The 22Ω Output Impedance
There were some questions over the AK100’s output impedance being quite high (22Ω), hence potentially problematic with low impedance headphone/IEMs. Pairing it with the excessively low Sony XBA-4 (8Ω), I didn’t find any obvious problems. Sure, low bass impact can be better, but low bass presence is all good and even with a good amount of resolution down below. Maybe electronic measurement devices can be more precise in this aspect, but my ears don’t notice anything obviously problematic. And while we’re talking about the XBA-4 pairing, I should also say that the AK100 happens to pair very well with the XBA-4 and perhaps is one of the better pairings out there. In fact, if you own the XBA-4 then you should look into the AK100.
I have a hit and miss problem with the fit of the XBA-4, sometimes the fit would be right and with the seal right on, the low bass is good: present and detailed. Some other times, no bass at all, but this was just fit/seal problems, nothing to do with the AK100’s output impedance.
The bass is also fine with the JH5Pro (21Ω), even great with the Sennheiser Momentum (18Ω), though a bit boomy with the Sony MDR-Z1000 (24Ω). Amp section is powerful even with the LCD-2 (though not as meaty as a powerful dedicated amp). Digital volume control is great, no imbalance with my ultra sensitive JH5Pro. But in the end I just don’t have any regrets in sending the AK100 sample back to iRiver. Definitely won’t be missing it.
It’s very convenient to have a digital in/out feature. The digital output uses a combo jack with the headphone out port, while the digital input on its own. There is no dedicated analog line out, however. So you portable amplifier users are forced to use the headphone out.
User Customizable Equalization
The interface for setting the user EQ is brilliant and the best I’ve seen. Simply by drawing a curve with your finger on the touch screen, the AK100 will dial in the appropriate EQ following that line. Certainly this is the best way to set up an EQ on a portable player, as it’s very easy and fast to do. The EQ also takes an effect if you’re using the AK100 as a digital transport, so the digital signal that is sent through the optical output would be affected by that EQ.
If you want to be more specific, the player will let you dial in a more specific level of boost/reduction on five frequency points (62Hz, 250Hz, 1kHz, 4kHz and 16kHz), but it was too tedious for me and the draw-a-curve option works much better for me day in and day out. I only wish there were more frequency bands. Seven, maybe even eleven would’ve been awesome since drawing a curve through 11 bands is not any more complicated than drawing a curve through 5 bands.
Going back to my sound impressions of the AK100, though an EQ may improve the tonal balance of a certain song/headphone combination, it still doesn’t take away the sound signature of the player.
Build quality wise, this is currently the best out there. But as you’ve read throughout the review, I do have a mixed impression with the player which eventually left me feeling cold for it. The sound, I think while they have achieved a very respectable level of technicalities (that black background is unmatched, the more I listen to the AK100), doesn’t quite work for me. I’m not a big fan of the Ibasso DX100, but I still prefer the DX100 over the AK100. Even as I’m playing a nice analog recording of Duke Ellington, still the AK100 implanted its cold signature into the sound.
What about those crowd who happens to be enjoying the AK100? Well it’s a good player after all, and as much as I don’t connect to the player, there is no denying that it scores pretty good in the technicalities sector. So, yes I think it’s going to be around and some people would enjoy the AK100 for what it is.
At the end I think, despite my personal feelings for the player, I have to give my kudos to Iriver for coming out with a player so well designed. I believe we’ll see more excellent products from Astell & Kern next year.
About the Red Wine Audio AK100 Mod, I got this message from iRiver:
I think you guys already known about “RWAK100”
Well, here are our mentions for this issue, please refer to it.
If you change AK100’s output impedance into 0 ohm (by taking off resistance)
1. Sound become powerful.
2. enrich sound of high impedance
3. better balance for Armature unit drive earphone.
1. Each headset has limitation of maximum output. By reducing impedance of AK100, there could be deterioration of headset and it cause short of circuit. In this case, it consume over 2W electric power and make damage of AK100 circuit.
2. When there is Static Electricity, it can easily damage of AK100. In this case, even it plays but there is no sound.
3. VOC and PL regulation issue will be happed by causing hypacusis and deafness.
4. Even it improves the sound power, it reduces smooth and delicate sound detail of AK100.
With these reasons, we do not recommend reducing impedance or any modification by users.
To prevent such unauthorized modification by end user, we use special screw driver for AK100. But if they carry out any kind of changes or modification by themselves and it cause any problem or issue, we are not obliged to provide C/S or A/S.”