FiiO M21 Review

Introduction

Back in March this year I reviewed FiiO’s bargain-tastic JM21 digital audio player and suggested it redefined what an entry-level machine could be and ought to cost.

Now I think I know what the ‘J’ stands for – it must be ‘junior’, because FiiO is back with the M21. It’s a little more expensive, it’s a little better specified and it feels a little more premium. Does it perform a little better than the JM21 too?

Design

• Aluminium and glass construction
• 121 x 68 x 17mm (HWD)
• Weighs 193g

It’s smaller than your average smartphone and lighter than many of them too – but the M21 doesn’t seem in any way built down to a price. Quite the opposite, in fact – the combination of aluminium chassis, AG frosted glass for the rear panel and an oleophobic coating for the 4.7-inch glass touchscreen at the front makes for quite a luxurious feel.

The screen itself is bright and, thanks to a combination of Android 13 with Qualcomm Snapdragon 680 running the show, very responsive. It provides a clean and useful interface for most of what you want your FiiO to do – in combination with some physical controls around the edge, operating the M21 is completely straightforward.

On the left edge of the player (as you look at the touchscreen) there’s a power on/off button with a little LED beneath it letting you know what’s what. Then there’s a volume up/down rocker and a multifunction button that can have its function defined as one of a dozen different options in the Settings menu. Below this is a Desktop mode on/off switch and a hold switch to prevent unintentional operation of the player.

On the right edge there are just three buttons: skip forwards, play/pause and skip backwards. On the top edge of the M21 are two outputs – one is a hybrid SPDIF/unbalanced 3.5mm analogue output, the other a fully balanced 4.4mm analogue alternative.

On the bottom edge you’ll find a microSD card slot – it will accept cards of up to 2TB, which is handy because only 52GB or so of the FiiO’s 64GB of internal storage is available for your use.

There are also a couple of USB-C sockets – both can be used for charging the 4000mAh battery. One is also for data transfer, the other also acts as a power supply – so when in Desktop mode the player is drawing power from the source player rather than using its own battery.

The M21 is supplied with a protective colour-matched silicone case – it spoils the feel a little, sure, but it keeps your player safe. And the company also offers you the (cost) option of the SK-M21C protective case – this is a relatively bulky cover that turns your M21 into something that looks for all the world like a cassette Walkman from back in the day.

You only have major controls available with this cover in place, and the touchscreen is disabled – but it’s a nicely frivolous touch from a company that’s ordinarily Very Serious Indeed.

Features

• 4 x Cirrus Logic CS43198 DACs
• Bluetooth 5.0 with SBC, AAC, aptX HD, LDAC and LHDC compatibility
• 32-bit/768kHz and DSD512

The M21 uses four Cirrus Logic CS43198 DACs in a fully balanced arrangement – they allow the player to be capable of dealing with digital audio files of up to 32-bit/768kHz and DSD512 resolution when used as a USB DAC.

They’re in their own heavily shielded area of the circuit board where they’re impervious to crosstalk and signal interference – in fact, FiiO has gone as far as to keep the control, digital and headphone amplification sections isolated too.

You may wish to use your M21 as a source device in part of a full system, of course, and FiiO has given you options. The hybrid SPDIF/3.5mm analogue output allows you to make a digital connection to a more capable DAC – and if you decide to let the player do the decoding and plug it into a system via one of its analogue outputs, there are a couple of gains settings, each with a different volume curve, to help match the M21’s output to the amplifier it’s connected to. This feature also means you should have no trouble driving even the most uncooperative headphones.

There’s dual-band Wi-Fi on board, so Apple AirPlay and Google Cast are options – and in addition, the M21 is DLNA-compatible and Roon Ready. It has further wireless connectivity available via Bluetooth 5.0, and in both directions – as a transmitter it’s compatible with SBC, AAC, aptX, aptX HF, LDAC and LHDC codecs, and as a receiver it can deal with SBC, AAC and LDAC.

No matter how you’re getting the sound out, its character can be altered (at least a little) thanks to the dozen-or-so EQ presets in the Settings menu. Bass, treble, balance and Stereo Expand adjustment is available too, and it’s possible to make (and save) very granular adjustments via a six-band equaliser. 

As far as battery life is concerned, the M21 is nicely above average. Use the unbalanced output at reasonably modest volume and a single charge should last you for 15 hours or so; even if you turn the wick up and use the balanced output you should still expect around 12 hours. PD2.0 and PD3.0 PPS fast charging are supported, so going from flat to full shouldn’t take forever (provided you have an appropriate charger, of course).

There’s more, of course – there’s almost always more when FiiO is specifying a product. The headphone amp section is split into two stages (voltage amplification and current expansion).

There are separate power supply paths for analogue and digital signals – and the analogue circuit is subdivided into multiple independent supplies.

The audio circuit uses thin-film resistors and low temperature-drift capacitors, and the most critical circuits feature low-impedance tantalum capacitors.

I could go on – FiiO has developed a custom crystal oscillator specifically for the M21, for instance. But I think by now the point is satisfactorily made: FiiO has left nothing to chance here, and has specified the M21 well in excess of its asking price.

Performance

• Assertive, open and insightful sound
• Dynamic and punchy, but deft and controlled at the same time
• Not a big fan of big volumes

In almost every way, and in the most positive sense, the FiiO M21 is unconcerned with what you listen to and how.

Obviously it does better work with a 24-bit/48kHz FLAC file of James Holden’s Common Land than it does with the 320kbps equivalent, and obviously it sounds better when feeding a pair of high-quality IEMs via its 4.4mm balanced output than when using AAC to wirelessly stream to a pair of affordable true wireless earbuds – but ultimately its fundamental sonic character comes through loud and clear.

And that character is a lovely blend of vigour and poise, detail and drive. It digs deep into the frequency range, and can hit good and hard – but the low frequencies it describes are properly shaped, rigorously controlled and loaded with detail both broad and fine. The speed and straight-edged attack of bass sounds means rhythms are expressed with real positivity, and momentum levels are always high.

The same is true of the rest of the frequency range. At every point, the M21 is able to tease out the finest, most transient details of harmonic variation or what-have-you and put them into convincing context.

The midrange communicates with real eloquence, so all the character and attitude in Lorde’s voice during a 320kbps Spotify-derived file of Shapeshifter is described just as readily as it is when listening to Levon Helm during a 24-bit/192kHz FLAC file of The Band’s The Night They Drove Old Dixie Down. And the shine and drive at the top of the frequency range is expertly balanced against substance – so treble sounds attack without becoming hard or splashy.

The soundstage the FiiO creates is open and confidently laid out – even complex, element-heavy recordings can find the breathing space they need to avoid sounding cramped. Dynamic headroom is considerable, so when a recording modulates through major shifts in volume or intensity the M21 is able to track these fluctuations faithfully.

At every turn, the FiiO is an impressive and engaging listen. It unifies those element-heavy recordings into singular occurrences. The balance between energy and poise it strikes is expertly judged. Leave the EQ settings alone and the tonal balance is neutral, while frequency response is even and naturalistic.

In fact, it’s only volume that comes anywhere near being the M21’s Kryptonite. Wind the gain levels up towards reckless and some of the composure, as well as the three-dimensionality, of the FiiO’s sound starts to desert it. Its stage becomes rather flat, and what used to be poise comes uncomfortably close to shouting. Mind you, there’s an easy remedy for this: turn it down a bit.

Should you buy it?

FAQs