 February 2020 I reviewed the Holo Audio May Level 2 DAC and was rather impressed by it. When I reviewed the Magna Mano Ultra MK3 Farad Streamer last week, I was lent the May DAC again. I found it a golden chance to listen to it again but this time on my heavily upgraded Reference Setup 1A. This is going to be a slightly different video than normal since I have already reviewed the Holo Maze extensively. If you haven't seen it already, you might want to watch it first since this is a follow-up on it. Links in the top right corner, in the show notes below this video in YouTube and at the end of this video. When I reviewed the Holo May I used my previous Reference Setup 1, the Audio Note Soro SE that was rather tweaked by Peter van Willenswijk with high quality capacitors and tubes. It drove the Audio Physics Scorpio loudspeakers. The Mitek Brooklyn DAC was fed by the SOtM-SMH200 Ultra used as Roon Endpoint. It was connected to the SOtM-SNH10G network switch. The Intel Noc 8 i7 ran Roon Rock. Today only the Noc and the Switch are the same. The Air AX520 amplifier drives the PMC FAC12 signature loudspeakers over AudioQuest Robinhood 0 loudspeaker cable. The Core Dave does the digital to analog conversion and the digital source is the Grim Audio Mule 1. Since my music collection is extremely large, I started using the Noc with Rock again as Roon Server instead of the Grim and used the Grim as Endpoint only. For such a large collection, over 11.000 albums, the i3 and the Grim was too slow. Sound wise nothing changed when the Roon Server is separate. The Grim is connected to the SOtM-SNH10G network switch. All is placed in a Creative Trend 3 rack. For this evaluation, the Holo May was placed side by side with the Core Dave. Each connected to one of the AES-EBU outputs on the Grim and the output level of the Dave was adjusted to have the same output level as the Holo May. Switching between the two was done on the amp. The distributor Magna Audio has set the PLL to OFF. PLL stands for Facelock Loop. This is a circuit that when it receives a digital signal, it tries to lock to it by slightly varying the clock frequency up and down. This assures that no bits get lost but it also means it passes on some degree of jitter. The amount of jitter depends on how far up and down the PLL will vary the clock. The less the frequency is varied, the lower the jitter but the larger the chance it loses the lock to the signal. This is the reason that cheap CD players have a better capability to play damaged CDs and also one of the reasons they sound poorly. But I digress. If you know the source offers a very clean jitter-free signal, the sound quality goes up when the PLL has a narrow catch range. Let me again recommend the video registration of my presentation at the Noir et Blanc Brussels Hi-Fi Show 2022 from 20 minutes and 26 seconds onwards where this is explained. Links at the top right of the screen, at the end of this video and in the show notes. The manual of the HoloMAO states that the PLL is either switched on or off. That could be the case but then there needs to be another circuit to lock into the digital signal unless the I2S input is used. In the video of the Magna Mano Ultra MK3 Farad I described the sound quality difference between I2S and AES EBU or rather the lack of it. Some time ago I came to the conclusion that provided the interface is of near perfect quality there will be no difference in sound quality between using I2S and AES EBU. Unfortunately there is a lot of equipment that has poor digital outputs whether it is AES EBU, I2S, SPDIF or any other interface. Magna knew I would use the Grimm U1 next to the Mano Ultra in the review. They already had the experience that the Mano Ultra over both AES EBU and I2S and the Grimm Audio over AES EBU sounded best with the PLL in the off position. I have tried the on position too only to find that they were right. The other option is to choose for op sampling or not. The May offers three ways of op sampling. Op sampling to a higher sampling frequency in a native format, so DSD is op sampled in the DSD format while PCM is op sampled in the PCM format. The second option is to op sample both formats to PCM while the third option op samples all signals to DSD. All four modes can be selected on the front or from the remote control. Switching to and between op sampling modes is instantaneous. Switching back to non-op sampling does take some time to settle back to the base sample frequency. I suppose this is because the AKM async op sampling chip is no longer in the signal path. I have tried it all and came to the conclusion non-op sampling would be my choice. Of course I had the op sampling and the 3DB headroom switched off in the grim audio. The latter, by the way, is to give the DSB some headroom and thus avoid the sample peaks. The HoloMay level 2 keeps impressing me, also in my current reference set of 1A there is a few notches up from the previous one. And yes, I love the art of understatement. What I've found remarkable is that the sound character was close to that of the chord. On many mainstream albums I hardly heard a difference. Only on the better recorded albums the chord had more detail in the highs, more textures in the low and a better micro-dynamics. Also the spatial projection was even more royal. The music came more alive on the chord in a direct A to B comparison. But the differences were not that big, while the chord is twice the price. There might be a simple explanation. If a DAC doesn't oversample, there is no pre-echo since there is no digital filtering. If then the analog reconstruction filter is done with the utmost care, the post-egos will not bother the air. The chord does upsample but with an extremely good algorithm in an extremely expensive FPGA chip. Also here the tensions are very clean because of very little time smearing. I rate the HoloMAY level 2 in the middle of my reference set of 1A, a place where normally more expensive DACs can be found. Let me get back on the i2S vs AES EBU question. The HoloMAY I got was only played one or two days when I received it. As always it was immediately connected to the mains and to a Roon endpoint. That was fed music from Roon 24x7 for 10 days before I did the listening for this video. But I couldn't resist comparing i2S and AES EBU coming from the Magnum Amano Ultra MK3 Farad I reviewed last week and that arrived the same day after delivery. So both had not played enough to be burned in at all. At that time i2S was clearly superior to AES EBU. It had more detail, a better stereo image, better lows and far better sibilance control. I think this has to be explained by the separation of the clock signal from the audio data. In AES 3 signals, AES EBU, SPDIF and TOSLINK, the clock signal is encoded in the data stream and that makes it harder for the power line might not be stable since capacitors have to settle and so on. Again see my presentation at the Noire Blanc-Mutt Brussels Hi-Fi Show 2022 from 20 minutes and 26 seconds for an explanation. And as said before, after a proper burning period, the differences between i2S and AES EBU was gone. This means that the implementation of both interfaces in both devices and the cable used were perfect. The whole of May level 2 had made a very good impression the first time I reviewed it. Now on my new reference set of 1A I am heavily impressed how much further the sound quality goes. Current EU price is €5,390 including 21% VAT. And although €5,000 is a lot of money, I confidently would name it a steal. And with that we come to the end of this video. I will be back next Friday at 5 p.m. Central European Time. If you don't want to miss that, subscribe to this channel or follow me on the social media so you will be informed when new videos are out. Help me reach even more people by giving this video a thumb up or link to this video on the social media. It is much appreciated. Many thanks to those viewers that support this channel financially, especially in these times. It keeps me independent and lets me improve the channel further. If that makes you feel like supporting my word too, the links are in the comments below this video on YouTube. I am Hans Beekhuyzen, thank you for watching and see you in the next show or on theHBproject.com And whatever you do, enjoy the music.