There are several reports about the under $100, ultra-compact SMSL SU-1 being a fantastic audio bargain. After reading/watching a few online reviews, I purchased a couple of them to try out with the intention of modifying one to see if any improvements over the stock unit were possible. I am happy to report that the SU-1 responds extremely well to modifications and has very much exceeded my expectation as to what is possible for a budget DAC. Summarized briefly, to get the SU-1 to sound at home in even a multi-thousand dollar stereo system, you'll need to:
- Power it using a high quality 5VDC linear, regulated power supply
- Upgrade the onboard opamp to a Nisshinbo Micro Devices MUSES02
First off, it should be noted that in stock form, the SMSL SU-1 is pleasant sounding device, albeit somewhat lacking in refinement and tonal richness. It features a cutting edge and very interesting Asahi Kasei Microdevices AK4493SEQ 32-bit, 2-channel chip. This DAC chip is part of AKM’s new and well-regarded Velvet Sound brand and sits one step below the flagship AK4499EX. Whether due to its implementation or the AK4493SEQ DAC itself, the SU-1 doesn’t have the pronounced digital glare of many modern DACs. Removing the 4 machine screws on the back panel and taking off the top of the chassis reveals an inexpensively built but rather stout SMT-based board that features either an OPA1612 or LME49720 output opamp depending on production run. Both opamps are generally well-liked and made by TI.
Now the SU-1 does not come with a power supply when purchased new. Those of you who might have read my Hagerman Bugle modification thread know I’m a fan of high quality, linear, regulated power supplies. Of course, I am not the first person to suggest this as an upgrade, but I can report that the SU-1 responds beautifully to being run on good quality power. I am presently using an Elenco XP-100 Deluxe Battery Eliminator, but any good 5VDC, 1A or greater linear regulated supply should produce great results. I found these outperform good quality, inexpensive switch-mode power supplies (like the Apple 20W USB-C power adapter) by a fair degree with the SU-1. The XP-100 also (surprisingly) outperforms my portable USB rechargeable power bank. While the SU-1’s output is very quiet using batteries, it lacks the drive and dynamics that are present with the XP-100. Also the XP-100 has sufficiently low noise to not adversely affect playback. It should be known that many DC power supplies use a 5.5 x 2.1mm plug, so in this case a DC 5521 female to USB Type C male plug adapter cable is needed:
https://www.amazon.com/dp/B0CR4B1YM7?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_10&th=1
The next modification involves removing the onboard SMD opamp and installing an 8-pin DIP to SOIC adapter like the one available at Cimarron Technology:
DIP-8 Adapter – BrownDog 201202 – Cimarron Technology. This is a slightly tricky procedure made easier by purchasing a hot air rework soldering station. If the adapter from Cimarron Technology is ordered with a DIP socket installed, a wide variety of opamps can be installed and tested for sonic compatibility with the SU-1. To that end and after many listening sessions with several different opamps, I am quite impressed with how the SU-1 sounds with a Nisshinbo Micro Devices MUSES02 opamp: extremely smooth, highly detailed, and with a magnificent rendering of voices. Best of all, there is virtually no digital glare, to the point where I sometimes forget I am listening to a digital source.
If you happen to be in the market for a new DAC and are handy with soldering SMDs, consider purchasing the SU-1 and performing the above mods. Also if you do, let us know how it goes. The SU-1 pairing with the MUSES02 opamp is so good you may find it to be your new favorite DAC. At present, I am using both the coaxial and optical inputs of my DAC (slightly preferring the coaxial) and as time permits I will start working on using the USB input. At minimum, this will require the use of a split cable that has a line for a separate DC input similar to the Ghent Audio U22 cable, but with a USB C connector. (
(U22) Type-A to Type-B Cable with DC-Input)
If you require a remote, the SMSL C100 is virtually the same DAC as the SU-1 but with a remote. Performing the same upgrades yields similar and substantial sonic benefits. Comparing the two, I find the modded SU-1 sounds a touch better, but the convenience of a remote may offset that small benefit. Lastly, due to the number of counterfeits, I purchased my MUSES02 directly from Mouser Electronics and would recommend anyone interested to make sure they are buying opamps from a reputable dealer or they might not get the same benefit described here.
I would like to send a huge thanks to
@desertrat748 and
@knotscott for testing out the different variations of the SU-1 and providing their extremely valuable feedback. I’m sure they will be active in replies to offer their long term testing opinions. Thanks for reading!!
