iFi Micro iDSD BL Review and Measurements

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Jan 20, 2020.

  1. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    This will be another one of my stream of consciousness deals as there's just too much to cover. This is the best way for me to let you guys know about as many aspects of the "Micro BL" as possible. Feel free to ask pointed questions.

    IMG_20200120_125922.jpg

    The iFi Micro iDSD BL could be the finest transportable all-in-one amp/DAC unit I have heard. It might be interesting to compare to the Chord Hugo 2 under more controlled circumstances (blind and in a home setting) however; but that may need to wait. Or maybe not, since the Hugo 2 at $2500 is meant for people who's parents in a totally different wealth bracket. For what it's worth, I didn't care for the Hugo 2. However to be fair, I may have judged it based on performance to cost, or I could have had the the wrong filter settings that did not suit my preferences.

    Here I've been comparing the Micro BL to the modest Schiit Hel in the past week. It's always good to have a reference.
    IMG_20200120_115342.jpg

    The sound of the Micro BL doesn't seem that totally far off from the Hel. I do prefer the Micro BL's sound slightly more. The Micro BL's sound seems to a departure from the Nano BL reviewed here: https://www.superbestaudiofriends.o...ds-el-dac-ifi-nano-bl.6313/page-2#post-208350). Unfortunately, the Nano BL got lost by USPS, so few SBAF members could ever experience it on the loaner program.

    The Micro BL can "slay slayer" so to speak more than both the Nano BL and Hel. Of these three AIOs, the Nano BL can be said to be the most relaxed or laid-back sounding, both in tonal presentation and attack. The Hel sounds more even in tone, neutral like the Micro BL. However, the Hel still has hints of the AKM AK4490's "Velvet" sound, where some listeners have complained about it hitting has hard as a wet noodle. The Micro BL relies on a x2 mono TI PCM1793 chip deal. While the Hel's AK4490 is AKM's latest and greatest, the PCM1793 has been around for a while. I figure iFi doubled them up to get better perceived resolution and linearity (THD) so they could compete with today's latest designs. I am impressed that iFi designers have stuck with an older part, and did everything they could to wring as much performance out of it. All too often we have found that newer isn't necessarily better.

    I do think the Hel just nicks the Micro in terms of plankton, or reproduction of low-level information. Not unexpected as this is one of the "Velvet" sound AKM's sound suits. But it's not really enough to make a difference considering the so many other aspects of the Micro which I prefer. The attacks hit hard and aren't as soft like on the Hel. This is evident from bass drum kicks, finger snaps, etc. from every track on Michael Jackon's Bad (Special Edition). There's more solidity, a more tactile sense, coming from the Micro BL. In addition, the Hel also seems a have bit murkiness which makes textures from bass instruments less evident - more smeared. I'm blaming the AKM DAC portion of the Hel here - it might be interesting to confirm by running an outboard DAC.

    A possible downside I can see with the Micro BL's presentation is that it can be unrelenting with certain headphones or recordings. At first, I thought the BL was glarey and difficult in the highs with too many recordings, but it turned out that I had incorrectly set the filter to minimum phase. I have always disliked minimum phase filters. There has been discussion on minimum phase filter's here: https://www.superbestaudiofriends.o...d-post-effin-ringing-and-shit-like-that.2627/. They might be good for gaming because of low-latency, but for musical enjoyment, I'd rather avoid them. Setting the filter to linear phase or "Bitperfect" (and running from the battery - more on this later) makes the high end so much smoother. Remind me to post FR and impulse response measurements so we can see what's going on here. Also note the IEmatch (for people with IEMs).
    IMG_20200120_124342.jpg

    to be continued.
     
    Last edited: Jan 23, 2020
  2. Lyander

    Lyander Official SBAF Equitable Empathizer

    Pyrate Contributor
    Joined:
    Feb 25, 2017
    Likes Received:
    10,961
    Trophy Points:
    113
    Location:
    Philippines, The
    EDIT: Forgot to point out, experience with BL variant is all store demos with sub-optimal comparison conditions. Nearly got one a while back but I figured it wasn't a massive enough difference to supplant silver version; operating under presumptions that filters and personal observations that overall sonic profiles are pretty similar between the two—sorry!

    f'ing rocking the Joe Grados, nice! That aside, very many silly questions below, apologies in advance:

    Likely low priority for you, but curious for a non-marketing explanation for the 3D stage expander on top of impressions of it— can't find anything on how it affects sound and makes for a more diffuse presentation other than there's a definite increase in treble presence despite no change to measured FR that I could find. XBass is a bit easier to wrap one's head around IMO: rather tasteful sub-bass rumble.

    Also, you can use the 3.5mm input on the face to test the amp as a standalone. Curious how that one stands up to the Heresy ;) or Hel. Never actually used Turbo but the differences between Eco and Normal seem to be pretty obvious— greater dynamic "swing" and range with the latter; Eco just seems to be wearing slightly too-tight pants to really kick. Wondering whether there's enough grunt to bring some more inefficient headphones to bear.

    I know you don't really do headstage but I think that's a relative strength of the iFi DACs— roomier than the Hugo v1 or Bifrost MB v1 by a fair margin. How's this one fare in the grand scheme of upstream crud? The background is leagues cleaner than on others I've had on hand, but that's a minuscule pool so I'm curious how it compares to those who've heard more than a handful of units. I'm also kind've a whore for sonic texture so would be interested in hearing how far up the discrete DAC ladder this transportable one goes, esp. when going off internal battery.

    P.S.
    As someone who struggles to hear differences between filters bar from how sedate (or opposite of sedate) the upper registers can be, what specifically can you hear is different between Measurement, Minimum Phase, GTO filter, or Bit Perfect? Moderate derailment, sorry, but I think it might be of interest and potentially useful for people still working on their listening skills (cough); I sometimes wonder whether I'm thinking myself into ruts stressing over minutiae, which is why I'm decided on keeping to modest DACs for now and focusing on other components.

    That said, there's a flash-able firmware that replaces current filters with a new in-house one (I think) called GTO; would be curious to compare notes on that one once you've had the opportunity to familiarise yourself with the other three.
     
    Last edited: Jan 21, 2020
  3. Yethal

    Yethal Facebook Friend

    Joined:
    Sep 23, 2018
    Likes Received:
    230
    Trophy Points:
    43
    Location:
    Poland
    If possible try running the iDSD using external power input. iFi's iPower has a dedicated adapter included for this specific purpose.
     
  4. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    I'm not totally sure, but the Eco, Normal, and Turbo appear to be gain. The settings actually sound slightly different after volume is matched. By extension, it would appear that higher gain (voltage) comes with associated higher power (given that current is not limited).

    On the soundstage, I hear you on this. Granted I'm using Joe Grados which are open sounding, but don't necessarily have the best depth, I do feel the iFi in general stages deeper than most Schiit gear (the Magni 3+ on high-gain seems good in this regard though). On the other hand, I also suspect higher gain (less feedback) of the Micro BL to be a factor role for the expansive staging. In "Normal" gain mode, I barely have to turn the volume to the 10:00 o'clock position to get a good amount of volume. More open loop (less feedback) tends to sound more expansive and lively, at the expense of higher distortion from steady state single sine wave tones.

    As for the "3D" switch, depending on the track, it can either be a moderate or excess effect. It sounds like a combination of crossfeed with one of those surround sound matrix effects, the latter I really could do without. It seems to work best with sparse music, e.g. Norah Jones Come Away With Me, but to be honest, I don't care for it. The fake surround effect is just a bit too much for most music that I like.

    The X-bass is a nice touch for bassheads. It actually works well with Grados. It's not totally overdone and doesn't explode the midbass to make Michael Jackson sound like Darth Vader, a la the Howard Stern radio show EQ to give Stern a more manly boomy voice.

    If I have time, will try to grab a few measurements to see what's going on at each gain setting and the X-bass.

    I would give that shot, but I don't have an iFi Power on hand. Also, not sure if I really have a desire. The intended use for me in regards to Micro BL is as a transportable without a mess of wires. I like that I only need one, exactly one USB cable to the laptop. And that if I so desired clear power, I could just switch to battery mode. One more wire for me means that I go to a small form factor separates desktop unit.

    In regards to battery mode, I wish there was a button where I could choose to use USB or battery power. As it stands, the procedure is a bit funky. To use battery mode, I need to turn the unit on, and then connect the USB to the laptop. Connecting the Micro BL USB to the PC before turning it on results in the USB power mode.
     
    Last edited: Jan 22, 2020
  5. Lyander

    Lyander Official SBAF Equitable Empathizer

    Pyrate Contributor
    Joined:
    Feb 25, 2017
    Likes Received:
    10,961
    Trophy Points:
    113
    Location:
    Philippines, The
    This makes my lack of engineering knowledge obvious but I honestly hadn't considered that the power modes might've been feedback-based. That'd explain why Eco sounds like it's stuck in skinny jeans.

    Agreed, 3D is a bit hit and miss but it works well in some cases for my tastes, though they do work well for 2ch, at least the budget tier stuff I've used it with. Just makes things sound way too diffuse, like it was a phase thing or what. Kinda redundant considering the inherently good soundstage.

    Just as a data point, posted some squiggles of the older silver Micro iDSD XBass's effect on the HD600 a while back— no small wonder it was a good pair cuz it was largely a sub-bass boost (I also enjoyed it on the Klipsches because... of course I did, hah). Curious how the BL's implementation compares given my subjectives thinking it was even more rumbly.
    [​IMG]

    Agreed too re: battery mode. It isn't as much of a problem once you get used to it, but I sometimes don't bother since I don't relish the thought of wearing my USB ports out by constantly plugging and unplugging; that's Hands's robot sex fetish, not mine ;)

    Oh, and be careful of the IEMatch switch. Apparently if it gets knocked around enough it could contribute to channel balance issues, though IME it depends on headphones. Not a big deal with DT880(250ohm) or HD600, but very obvious with TH-X00EB, Meze 99 Classic, and HP-3.
     
  6. Brooko

    Brooko Facebook Friend

    Joined:
    Oct 16, 2017
    Likes Received:
    132
    Trophy Points:
    33
    Location:
    New Zealand
    Marv, try the 3D with active near-fields. Its really what it was designed for - speakers rather than headphones. Totally agree with you - with headphones it sounds unnatural (and engaging it with headphones adds a slight haze IMO). I have the older original silver iDSD as my main dac/amp (coupled with an iUSB / power filter), itube for my near-fields and a VE Enterpise full tube as main power amp if I'm using the HD800S or HD600.

    The 3D with speakers is more subtle and can actually sound quite good - especially if they're in close proximity. I have a pair of JBL LSR-305s on my desk and combined with the iDSD and itube they sound pretty good. And the 3D is a nice tweak.
     
  7. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    This is what the bass boost switch on the Micro BL does:
    upload_2020-1-23_11-32-39.png

    +8db by 20Hz, which is the same as the Micro Silver. However, it appears that the boost starts earlier on the BL with a 2.5db boost by 100Hz already. I would have preferred the the bass boost on Silver (I blame Sean Olive for all this :(), but this one ain't so bad.

    Confirmed with an actual headphone (Grado Magnum) measurement below
    upload_2020-1-23_11-39-52.png

    Difference plot from the above frequency responses recorded from headphone output
    upload_2020-1-23_11-41-38.png
     
  8. Lyander

    Lyander Official SBAF Equitable Empathizer

    Pyrate Contributor
    Joined:
    Feb 25, 2017
    Likes Received:
    10,961
    Trophy Points:
    113
    Location:
    Philippines, The
    The +8dB at 20Hz is nice, not so much the earlier start. Thanks for confirmation it actually is warmer. Still, might be better for thin headphones like the TH900 or X00 than the silver!

    Nitpick, I just double checked and it's actually +5~6dB by 20Hz on my rig, but yeah negligible differences that low down.
     
  9. Biodegraded

    Biodegraded Friend

    Pyrate Contributor
    Joined:
    May 28, 2017
    Likes Received:
    7,975
    Trophy Points:
    113
    Location:
    Vancouver BC
    Request for yet another parameter, sorry...

    I'd be interested to see the impulse responses and how they compare with the ones you did for the Nano BL. There was discussion of how iFi's definition of 'minimum phase' was odd - wonder if that's still the case, what the effect of the new filter(s) (GTO, or whatever it's called) is, and whether polarity is reversed on the Micro too.
     
  10. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    It's possible those results might be wrong. I believe I recorded them on a Focusrite 2i2, which isn't exactly lab grade equipment and could have introduced its own effects during AD conversion. In addition, I don't believe it was labeled as minimum phase, just "measure" and "listen". IMO, iFi should have just offered "listen"*, but I figure they were ahead of the game in case measurement extremists showed up at the door. Anyway, I do plan on posting measurements related to the three filter settings.

    *Personally, I prefer simple: give me what you think sounds best. I hate options. Stuff like eco mod, sport mode, track mode, that affect steering, shifting, and suspension on cars drives me nuts. I understand that many customers do like to tweak stuff though.
     
    Last edited: Jan 23, 2020
  11. iFi audio

    iFi audio MOT iFi Audio

    Joined:
    Oct 3, 2017
    Likes Received:
    1,284
    Trophy Points:
    113
    Location:
    Many places.
    Home Page:
    Pelase do, that's brilliant what you did, much appreciated!
     
  12. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    This is the best I can do without an AP. I couldn't get consistent impulse responses that made sense, but I can record filter behaviors. Don't mind the wiggles because its noise averaged over time. I fed 44.1kHz pink noise from one laptop to the Micro BL. Then plugged the output RCAs into another laptop recording at 96kHz.

    The Standard Filter looks good. I'm assuming linear phase, steep knee, and decent drop (stopband attenuation is higher). I've always liked this kind of filter. It's "boring" standard with no specialness, but that's always a good thing.

    Standard Filter
    upload_2020-1-23_16-20-6.png

    Surprisingly, the minimum phase filter has a slower knee.

    Minimum Phase
    upload_2020-1-23_16-20-51.png

    And here is BitPerfect. I don't know we are getting a response past 22.5kHz, but it could be some form of proprietary noise shaping in the stopband. We are seeing early attenuation in the password, but I doubt most people will be able to hear it. The stopband attenuation is shallow. Typically shallow stopbands will have the smallest magnitude of ripple in the impulse response. Whatever magic sauce iFi has done with their BitPerfect filter, I've always preferred it because it minds me most of an R2R approach.

    BitPerfect
    upload_2020-1-23_16-23-13.png
     
  13. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    Well, it appears that Eco is unity gain. I'd agree that the sound is more constrained. The Normal seems just right in terms of volume knob adjust-ability and sound quality. Turbo is the more lively, responsive, and expansive, but maybe a bit too much on the transients, where I would avoid leaner or brighter headphones, or headphones with fast transients. However, the HD650 seems just right for the high-gain mode, although limited usable volume knob range may turn people off.

    These impressions are after adjusting volumes to the same level after the gain is adjusted. (As an aside, it may be interesting to conduct a a more controlled blind test, using two of the same amp, set them on different gains, adjust the output output to within 0.001 volts, and then conduct a triple-blind test per this: https://www.superbestaudiofriends.org/index.php?threads/magni-3-heresy-and-3-blind-listening.8663/)

    Micro BL Gain Settings
    RED = Turbo 22.29db or x13.02
    BLUE = Normal 9.04db or x2.83
    GREEN = Eco 0.37db (essentially unity gain)
    micro BL gain.png

    The above results were with external signal generator. FWIW, I also did the performed similar measurements via the SPDIF input to determine that the internal DAC's output is approximately 9.3dBU. 9.3dBU = 2.26VRms = 6.4Vpp. The BB1793 has 3.2Vpp output per the datasheet. With two of them in the Micro BL, each one running balanced, that just happens to be 6.4Vpp

    I'll post THD and power vs THD measurements next. This presents a challenge of sorts because this is an AIO DAC/amp. Let me know if anyone would like to see anything particular (measurements using AverLAB generator vs. built-in DAC, etc.)
     
    Last edited: Jan 23, 2020
  14. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    I'm going to pare down these measurements to typical use cases, yet at the same time try to hit some of the standard values that @atomicbob and @ultrabike have discussed (0dbU, -10dbU, and -20dbu or 0.775Vrms 0.225Vrms, and 0.0775Vrms respectively (as opposed to random numbers like 2Vrms or 4Vrms that I will pull out of my ass). Note that 0dBu or 0.775Vrms is enough to drive headphones like the HD650 to 110dbSPL. Please make any specific requests.

    The first few measurements I will use the volume knob to manually dial-in the output, instead of maxing the volume out and letting the signal generator do the job. Anyone who owns one of these knows that's a loud volume position for efficient Grados or IEMs (normal gain, no IEMatch).
    IMG_20200123_180410.jpg

    Micro BL
    -20dBu at output, referenced to 0db line
    into 32-ohms (thinking Grado or IEM use case, which is immensely loud)
    Normal gain 9db, no IEMatch, USB power
    1kHz steady state sine wave
    AverLAB generator
    upload_2020-1-23_18-2-21.png

    -20dBu at output, referenced to 0db line
    into 300-ohms
    Normal gain 9db, no IEMatch, USB power
    1kHz steady state sine wave
    AverLAB generator
    upload_2020-1-23_18-10-24.png

    Small AC mains and harmonics evident, a little bit over -100. Small tiny blip of 2nd harmonics. Low noise. No one will hear any of this stuff.
     
    Last edited: Jan 23, 2020
  15. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    Let's try a higher volume level. Note: that's insanely loud for an HD650.
    IMG_20200123_181656.jpg

    0dBu (0.775Vrms) at output, referenced to 0db line
    into 300-ohms
    Normal gain 9db, no IEMatch, USB power
    1kHz steady state sine wave
    AverLAB generator
    upload_2020-1-23_18-36-47.png

    0dBu (0.775Vrms) at output, referenced to 0db line
    into 300-ohms
    High gain 22.29db, no IEMatch, USB power
    1kHz steady state sine wave
    AverLAB generator
    upload_2020-1-23_18-28-24.png

    At higher levels, we start to see the AC mains noise creeping in. But seriously, it's all context. With the HD650 blaring at 110db, AC mains noise at -100db is not going to be an issue. Typical ambient in a home will be 30dbSPL at best, unless you happen to live in a soundproof dungeon out in the boonies.

    Bottom line is these particular 1kHz steady state sine wave measurements don't show us anything interesting that would correlate to human perception or say that something is wrong. At least for the amp section.
     
    Last edited: Jan 23, 2020
  16. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    Now let's do the same using the internal DAC fed SPDIF, as a full AIO, still using volume knob to adjust output levels.

    Micro BL
    -20dBu at output, referenced to 0db line
    into 32-ohms (thinking Grado or IEM use case, which is immensely loud)
    Normal gain 9db, no IEMatch, USB power
    1kHz steady state sine wave
    Internal DAC fed SPDIF
    upload_2020-1-23_18-58-29.png

    Micro BL
    -20dBu at output, referenced to 0db line
    into 32-ohms (thinking Grado or IEM use case, which is immensely loud)
    Normal gain 9db, no IEMatch, battery power (USB cord disconnected)
    1kHz steady state sine wave
    Internal DAC fed SPDIF
    upload_2020-1-23_19-3-0.png

    Battery power does measure better. As I mentioned earlier in the subjective impressions, I did feel the battery power sounded better, particularly in the highs which were smoother and less rough. The first graph may look "bad", but in the context of things, it really isn't. The AC mains are still -75db down. Can you hear a whisper at 25db while listening to music with peaks at 100db SPL? I think not.

    Also please keep in mind that these measurements are at somewhat realistic (still extremely loud) power levels. I'm not pushing 2Vrms or 4Vrms into headphones that would make them light up on fire, that is not after your eardrums exploded. We are talking about 0.775Vrms. Headphone only need milivolts to sound loud.

     
  17. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    Finally, let's take a look at the HD650 use case with the Micro BL as an AIO.

    Micro BL
    0dBu at output, referenced to 0db line
    into 300-ohms

    Normal gain 9db, no IEMatch, battery power (USB cord disconnected)
    1kHz steady state sine wave
    Internal DAC fed SPDIF
    upload_2020-1-23_19-10-12.png

    A few harmonics, the second harmonic just above -95db. I wouldn't worry about it. CD audio has a theoretical max of 96db of dynamic range. Even if CD has more bits, no human can hear this stuff. If the Micro BL sounds different from other amps, it's because of other reasons unrelated to a steady state 1kHz sine wave.
     
    Last edited: Jan 23, 2020
  18. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    THD+N vs. Frequency
    0dBu at output
    into 300-ohms
    Stepped single steady state sine waves
    Bandwidth 44000
    Normal gain 9db, no IEMatch, battery power (USB cord disconnected)
    1kHz steady state sine wave
    Internal DAC fed SPDIF
    upload_2020-1-23_19-19-53.png

    A slight rise in THD as we go up in frequency, particular in a last octave, but nothing concerning.
     
  19. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    THD+N vs. Frequency
    -20dBu at output
    into 32-ohms

    Stepped single steady state sine waves
    Bandwidth 44000
    Normal gain 9db, no IEMatch, battery power (USB cord disconnected)
    1kHz steady state sine wave
    Internal DAC fed SPDIF
    upload_2020-1-23_19-23-43.png

    THD is flat and the same, regardless of frequency.
     
  20. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    89,771
    Trophy Points:
    113
    Location:
    Padre Island CC TX
    I'm about done, will post power measurements next. Maybe tomorrow.

    Maybe some level matched blind tests compared to the likes of JDS Atom with a Modi 3 as source (to keep things even). I'm thinking I already much prefer the sound quality of the Micro BL to the Atom, but perhaps a test would be warranted.
     

Share This Page