Reference-Level Audio on the Go: iFi's iDSD Diablo DAC Allows for Lightning-Fast MQA Streaming in a Brilliant, Portable Package
For the top-of-the-line entry in iFi's range of transportable DAC/amps, the company's engineers were laser-focused on sonic clarity to create the iDSD Diablo DAC. The fiery red Diablo will satisfy even the pickiest audio connoisseurs, regardless of which style of headphone they prefer. Featuring a built-in battery, it delivers up to 5,000mW of prodigious power, while still retaining the finesse to provide nuanced textures and fine sonic details. The engineers' goal was to deliver reference-level audio for headphone lovers on the go – something that has been utterly elusive – until now.
With full MQA decoding of files up to 384kHz, the devilishly clever Diablo allows you to enjoy TIDAL Masters recordings anywhere you go.
Equipped with a Burr-Brown chip set – complete with a16-core XMOS microcontroller that processes data via USB and S/PDIF inputs – this DAC can deliver bit-perfect music at 768kHz PCM, DSD512, and double-speed DXD.
The DAC section benefits from an ultra-low-noise regulator with additional passive filtering, reducing high-order harmonic distortion. Consequently, this design also addresses the annoying problem of jitter.
Using the USB port, the iDSD Diablo can access cutting-edge Roon software by connecting to a Roon Nucleus player or to your computer. (This is different from a standalone, Roon-ready device, which has the RAAT network interface code preinstalled.) Thanks to its ability to access Roon software, the iDSD Signature can help you explore a vast expanse of new music or take a deep dive into your favorite artist's work.
Three settings on the front of the Diablo chassis allow you to adjust power and gain to fit your taste and your style of headphones. The Turbo setting is for headphones that need a lot of current, the Normal setting is suitable for most on-ear 'phones, and you can use the Eco setting to dial things down for sensitive, in-ear monitors.
The front panel also includes a 6.3mm single-ended headphone socket, along with a 4.4mm output for headphones offering balanced connection. The back panel has two digital audio inputs: USB-A and a S/PDIF socket that accepts both electrical and optical signals (the former via a 3.5mm connector and the latter via a supplied adapter). A separate USB-C charging port is included, along with a 4.4mm balanced output to connect to an external amp.
Because the iDSD Diablo can be powered from the mains, as well as by its built-in battery, it comes with a noise-cancelling iPower 5V AC/DC adapter to ensure optimal sound quality. Also included is a 4.4mm Pentaconn to twin XLR balanced interconnect cable to connect the iDSD Diablo to an amp and speakers (or a pair of active speakers) with balanced XLR inputs. Additionally, there is a USB-C to USB-A audio cable, as well as an extension cable, plus a USB-C charging cable and an adapter to connect headphones with a 3.5mm jack to the 6.3mm single-ended output.
"[The iDSD Diablo is] the Ferrari of iFi's portable devices."
– Becky Scarrott, What Hi-Fi?
The Beauty of Battery Power
Battery power provides ultra-clean and stable DC current for the iDSD Diablo, thus avoiding the problems of mains electricity – dips, spikes, and noise-inducing RFI/EMI pollution. There are, however, sonic issues resulting from low output voltage and inconsistent output impedance as batteries discharge. However, the resourceful iFi engineers devised a solution to this problem. In order to fuel less eﬃcient headphones, like planar magnetics, the voltage needs to be stepped up from 3.7V to +/- 15V. The Diablo uses a step-up converter running at 1.2MHz – a frequency far beyond audibility that is easier to filter than a typical switch-mode supply, enabling high linearity and ultra-low noise.
A balanced, differential analog circuit design reduces noise and crosstalk within the signal path by fully separating the left and right channels. With PureWave technology, the iDSD Diablo benefits from further refinements to balanced, symmetrical dual-mono topologies with short, direct signal paths.
XMOS 16-Core Chip
The XMOS 16-Core chip processes the audio data received via the USB and S/PDIF digital inputs. This low-latency XMOS microcontroller features greatly enhanced processing power. Compared to eight-core chips, this 16-core IC delivers double the clock speed (2000MIPS) and four times the memory (512KB), as well as the latest SuperSpeed USB standard.
iFi's in-house development team has programmed the XMOS firmware to optimize sound quality and ensure a perfect partnership with the Burr-Brown DAC.
Many audiophiles know that negative feedback is used in amplifier circuits to compare the output signal with the input signal and correct errors, in order to control gain and reduce distortion. For sound quality, this is positive; however, the commonly applied, one-size-fits-all "global negative feedback" approach can exacerbate some problems while simultaneously solving others. Corruption of the error signal, phase shifts, group delay, and other factors can have a negative impact on sound quality.
The iFi engineers recognized that different parts of a circuit benefit from specifically optimized feedback loops. Consequently, they developed a negative feedback system that is much more accurate than the usual approach. The design incorporates multiple feedback paths (instead of a global loop), with each path optimized for a particular function and working synergistically with the others to deliver optimal overall performance.
The iDSD Diablo is constructed with extensive jitter-eradication technologies, including iFi's GMT (Global Master Timing) femto-precision clock and an intelligent memory buffer.
High-bandwidth power supply circuity is dedicated to each critical part of the iDSD Diablo's design, with independent linear regulation delivering excellent PSRR (Power Supply Rejection Ratio) performance.
OV Series Operational Amplifier
A custom OV Series operational amplifier is included for extremely low noise, low distortion (0.0001%) and wide bandwidth.
Texas Instruments low-noise ICs offer great unity-gain bandwidth, very low noise and distortion, high output drive capability, Common-mode and Power Supply Rejection Ratios of over 100dB, wide maximum-output-swing bandwidths, and high slew rates.
Panasonic OS-CON Capacitors
Panasonic OS-CON capacitors totaling 5,410uF give very low Equivalent Series Resistance (ESR), as well as excellent noise reduction capability and frequency response characteristics. In addition, OS-CONs have a long lifespan, and the ESR changes little, even at low temperatures.