The Raspberry Pi small board computer (RPi SBC) — add suitable HAT (Hardware Attached on Top) and for a total of less than £50 – e.g. an RPi Zero with IQAudio Pi-DACZero – we can snag ourselves a decent little streamer/DAC combo. If we pay even a little more, we get more: don’t be fooled by the Allo Boss DAC’s US$59 price; it’s a righteous contender, even when sat among far more expensive entry-level streamers.
Allo’s Katana Player is an RPi + audio board/s + power supplies. It swings US$339 in its most basic configuration, US$528 fully loaded (see below), potentially testing price expectations for SBC-based units.
Or does it? The Pro-ject Stream Box 2 Ultra (review here), that replaced an Allo USBridge (£150, review here) as my daily streamer, sells for £600 and is based on a commercial version of the RPi. It’s a cracker.
Preconceptions to one side – mine at least – how does the Katana fare against similar equipment? Or more expensive? Allo claims that the Katana ‘blows away any DAC made by anyone under $1000’.
What is it?
First the basics. The Katana Player is a DAC and (RPi) streamer in one unit.
Katana is not as simple as a single DAC HAT board piggybacking an RPi. Instead, we have a handful of boards to stack on top of the RPi:
- We start with the Katana DAC board that sits directly on top of the RPi
- Above that, an Op-Amp board serves as the DAC board’s analogue output stage. We choose at the time of purchase between the “best-sounding” or the “best-measuring”, with only one installable at a time. A second board can be purchased for an extra US$50.
- A micro-controller board tops out our four-tier stack
- As an option, Allo’s Isolator board (+US$40) can be inserted between the RPi and the DAC board to provide galvanic isolation between the RPi and the Op Amp (output stage) board. If so that’s five layers in total
Its permutational complexity means the Katana requires methodical and careful assembly.
Otherwise, we can go for the ready-built Katana Player with a choice of DietPi, Volumio, or Moode pre-installed to the microSD card. These operating systems will, of course, also work if installed manually, as will Max2Play and PiCorePlayer and others. Check with Allo if your preferred OS isn’t mentioned. I used DietPi for its Roon integration.
Deep breath. We’re not done with options just yet.
The Katana can be juiced by one, two, or three power supplies. Allo recommends two 5V supplies for the Katana, I tried two price points…
- Two standard switching RPi supplies at £8 each. These get us going, swallowing £16 as/when the upgrade bug bites is hardly painful in this game. So low cost, but what about performance?
- Allo’s linear Shanti supply (+US$149) provides two feeds simultaneously – 1A and 3A. Costlier, but better quality according to Allo, and one fewer box.
It’s worth mentioning that the Shanti power supply is somewhat utilitarian in its appearance and because its case is 30cm long and because it runs warm, stashing it behind the rack isn’t a realistic option.
The manual says to power things up in sequence – clean side, then dirty. In practice, only an SBooster power supply caused problems, the RPi sometimes failing to boot properly. Sequencing the power on is a real pain, so the (otherwise excellent) SBooster sat out the rest of this review.
Today, we’ll take aim at the sound quality of the Katana fitted with the ‘Best Sounding’ Op Amp board plus the impact of different power supply options and what difference the Isolator board makes.
Why not the ‘best measuring’ Op Amp board as well? Do the maths and the reason becomes clear – there are just too many options to consider. Two Op-amp boards with two power options (see below), each with and without the Isolator – eight combinations overall, and that assumes the Katana stands up to all that dismantling and rebuilding.
Connectivity & bit rates
Analogue outputs are RCA phono unless you’re handy at soldering, in which case XLR is achievable. I’m not and it wasn’t. On digital inputs, the Katana can play from a USB thumb drive but the primary streaming input for most people will be Ethernet, which I used to run Roon. Wi-Fi / Airplay capabilities depend on the choice of operating system for the RPi.
Via its DAC board’s ESS 9038Q2M chip, the Katana can decode PCM up to 32bit/384kHz, and DSD 128 via DoP. Very respectable if you’re a fan of harder to find formats (or upsampling). With the Isolator board in situ however, those glass ceilings drop to 192kHz and DSD 64. No MQA.
Looks, fit, finish
Allo’s products, like many RPi-based streamers, have a distinct air of Lego-Fi, the Katana more so given its five possible tiers. Those considering an SBC solution such as this will most likely have accepted the DIY-esque appearance at the time of purchase though.
The Katana differs slightly from other Allo products in having cutouts in the top panel of the case to accommodate larger components. This makes it more vulnerable to knocks, so handle with care. The first review sample failed and I know not why. The Katana runs warm so squirrelling it out of sight could be challenging.
My perennial Ayre AX-7e ($3,950) and Graham LS6 standmounts (£2,200) tethered by TQ Black2 speaker cables (£270) were deployed. Spendor Classic 1/2 speakers (£5,500, review soon) were also pressed into service. For comparison a Pro-ject Stream Box S2 Ultra (£600) and Mytek Liberty / SBooster power supply (£900/£300) took on streaming & DAC duties – a stiff test, but then Allo invited it.
Sound quality – with Isolator & Shanti
First impressions are good, with Secret Machines’ Now Here is Nowhere blasting into the room via the Ayre & Spendors. Attention is drawn to the overall performance rather than any one aspect, how well it supports the big speakers, a slightly slow bass seemingly the only nick in the Katana’s armour. The Graham speakers only confirm the Katana’s standing, the slower bass less of an issue as the LS6 don’t go as low as the Spendor.
Daft Punk’s Random Access Memories, Liane Carroll’s Seaside, Barrueco’s ‘Koln Concert’ – different music but a consistently engaging performance. Impressive given that the speakers sell for ten times the Katana. Heard in isolation, it would be a quick review – thumbs up, grab a beer, load a playlist and sit back.
Enter the Mytek
The Katana is no giant killer though. The Pro-ject/Mytek/SBooster combination justifying its thrice costly asking by adding things we didn’t realise were previously missing: more air on top, greater detail, a more spritely sound. There’s also less bloom on lower guitar strings, the overall balance shifted up, not least because of the greater bass control. Bigger soundstage too, and more refined. And significantly increased dynamics.
If this sounds damning, it’s not. Back to the Katana and after 5 mins of re-acclimatisation, we might not worry about what the Pro-Ject/Mytek/SBooster showed us.
Ditching the Isolator
If the Katana benefits from better power supplies – they’re less noisy – do we still need an Isolator? Removing the Isolator but keeping the Shanti power supply in place moves the Katana’s audible performance two or three notches UP (not down) the ladder. Interesting!
Sound quality from the Isolator-less Katana is much closer to the Mytek combo, increased dynamics being the most obvious change. Now Here is Nowhere leaps from the speakers more forcibly without the Isolator in place. There’s better detail retrieval too, a larger soundstage, tighter bass. The Mytek still bests it – in the same areas as before – but it’s a more closely fought fight. The Katana is now an equal member of the Ayre and Graham team rather than just keeping up.
Standard power supplies, no Isolator
Out with the Shanti, in with two standard RPi supplies, the Isolator still has a choking effect on the sound. Dynamics are constrained, treble muted and bass is less well defined. Still a good sound overall mind, just better without the Isolator.
The entry-level power supplies allow the Katana to give us very respectable sound quality. However, against the Mytek, the Katana now rounds transients, retrieves less detail and provides less control. Overall, it’s a less palpable picture than with the Shanti. You’d expect the Mytek rig to be better but the base level Katana doesn’t disappoint in comparison.
That’s a good result given the 5x cost divider and it shows juicing the Katana with expensive power isn’t necessarily a prerequisite. The upgrade path also becomes clearer – better power supplies as funds permit but, in my experience, I’d not bother with the Isolator.
Plug ‘n play the Katana is not. Tweakers will delight in the permutations open to them but those same choices might be off-putting to newcomers.
However. That the Isolator worsens sound quality – in my setup at least – and that Allo prefers the best-SQ op-amp board to the best-measuring means see those possibilities quickly narrow. That simplifies things, allowing us to focus on the power side of the Katana equation. Both the low and higher cost power supplies considered here worked well. iFi’s £50 supply is also worth considering.
With Shanti in tow, the Katana was more than comfortable fronting a £5k+ Spendor Classic S1/2 loudspeaker system. The market isn’t short of good DACs at this price but in its considerable favour, you get a good streamer thrown in. If you’re cool with the DIY vibe and happy to get your hands dirty in trying different configurations, the Katana is worthy of your consideration.
Further information: ALLO