Lotoo's use of the Analog Devices Blackfin BF706 DSP microprocessor is the stuff of legend by now, with the code written and loaded up over multiple firmware upgrades and several years a technique these Taiwanese coding innovators have made their own – so much of how each of Lotoo's classic DAPs sound is owed to this.
The generation of pristine I2S is the ultimate goal for LPGT2's DSP. But even the best digital trickery in the world needs a hardware platform sufficiently capable to execute software. Enter Asahi Kasei Microdevices (AKM)’s resurgent flagship DACs.
These Japanese giants, back on their feet with a clean slate, started afresh expanding the basic footprint of a single DAC chip IC into three separate parts – to similarly multiply capabilities by a factor of three.
AKM’s AK4191EQ is the brains of the operation, receiving pristine I2S clocking and data from LPGT2's Blackfin. Aboard, AK4191EQ’s delta-sigma modulator takes advantage of its expanded, dedicated, silicone footprint to lay claim to the title of the first chip IC working at seven bits.
These seven single-bit modulators flow on into LPGT2's dual AK4499EXEQ DACs, one for each channel and built with a single purpose in mind: to turn the interpolated, noise-shaped, digital data it receives into the most precise analog waveform possible afforded by its large footprint.
Silicone size matters when it comes to a great DAC IC, and AK4499EXEQ has it. Enabled by much more exact, matched resistors and capacitors aboard for precise DC single-bit decoding, and dynamic element matching that is less burdened by switching errors – granted by parts accuracy from a bigger footprint.
Any conversion errors from AK4499EXEQs outputting in current manifests as DC offset, and not total harmonic distortion, that is easily filtered out. That's expected of any source claiming to be high performance.
A high-quality current-to-voltage I/V section follows these AK4499EXEQs, befitting of chips that output in current for best distortion performance and indeed more expensive players. The second Lotoo device after Mjolnir this decade to boast such a circuit, LPGT2 brings those benefits to a portable device 10 years after the first generation LPG in 2014.
Once again, LTTP allows you to get high-res lossless from your favourite streaming app on your smartphone to LPGT2, adding to its versatility beyond its 2TB SD card capacity.
Running on Lotoo OS 1.6, LPGT2 once again eschews Android operation for the cleanest, lowest interference and CPU noise for a black background. That's only helped by an eight-layer PCB with shielding for the analog circuit, preserving all the analog resolution dual AK4499EXEQs can produce.
This high-fidelity is amplified and flows on to powerful op-amp output buffers that supply current and mean Lotoo's flagship promises high damping factor while maintaining its low distortion into low impedances typical of IEMs, Focals, Fostexs and Rosson Audio Designs.
Specially selected by Lotoo, LPGT2 boasts Texas Instrument parts that are ideal voltage sources and stable into capacitive loads, with their gain bandwidth product ensuring frequency response extends well beyond the human hearing range for excellent phase response and taut, impactful dynamics in the human hearing range.
Still the closed-loop internal gain remaining after the mandatory application of negative feedback around Lotoo's analog circuit remains high, so where she really can shine is in swinging +20.3 dBu of voltage, opening up the sound of any high-impedance Audio-Technica, Sennheiser and ZMF Headphones while barely breaking sweat.
Indeed, this latest evolution of Lotoo's beloved Paw Gold concept ensures it's totally future-proof, ready for whatever the bright future of the rapidly-advancing world of Head-Fi throws at it, on the digital and analog fronts.
After LPGT2, keep up to date with the fantastic staying power Lotoo releases have here, or view all our other music players here.
DAC 1 X AKM AK4191EQ + 2 X AK4499EXEQ
Amp Quad TI BUF634A op-amp output
SNR <134dB