Lotoo S3

Wireless Perfection!

PROs: GT2’s “mini-me” level of sound performance, neutral signature with a natural, transparent, resolving tonality, huge 3D soundstage expansion, super-black background (even with sensitive IEMs), 3.5mm/4.4mm PO and LO outputs, 2” display, fast LTOS w/lots of settings and signature Lotoo sound effects, solid build of stainless-steel chassis, wired and LTTP (wireless) support.

CONs: price, no Bluetooth support, requires an LTTP adapter (additional purchase if you don’t have one already).

These products (S3 with WT-2 and GT2) were borrowed from Musicteck for review purposes in exchange for my honest opinion.

The manufacturer’s website: Lotoo. It can be purchased from authorized retailers, such as Musicteck.

*** UPDATE *** After publishing this review and sending S3/WT-2 back to Musicteck, I received a notification that Lotoo has just released a new S3 FW update that implements Play/Pause functionality under LTTP. And, WT-2 FW was also updated to support this feature.

Intro.

Lotoo is one of those manufacturers who don’t like to spoil us with new releases every year or two. Instead, we usually have to wait 5-6 years, as with GT2, the LPGT2 successor to their popular LPGT. When Lotoo announced a new version of their S-series DAC/amp dongle, I had to dig through my review archive to realize I had covered the S2 five years ago. One of the main reasons a DAP can maintain this kind of longevity and relevance, even after half a dozen years, is by keeping it pure and basic, without relying on Android OS updates or chasing the latest SoC processors, all of which do get dated. But how about something as simple as a dongle, in an already saturated market?

That question came to mind as soon as I heard the S3 announcement, which is why I was curious to check it out. I still recall how close S2 sounded to their PAW6000 DAP, and I was hoping to draw parallels in sound performance between the S3 and maybe their current flagship DAP. Plus, with the integration of Lotoo’s own LTTP protocol support, I also wanted to find out how close its wireless connection comes to wired sound performance. While I only had the S3 for a week and hope to spend more time with it in the near future, I dedicated a lot of time to testing and comparison and would like to share what I have found with you. So, let’s go!

Unboxing and Accessories.

Since I only received the S3 in bubble wrap, along with the WT-2 LTTP adapter, I can’t talk much about the unboxing experience. But Lotoo’s website mentions that the S3 comes along with a data cable (USB-A to USB-C), a protective case, a pair of screen protectors, and a manual. The manual can also be downloaded directly from the Lotoo site. Also, when searching online for more info, I found that the included protective case is silicone and has MagSafe-compatible backing to attach to your smartphone or compatible cases.

There was no mention of a USB-C to USB-C cable, which you would need for a wired connection between the smartphone and the S3. Don’t want to speculate, but maybe Lotoo assumed that audiophiles already have a collection of these short OTG cables, or they will use the S3 wirelessly with a smartphone. Also, the LTTP adapter is not included and must be purchased separately. I can only assume here that the adapter is an optional accessory, since some might already own either the WT-1 or WT-2 for use with GT2, Mjolnir, Gungnir, or PAW D3, with S3 now added to this list. Again, please keep in mind that since S3 doesn’t support Bluetooth wireless connectivity, you will need to use an LTTP adapter, such as the WT-2, to connect this dongle wirelessly to your smartphone or other sources.

Design and under the hood.

With dimensions of 87x55x21mm and weighing 180g, S3 is not as compact or lightweight as some other basic small dongles without batteries, but it is also smaller than most dongles with batteries. And if you consider its stainless-steel, titanium PVD-coated chassis, and take into consideration an ample 3300mAh battery (yielding up to 10hrs of playback) and 2” IPS color display, this palm-size pebble with rounded edges is rather portable. Plus, with the provided MagSafe-compatible case, you can attach the S3 piggyback to your smartphone, whether wired or wireless. Or keep your smartphone in a pocket or bag/purse/backpack and, while connected wirelessly, use your wired IEMs/headphones to handle the S3.

As already mentioned, on the front you will find a 2” IPS color display. The top has 3.5mm SE and 4.4mm BAL ports, which double as PO and LO and are selectable in the settings. Also, the upper right corner features a plastic-encased protrusion, covering the wireless antenna, the only part of the surrounding chassis that is not stainless steel to make sure the wireless signal is not blocked. The bottom has a USB-C connector, used for charging and data transfer. The right side is where the buttons are located: 5 equal-sized round plastic buttons, with Power on top (long press for power on/off, short press for display on/off), then three grouped Volume+, Play/Pause, and Volume- buttons, where V+/- are also used for Settings menu navigation, and Play for the selection, followed by the Fn “Function” button at the bottom, which enables you to enter the Settings menu and is also used as a back/return button within that menu. Obviously, V+/- adjusts volume during playback, while Play/Pause controls playback when the S3 is connected to a wired USB DAC. Since the S3 doesn’t support Bluetooth and instead uses a proprietary LTTP protocol, Play/Pause doesn’t operate over a wireless connection. Not sure if it is feasible, but I wishful thinking that Lotoo can figure out how to make it work, since Play/Pause is a very important function during remote operation. *** UPDATE *** Lotoo just released a new S3 FW update that implements Play/Pause functionality under LTTP!!!

Under the hood, at the heart of the S3, you will find an AKM AK4493SEQ DAC that supports PCM up to 76kHz and DSD up to DSD512 in wired connection mode. Without a surprise, you will also find a bulletproof ADI BF706 (Blackfin 706) DSP chip, which they have featured for a decade in everything including PAW Gold, LPGT, GT2, PAW6000, S3/S2/S1, PAW PICO, etc., which, among other things, enables PMEQ + ATE sound processing. Just keep in mind that in S3, as with their previous dongles, the PMEQ presets are not editable due to interface limitations. And, just like in their other devices, the S3 runs on Lotoo OS (LTOS), a bare-bones, single-purpose system designed exclusively for immediate audio processing, ultra-low latency, and fast boot times (under 3 seconds). It handles tasks synchronously at the hardware level without the heavy layers of a desktop or mobile OS kernel.

With its internal amp powered by 4x dual-channel SoundPlus series TI OPA1622 OpAmps, the S3 delivers up to 550mW @ 32ohm load from BAL and 250mW @ 32ohm load from SE outputs in Super High Gain. The output was optimized to yield an ultra-low noise floor of 0.7 µV. This is not just on paper; you can actually hear a pitch-black background with zero hiss, even with ultra-sensitive IEMs, while also driving high-impedance, low-sensitivity, demanding headphones with plenty of headroom, without issue. These PO ports double as LO ports, where you can select either fixed voltage levels or variable (unfixed) to adjust the line-out output.

As was already mentioned, the internal 3300mAh battery supports up to 10 hours of playback, though I didn’t have enough time to confirm it. It is very convenient to use with a smartphone without straining its battery. But you do have options when the USB-C port is connected to the source. Once plugged in, a Mode setting menu pops up with options to Charge Only (to charge the S3 device), Phone DAC (to use the S3 internal battery to avoid draining your phone’s battery), or PC DAC (to charge the S3 while connected to the USB port of your PC/laptop).

WT-2 LTTP Transmitter.

While the star of this review is the S3, I wanted to quickly go over the design behind Lotoo’s LTTP transmitter, which is required for a wireless connection to this DAC/amp dongle.

LTTP stands for Lotoo Tele-Transport Protocol, an enhanced wireless transmission protocol. LTTP is Lotoo’s proprietary protocol featuring adaptive bandwidth and high-precision clock management to enable high-resolution & lossless wireless audio transmission up to 96k/24b for hi-res audio and 48k/24b for true lossless audio over 2.4GHz as an alternative to standard Bluetooth. Under this protocol, they can ensure a maximum transmission rate of 1.5 Mbps, unlike LDAC, which supports 990 kbps, and dynamically adjust bandwidth based on file format and wireless interference. I will talk more about wired vs. wireless transmission in my sound analysis section, but it does come pretty close in sound quality.

The updated design of the WT-2 transmitter is intended to raise the wireless resolution ceiling to 192k/32b with S3. It also supports low-latency and high-resolution modes, which you can select in the S3 settings. The original WT-1 had a modular connector that let you switch between USB-C and Lightning plugs to accommodate older iPhones. WT-2 has a fixed USB-C-only connector, since iPhones have moved on, and a fixed connector is more reliable down the road. The transmitter itself is very slim and ergonomic, weighing only 6.6g and measuring 47mm in length and 8mm in height. The transmitter’s width is 17mm without the connector and 28mm with a USB-C connector. The connector extends enough to fit even some of the bulkier phone cases, but not so far as to put extra bending pressure on the connector when in your pocket. And just like a typical dongle, it draws power from the source’s USB-C port and doesn’t need to be charged.

Also, WT-2 features a function button on the side, a multi-use hardware key for pairing control and managing the built-in status indicator light. You long-press it to enter pairing mode, while holding it for 3 seconds forces the transmitter to disconnect from any saved connections and enter a new pairing mode. And if you short-press it, it will toggle the status LED on/off, turning off the indicator light if you find it distracting in the dark. Pressing it again turns it back on.

*** UPDATE *** Lotoo just released a new WT-2 FW update that adds Play/Pause functionality under LTTP, as well as higher resolution for wireless transmission.

GUI.

Lotoo’s OS, LTOS, loads very quickly, and the device powers up in about 3 seconds or less after the power button is pressed. Once powered up, its large 2” IPS screen gives you a clear, bird’s-eye view of all relevant playback and settings info at a glance, such as (line-by-line on the display):

Play/Pause status, Gain level, Volume level, Battery percentage
Mode of operation (LTTP, DAC, etc.)
Dynamic VU meter
EFX: ATE or PMEQ selection and present name
LO: Voltage level
PCM/DSD decoding, Sampling rate, Bit depth

One thing to keep in mind: unlike Lotoo DAPs, where you can customize PMEQ presets, here you can only select the provided presets, as with previous Lotoo dongles.

To enter the Settings Menu, press and hold the Fn button to bring it up, then use the Vol +/- keys to scroll and the Play/Pause keys to select. Then, use the Fn again to go back to the previous screen. The following are the available menu options and their corresponding settings:

Working mode: Auto, Phone DAC, PC DAC, LTTP Client, LTTP Client Settings
LTTP Tx Mode: low-latency or high-res fidelity modes
Output type: HP out, Line out
4.4 LO Level: 1Vrms, 2.1Vrms, 4.4Vrms, Unfixed
3.5 LO Level: 0.7Vrms, 1.2Vrms, 2.9Vrms, Unfixed
HP output gain: Super high, high, low
EFX: None, ATE- Movie, Game, Radio, Vinyl LP, Cassette, Dental, Near field, and Far field, PMEQ- ACG-1, Headphones, Rock, Pop, Classic
Filter: PCM- S-delay sharp rolloff, Sharp rolloff, Slow rolloff, S-delay slow rolloff, Super slow rolloff, Low dispersion S-delay, DSD- LPG Normal, LPG Extended
Smart charging: off/on
Screen off: off, 10s, 30s, 60s
Auto power-off: off, 30s, 60s, 3min
Language: English
Version: 1.4.10.130
S/N: #
Reset – Factory reset