Synergy
Power
The Questyle SIGMA Pro pairs best with dynamic drivers over planar magnetic headphones most of the time. I prefer how the SIGMA Pro handles dynamic drivers and would consider them the best headphones to use with this device.
There are not many studio monitors that are planars. I could recall the Audivina from HIFIMAN, but I prefer the LE version over the more expensive original model. Power-wise, the Audivina LE pairs well with the SIGMA Pro since it’s a very efficient model.
On some headphones, like the HE1000 Unveiled, I desired more grunt in the lower region for me to be satisfied. I tended to gravitate to some form of sound-shaping EQ to satisfy my taste in the lower bass region, and thought, perhaps, the available power wasn’t enough.
Pairings
Again, we’re dealing with a component that claims studio-like sonics, but that doesn’t mean that one has to stick to cans like the Audivina LE or the Sennheiser HD490 Pro, and is obligated to stick with cans labeled studio monitors.
I had lots of fun listening to IEMs like the FiiO FX17 on the SIGMA Pro, which, on some dongles, sounded too forward or too truculent. These FX17 opened up and brought lots of detailed nuances upfront. These were best on low or high gain. The studio setting was overkill.
The sweet balance of the Grand ORIVETI Supremacy also shone when paired with the SIGMA Pro. But the high frequencies were brawly with other frequencies, and I don’t recall that on other gear, like the Rose Technics RT-5000, or on my daily, which is an SMSL SU-X and SH-X combo.
Select Comparisons
Questyle SIGMA
Technical
The SIGMA is a spinoff of their CMA18, and a contender to the veneered Chord Electronics Mojo 2, and the iFi audio xDSD Gryphon portable DAC amplifier combo units. The SIGMA Pro is not far from them either.
The SIGMA DAC section uses a set of AKM AK4493 DACs that are capable of similar digital format playback compared to the SIGMA Pro.
The SIGMA non-Pro version comes equipped with a similar current mode amplifier to what’s inside the SIGMA Pro. I find it odd that both can produce the same amount of power, which is rated at 1200 mW on a 32Ω load.
Design
The general design aspects are similar in that both use an aluminum chassis and clear glass to give you a clear view of some of the internal components.
The only major differences are the positioning of the push buttons, the size, and the omission of the volume knob.
The SIGMA is more appealing when in use due to displaying more LEDs behind that transparent glass. Of course, the SIGMA Pro variant has more features.
However, the SIGMA is better for portable use since it’s considerably smaller. It still feels rather slippery with little to no grip. I would be careful not to drop the SIGMA either. It doesn’t come with any protective cover or case either, just the same.
Performance
I went all in with the HIFIMAN HE1000 Unveiled with a Meze Audio Upgraded Silver cable and went to work on A/B comparisons.
The more linear-sounding of the two is certainly the SIGMA, but it’s also the more vivid-sounding of the two amplifiers. Only that the SIGMA sounds a bit closer, and there’s a slight narrowing of width in particular.
The SIGMA Pro also produces a higher amount of microdetails. The SIGMA Pro champions being more detail-oriented in that small microdetails are brought forth more so than the SIGMA.
Power delivery-wise, I couldn’t tell the difference, as if they had identical amplifier sections, powered by an identical battery pack. It all boils down to which DAC sounds best to your ears.
The AKM variant, to me, is extremely linear and somewhat bright, but the ES9069 produces music with more body, although most will feel a sense of linearity on the SIGMA Pro; it’s just a hint of radiancy and balminess.
iFi audio iDSD Diablo 2
Technical
Most audiophiles keep the iFi audio iDSD Diablo 2 as a backseat passenger due to a controversial claim that iFi audio misquoted the power output rating.
They didn’t specify if the claimed 5 watts were achievable, since measurements only reached 2 watts. They forgot to mention it was a peak power rating, that’s all.
Two watts from a small DAC amplifier with portability capability is still a formidable amount that surpasses some desktop models.
That amount of power is delivered cleanly by the Diablo 2 to a point where it sounds like an exotic component with the right headphones.
It doesn’t carry along any of the features found on the Gryphon, for example, which has Xbass and Xspace onboard and selectable digital filters. It’s just a DAC amp with a gain feature.
One thing the iFi audio iDSD Diablo 2 has going for it is that it can handle aptX Lossless audio Bluetooth, while the SIGMA Pro only goes as high as LDAC. Even though the SIGMA Pro is the newer model, it doesn’t carry that high BT codec badge.
Design
This red devil comes with some removable brackets, two sets in total, which give some height to the chassis while on a desktop. It allows air to flow beneath the unit, allowing extra cooling efficiency, although the Diablo 2 runs rather cool, and warm at times.
That implies that it’s best suited for home use, just as the SIGMA Pro, but that’s just my opinion. Both have built-in rechargeable batteries that allow you to take them on the go, and that’s what makes them portable capable.
Both also have 6.35mm headphone outs, implying even further that their design is optimized for home use.
Both models use a chassis made of metal. The Diablo 2 comes in an anodized devilish red, while the SIGMA Pro comes in Black or Silver, but that’s trivial, and personal taste will dictate which model looks best to you.
They both come equipped with a rotary volume knob, but iFi audio’s knob is notoriously problematic with very sensitive IEMs due to a low volume channel imbalance that makes it hard to listen to at very low volume levels.
That’s not the case with the SIGMA Pro since it seems to be digitally implemented.
Performance
I’m finding that the iFi audio iDSD Diablo 2 has a lusciousness about the vocal presentation that these other two models can’t match. The vocal presentation is more laid-back on the SIGMA Pro.
The Diablo sounds more like music is being produced inside a large, personal space, while the SIGMA Pro sounds wider, deeper, without any loss in focus or aura smear. The SIGMA Pro produces sonics with a better sense of presence.
The iFi audio iDSD Diablo 2 is certainly the warmer-sounding of the two, of course, since it comes from warmer lands. I heard it’s quite warm down there. Smirk. That was a hellish joke, no pun intended.
Power-wise and the driveability aspect are similar on both these models, making me doubt more in that max power rating, but both models pushed my entire collection of headphones to volume levels that can be deafening.
The kicker here is that Questyle managed to extract more detail out of what you’re playing. The recordings sound taller. Perhaps there will be a Diablo 3 with Xspace, which would have improved the iFi audio iDSD Diablo 2 in that respect.
My Verdict
The Questyle SIGMA Pro Current Mode portable amplifier and integrated DAC will cater best to audiophiles who prefer an analytical character and a balanced sound signature over coloration and toasty-sounding components.
The SIGMA Pro is also big on micro-detail and serves up a sonic profile that belongs in a monitoring setting.
It’s a versatile model with lots of IO options and one sonic profile. It relies more on a headphone’s virtues and sonic capabilities, and the source quality over all else.
If you like a clean, unaltered sound, and you want to hear all the dribblets and granules some other components leave behind, like dongles and similar portable DAC amp combo components, then in those sonic aspects, the Questyle SIGMA Pro is certainly a step upwards.
If you want to go portable, there are not many components out there that can outperform the Questyle SIGMA Pro. Just don’t drop it because that will ruin your day. I’ll keep mine at home where it’s safe, cozy, and always ready to go.
Questyle SIGMA Pro Technical Specifications
- PCM:441 kHz – 768kHz/32 bit
- DSD native: DSD64, DSD128, DSD256, DSD512
- DSD DoP: DSD64, DSD128, DSD256
- MQA: MQA rendering and MQA full decoding
- Supports UAC 2.0
- Support: Win XP, Vista, Win 7, Win 8, Win 10, Win 11
- Support for Linux, Android, HarmonyOS, macOS, and iOS
- Optical input: PCM 44.1kHz-192kHz/24bit
- Coaxial input: PCM 44.1kHz-192kHz/24bit
- Bluetooth: Bluetooth 5.4
- SBC, LE audio, aptX, aptX HD, aptX Adaptive, LDAC
- 5mm Sein: standard level 1Vrms
- 4 Bal in: standard level 2Vrms
- Headphone out: 3.5mm / 6.35mm SE / 4.4mm balanced out
- Max analog output: 3.5mm 3.3V @ 300Ω / 4.4mm 6.6V @ 300Ω
- THD+N: SE 0.0002% / bal 0.0002%
- Max output power: 120 mW @ 32Ω
- THD+N: 0.0002% @ 300Ω
