This is a review, detailed measurements and comparison of Schiit Jotunheim Headphone Amplifier (with its optional Multibit DAC) and iFi micro iDSD Black Label DAC and Headphone amplifier. Both are on kind loans from members and arrived on the same day. Seeing how their prices are similar, I decided to compare them to each other. The iFi however, has built-in battery, is far smaller and less power hungry, making it suitable for portable use in addition to desktop. The Jotunheim on the other hand, is firmly a desktop product, in a pretty heavy case for its size and is mains powered. Here they are together:I say the minimalist look of Schiit products is best represented in this form factor. I also like the heft and feel of the large volume control.The ifi is quite cute and nicely done from style point of view. Alas, I don't like switches spread everywhere on the side and bottom. Placement is more optimized though so perhaps that is good for performance.As mentioned, the Schiit Jotunheim came with its optional DAC board. With the included DAC it retails for USD $599 plus shipping direct from Schiit (they don't sell any other way). The iFi iDSD Black Edition seems to be listed at the same price. So it is a fair comparison from that point of view.Both worked in plug-and-play mode with Windows 10 Creators edition. For measurements I used ASIO4ALL to create an ASIO interface for my Audio Precision analyzer software to control them. For listening, I used WASAPI interface in Roon player.iFi iDSD Black supports DSD up to 512 whereas Schiit Jotunheim DAC does not support DSD at all. On the other hand, the Schiit Jotunheim has both balanced analog inputs and outputs in addition "balanced" headphone out. I did not test any of the balanced functionality in this review.I am sure you are all anxious to see how they measure so let's get into that:Let's start with our usual Dashboard of iFi iDSD Black:I have set the level of the headphone output to 2 volts to more or so match the nominal RCA DAC outputs. At 93 SINAD (signal over distortion+noise) fidelity is respectful. No, it is not at the state-of-the-art desktops that go 110 dB and beyond but pretty good for a portable USB DAC with headphone output.Switching to Jotunheim, we see clearly reduced performance at the same 2 volt output:We lose 10 dB of SINAD. And we see that mains hum in the FFT spectrum as indicated.The story does not end here though. By chance, I put my hand on the Jotunheim while having my other hand on the metal case of my laptop and to my amazement saw that mains hum go right down! What the heck???I disconnect power and pull out the power and check for grounding. I first test to see if there is continuity between mains safety ground and unbalanced/RCA signal ground:We get 0.2 ohms which essentially says they are connected. Now the same test but this time with the upper part of the case:Yup. "OL" means open load or no connection whatsoever! Notice how I am poking my sharp leads into the drilled holes of the upper case. There is some kind of coating on it that insulates electricity which I suspect the reason it is not grounded. However it is screwed to the bottom (which is grounded), there is no electrical connection.So I ground the upper case using the same drilled holes to the RCA connection as such:And our dashboard now shows:Look at the FFT. The mains hum is gone, gone, gone! The worse channel (#2) shows 1.6 dB of improvement in SINAD. All with a 10 cent wire jumper!Note that the difference was more dramatic at other times.The Jotunheim like other Schiit products uses an EI core transformer (as opposed to toroidal) so it is essential that the entire case is grounded to keep the magnetic field from coupling into the audio circuit.More important, this is a three-pronged mains input in a device with metal case. This means it is NOT double insulated and as such, from safety/UL point of view, it most definitely needs to have the entire chassis connected to mains safety ground. Should the hot lead come in contact with the upper case holes, it will energize it and no circuit breaker will trip! Yes, it is a one in a million chance of happening but if it happens to you, it will be a one in one chance.This problem needs immediate investigation by Schiit. I suggest that owners get an ohm meter with sharp probes and repeat my test above. If you get an open load as I did, contact Schiit and ask them to investigate and repair.Anyway, let's continue with distortion versus frequency measurement:Once again, the iFi DSD Black provides competent performance whereas the Schiit has that odd rising distortion with frequency. 0.3% distortion at 20 kHz in this day and age? Really? This is unacceptable. It is likely running out of gain to provide feedback and reduce distortion.Here is the intermodulation distortion versus input level:Looks like one channel in iFi iDSD Black is noisier than the other. As the signal gets larger, that difference gets lost in the noise literally and performance is good. But again, not in desktop category as shown by the Oppo UDP-205 -- one of the best measuring DACs out there (really a UHD Blu-ray player). The Schiit Jotunheim underperforms the iFi iDSD Black by 10 dB or so. This is very significant difference.How about jitter and noise?While iFi iDSD Black outperforms the Jotunheim by 10 dB again in noise, the latter seems to have a decent performance too. So not much to complain about.And oh, here is the frequency response for iFi at 44.1 kHz CD sampling:And Schiit Jotunheim:The reconstruction filter in the DACs rolls off the highs in both starting at 17 kHz. Not an issue for us older folks but for younger crowd, it would be good to have this be a couple of kilohertz higher.As headphone amplifiers, probably the most important measurement is distortion versus output power. These are newly styled measurements that show the power directly. They rely on me remembering to set that parameter correctly which I think I have (crossing fingers). First at 300 ohm load to simulate a headphone like Sennheiser HD-650:The iFi iDSD Black yet again shows off its lower noise but I was very surprised to see it outperform the Schiit Jotunheim on power! The iFi is a USB powered product folks. Yet it is pushing more power and cleaner level than Schiit Jotunheim which seems to have some kind of internal limiting.Stepping down to 150 ohm we get this:Same differential in performance in favor of iFi.And 33 ohm:Amazing. The iFi continues its lead at all output loads/impedances.Finally, let's look at channel imbalance as I in real-time adjust the volume control and the analyzer plots the power (at 300 ohm load) versus channel imbalance. First iFi iDSD Black:I put both units in their lowest gain mode because that is the most useful scenario. There, the error for the iFi is below 0.3 dB or so until the very end/minimum level. Audibly you can easily tell one channel cuts out earlier than the other in high-gain mode. In low/eco mode, it is much, much less noticeable. With three different gain settings, I don't think this is a problem for the iFi.Here is Schiit Jotunheim:The Jotunheim is more well behaved here with channel balance maintained much better at the limit.Output impedance was excellently low in both with iFi landing at 0.9 ohms and Jotunheim at 0.8 ohms.Let's get into how they sound.I usually perform level match testing of headphones. This time I thought I do as others do, listen to music and quickly switch the headphone jack back and forth (playback is ganged through Roon). Even though the tests are sighted and obviously not level matched, I think the results mirror measurements pretty well because focus is on power delivery and clarity. Then again, they may just be my imagination so read with caution!I started my testing with my Sennheiser HD-650 headphones. I seem to never have enough power to drive these. Well, that changed with this review.I started with my electronic tracks which I find most revealing with headphones and headphone amps. To wit, this track from 20 KID: https://suiciderobot.bandcamp.com/track/switch Here is another one of their tracks:I must say, I didn't there was a such a thing as "subwoofer for your ears" but this is the best analogy I can come up with when driving the HD-605s with iFi iDSD Black. At mid-levels before pain sets in, you can feel your ear lobes vibrating and the headphone cups taking flight! Yes, the cans start to physically vibrate back and forth. It was an incredible and highly satisfying experience I had not had with headphones!What is that? Speak up, I can't hear you!Yes, it was loud, but not too loud for a few seconds of testing.Too loud came after turning up the level even more!It now feels like my head is inside the drums. What an experience. If I did not fear permanent hearing loss, I would listen like this all day! I must say, the sound stayed clean until I got too scared to turn it up further.I then switched to Schiit Jotunheim. It too had incredible power able to make the headphone cups run for their lives. Alas, the bass is less clear and distinct than the iFi. And highs have this smeary slightly weird sound to them.Mind you, the extra power of the Jotunheim is quite a bit more satisfying than lower distortion but lower power headphone amps. It is just that in the presence of the iFi iDSD Black, it had power but without the finesse. So I can understand the praise this unit gets.I should say that the iFi iDSD Black as the measurements showed, has more power and headroom than Jotunheim.Next I switched to a low impedance Grado SR60e. With ifi at low volume the experience is quite satisfying with highly dynamic sound. Turn up the volume just a quarter though (in "turbo" or highest gain mode) and the Grado starts to cry. The drivers start to rattle and buzz. Prior to that there is a transition period where distortion sets in. It is fascinating to see the headphone distort well before the amplifier does.Using the Gradoes with Jotunheim was unpleasant after listening to iFi drive them. High frequencies are more distorted at almost all listening levels.Next was Sony MDR-V6. At more than a quarter volume with the iFi, it felt like the drivers were going to tear up! These headphones simply can't handle power. Driving them with Jotunheim delivered a dull experience in contrast. Detail and distinction in bass gets lost due to the amp and the driver distortion screws up the rest.Last but not least is HiFiman HE400i. What a delight these headphones are. As with Sennheiser HD-650s, they easily handle enough power for the cans to take flight and your hearing anatomy dance to the pressure waves of the music! Distortion was so low that I could turn the volume enough until my cheeks started to resonate with music! Too scared to push the volume above 2:00 o'clock position.The experience with Jotunheim was muddy and dull again. Yes, the power is there to rattle my teeth just fine. But the overall fidelity simply is not there compared to iFi iDSD Black. As you turned up the volume to the end, distortion gets really bad and obvious. This is in sharp contrast to the iFi which would deliver clean power to the extreme.It was great to test these two high-power headphone amplifiers. They forever changed my experience and expectation of headphone amplifiers. Between the two, the iFi iDSD Black Edition is a clear winner. It is so both in objective measurements and subjective listening tests across multiple headphones.The lack of upper lid grounding in Jotunheim is a safety concern and likely the cause of hum and noise in its user base. It produces higher distortion and noise which I find audibly objectionable. It also generates fair bit of heat. The top is borderline too hot to put your hands on.In sharp contrast, the iFi iDSD Black barely gets warm and delivers power that belies its diminutive size. The fact that this much performance is also portable with battery power, is incredible.Well done iFi.-------------As always, questions, comments, recommendations, etc. are welcome.If you like this review, please consider donating funds for these types of hardware purchases using Patreon ( https://www.patreon.com/audiosciencereview ), or upgrading your membership here though Paypal ( https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054 ).