Hardware Reviews

ifi Pro iDSD: a genuine cracker

iFi Pro iDSD-BB2

ifi Pro iDSD DAC & headphone amplifier

Ifi have a good go at blinding you with science on the webpage for the Pro iDSD, the list of features and technologies is confusing even if you know what half the terms mean. This is a marketing approach that is often inversely related to the sound quality of a product, but this is the exception that proves the rule, the Pro iDSD is an exceptionally musical and revealing converter. Don’t let the technobabble put you off, this is the real deal.

From a review point of view it’s hard to know where to start but essentially this is a multi filter, multi output stage, digital to analogue converter with a serious headphone output and more inputs than most. Alongside the usual connections there is an ethernet port even though the Pro iDSD is not a streamer in the normal sense, but it has it has the means accepts signals streamed to it. Which means you can connect it to the network (with or without wires) and use an app called Muzo Play to stream from local libraries, Spotify or Tidal, so it is a streamer in all but name.


28625 iFi Pro iDSD rear


The Pro iDSD has four DAC chips and an FPGA processor to upsample incoming signals (DSD to DSD1024, PCM to 768kHz), which is the highest number quoted by anyone for this process. An XMOS processor handles the interfaces, including USB connections, SPDIF/AES-EBU Connection and I2S input from the WiFi/Network Audio module. All inputs are decoded, pass through a memory buffer, then DSD/DOP decoding is applied and MQA decoding. The entire user interface, display control etc. are also handled by this processor. Incoming signal is de-jittered using a buffer and reclocked by the onboard ‘Master Timing’ clock that runs the entire DAC.

There is the option to choose between three output modes, the glass dome on the case covers a pair of NOS (new old stock) General Electric 5670 triode tubes that form the basis of the tube and tube+ outputs, the latter is used with lower negative feedback making it the more purist approach. There is also a solid state output circuit that has JFETs for a less tubey sound, I found that both are great but certain types of music work better with one than the other. Both output stages have balanced and single ended connections and these can be fixed or variable, a motorised Alps Japan pot will adjust output level or you can bypass it by switching a rotary in the back panel. This can also be used to increase output level in situations where that’s required.


Pro iDSD close angle


Headphone enthusiasts will know that ifi has a particular affinity to their way of listening, a situation made clear by the presence of a quarter inch jack and two mini jacks; single ended and balanced. Gain is also adjustable in three stages so that almost any headphone can be driven with ease.
While the casework reflects the price point, you’d have to pay twice as much for a machined billet aluminium case, the Pro iDSD metalwork is well thought out with corrugations to increase stiffness and cut-outs to ventilate the glassware. I like the backlit ifi logo and really like that it changes colour to reflect the output mode selected, white for transistor and orange for tube (or green when it’s idling). I also like the relay operation of this DAC, it’s a classy touch that’s uncommon in electronics at this price. One nice touch is that that volume is automatically minimised when you power down the unit and taken back to the same level at switch on.

I was surprised to find an outboard switched mode power supply (SMPS) on this DAC and slightly mystified that putting this next to the power supply for my turntable resulted in a pulsing through the speakers, moving it away solved the problem. Designer Thorsten Loesch says that the SMPS was chosen not because it’s the least expensive option and the easiest for international sales but because “We have spent substantial time and resources refining SMPS technology, to a point that our own refined design of SMPS now consistently deliver noise level much lower than most linear power supplies and approach or exceed the noise from batteries (depending on exact battery chemistry etc.). With the iPower Range we substantially lowered noise again over our previous design by further circuit optimisation and adding active noise cancellation.” Adding that “Actually, the internal PSU of the iDSD is more important than the external PSU. The incoming DC is converted into a 1.2MHz wave which largely blocks any noise at lower frequencies and then rectified and applied to a choke input filter. The very high frequency means even very small capacitors and chokes have tremendous filter effect and the rectification is much easier filtered to extremely low levels.”


28634 iFi Pro iDSD circuit boards detail



Sound quality

As I generally find that Ethernet connections sound better than USB ones that’s the way listening started with the Pro iDSD, but it didn’t stay that way for long. While the initial result was appealingly immediate with excellent bass and plenty of detail it became apparent over the course of a few tracks that the treble was a little edgy or grainy. Moving to USB the treble became far cleaner and more fluid, it had all the positive qualities encountered with Ethernet without the drawbacks. Then I managed to find identical Chord Sarum T examples of both cable types, and the difference went away so clearly this is a very sensitive DAC, what you feed in will come out, that’s the price you pay for transparency.
Once the Innuos Zenith SE was connected with USB cable to the Pro iDSD I couldn’t stop listening to it, so compelling was the music that this pairing produced. Most of the listening was done in Bit Perfect mode (non oversampling) and in the first instance I used the DAC’s tube output which has a beautifully analogue sound and produces strong 3D imaging and irresistible timing, it is almost impossible to sit still when playing rhythmically strong music. I’m sure there are those who could achieve this but in my book it’s a very good sign, it means that there is little or no time smear which is a fundamental aspect of music reproduction that often gets lost in the quest for transparency, image precision and refinement. The Pro iDSD also makes the ‘other’ tracks on an album sound much more interesting than usual, typically that’s the tracks that follow the favourite one. For instance on ZZ Top’s TejasI love ‘Enjoy and Get it On’ and usually stop play once it’s finished, but it only took a bar of ‘Ten Dollar Man’ to make it impossible to press the pause button. And this happened again and again, this ifi DAC is brilliant at opening up a piece of music and showing you what’s great about it, and that is a very rare quality especially in digital audio. Effectively it means that there is more to listen to in your music collection, and that’s a major bonus in my book.

I also tried the valve plus setting and gave In a Silent Way a spin, this is perhaps the most ambient of Miles Davis’ albums and it’s easy to let it play in the background, creating a good vibe but not intruding. With the Pro iDSD it becomes essential listening, a case of ‘put down the phone or laptop and pay attention because there is some great music being made’. I’ve never had this title on vinyl which would probably have drawn me in to the same extent, so discovering that the standard CD or the data there from could deliver this degree of communication was revelatory. It spurred on a voyage through the digital archives that proved totally diverting. Switching back to the regular valve output made the sound a bit softer and more open and relaxed, less muscular but great for vocals, some vocals that is, others like Van Morrison on Veedon Fleece were a little too forward and exposed. Not so much so that I was put off listening however, once again I found that ‘Fair Play to You’ {the track after the favourite, ‘Streets of Arklow’) is also a beauty with some fabulous playing. But the next album, ZZ Top’s Tres Hombres didn’t work so well, it lacked weight and while it had fabulous pace and reverb something was missing so I switched to the transistor output and got a less immediate but open sound that benefitted this and other rock tracks quite significantly. The extra grip it brought to the Van Morrison made it easier to enjoy at higher levels, the voice is still prominent because that was the way it was recorded but the bass line balances it more effectively and there’s a little more focus to the presentation.


Pro iDSD close bubble


As this DAC has DSD in its name I thought I should try that format and gave La Foliaa spin (Gregorio Paniagua, Atrium Musicae De Madrid, Harmonia Mundi) this changed the display from the 44kHz it had been showing for most of the tracks to 2.8MHz and had the wide open sound that you expect from the format. It proved a better match to the tube output because of the all acoustic instrumentation and sounded extremely good, the timbre of the instruments coming on strong and the whole ensemble being presented in highly coherent synchrony. The Pro iDSD does a lovely job with whatever format you present it with and reveals the quality of the source with ease. Everything was going smoothly until I put on Led Zeppelin’s Physical Graffiti, an old favourite that I rarely play on digital because the vinyl is so good (especially the Classic Records pressing from a few years ago). Next thing I knew I was off the sofa and in the band, at least in my head, this proved a truly transcendent experience and the most fun I’ve had with my clothes on for some time.

This sort of thing doesn’t happen very often with digital audio systems, especially those that are fairly affordable. The source is important but it was ever thus, no DAC can turn a noisy signal into beautiful sound although some do better than others. Ultimately you want transparency to detail, imaging and timing and the Pro iDSD is exceptionally good at all three with or without the charm of a glowing valve. I don’t think there are many DACs that have the feature list that the Pro iDSD offers at any price, but that would be meaningless if it didn’t make you want to listen. Fortunately that’s all you want to do when it’s in the system, I highly recommend you risk falling for it yourself.

Ancillary equipment
Source: Innuos Zenith SE server
Amplifier: PMC cor integrated, ATC P2 power
Loudspeakers: PMC fact.8, Bowers & Wilkins 802 D3
Stands & supports: Townshend Seismic Bases and equipment rack
Signal cables: Townshend Fractal interconnect and Fractal F1 speaker cable
Power cables: Isotek, AudioQuest


Type: Digital to analogue converter, preamplifier and headphone amplifier

Digital inputs : USB, BNC (SPDIF or sync), coax, AES3 XLR, Toslink/optical (44KHz-192KHz), RJ45 for ethernet
Streaming sources: DLNA network, AirPlay, SD card
Streaming services: Spotify Connect, Apple Music, Amazon Music, Tidal, Qobuz, Deezer, Napster
Analogue outputs : balanced XLR, unbalanced RCA
Headphone outputs: 6.3mm jack, 3.5mm jack balanced, 3.5mm jack SE
Sample frequencies : PCM up to 768 Khz, DSD up to DSD1024
PCM filters: Bit Perfect (NOS), Bit Perfect+, Gibbs transient optimised, Apodising, transient aligned
Weight: 1.98kg
Dimensions HxWxD: 63.3 x 220 x 213mm
Colour: silver
Price when tested:
Manufacturer Details:

ifi Audio


DAC preamplifier headphone amplifier


Jason Kennedy

Distributor Details:

Select Audio
T 01900 601954

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