GW Labs 270 Tube Amplifier

GW Labs 270 Tube Amplifier

Constantine Soo

1 June 2001


Power Output: 70W/channel RMS, 20 Hz-20 kHz 8 ohm
Frequency Response: 10 Hz – 80 kHz
THD+N: 0.65% / 1 kHz / 70W / 8 ohm
Input Impedance: 150 kOhm
Input Sensitivity: 0.775V RMS / 1 kHz / 70W / 8 ohm
Tubes: 12AX7 × 2; 12AT7 × 2; SV6550C x 4
Power: 110-120 / 220-240 VAC, 50 / 60 Hz, 420W maximum
Dimensions: 15.5″ (39.4cm) W × 7″ (17.8cm) H × 14″ (35.6cm) D
Weight: 31 lbs (14.1kg) net/ 35 lbs (15.9 kg) shipping
Warranty: 2 years limited parts and labor; 3 months on tubes
The GW Labs 270 is a 70 wpc, push-pull tube amplifier with an MSRP of $2,450.

CII Centasound International Inc.
PO Box 210377, San Francisco, CA 94121
Tel: 415.668.9003
Fax: 415.668.9638

GW Labs 270The proprietor and designer, Mr. Godfrey Wang, holds a law degree from England and worked in the Hong Kong Finance sector before he came to the U.S. Currently, he pursues other interests in the U.S., with high-end tube amplifier design being one of them. There is a limited but growing number of dealerships for his products. AudioGon, an internet store, handles the sales of his Cyclops, a minuscule, zero-feedback, low-powered integrated amplifier. Readers who live in areas with no GW Labs dealers may contact Mr. Wang for direct orders. There is a 10-day return policy.

Mr. Wang looks at reliability as the most important design element of his products. He believes that sound quality is of secondary importance to reliability.

When I asked if GW Labs would make pure triode amplifiers, Mr. Wang replied negatively. He considers the market for the limited output capability of a pure triode amplifier too specialized. I agreed. I believe Mr. Wang would be in a better position to address the particular needs of the “Triode Guild” once his core business is well established.

Although I am not a feverish proponent of tube amplification, I do have a Music Reference RM9 II of Ram Labs’ Roger Modjeski fame as my long-term reference. An Audio Research D76a tube amplifier also served me well for quite a while before I sold it for a Krell KST-100. Although I am using a pair of the Monarchy Audio SM-70 as monoblocks in my system, the RM9 II remains semi-active and is put to use whenever the need arises. It is the age-old debate of tube vs. solid-state. Purveyors of each design’s state of the art offer valid opinions regarding the beauties and strengths of either. However, since the job of an amplifier is to amplify the incoming signal with maximum integrity, in my opinion, progress will some day have the best from solid-state and tubed amplification designs arriving at an impasse where either yields the same sonic accomplishments.

The Amplifier

GW Labs 270 back viewThe GW Labs 270 chassis bears a striking resemblance to that of the renowned Golden Tube Audio SE40. Having no affiliation with the husband and wife team who owned and operated the Golden Tube Audio, GW Lab contracted the shop that serviced GTA for its chassis design. This is where the resemblance ends.

The GW Lab 270 sports two 6550 output tubes per channel. Two 12AX7s and two 12AT7s act as driver tubes. Original product literature describes the 270 as running in triode for the input and ultra-linear push-pull for the output.

The front panel has only a rocker power switch, and the back panel provides five-way binding posts for 0 (negative), 4 and 8 ohms impedance connection. Only RCA inputs are provided. The power cord is detachable. As of this writing, a cage is not available as an option.

This amplifier features a soft-start process, during which initial power-on heats the filaments without powering up the tubes in the first 45-55 seconds. According to Mr. Wang, this prevents electrical jolts, which would curtail the tubes’ useful lives. I enjoyed watching the 270 switch over from soft-start to full power, the output tubes changing from amber at soft-start to amber with blue.

Other interesting features include two “double C-core” output transformers, a non-magnetic aluminum chassis, a .375-inch brushed and anodized aluminum front panel, polypropylene coupling and bypass capacitors, and close tolerance (1 & 2%) film resistors.

Preliminary Outline

Because of the even-order harmonic distortion tube amplifiers produce when pushed hard – sonically less prominent than the odd-order distortions of transistor amplifiers – one tube watt can sound as loud as two transistor watts.

The GW Labs 270 initially drove several pairs of loudspeakers for comparison. Then I decided on concentrating this review on two: the Apogee Duetta Signature and the Celestion SL700. These represent different levels of inefficiency, the Apogee being the less efficient. This should provide the most informative glimpse into the potential and shortcomings of the GW Labs 270.

I had developed a guilty conscience over my long-term loan of the GW Labs 270. My heartfelt thank-you goes to Mr. Godfrey Wang for his seemingly endless patience. But did I have fun!

Audition 1: Driving the Celestion SL700

At 82dB/w/m and 8-ohm impedance, the inefficient Celestion SL700s require a high-wattage amplifier to properly drive them. The Celestions are bi-wired.

When I purchased the Celestions in 1993, I used a Krell KST-100 power amplifier with the KSL-2 line stage to drive them. Although this matching had dynamic power, it was only marginally musical. The soundstaging was barely perceptible; the sound, mechanical and edgy, at high volumes was almost repellent. I replaced the Krell KST-100 with a Stereophile-recommended Music Reference RM9 II. At an output of 125wpc, it utilized four EL34s for each channel and three feedback settings. Running at the highest output/lowest feedback setting, it brought out a new degree of transparency and dimensionality to my SL700s. In addition, tonalities became more discernible, with textural edginess largely eliminated.

The GW Labs 270, being a tube-based design as well, bears an audibly different approach from ordinary tube amplification. It also runs much hotter than the Music Reference RM9 II, despite its fewer tubes.

I played progressively louder until the Krell KRC-2’s volume control in high-gain mode reached the 12 o’clock position. At that point, the dynamics and loudness produced were among the most extreme I had ever heard from the Celestions. The 270-driven Celestions actually played loud without strain. The seemingly fragile, one-inch dome tweeter revealed every detail with volume to spare.

Amplified by the 270, the towering dynamics and heart-stopping transients in A Night On the Bald Mountain (The Stokowski Sound, Telarc CD-80129) revealed an incisiveness not heard from the Music Reference RM9 II. However, the RM9II made the strings sounded distinctively smoother and airier, while the 270 offered added focus on individual instruments. The sounding of the morning bell at the end of the track received a more lingering treatment by the RM9 II over the 270 – well after the orchestra faded away.

Track 2, “Dies irae,” of the Sony SACD Verdi Requiem (Sony SS 707) captured the engulfing effect of hall ambience. The SACD’s superior resolution enabled a bandwidth with information at both ends of the spectrum in such abundance that, although systems with limited bandwidth may retain their midrange prominence, they would seriously truncate the accompanying dynamics and ambience. Devoid of compression and eerie sonic artifacts, the 270-driven Celestions excited the air around them with definition and upward extension.

At the bottom end, the 270 actually allowed the SL700 to sound more solid than my 125-wpc Music Reference RM9 IIs. For a clearer perspective: the Celestions’ 6.5-inch Cobex woofer is renowned for its macrodynamic capability and punch. Spontaneous bursts of in-room energy in the low 50Hz can be generated. In my audition, I would hesitate to claim a high 30-Hz extension in the absence of actual on-site measurements of these mini-monitors. However, the bass drum’s hellish strokes nearing the end of A Night On the Bald Mountain unleashed the kind of bass response the Celestions are not supposed to to attain.

To further illustrate the GW Labs’ power coupled to the Celestions: the “Dies irae” from the same Sony SACD depicts Judgement Day in all its might. The famous introductory bass-drum blows convey the fury and devastation of the end of the world with destructive fury. It’s a wonder the drum actually survived the performance. An overwhelming current of overtones further enhanced the instrument’s realism. At an 11-o’clock volume setting, the immensity of the power the SACD released, as empowered by a stable 270, almost pulverized the 6.5inch Cobex cones.

In retrospect, the 6.5inch woofer could not roll out the undercurrents of full-range systems, as evident in the synthesizer’s driving bottom octave in “Incident at Isla Nablar” (Soundtrack of “Jurassic Park,” MCAD-10859). However, both quality and quantity of the Celestions’ bass in conjunction with the 270 was consistently superior to that of my RM9 II. This level of performance from the Celestion SL700 as enabled by the 270 was not only surprising but also gratifying. Every time a pair of so-called mini-monitors exhibits their ability to produce devastating dynamics, we know that the audiophile doesn’t need a huge room in order to attain musical nirvana on a realistic scale.

Audition 2: Apogee Duetta Signature

The next speakers I put the GW Labs through were the Apogee Duetta Signatures. At 86dB/w measured at 3m distance, and with 4ohms average impedance, the Apogees feature two 5-foot-tall panels, each containing large, air-vibrating ribbon areas. Most Apogee users rely on high-current solid-state amplifiers, like products from Krell, Aragon, Threshold and Forte, to name a few, for providing adequate volume and driver control for their speakers. For more information, check out the Apogee Speaker Users Website at

The Duetta Signatures facilitates bi-wiring and bi-amping functions. Its own passive crossovers cut off frequencies at 1000Hz. The terminal also allows users to control the ribbon tweeter output at the levels of Low, Normal and High. Driving the Apogees’ tweeters with different amplifiers revealed interesting results.

I used an Aragon 2004 to drive the full-range Apogees to very high volumes without audible distortions. The Aragon put out 200 wpc at 4 ohms, exerting adequate control over the bass ribbons. The result is one of weight and speed. The rather mild top end of the Aragon also nicely compliments the Apogees’ high tweeter output setting. Imaging is acceptable in terms of soundstage stability and width, but areas I find wanting are sharper images, deeper soundstaging and richer ambience.

Despite the aforementioned Aragon shortcomings, the Apogees, with their adult-height ribbons, nevertheless demonstrate themselves as soundstaging champions, capable of three dimensionality surpassing even that of the Celestion SL700. That dimensionality became more prominent when the GW Labs 270 replaced the Aragon. In addition to tube amplifiers’ well-known dimensionality capabilities, another contribution was the 270’s top-end extension. Instrument placement was specific and well defined on the vertical and horizontal planes.

By the same token, the high ribbon-tweeter setting sounded overly bright with instruments like triangles and cymbals. Violins and brasses also exhibited an extra degree of sharpness. Resetting the tweeter level to normal or sometimes low alleviated the symptom. The setback was a loss of soundstaging finesse. Even so, the Apogees still excelled in lateral and horizontal soundstage portrayal.

Noteworthy again was the 270’s ability in bass control. The same cut from Jurassic Park received a more thorough treatment. With the Apogees’ full-range capability, the synthesizer’s bass notes were clear and full-bodied. The Apogees, with their 30-Hz low end limit, sustained the rumbling notes. The 270 was surprising competent in energizing the ribbons at their bottom end.

The 270-driven Apogees also did well in the areas of mid-range transparency and soundstaging. Image localization was impressively three dimensional for most recordings. However, at screamingly realistic sound levels, noticeable soundstage deterioration developed when relentless dynamic contents were being fed. When playing the SACD track “Dies irae,” the bass drum information drained the resources of the 270, infecting the entire performance. Not only did soundstaging suffer in terms of loss of definition, instrument imaging smeared and macrodynamics compressed.

Substituting the GW Labs with the Music Reference mitigated the problem. Though not as extended at the frequency extremes as the 270, the RM9 II carried the performance through all challenges with ease. Power became the key in this instance.

Another trade off: the Apogees’ imaging sounded closer when amplified by the Music Reference, whereas the GW Labs took the listener a few rows back. I prefer the GW Labs’ character because orchestral passages as produced by the 270 sound more spectacular in my listening room. You may opt for the proximity offered by the Music Reference and find it more enjoyable. In fact, I believe my room may be too small to realize what a more powerful combo like RM9 II and Apogees can do.

Apogee’s Website features users’ viewpoints and experiences in getting the best out of these speakers. The forum’s most prevalent and admired amplifiers are the Krells and Thresholds, high-power, high-current, microwave-size amplifiers.


At an MSRP of $2,450, the GW Labs 270 should appeal to budget-minded audiophiles.

The 270 has a cunning ability to drive less efficient speakers to very high volumes before strain or distortions become obvious. Its unique, transistor-like stability preserves the recorded frequency spectrum while its tubey heart precludes transistor-like and ugly odd-order harmonic distortions.

The 270’s midrange reveals the purity one would expect from a tube design. However, there isn’t a hint of the typically soft and tubey sound. In fact, the amp sounds quite modern, with its extended frequency response and superb analytical ability. Information like soundstaging, frequency extensions, transient attacks are all produced with glory and flare at very high decibels. I suspect the 270’s dual “double C-core” output transformers are the contributing element in its ability to deliver full power at all frequencies. This type of transformer ability in delivering perpetual, uncompressed power at 18kHz and above is vastly superior to the regular EI transformers, which run out of power almost entirely at that range.

In the case of my Celestion SL700, the 270 was able to drive them to extremely high sound pressure levels without strain. Remembering how the solid-state Krell KST-100 fared in my system, I believe the GW Labs 270’s fundamental tube design – in conjunction with the dual “double C-core” output transformers – allowed the delivery of full power into inert loads, while maintaining equal signal transparency throughout the frequency spectrum.

Given the performance of the GW Labs 270 in the company of my inefficient Celestion SL700, I can imagine how more fantastic my Apogee Duetta Signatures would sound like with two 270s bridged into monoblock operations. My ongoing schedule prevented me from trying that; but I hope there is a chance of doing this in the future.

Regarding monoblock configuration, the utilization of output transformers in tube amplifiers enables reconfiguration by the user, to make two similar amplifiers function as monoblocks. Contact Mr. Wang for easy user-friendly configuration details.

The sonic signature of the original 6550 tubes may not appeal to all tastes. Sonic characteristics will change considerably with compatible tubes, such as KT-88 or KT-90. Seriously interested readers may also want to check out the premium 6550 variety from a European maker named Electro-Harmonix.

The one important aspect of acquiring the GW Labs 270 is the means to match it with a high-output preamplifier. This is particularly important if inefficient speakers are to be driven. It was the high-gain mode of my Krell KRC-2 that played a pivotal role in extracting the best out of my Celestion SL700. Therefore, for the power of the 270 to be fully appreciated, a high-output preamplifier is recommended.

Current owners of the Celestion SL700 and inefficient mini-monitors alike should give the GW Labs 270 a try just to experience the extraordinary dynamics and musicality accorded. For readers who have other kinds of exotic, inefficient speakers, a pair of 270s will probably fall into your budget for amplifiers. As monoblocks, the GW Labs 270s will drive some of the most difficult loudspeakers to very realistic levels in the glories of tube purity and spectral integrity.

Tube amplifiers have not been my usual preference for the most part – the maintenance-free aspect of solid-state amplifiers holds a good chunk of my votes of approval. However, Roger Modjeski’s Ram Labs Music Reference RM9 II, and now Godfrey Wang’s GW Labs 270, proved their designers’ genius profoundly in both their asking price and the excellence of the performance.

In my opinion, readers who favor jazz music will likely find the GW Labs 270’s evenness of clean-cut precision instrumental in portraying an energetic performance. Its orchestral music rendition is characterized by wide bandwidth interpretation. The RM9 II’s orchestral music portrayal has more of the tube’s emphasis in tonal beauty as opposed to the 270’s extended bandwidth.

Ladies and gentlemen, this could be the beginning of a new generation of “advanced” tube amplifiers.

My next review is on the diminutive Decware SE84C triode single-ended class A tube amplifier. It will be interesting to see how the dominating Klipschorns will sound as driven by this modest-looking design.

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