S9 Pro Plus Martha HiFi Balanced Dongle DAC & AMP, 768kHz/32Bit, DSD512 Portable Audio Decoding Amplifier for iPod Android PC with Windows/Mac OS/iOS/iPad OS System (Black)

I had the opportunity to try this 'Martha' DAC from HIDIZS; I'll be reviewing this as the average layman - because I am one!The closest to a similar device I have used in the past was an amplifier dongle that also provided virtual surround sound - a far cry from what is offer here. While I understand the terms used when discussing this DAC - I don't really have the ability to judge how they affect the performance. What I do have is a pair of ears though - so that is what I'll offer (audio quality comparisons - not my actual ears...).While I have tested this on Windows - most of my testing was done on a MacBook using Apple Music.The dongle is a fairly unassuming little metallic job. It comes with a fairly short USB-C to C cable plus an USB-C to A adaptor. The only controls are volume up and down (which in terms of a Mac control the system volume). There's a 3.5mm socket and a 4.4mm one. Being quite honest - I'd never even heard of that standard.Firing up Apple Music I dipped into the settings first to change to lossless formats. If you select "Hi-Res Lossless (ALAC up to 24-bit/192 kHz)" you get a warning that you will need an external DAC - which this Martha unit has you covered.Right - how to describe it. If you've tried various headphones in the past you probably know about different groups of qualities. Some have good middle but no bass, some have really good bass but the middle is 'muddy' etc. Then you get that occasional pair where everything clicks? The bass is punchy but not overwhelming, the middle is distinct and easy to pick out and the top end is clear and present - not thin. Now think of that as one blended audio image. What you get here is every instrument/element of the track feeling like it's lifted out of the 2D audio and positioned exactly where the engineer meant it to be. A "wide" sound is an understatement.I always use the same 2 tracks when testing audio equipment - Clearest Blue by Chvrches and One Day Remains by Alter Bridge. 2 reasons: one - I like them (which always helps!) and two - they both are quite heavily layered, always-on tracks. For the latter, the rhythm guitar stood out way more than it normally does and was quite distinct. With Clearest Blue - which is a mainly electronic track - I was picking up subtle echoes and reverb especially on the backing vocals that I'd never even noticed before!So yes - this works fantastically well. I really can't offer an opinion on value for money though. I'm the sort of person who has never spent more than £50 on headphones so stumping up £74.66 for "an enhancer" isn't something I would likely do - however I know there are audiophiles out there! In terms of sheer quality of output alone this has to be 5 stars.