Review and Disassembly of the KA17: Dual Type-C Port USB Dongle/Desktop Headphone Amplifier
Upon seeing the KA17, my first question was: which model of the FIIO USB dongle is it upgraded?
Based on FIIO's naming convention, the predecessor of KA17 should be the KA7. However, there seems to be no such model in FIIO's product lineup.
The KA17 and KA13, both belonging to the "KA" series, share a similar appearance, but the KA17 appears to be of a higher level because it has a display screen, while the pentagonal window on the KA13 is just an LED transmission window. Additionally, the KA17 is larger compared to the KA13.
The KA17 is one of the only two models in FIIO's USB dongle series with a screen, the other being the KA5. Furthermore, the KA17 not only has a screen but also features a D.MODE switch for desktop mode.
Moreover, the KA17 boasts a more explosive configuration with two Type-C ports on its body. The last time I saw a similar configuration was on FIIO's brick-shaped DAC and headphone amplifier, the Q15.
In addition, the UI of KA17 is not only rich in options but also offers a unique feature of a language option among USB dongles.
After this comparison and analysis, a general impression can be drawn: the KA17 excels in both high output power and rich UI control options.
Audio testing: Previously, on the KA13, I experienced the power of the D.MODE switch, which allowed the maximum output of the balanced port to reach 567mW (tested by AudioTOP). This time, under the collaboration of D.MODE and dual Type-C ports, the KA17's maximum output for the balanced port has surged to 649mW, once again breaking records.
According to our observations, the D.MODE switch has an immediate effect on the maximum output of both the single-ended and balanced ports.
When turned off: single-ended output power goes up to 148mW; balanced up to 261mW; When turned on: single-ended output power goes up to 289mW; balanced up to 649mW.
In other words, when the desktop mode is activated, the power of the single-ended port increases by 95%, almost doubling it, while the power of the balanced port increases significantly by 149%.
With robust power output, the suppression of THD+N distortion and background noise is quite good instead of losing one thing or the other.
Furthermore, we noticed that after enabling the desktop mode, the static power consumption of the KA17 increased from 0.78W to 1.14W. In comparison, the KA13's power consumption remained around 0.72W with little variation, regardless of whether the D.Mode switch was on or off. Therefore, the headphone amplifier circuit structures of the two USB dongles must be different.
More details and reasons about this will be further analyzed during the disassembly process. Anyways, the KA17's unique characteristics necessitate a second Type-C port, allowing third-party power sources beyond just mobile phones.
Based on past usage experiences, USB dongles tend to draw a significant amount of power from the phone's built-in battery. Unknowingly, this could deplete the phone's battery to a large extent, causing battery anxiety.
However, during the use of the KA17 this time, with the assistance of the unlimited power supply from the second Type-C port, the battery icon on the phone remained unchanged regardless of how long I listened to music. Hence, the manufacturer's designation of it as a "mini desktop DAC/Amp" comes with a reason.
The disassembly of the KA17 this time was quite unusual. After several unsuccessful attempts using the traditional method of heating and suction cups, as you can see, I used a Zippo lighter with strong double-sided tape to open the cover.
The back panel departed from the usual glass material and instead adopted a metal plate. Coupled with a thermal conductive pad, it facilitates faster heat dissipation for the internal circuitry, primarily the headphone amplifier chips.
Removing the first circuit board, we can see a smaller thermal pad sandwiched between two headphone amplifier chips.
This board contains all the audio circuits, with the core components including two DACs and four headphone amplifiers, distributed on both sides of the board.
The DACs are ES9069Q, one for each channel. The ES9069Q incorporates ESS's latest fourth-generation Hyperstream modulation engine, with a channel count of 2ch.
The headphone amplifier chips are the SGM8261-5. This is a dual-channel chip, so the KA17's headphone amplifier channels can reach up to 2x4=8.
How do so many channels coordinate? According to the datasheet, the typical power consumption of each SGM8261-5 is 0.2W. It can be inferred that when the D.MODE is off, only two SGM8261-5 chips are involved in amplification; when the D.MODE is on, all four SGM8261-5 chips are working.
Continuing with the disassembly, remove the metal piece sandwiched between the two circuit boards.
The lower-level circuit board is collectively referred to as the main control board, containing multiple functional sections, such as display, control, input, USB bridge, and audio data processing. You can see a 16-core XMOS chip and two Type-C ports on it. The red interface on the side is dedicated to power input, but not data transfer.
All buttons and switches are mounted on a small metal bracket, which absorbs and isolates all operation pressure, ensuring durability for long-term use.
The OLED screen closely fits the panel glass.
The KA17 is FIIO's most component-rich and structurally complex USB dongle to date. The disassembly process was relatively difficult, and users are not advised to disassemble it themselves because the probability of non-destructive reassembly is very low.
Despite its complexity, the structure remains orderly. Within the compact layers, both digital/analog isolation and circuit cooling are well maintained.
The KA17 adopts a new DAC chip from ESS, and the configuration of the headphone amplifier section not only features a large number of chips but also exhibits a unique mode of operation among headphone amplifier chips, unseen before. With the hardware architecture described above and the assistance of D.MODE and dual Type-C ports, the KA17 vigorously raises the ceiling.
At the same time, it breaks down the boundary between USB dongle and desktop headphone amplifiers. While the inherent label of USB dongles is portable and easy to carry around, now with an additional power input port, its application value in desktop scenarios will also be explored by users. Moreover, the bilingual display interface unique to FIIO further reduces usage barriers.
Author: AudioTOP Edited on 19/02/2024
Original text:
https://weibo.com/ttarticle/p/show?id=2309405003262897291672
