PHAT is an acronym from the initials of Portability, Headphone, class-A, and Tube. It represents our idealism catering to what audiophiles demand for music enjoyment in the era of mobility.

Headphone has been around for more than half century. There have been lots of breakthrough and milestones in headphone technology recently, followed by release of flagship models from mainstream brand names with unprecedented audio quality. needless to say models from audiophile oriented small to medium brands.

By leveraging the high performance headphones, Phatlab is determined to duplicate the experience of hi-end stereo performance in headphones and beyond through proprietary headphone amp technology.

  • PHANTASY

    Pure Class-A Single-ended Triode Portable Headphone Amplifier

  • Sassy GT (Gold Tuned)

    Single-Ended Triode/Solid-State Hybrid Portable Headphone Amplifier

  • Sassy II

    Single-Ended Triode/Solid-State Hybrid Portable Headphone Amplifier

  • SASSY

    Hybrid Single-ended Triode Portable Headphone Amplifier

  • PHANTASY

  • SASSY GT

  • SASSY II

  • SASSY

Phatlab

Build a Portable SET (Single-Ended Triode) Amp Like Never Before!

PHAntasy is the first member of our Portable Headphone Amplifier (PHA) series. When we kicked off the development of PHAntasy, we determined to achieve two major goals; One is to preserve the true spirit and performance of SET amplifier, pure class-A, transformer coupled output and most important of all, sensational music presentation as we ever experienced on best SET amplifier, and the other is true portability with rechargeable battery via 5V USB port. We examined every detail of SET topology and audition every possible valve candidate and come up with JAN6286, a military grade directly heated triode (DHT). We examined the topology and each element of the amplifier – JAN6286 tubes, boost converter, filament supply, Battery configuration, and Passive Components - to find the best sounding components and combination. As we put them all together we ended up with The PHAntasy, a true fantasy to audiophiles.

The Heart of PHAntasy, JAN6286 Directly Heated Triode (DHT)

At the center of PHAntasy are a pair of JAN6286 valves, each one is soldered on the board and responsible for major amplification of each channel. They are well damped on the PCB and the whole enclosure provides solid chassis to isolate them from external vibration that causes microphonics.

A triode is unique as gain device that tends to generate more even harmonics than odd ones if any. The result is music sounds airy, smooth, and natural than other type of devices. JAN6286, a directly heated triode, instantly enters working condition after power on and provides intimacy and lifelike sound stage more than none filament type triode.

There is only current buffer between JAN6286 and output transformer. The buffer is highly linear and extremely low distortion that adds nothing but driving current. All circuitry are running in pure Class-A mode. JAN6286 designed for military purpose and driven by smart filament bias inherently has ultimately extensive lifespan. There is no obvious degradation of tube performance for 10 years of usage.

Supreme Iron Core

PHAntasy is a masterpiece loyal to the original spirit of SET amplifier. Its output transformer is the last mile in delivering music energy to headphone. The bandwidth, dynamics, distortion, and maximum output power are limited by this iron core. No matter how well active circuitry performs, a worse transformer will choke them all. The output transformer might be the only component that spent more effort than tube in design process. The nickel core and multiple winding transformer is a custom version dedicated for PHAntasy. Unlike home stereo SET dealing with only 16,8,4-ohm loudspeakers, PHAntasy is dealing with headphones’ impedance from 600 down to 30 ohm that complicates things even more. A choice of nickel core is to ensure widest bandwidth and minimal size for portability, otherwise, the transformer will be triple its size and weight. A multiple secondary windings are wisdom to cope with widest impedance range instead of traditional single winding multiple taps.

Simple and Beautiful

PHAntasy is a pure analog and full discrete amplifier. A frequently asked question is why we dare to reverse the trend of integrated DAC. The answer lies in our belief that SET amp is simple and beautiful. We can only make it best instead of adding an average DAC. An amplifier shall explore the full potential of headphone and gives user the freedom to formulate his/her own recipe like what we did in top-notch stereo system. The fact is that even using mobile or tablet as source playing CD-quality music, PHAntasy delivers warm and detailed music on lifelike sound stage you ever experienced.

Pure Power

The filament of directly heated triode is most sensitive to power quality. Any careless treatment or corruption of filament supply easily leads to amplified noise or distortion at output. We separate filament power supply from the rest of system starting from a dedicated battery cell for most pure supply. Though JAN6286 tube is specified for portable device, it still needs high voltage rail to operate similar to all other valves, which is good, especially when we target to drive the notorious high impedance headphone to maximum. It is a painstaking process to create high voltage from a single battery cell. The noise and regulation of boost converter are monsters to deal with in such a tiny space. Our efforts have finally paid off. Combined with smart SET topology and high efficiency booster, you hardly hear any hiss or noise with most sensitive headphones; the driving power and bass slam are realistic and stunning even on the most difficult variation of headphones’ impedance.

Smart Power

Designing a portable version of SET amp is ambitious; designing a portable tube amp with 5V DC rechargeable battery is equally challenging. For the high rail of tubes, designers usually go for battery pack (something like we use in notebook PC) with tens of volt to cope with the supply issue. There is nothing wrong with the decision as battery pack is matured and economical. The real issue is at users’ daily life. When traveling for extensive period of time, a specific high voltage adaptor needs to carry along and true portability is compromised. On the other hand, PHAntasy is rechargeable through mobile phone adaptor, power bank, and notebook PC. An even better scenario is you can listen to music while recharge, of course, with longer charging time.

Awesome Design

Inspired by team’s prior background on high-end stereo system, PHAntasy is as solid and delicate as any high-end stereo gear. The enclosure is machined from solid aluminum brick to ensure best rigidity and precision, even the bolts supporting PCB is directly grew from the chassis. The marking is laser trimmed on. There is nothing shaky or loose in PHAntasy. It is designed to last from ground up.

Specifications

Frequency Response

30 Hz – 40 kHz (-3dB)

10 Hz – 60 kHz (-6dB)

Output power

250 mW + 250 mW (300 ohm)

200 mW + 200 mW (75 ohm)

Headphone impedance

30 ohm – 600 ohm

60 ohm – 600 ohm (recommended)

Power supply

5V/1A via micro B USB port

Operation time (on battery)

Approx. 8 hours

Charging time (>1A supply)

Approx. 4 hours

Dimensions

165 mm x 95 mm x 35 mm

Net weight

750 gram

Phatlab

A portable Single-Ended Triode for Everyone Everyday

Sassy is designed for every enthusiast and audiophile who enjoy sound of SET amp while demands more portability and practicality. Sassy as 2nd member of portable headphone amplifier (PHA) series has inherits many technologies and advantages developed for PHAntasy, the bigger sibling. One may immediately notice Sassy’s extremely compact and light-weighted ever seen for a tube amplifier. The secret is elimination of output transformer and choice of high efficiency subminiature tube. A newly developed full-discrete solid-state output stage replaces costly output transformers, which is capable of delivering precise and powerful energy into headphones no matter what impedance and sensitivity.

The Heart of Sassy, JAN6418

At the center of Sassy are a pair of JAN6418 tubes, each one responsible for major amplification of left and right channels. JAN6418 is a triode-connected filament type pentode in Sassy. The main amplifier topology is Single-Ended Triode (SET) from input up to voltage gain stage to preserve sound signature of Directed Heated Triode (DHT) followed by solid-state output buffer. A triode is unique as gain device that tends to generate more even harmonics than odd ones if any. The result is music sounds airier, smoother, and richer than other type of devices. JAN6418, a directly heated tube, instantly enters working condition after power on and provides intimacy and lifelike sound stage more than none filament type tubes. Hand selected JAN6418 driven by smart filament bias has extensive lifespan. There is no obvious degradation of tube performance for 5 years.

High-fidelity solid-state output stage

The biggest difference sets Sassy apart from traditional SET amp is solid-state output stage. The effort is beyond imagination and takes much longer time to come up a viable solution with satisfactory performance. The challenge is to make it stable and consume extremely low power, while faithfully delivering SET signature of sound and plenty of energy on demand. The efforts have finally paid off. Sassy is capable of up to 20V and 1A output that is something never been done in such a small form factor. Sassy meets the balance of both worlds with sweetness of Single-Ended Triode and precise slam of power transistor. Sassy’s overall tonal balance and driving capability are comparable to best amplifiers either desktop or portable formats.

Simple and Elegant

Sassy is a pure analog and full-discrete design. We make Sassy as pure as possible by doing the best in analog domain and leave the freedom to users for choice of front end as concept in hi-end stereo. Disregard the simple connectivity and control, Sassy can handle plenty energy dynamically for any types of headphone. Users can choose whatever they prefer without concern of impedance and sensitivity, A small form factor forges Sassy’s simple and elegant look in aluminum enclosure and machined panels, yet the inside complexity and technology.

Pure and Smart Power

Sassy is capable of playing music over 10 hours on battery (*1). This is unprecedented achievement for a tube amplifier. Instead of using two batteries like PHAntasy, there is only one cell in Sassy to supply both filament bias and amplifier. A filter in front of filament supply ensures the purity of power. Careful ground planning and layout topology guarantee minimum interference between blocks. And, as always, we adopt USB port as DC 5V charging supply for best convenience and true portability.

(*1) the actual time depends on type of headphone and sound level of playback

Minimal Design

From the beginning of project, we intend to design a simple yet high performance amplifier for daily life without concern of control manipulation, trouble of carrying adaptor, choice of suitable headphones, etc. We are proud to say the goal has achieved. By leveraging the sweetness of tube and power of solid-state devices, Sassy is able to deliver touching and powerful music anytime anywhere. Following the adaptive nature of smart design, Sassy eliminates all the unnecessary switch and control. It is so much more comfortable to use Sassy without hassle, just plug and play.

Specifications

Frequency Response

10 Hz – 100 kHz

Output power

180 mW + 180 mW (300 ohm)

1000 mW + 1000 mW (30 ohm)

Headphone impedance

30 ohm – 600 ohm

Power supply

5V/1A via micro USB port

Operation time (on battery)

Approx. 10 hours (depends on headphone impedance)

Charging time (>1A supply)

Approx. 3 hours

Dimensions

119 mm x 93 mm x 23 mm

Net weight

270 gram

Phatlab

A Powerhouse refined

Ever since the debut of Sassy in 2015, everyone is astonished by its energetic performance accompanied by rich and warm sound of valves. Sassy can handle most planar magnetic and high impedance headphones by its uniquely designed tensionless hybrid topology. But there are requests from enthusiasts who hope to enjoy same sound quality and compactness with their favorite earphones. Introducing the Sassy ll, born on the expectation of many enthusiasts and beyond.

A Flexible Gain Switch for Both Headphone and Earphone

Functionally, Sassy II is equipped with a gain switch compared with Sassy. It is easy to implement gain switch in an OpAmp topology by simply changing the feedback ratios. However, it also changes the transient characteristics of amplifier that leads to sound quality changes.

On the contrary, it is not easy to add gain switch in Sassy's full discrete and zero global feedback topology. It took our engineering team months of trial and error to find the perfect solution. The mechanical switch is outside the signal path to ensure no deterioration of signal integrity and S/N ratio. We have achieved the same sound quality between two gain settings. Considering the large difference in sensitivity between general headphone and earphone, we have chosen a -10dB for low gain mode. By lowering the gain, the noise floor is also 10dB lower and there is no trace of audible noise even with most sensitive earphones.

Quieter, Purer, yet more Powerful

The improvement of Sassy II is not just plain and simple functional change. The whole physical layout and signal paths was scrutinized and reorganized. The key components were revisited for cleaner and sensational sound quality. The output stage is redesigned to cope with heavier load. The noise floor is generally below -110dB and sound quality is purer even with the most sensitive earphones.

A Superior Sassy in Every Aspect

There is always tradeoff in one way or another when we improve a good design. However, we broke the rule in Sassy II. We are proud to say Sassy II has surpass Sassy from measurable electrical parameters and sound quality.

Specifications

Frequency Response

10 Hz – 100 kHz

Output power

180 mW + 180 mW (300 ohm)

1000 mW + 1000 mW (30 ohm)

Headphone impedance

30 ohm – 600 ohm

Gain Switch

High: 0dB / Low: -10dB

Power supply

5V/1A via micro USB port

Operation time (on battery)

Approx. 10 hours (depends on headphone impedance)

Charging time (>1A supply)

Approx. 3 hours

Dimensions

119 mm x 93 mm x 23 mm

Net weight

275 gram

Phatlab

A Portable Gran Turismo Amplifier

Ever since the 2015 debut of Sassy, everyone was astonished by its energetic performance accompanied by rich and warm sound of valves. Sassy handles most planar magnetic and high impedance headphones by its uniquely designed tensionless hybrid topology. In extreme cases, Sassy may deplete its fuel due to compact power reservoir (electrical capacitance) and low biased output stage. During the development of Sassy II, we have come up with a derivative proposal to exploit the extreme potential of Sassy hybrid topology. Sassy GT is the result.

Without changing the basic topology and compactness, we revisited the design to find out the power delivery bottleneck in extreme cases. The study concluded that the two most effective factors are:

• Power reservoir, equivalent electrical capacitance, which holds the energy for instantaneous demand during highly dynamic music passages.
• Thermal stability of output stage after increasing the static biased current.

The power reservoir is doubled in Sassy GT and the output stage is covered with a thermal pad to facilitate thermal spreading and to reach thermal equilibrium. These implementations ensure dynamic performance and long term reliability. Besides the component upgrades, the vacuum tubes, JAN6418, are hand-selected among hundreds of tubes from the same batch based on the requirement of high current gain to match the newly specified high power operating point. Only 10% of tubes can pass the strict criteria.

Recommended Sassy GT Application

Just like Gran Turismo vehicle, Sassy GT consumes more power for higher driving capability. A simple comparison is; if Sassy II can run 10 hours on battery, then Sassy GT will run for 6 to 7 hours. Additionally, Sassy GT has a 3dB gain over Sassy ll. We recommend Sassy GT for audiophiles who own extremely low sensitivity headphones that demand the most from the companion amplifier.

Specifications

Frequency Response

10 Hz – 100 kHz

Output power

180 mW + 180 mW (300 ohm)

1000 mW + 1000 mW (30 ohm)

Headphone impedance

30 ohm – 600 ohm

Gain Switch

High: 0dB / Low: -10dB

Power supply

5V/1A via micro USB port

Operation time (on battery)

Approx. 6 hours (depends on headphone impedance)

Charging time (>1A supply)

Approx. 3 hours

Dimensions

119 mm x 93 mm x 23 mm

Net weight

285 gram

Phatlab

Why not include a DAC in Phatlab’s amplifers?

This may be the most frequently asked question since most of current products integrating a DAC inside. We, in Phatlab, have asked ourselves a question during product development. What is the current bottleneck of hi-end headphone system? Is it the (digital) source? Or the analog amplification? There is no easy answer to the question, but we believe the improvement on both domains can benefit the final playback. Since there are countless products and development focusing on digital source while integrated with a more or less compromised amplifier. Phatlab has determined to do best amplifier to cope with the wide impedance of headphones, especially in a battery-powered portable format that we believe is a missing link in current hi-end playback system.

Why choose single-ended triode vacuum tube as key amplification device?

As enthusiasts and manufacturer of high-end stereo system for a long time, our staff are fans of single-ended triode amplifier, even though it has extremely low output wattage and demands high sensitivity loudspeakers. Once hit, the sensational performance is second to none. When we start up Phatlab focusing on personal audio sectors, we immediately decide to adopt directly heated triode, a tube much like famous WE300B power tube but in a much smaller scale, for its unprecedented music quality.

Phatlab

Well! Here comes a question. If Sassy is as capable as described, what is the differentiation and value of PHAntasy?

PHAntasy is faithfully binding to the original spirit of SET (single-ended Triode) amplifier. The whole machine is working in pure class-A state and the output transformer is designed with taps for impedance match and handcrafted by highly experienced manufacturer. User can easily indulge himself in the traditional SET amplifier’s sensational performance. On the other hand, Sassy brings in more energetic performance and extensive bandwidth on both ends at a more straightforward and a few less sentimental styles.

How to choose between PHAntasy and Sassy?

Both are phenomenal products and rare to find equivalent on the market, especially when considering their portability and extensive battery life. However, if you consider yourself as hardcore SET audiophile, then PHAntasy might be your only choice. On the other hand, if you prefer extensive bandwidth on music playback, Sassy is the one.

What is the lifespan of vacuum tube?

The tubes used in Phatlab’s amplifiers are military grade featuring extreme long life and ruggedness. Considering their original design target and verification, they are expected to last for over 5 to 10 years under normal usage. Besides, the tubes used in our amplifiers are 100% selected for noise and electrical parameters specific for performance in audio amplification that further guarantee its quality.

Why sometimes there is ringing noise when plugging or unplugging connectors?

It is called microphonics, a specific noise induced by vibration of vacuum tubes. It is highly recommended to turn off the amplifier before connecting phone jacks. Since tube is electrical device built on mechanical structure, any vibration of internal electrodes will induced electrical noise. Though the tubes is well damped and the chassis is highly rigid to avoid excessive vibration, a direct plug or unplug of phone connectors is inevitable pose a shock to the tubes and follow-up noise.

Phatlab

Why super tweeters?

The traditional tweeter in a full range loudspeaker system usually covers a wide frequency range, generally from 2.5k to 20kHz (2-way system) or 5k to 20kHz (3-way system). Unlike the response curve from the tweeter specification that is tested with single tone (frequency) swept from low to high, the real music passage contains many tones with complex spectrum at any given moment.
When a tweeter is driven to output complex music passages, regardless of how well its design is perceived, extreme high notes critical to the musical effect of vividness and atmosphere is easily muffled by relative low frequency elements. An electronic intermodulation (IM) distortion in its mechanical form is a good example.

Why super tweeters?

The traditional tweeter in a full range loudspeaker system usually covers a wide frequency range, generally from 2.5k to 20kHz (2-way system) or 5k to 20kHz (3-way system). Unlike the response curve from the tweeter specification that is tested with single tone (frequency) swept from low to high, the real music passage contains many tones with complex spectrum at any given moment.
When a tweeter is driven to output complex music passages, regardless of how well its design is perceived, extreme high notes critical to the musical effect of vividness and atmosphere is easily muffled by relative low frequency elements. An electronic intermodulation (IM) distortion in its mechanical form is a good example.

Why super tweeters?

The traditional tweeter in a full range loudspeaker system usually covers a wide frequency range, generally from 2.5k to 20kHz (2-way system) or 5k to 20kHz (3-way system). Unlike the response curve from the tweeter specification that is tested with single tone (frequency) swept from low to high, the real music passage contains many tones with complex spectrum at any given moment.
When a tweeter is driven to output complex music passages, regardless of how well its design is perceived, extreme high notes critical to the musical effect of vividness and atmosphere is easily muffled by relative low frequency elements. An electronic intermodulation (IM) distortion in its mechanical form is a good example.

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