A high-resolution headphone amplifier backpack that provides true audiophile power for smartphones, and more.
The Tea headphone DAC/amp is Khadas’ new ultraslim headphone amplifier for smartphones, still on pre-sale at the time of this publication. It is designed for users to be able to listen to high-definition music and lossless streaming audio directly from an iPhone or Android smartphone.
Opening the box and feeling the Tea in real life is a “wow” experience, as this is a clear innovation in form factor and attachment (magnetic!) for this sort of device. Until now, most options have been limited to dongles or portable DAC/amp combo units ranging in size from small to large. In order to mate them with a phone, a user could tape, glue, or rubber band them together in some way.
Most of these options are quite unappealing.
The Tea, like the bigger brother Tone2 Pro which I reviewed last year, feels remarkably solid and pleasingly substantial for something so small. The saturation of color in the metal housing is excellent and consistent. The fit and finish alone inspire confidence.
Khadas (Khadas Technology Co., Ltd.) focuses on developing, manufacturing, and marketing superior quality, high-performance Amlogic and Rockchip single-board computers (SBCs) for the open-source community and streaming media player industry. Most recently, Khadas added audio products to their lineup, including the Tone2 Pro Hi-Fi DAC and Khadas balanced RCA connectors. Their parent company, Shenzhen Wesion Technology Co., Ltd. was founded in 2014.
- Form: Ultraslim Hi-Res headphone amplifier for smartphones
- Connectivity: USB-C 2.0, 3.5mm headphone jack
- USB DAC: ESS ES9281AC Pro DAC
- Bluetooth: Qualcomm QCC5125
- Audio Formats:
- USB: MQA (Renderer), AAC, FLAC, APE, WMA, WAV, OGG, MP3
- Bluetooth: SBC, AAC, Sony LDAC, Qualcomm aptX, aptX Low Latency, and aptX HD
- Headphone Amplifier: RT6863D (Buffer Stage)
- Headphone Amplifier Performance:
- Output: 3.5mm Headphone
- Output Impedance: <0.3Ω
- THD+N, 1kHz, 300Ω: 0.000355% (-109dB)
- THD+N, 1kHz, 150Ω: 0.000355% (-109dB)
- THD+N, 1kHz, 32Ω: 0.000447% (-107dB)
- THD+N, 1kHz, 16Ω: 0.000708% (-103dB)
- Noise: < 3.2uVrms
- SNR, high-gain mode: 116dB
- SNR, low-gain mode: 112dB
- DNR, high-gain mode: 115dB
- DNR, low-gain mode: 111dB
- Max Output @300Ω: 20.8mW (2.5Vrms)
- Max Output @150Ω: 42.7mW (2.5Vrms)
- Max Output @32Ω: 165mW (2.3Vrms)
- Max Output @16Ω: 130mW (1.44Vrms)
- Crosstalk, 600Ω: > 113dB
- Crosstalk, 32Ω: > 70dB
- Frequency Response: 20Hz～20kHz: ±0.05dB
- Output: 3.5mm Headphone
- Sampling Rate:
- USB Input: PCM up to 32bit, 384kHz
- USB Input: DSD 256 (Native)
- Bluetooth: up to 24bit, 96kHz
- O/S Compatibility: iOS, iPadOS, macOS, Linux (with UAC2 compliant kernel), Android (supports OTG function), Windows 7, 8, 10, 11 (Khadas USB ASIO driver required)
- Rated Voltage: DC 5V
- Power and Battery: DC
- 1160 mAh rechargeable lithium polymer battery; up to 8 hours of continuous music playback
- Lithium polymer battery: CB, KC, UL, PSE, UN38.3
- CE, FCC, KC, TELEC, SRRC, RoHS
- Sony LDAC, Qualcomm aptX, MQA, and Apple MFi 3.0
- Size: 95.5mm (l) x 63.8mm (w) x 6.25mm (thickness min) / 7.95mm (thickness max)
- Weight: 73.5 grams
- Warranty: 1 year limited hardware warranty
The Tea is housed in a small, tidy, well-constructed premium two-piece white box with pictures of the Tea from each side on corresponding sides of the box. Inside and under the top cover is the device, under which are the cables and documentation.
In the box
- Lightning to USB-C Cable for iOS devices (0.1m with plugs, data only); MiFi Certified
- USB Type-C to C cable for Android devices (0.1m with plugs, data + power)
- Instruction manual and one-year limited warranty card
The housing is impressive and feels entirely premium, with no harsh edges or obvious imperfections. This “Teal Blue” unit is made from one piece of CNC-machined anodized aluminum, covered with anti-glare tempered glass. It is quite slim and lightweight despite its material strength.
Khadas has specifically identified Apple users as their target. What makes this device so unique is its form factor and perfect pairing with newer iPhones – they match beautifully. The back is flat and ensures a solid magnetic connection to an iPhone 12 or 13 series (MagSafe built-in) or an older iPhone equipped with a MagSafe accessory case.
The front side has raised areas, one for the battery, another for the printed circuit board (PCB) with DAC and Bluetooth chips, and a third that houses the headphone jack. The left side button is for powering the Tea on and off and can manage play functions. The right side has two easy to feel volume up and down buttons. Everything feels tight and secure, with the buttons providing firm tactile feedback.
While I have not been bold or unfortunate enough to test its impact resistance, the Tea seems like it will handle some impact without excessive damage. Keep in mind that it does not have a case nor a rubberized coating. In the future, it may be nice to see some piping around the edges or other protective bumpers to help avoid scratching.
Thankfully for non-Apple users, there is a mounting solution!
To test this out, I ordered a set of adhesive metal ring stickers that are supposed to be an alternative to having an “official” MagSafe case. I affixed one to the back of a smooth, flat case. The ring has performed better than I expected, with a strong magnetic attraction that holds the Tea relatively securely to the back of the phone.
Before I had the Tea, I wondered if the placement of the headphone jack, and the thinness of the device, may present a problem for cables with larger plugs. As it turns out, there is no cause for concern. I placed the ring, and then the Tea, in a position that allows the Tea to closely align to the bottom of my phone, eliminating any physical compatibility issues.
As impressive as the thin and compact form factor is, the technical specifications may be even more so.
Even though the Tea has a long-life battery (~8 hours) to avoid drawing power from your phone, it barely produces any heat, surely helped by the aluminum case. Featured are a high-quality USB ESS ES9281AC Pro DAC and a Bluetooth and Qualcomm QCC5125 chipset.
An additional unexpected (and incredibly thoughtful) standout is the inclusion of two inbuilt microphones so you can receive and make calls without removing your headphones. Genius, especially for on-the-move audiophiles. Press the ‘power’ button to accept the call and speak into the microphones located next to the USB-C port. They work very well.
In theory, firmware should be fully upgradeable. In addition, Khadas Tea owners can expect the near-future release of a phone app that will allow users access to much additional functionality.
The Tea is capable of up to 32bit, 384kHz sample rate (PCM), bit-perfect DSD 256 (playback hi-res DSD files from 64 to 256 Mbps rates), and Bluetooth up to 24bit, 96kHz. It also provides hardware MQA Decoding (“unfolding”), specifically designed to work with Apple devices and support high quality audio for Tidal users.
While the Tea comes with two short USB-C jumper cables, it can connect to a source device via Bluetooth, eliminating the need for a wire. This will prove to be very useful in a handle of scenarios, particularly when your source device is not on your person. For example, if I’m moving about my office and listening to music, I don’t have to carry both the phone and the Tea – only the Tea!
The Tea as a Bluetooth receiver is capable of processing up to 24bit, 96kHz transmissions, which meets the commonly used reference minimums for high-resolution (“Hi-Res”) audio. For reference, CDs are standardized at 16bit/44.1kHz. That is remarkable, as these specifications are much higher quality than most people can distinguish any differences between wired or wireless.
Tea Performance and Sound
The Tea itself is noiseless when powered on. It is optimally designed to drive headphones equal to or less than 300 Ohms. The power (130mW@ 16Ohms) of the single-ended output on the Tea is similar to the 4.4mm balanced output of the also excellent TempoTec Sonata E44 dongle DAC/amp.
So can the Tea drive demanding full-size headphones? I tested the Beyerdynamic 250 Ohms DT990 (96db sensitivity, 250 Ohms) and the Massrdrop x Sennheiser HD58X Open Back Professional Jubilee Headphones (104db sensitivity, 150 Ohms) to confirm that the answer is yes, they can – with ease.
Regarding performance, I have three main priorities with DAC/amps:
- Low noise
- Low distortion
- Clean power
I tested the Tea with multiple sources (wired and Bluetooth) and many headphones and IEMs of varying impedance and sensitivity. A critical test for me given the priorities above: plug in the headphones/IEMs and turn the volume up on the original source to maximum (with no signal playing), followed by increasing the volume on the amplifier. Listen for hiss or noise.
The Tea has a very low noise floor, with little detectable noise, even with highly sensitive IEMs. If it were not for the tiny LED indicator and the production of sound, I would not know if it was on.
Regarding the sound output, the Tea may sound different than your source, which is likely attributable to both the DAC and the amplifier power. While I’d really like to see some frequency graph data for the data to better understand its tuning, that is not currently available.
In comparing the Tea to the Tone2 Pro, I cannot hear a significant difference between their sound signatures – which I believe is a very good thing indeed.
Across almost all of my testing, I am unable to easily distinguish if the DAC is altering the sound quality or frequency response per se. Everything sounds clear and clean, with no notable ‘coloration’ of the sound. Sound reproduction is strong, with no unexpected or unwanted audible artifacts.
I only noticed briefly on a few tracks a substantial lift in the upper midrange and lower treble that can give the impression of greater details, as compared to a standard Android smartphone with a headphone jack, like the Samsung Galaxy A71. Most notably on poorly recorded or mastered tracks, this may result in certain sources sounding a touch shouty and splashy, a touch on the sharp side.
The Tea is a much higher-powered device than most phones, the effect of which is an improvement in dynamics and clarity.
Power advantages, especially compared to standard smartphones, are authoritatively clear. Power delivery is linear and clean. There are not, and most likely will not be, any IEMs that the Tea will not have more than ample power to fully drive. For full-size headphones, the Tea will be adequate for most.
Where to Buy
The Tea is clearly not going to make any sense to the hordes of users who believe that the greatest sound devices ever are their true wireless (TWS) IEMs. Or to those who rhetorically ask, “Why would you possibly want to use anything with a wire for sound anymore?”
With a brilliant, well-executed, first-of-its-kind innovative design, the Tea has defined its own niche for those who value and prioritize portable sound quality. With serious specifications and the power to meet most on-the-go enthusiast and audiophile demands, this is a remarkable achievement.
In my previous review of the Tone2 Pro, I noted that there is little to critique and therefore little to improve upon regarding performance. The same applies to the Tea. At this price, it’s an overachieving bargain compared to other portable DAC/amp devices.
The robust internal battery results in no precious battery drain from your device. The sleek form factor is particularly convenient and will not get in your way. Controls are as simple and useful as they come.
For enthusiasts and audiophiles, wow, this is a phenomenal time to be into this hobby! Incredible gear at highly affordable prices, epitomized by the Tea, are becoming the norm. This is a sea change from the aspirational and the “cost as much as a used car” high-end audio gear of the past decades.
I may adjust the Tea’s rating upward even higher after Khadas releases a highly anticipated iOS/Android app, presumably for customized sound quality/EQ controls, source and file quality information, manual gain selection, etc.