ubiquitously as both interconnects and speaker cables, whereas in the latter application, users are to strip off the jacket for bare speaker connection. 

For use as interconnects, Mr. Kimura’s OTA was a most interesting solution to connector-related signal degradation, by substituting the traditional RCA with two non-conductive, machined individual plastic plugs. Two runs of the Stratos make one channel, with the first run wrapping around the plastic center pin plug, and the second run on the outer ring plug. When the center pin plug is positioned through the central opening of the ring plug, resembling the standard, one-piece RCA connector, signal transfer takes place with a theoretically unprecedented level of signal retention.

Despite the elegant and visually appealing solution offered by the OTA in connection with the featherweight Gaincard, it is sonically inferior to my GA #470 and Cardas Quadlink 5C. The benefits introduced by the 2-piece plastic plugs are summarily offset by the limitations of a thin strand of copper. 

In summary, the design is faced with two primary dilemmas; the open architecture subjects signals in transit to airwaves and electrical interference and the open architecture incapacitates the use of choice audiophile metal, namely silver, as the design subjects the metal to oxidation.

For high-end considerations, the OTA cannot compete with the likes of silver. May I remind Mr. Kimura that silver’s atomic number is 47?


The Gaincard is the triumphant materialization of an ingenious concept, achieving the supreme goal of eradication of intrinsic signal contamination. Its incredible reactivity to changes in upstream components, whether it is cables or equipment, is the most exemplary among all amplifiers I have ever used so far, making it a reviewer’s most indispensable tool.

In creating his own amplifier, the 4705 Gaincard, Mr. Junji Kimura of 47 Laboratory capitalized on the singular design concept of minimization, including number of parts, length of signal path, amount of negative feedback, size of filter and condenser employed, functionality and the dimensions of the device itself. His highly original and methodical concepts in mechanical stress management, circuitry simplification and power supply segregation reflect an evolved, meticulously implemented simplicity from complex origins. 

The Gaincard’s exceptional, unprecedented fidelity to the changes in dynamic transients and tonal complexities is in contrast to my reference preamplifier, the Audio Note M3, in its signal-nurturing nature. While the M3 endeavors to preserve signal integrity by means of active power coupling and by routing the signals through premium components, the 47 Lab adopted utmost simplicity. Nevertheless, Mr. Kimura’s passive preservation of all the subtleties and power of the original signal represents one extreme, but fruitful, implementation in amplification. And most of all, although the Gaincard S’ methodology differs from that of the M3 in its supreme ability of instrument totality preservation, the 47 Lab is nevertheless capable of such superb tonal delicacy via its power amplification stage that it defies summary dismissal from either transistor or tube enthusiasts. 

The Gaincard is not a solid-state user’s alternative for a more tube-like sound; neither is it for those of us that are adamant of a certain solid-state or tube sonic preference. Audiophiles favoring single-ended tube devices and solid-state amplifiers steeply biased into class A will most likely find the 47 Lab bland to their tastes, because it does not have the vividness of the 300B, single-ended sound or the punch of powerful solid-state. Retrospectively, the Gaincard sound represents extremes in unpredictability and excitability. 

While I believe Mr. Kimura’s chassis stress management technique plays a vital role in the excellence of the Flatfish CD transport and Progression DAC, I feel the more profound factors attributing towards the Gaincard’s excellence are its unique channels and power supplies segregation and signal transfer handling. 

Therefore, for a $700 difference between the 50 Wpc Gaincard S and the 25 Wpc Gaincard, unless an audiophile intends to utilize minimal output to drive his or her speakers, the $4,000 Gaincard/Power Humpty S with twice the power over the $3,300 standard Gaincard is a worthy consideration. When coupled to a high efficiency speaker, the single-PH Gaincard was already capable of extremely meticulous handling of transients and tonal shadings, according some of the most resolute top-end rendition I’ve heard to date in its delicacy and texturing.

In terms of fidelity, the $4,000 25 Wpc 47 Lab Gaincard S is just as worthy an amplifier to the AN M3 as its own $4,000, 9 Wpc Quest 300B monoblocks, and I have yet to hear a preamplifier/amplifier combination at $4,000 possessing comparable finesse. One simply has to experience the 47 Lab’s rendition of music, in its very lovely flirtation of signal delicacy and cunning and unswerving reaction to changes in dynamics, to appreciate the efforts of Mr. Junji Kimura. In a market filled with comparably priced SET’s, the $4,000 Gaincard S is the “one-in-a-million” solid-state alternative. 

Adding the extra Power Humpty S for a dual-mono power supply configuration pushed the performance envelope further, with the most notable gains in dynamic contrasts and scale even when driving efficient speakers. While endowing extra drive capability and superior channel separation, the addition of a second PH S transforms the Gaincard S into a staggering $6,500 amplification system. 

Unlike most other comparably-priced amplifiers, the Gaincard S will not mate well with speakers of a 4-Ohm impedance rating or below, in which case the $6,500 is better spent on amplifiers that are more functional, more user-friendly and have 5 times the output power. Therefore, justification of buying the 50 Wpc, dual mono Gaincard S will be an utmost appreciation of its aforementioned level of fidelity. 

The fact that the twin-PH Gaincard S was able to drive all aforementioned speakers on its own to beautiful fruition, but required the additional gain of the AN M3 preamplifier only when driving the 89 dB/4 Ohm ELAC 518, was indicative of incompatibility with speaker impedance below 6 Ohms. The Gaincard chassis was burning hot when driving the 6-Ohm Genesis VI, and was possibly at its most linear when driving the Celestion SL700, because at a near-limit 4 o’clock volume setting, it was able to induce from the minimonitors thunderous dynamics in a stable soundstage. In retrospect, the M3/Gaincard S collaboration had tremendous merits, creating the most detailed and communicative presentations I’ve ever heard in terms of dimensionality, image specificity, timbral delicacy, tonal abundance and resolution. 

With sonic dispositions as ideal as the Gaincard’s for use as a reviewer’s tool, I concede that the Dream Gaincard would be one with chassis measuring 10-inch long, 5-inch high, 10-inch deep, 30lb heavy, 3-input selectivity and, most importantly, high-quality 5-way speaker binding posts! And Mr. Kimura, will you consider utilizing a vacuum-sealed silver-contact infinite volume control with a big dial on the front? 

Once in a while, a visionary will come among us and introduce an idea that will whet our expectations and perceptions. This time, Mr. Kimura represented one more stunn.

Manufacturer’s Response

Dear Stereo Times and Mr. Constantine Soo:

Thank you very much for the very accurate portrayal of 47 Laboratory Gaincard S. Mr. Soo’s crisp description of what it does and doesn’t do, in contrast to the flood of dogmatic review styles with ambiguous praise, is very refreshing. 

As Mr. Soo correctly pointed out, Gaincard is unusual in its design, both technically and cosmetically, and idiosyncratic in its user interface. However, behind those unusual and idiosyncratic appearances lies Junji Kimura’s uncompromising design philosophy and logic. He has eliminated the heavy-duty speaker terminal through which the signal has to go through the plating and a chunk of metal (always a source of energy storage). The rigid and compact structure of the casing allows the quick release of unwanted resonance. The volume pot can be tailored to the customers’ request, but so far we have had only one customer who has thought that it was necessary.

We didn’t realize that silver’s atomic number is 47! Although silver is superior than copper in its electrical conductivity, how it translates to the resulting sound is a different issue, and Junji believes it’s more a matter of taste and not whether one is better than the other. But if I tell him about the atomic number of 47, well, he may change everything to silver!

Mr. Soo’s conclusion about OTA cable is somewhat puzzling to us. OTA cable kit is our best selling product and over a hundred of customers seem truly satisfied with its performance. It is not designed specifically to use with 47 components. One customer use it happily in his Esoteric P-0 transport-dCS Elger DAC-Lamm pre and power amplifier-Wilson Grand Slam system.

  1. The simple construction (what Mr. Soo calls “open architecture”) of OTA cable does not subject the signals in transit to airwaves and electrical interference any more than any other unshielded cables. Airwaves and electrical interference has to be dealt electrically rather than mechanically. When considering material resonance and vibrations, heavy jacket and construction works as a damping, making and storing more complex modulations.

  2. The open architecture does not incapacitate the use of metal of audiophile choice. You can use a silver cable with the same diameter (0.4mm) with OTA plugs. Be it copper or silver, oxidation occurs when exposed to the air. To prevent it, terminals are usually plated, another source of modulation. We just deal with it by cleaning or peeling a new tip of the cable.

The cable used in OTA was originally developed by one of the major telecommunication companies in Japan and was modified to 47’s specification. As of today, nobody exactly knows how the signal acts in different types of cables and how it’s related to what we hear in the resulting sound. OTA cable was chosen by 47 Lab after an extensive listening session with different types and configurations of cables. It is very fast and very coherent sounding. 47 Lab does not/can not say why it sounds the way it does (they say they can only speculate), nor do they say it’s the best cable in the market, but we believe it is one of the best sounding cables regardless of the price, and one of the biggest bargains on the market.

Thank you very much again,

(47 Laboratory US distributor)

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