Sony MDX-U1
The first automotive MiniDisc head unit
To fully appreciate the Sony MDX-U1 in its entirety, you’ll have to take a good look at the world of electronics in 1992 – specifically car audio in this case. The most prevalent at the time was the cassette, which mostly everyone is quite familiar with. The sound quality was not the greatest, and arguably worse (uses may vary) than the outgoing 8-track format which preceded it in popularity. While CD had already been released for 5 years, it’s mass use prevalence was very small. And although CD quality was fantastic, there was no way to record your own CD’s at the time of 1992 – not for the general public at least. Finally, there was DAT, and Sony did release it’s one and only in-car DAT head unit in 1990. The sound quality was exceptional and recording your own DAT tapes were also possible, but the cost of entry was much too high.
Cost of entry
Enter the MiniDisc. More compact that any other physical media at the time, extremely durable, and although expensive, was within reach. Much like the portable MZ-1, the cost of the MDX-U1 was not cheap at approximately $800USD ($1788 as of January 2025). Mind you, all car audio was quite expensive when compared to what people pay today. Nevertheless, you’d be paying more than the average head unit… but in return, you would be getting something that was rather feature rich at the time.
Features
The Sony MDX-U1, was positioned as an upper tier unit. Much like the previously released DTX-10 DAT head unit, the MDX-U1 was also a dead head – essentially a head unit that did not have built in amplification. The purpose of not including built in amplification was for two main reasons:
- Squeeze in as much good tech as possible
- Allowing the end user to pair it up with external amplifiers which would always be better than what could be built in at the time.
The MDX-U1 also offered a detachable face and a remote which was typically reserved for higher end units. The wireless remote that came with the unit was also fairly unique – at the time shared with only one or two other units. The norm at the time was to have wired remotes for top tier models – so wireless was quite impressive for its time. Additionally, not many head units had detachable faces, and this feature was pretty much introduced during the beginning of that trend, replacing the previously popular “pull-out” head units of the 80’s and early 90’s.
More importantly, the price of entry in the car audio minidisc world meant that some features were new – most notably Album and Track Titles. This was definitely something that wasn’t available to any physical media, and with the MDX-U1’s bright display, it was showcasing that feature with style. Interestingly though, with this new feature ability to show titles, the MDX-U1 does not show Japanese Katakana script unlike the newer portables. Rather, it Romanizes the Katakana script which I thought was pretty interesting – It shows that the devices does have the capability to read/decipher the characters. A much better solution than leaving the display blank.
Unbeknownst to those who bought the unit brand new in 1992, the MDX-U1 actually had features which would allow it to be relevant for a while. It was supplied with Sony’s Unilink capability which was Sony’s communication method for adding accessories like CD Changers, equalizers, etc. The interesting part is that the MDX-U1 came out about 3-4 years before the first Sony MiniDisc changer, yet it has the protocols to control it properly. This amazed me because I had also recently found out that newer head units had lost the ability to control MD changers – Sony engineers deliberately took out that ability for some strange reason. Additionally, it was one of the few units that Sony offered – EVER – with an optical digital input. While this uses a very specific proprietary optical adapter, it was actually included in the box when you bought the MDX-U1 new. There aren’t many good reasons for why Sony would have included this feature other than to showcase the built in DAC. Oddly enough, there weren’t many CD changers that had an optical output to work with this head unit at the time. In 1992, that would be the CDX-U606 10 disc CD changer… and that’s it. A cool feature, albeit rather limiting at the time. Sony would later release about another handful of changers with optical outputs over the next decade though.
Listening
So with what seems to be a fairly future proof head unit, how does it actually sound? And how does it hold up to 2025?
So lets start with it’s competition in 1992. This head unit would have been pretty much top tier but falling behind the statement lineups from Sony (XES line – the one line higher than ES), Pioneer/Carrozzeria ODR, and Clarion ADSC-1 (which no one cares about sadly). It also wouldn’t be able to keep up with Alpine’s flagship 7909 either. Those aside, this head unit would sound as good, if not better, than most CD head units at the time. Needless to say, it sounded better than all cassette units – except maybe the Nakamichi TD-1200ii… but that’s something I don’t have to compare with.
The output, being limited to pre-out, relied heavily on the quality of the amps you end up using. But that said, the MDX-U1 is a good pre-amp. While it’s not going to have the higher voltage outputs you’d find in newer units, it’s definitely no slouch. And in 90’s, it would have been common to use line drivers to increase line output.
So what about the digital input? Personally I think this didn’t go as well as Sony had intended. The MDX-U1 doesn’t exactly have a stellar DAC. It’s definitely not the fancy DAC’s used in the flagship units like the aforementioned XES or ODR, so when you playback with the CDX-U606, don’t expect anything special. It definitely works and when put into perspective of use case scenarios, it’s a good feature. I say this because it would have been common to place CD changers in the trunk at the time. Without the optical digital connection, you would have to run an analog cable along the whole length of the car which would be prone to picking up RFI/EMI associated noise. In my opinion, it would have been nice to offer the MDX-U1 with an optical output, rather than an input. Sony’s external processors, like the XDP-210ES would have been released a few years later but in my opinion would have made this a much better sounding unit. Sadly, I don’t think Sony ever offered an MD head unit with an optical output.
Using the MDX-U1 today, it’s a good solid head unit. It obviously doesn’t carry fancy features you would find in head units later in the 90’s, but that’s a given. There aren’t any processing DSP/Xover features beyond Bass and Treble. There aren’t any flashy lights or any bypass audiophile features like one would find on the Alpine 7909, for example. It’s easy to use and it still sounds solid. The mechanism, being the first ever, is clunky – but honestly, it’s no different than some newer Clarion units I’ve used. But it’s definitely not as smooth as the later generation Sony head units. Fidelity wise, it’s ATRAC 1, and sounds the part. With newly recorded discs, it still sounds very good. All the details are there, I wouldn’t say that anything is missing in terms of music delivery. Even the imaging is rather good, as is stereo separation. If I were to nitpick, it would just be the ultimate clarity is just not as top tier. But that said, it’s extremely good for 1992 – and I’m listening to it as I write this. The output is very balanced across the frequency range – you’d be surprised how other units/brands have imparted a certain “flavour” into the sound processing where it may accentuate the bass or the treble. The MDX-U1 doesn’t exhibit any of that, and I appreciate that.
All in all, this was a fantastic start for minidiscs. It works flawlessly, there are no strange user interfaces, and it sounds impressive for its time. Would I recommend anyone to find one? Not particularly – there are better options in terms of features and sound quality. However, if you need something that is period correct, this is a great option. Also, one of the nicest features is the MiniDisc logo on the front face – it lights up!
Equipment used with the Sony MDX-U1:
Cascade Audio Engineering 90A power supply
DIY speakers featuring Madisound designed crossover, with a Scanspeak R2904/70000 tweeters, and Focal Utopia 6W2 Be midrange
Mogami and Ultralink cabling
Amplifiers used: Sony XES-M50, Sony XES-M3, Signat Rambo, McIntosh MC431M, Soundstream Class A 10.2, Phoenix Gold ZPA 0.5
Recommendation if you choose to use this head unit:
Use a line driver, or even better, a balanced line transmitter to increase the signal voltage. Additionally, use a higher power amplifier. While the XES-M50 and Soundstream Class A 10.2 sounded great, the potential of this head unit really didn’t shine unless I used something with higher power like the XES-M3 or McIntosh MC431M. While my speaker has an impedance of 6ohm, it’s not likely you’ll notice much difference with a standard automotive speaker setup with an impedance of 4ohm.
Review and photos by Eddie Chan (@minidisc_4eva)