My friend AudioPhil is really into his headphone gear. Recently he acquired the product above and asked if I might want to play with this for a few days... Sure, this looks interesting!
This is the new iFi GO bar (around US$320), a portable headphone DAC/amp. The USB interface is a USB-C form factor (480Mbps USB2.0 Hi-Speed), and there are outputs for single-ended/unbalanced 3.5mm TRS and balanced 4.4mm pentaconn. Interestingly, the company (iFi, subsidiary of AMR/Abbingdon Music Research) does not specify which DAC chip is used inside. Suspicion is that it's likely the Cirrus Logic CS43198 or CS43131, both are recent chips circa 2017 capable of "pseudo-differential" outputs and low-power consumption <40mW with rated THD+N of -115dB, DR 130dB, maximum PCM 32/384, and DSD256. The specs look good but don't get too excited about these ideal numbers when implemented in a USB dongle.
I don't know what's the point of being so secretive about the DAC chip used (Crutchfield says it's the 43131).
Here's a better look at the side where we see a small switch for "iEMatch" which can be applied to either the 3.5/4.4mm outputs for sensitive IEMs:
|Notice that I'm angling it a bit against the light to highlight the text which can be hard to read due to low contrast and small fonts.|
Yeah, it has MQA support (not tested).
As you can see from the side view, it's got a switch to tell it when you're using an IEM so as to reduce the output level, also there's an XBass+ bass boost, let me show you what they do:
As you can see, the iEMatch feature turned down the gain by -6dB to accommodate sensitive IEMs and might increase the output impedance (presumably this is done through a voltage divider as per this ASR discussion, effectively reducing the efficiency of the amp). And the XBass+ feature basically gives a boost in the bass starting around 200Hz and up to +7dB at 20Hz; potentially a pleasant EQ for many headphones. Otherwise the DAC/amp has a nice and flat frequency response.
The XSpace feature is a spatialization effect to increase the sense of 3D imaging. The iFi marketing page suggests it's not standard crossfeed but seems to act like it (we can see an increase in stereo crosstalk - see RightMark results further down). The manual states that both XBass+ and XSpace are implemented in analogue circuitry, not as DSP.
I made sure the firmware was updated to the latest version at the time of measurements - the device was shipped with version 1.48, updated to 1.70 for these measurements:
Bit Perfect (BP) [misnomer, should be "NOS"] – no digital filtering, no pre or post ringing
Standard (STD) – modest filtering, modest pre and posting ringing
Minimum Phase (MP) – slow roll-off, minimum pre and post ringing
Gibbs Transient Optimized (GTO) – minimum filtering, no pre-ringing and minimum post ringing
We see that this DAC is capable of up to around -93dB THD+N at -10dBFS or so with the 4.4mm balanced output and Turbo Mode ON.
Similarly, if we look at the 3.5mm unbalanced output, we see that at best, it's capable of about THD+N -90dB at -16dBFS:
For both balanced and unbalanced, the right and left channels are well matched with basically identical distortion characteristics. Using those unbalanced stepped sine results, we can look at output linearity:
Looking closer at the FFTs, here's the -60dBFS 1kHz for measurement of dynamic range:
At -12dBFS level; this is about the best result one will see with this DAC on THD+N:
Let's have a look at some J-Test, jitter results:
Headphone Amp Resolution under load:
While we could use it as a DAC, this dongle obviously is meant to act as an amplifier connected to headphones with varying impedances. Using loads at 20/75/560Ω, we can create a picture of distortion at increasing output levels (graphed in Vrms); these were done with the unbalanced 3.5mm output with Turbo Mode ON:
Notice that the lowest THD+N is achieved around 0.7-1Vrms ranging from -87 to -92dB. At 1% distortion, the amplifier is able to provide >300mW into a low impedance 20Ω load, >150mW into a medium impedance 75Ω load, and >3.8V into high impedance 560Ω. These are in line with the published specs from iFi.
You might be curious about Turbo Mode OFF:
Subjective Impressions & Summary:
|Listening to some Guardians of the Galaxy Awesome Mix Vol. 1.|
|iFi stock image. This special edition costs US$500.|
To end off, I thought I'd take a picture of the current lineup of balanced / unbalanced headphone connectors that I have here among my devices and adaptors. I've also labeled the typical pin connections for R/L/GND and +/- for comparison:
|Sabaj A20d 2022 Version DAC with headphone out.|