Introduction

Before I begin, I just wanted to send out a special thank you to Karina from ifi Audio for providing me a temporary loaner unit for the purpose of writing this review. I am ever so grateful for this wonderful opportunity.

Another little tidbit before I begin, this is my first major review on Head-Fi for any piece of audio equipment aside from impressions of various headphones and the like that I've posted in various threads. So with said, I hope this review will provide useful and educational information for people trying to get an idea of how this DAC sounds and seeing if it's a right fit for them or not. So with that said, lets jump right in!

Packaging and Box-o-goodies!


When I first got the Signature, I was a little surprised at how small the box was. For the amount of power this thing can put out, I was expecting a much bigger footprint. This could be my inexperience or ignorance about never seeing/hearing the micro iDSD BL, but nonetheless, it was a pleasant surprise to see that it wasn't the size of an XBOX 360 power brick. Man those things were huge....!



So inside the box comes with a slew of accessories.

The list includes:
- 6.35mm adapter
- USB OTG cable, adapter OTG
- 2 rubber bands for stacking
- optical adapter
- RCA cables
- carrying pouch
- USB-C cable
- manual
- warranty stuff

I was pretty impressed with the packaging and how everything was neatly packed in smaller boxes in their own compartments. Very neat and organized. The only thing I find missing in this set is a 4.4 balanced adapter. Personally I didn't mind too much because I had 2 of my own, but for someone that only has a 2.5mm balanced cable would need to shell out some extra cash for a quality adapter. But truth be told, if I had to choose between having only 1 adapter, I would have gone with the 6.35mm adapter for sure. For someone like me that only owns IEMs, a 6.35mm adapter is not something I just have lying around. But if 1 adapter is already included, why not the whole set? But no biggie. Just a small nitpick.

Hardware

Battery Life
Generally I don't pay too much attention to the battery life on my DAC's because I hardly ever use them on the go. I primarily use them as Desktop units when I'm at work and pretty much have them charging while I'm listening to them. But for the purposes of this review, I did let the battery run down a few times on various power stages just to see how long it lasts. And I must say, for it's 4800mAh size battery, it does a great job of providing enough juice for long listening sessions.

When I first got the Signature, I listened to it straight out of the box on Normal mode with no xBass+ or 3D+ for about 2-3 hours straight while it was still on the green indicator. I'd say keeping it on Normal mode listening at moderate volume levels will last for about 6-8 hours from my experience. When put in Eco mode, you'll get even more battery life out of it. But bumping it up to Turbo mode its another story... This is the highest power stage of the Signature and thus, sucks up more juice given its higher power stage and demand on the battery. For the headphone configuration I was using, I found myself putting it on Turbo mode a lot (mainly because I like to listen to music at deafening volume levels), but I found the battery life to be about average. About 4 hours or so tops if solely using Turbo mode. Which again, is fine by me, seeing that I can just plug it in whenever it gets to the red indicator.

Speaking about the indicator, I don't think I've ever seen a smaller one on a DAC this size. Like ever. I can understand the idea of maybe taking the minimalistic approach or putting things in common locations like a battery indicator right next to the charging port, but the indicator is just so darn small that you gotta be looking directly at it at a distance of 6 inches or less to see it clearly! If it was bigger then I wouldn't have listed it as a Con in this review. Or if you wanted to keep it the same size, at the very least move it to the front of the device for easy viewing.

I always find myself physically turning the device as Im listening to it just to get a glimpse of battery indicator. But in the grand scheme of things, it really is a small nitpick. It's more of an annoyance than anything. Now if there was no battery indicator at all, then I'd be docking some points on this review, but that's not the case thankfully.

Inputs/Outputs
Before I say anything in this section, I have absolutely zero experience with the SPDIF input, so I will not be covering any information on it. I primarily used the Digital Input as my main source for connecting to my computer.

With that said, the Signature has two main inputs - SPDIF and Digital. Again, I exclusively used the Digital Input with my setup and gear.


On the Output side of things, its a quite interesting affair here. It has 2 headphone jack outputs:
1) 6.35mm SE Output
2) 4.4mm S-Balanced Output


In addition to these two headphone outputs, it also has a Line Out RCA SE Output in the back of the unit.

Now here's the interesting part with the Outputs. All of the Outputs on the Signature can be used to feed into another Amp of your choosing, but the RCA Line Out is the only one that bypasses the amp in the Signature and treats it as a true line out, as opposed to the 6.35mm and 4.4mm outputs where it goes through the Signatures amp and also enables the use of xBass+ and 3D+. The RCA Line Out disables these features. Here's a table to better explain:


Honestly, I didn't mind which output I used because it all sounded great whether I was using RCA, 6.35 or 4.4. The only thing I will say is that I've noticed when using the 4.4mm Balanced Output, whether using it as a line out or directly plugged into my headphones, there was a noticeable difference in instrument separation and better definition overall - especially in the highs compared to the RCA and 6.35 Outputs.

DAC

Filters
The Signature has 3 filters that you can select from. Here is excerpt directly taken from the user manual:

DSD: Extreme/Extended/ Standard Range (analogue) filters
PCM: Bit-Perfect/Minimum-Phase/Standard (digital) filters
DXD: Bit-Perfect Processing (fixed) analogue filter

Tip: For PCM we recommend ‘Bit-Perfect’ for listening and ‘Standard’ for measurements. For DSD, select Extreme/Extended/Standard to find the one that sounds best for listening and ‘Standard Range’ for measurements.

Unfortunately I didn't have any music in DSD format to try with the Signature, So I can't speak to that point. I primarily listen to Tidal and Amazon Music HD and tested everything from HD (16-bit 44kHz) to UHD (24-bit 96kHz) to MQA. I found that Bit-Perfect was the "best" and most expansive and spacious sounding filter for me.

After doing the initial test between all 3 filters, I ended up settling on Bit-Perfect and never changed it again.

Firmware
I have to be honest here. I didn't really pay much attention to the Firmware versions out there for the Signature for the majority of time I had with it, because A) I didn't know the Signature had different firmware versions, and B) I didn't know there would be any sonic difference between the firmware versions.

For the last month or so, I've been listening to the Signature with the base 1.0 firmware out-of-the-box, and I was quite impressed with its performance. When I learned about the different firmware versions available for the Signature, especially the 7.0c GTO firmware, it just made everything sound that much better! The firmware upgrade offerings are as follows:

7.0 - It supports MQA, DSD (up to 256) and PCM (up to 384kHz). This will probably suit most people's sound processing needs, especially if you just stream music and don't have any uber high quality music.
7.0c - The most interesting firmware of the bunch - the 7.0c firmware is the GTO filter variant which replaces the Minimum Phase Filter and upsamples USB audio. The only negative impacts this firmware has is that it has no GTO for SPDIF signal, no DSD512 and no PCM 768kHz. Other than those negatives, this firmware is probably the best of the bunch, adding tighter bass response and more body to the overall sound, and to my ears, improved the attack of each note more accurately.
7.2 - Supports DSD (up to 512) and PCM (up to 768kHz). No MQA support. This is the firmware you want when you have super high audio samples and want to hear them in all their wonderful glory.

AMP

Plain and simple, the Signature has power for days... Just like its other sibling, the micro iDSD Black Label, the power specs are very similar. With a max power output of 4100mW (in Turbo mode), the Signature can power virtually any set of headphones out there with ease.

I primarily have IEM's and don't need all the raw power Turbo mode has to offer, but with the addition of impedance adapters in series with some of my IEM's (mainly the Thieaudio Monarch), its almost necessary to use Turbo mode get the volume I want out of them.

Just like the filters, the Signature also has 3 power stages - Eco, Normal and Turbo mode.
Eco Mode - 2V/500mW @8 Ohm (Max)
Normal Mode - 5.5V/1900mW (Max)
Turbo Mode - 10V/4100mW (Max)

For most users that value their hearing, Normal mode is all you'll ever need.

Sound Impressions

Ah yes... The meat and potatoes of the review! Just what I've been waiting for.

I'm a man of function over form. Especially when it comes to audio equipment and gear. Sound Quality, to me personally, trumps all. The DAC/DAP/Headphone can be the most beautifully constructed work of art with all the bells and whistles attached with everything that audio technology has to offer, but what is it worth if it doesn't sound any good?

Fortunately for the ifi micro Signature - in addition to the build quality, construction and features, the sound is top notch and puts a smile on my face every time I listen to it.

If I had to pick 3 words to describe the Signature, they would be: TRANSPARENT - DEFINED - FULL BODIED
Ok maybe 3.5 words...

Transparency & Definition
The Signature offers a very clean, transparent and well-defined sound to my ears. Listening to it straight out of the box without touching any of the filters, firmware or add-ons (xBass+/3D+), it provides an enjoyable listening experience with no coloration of any kind from Bass to Treble. This creates a cohesive and extremely smooth sound where nothing sounds disjointed. But to me, sounding smooth isn't enough. Smooth sounding DAC's are a dime a dozen these days and this would just be one more added to the mediocracy category.

But with the addition of impeccable definition and articulation - each note is discernable and is crystal clear where a note begins and ends. It also make's it super easy to pick out and clearly discern different instruments as well as heightened instrument separation. This is extremely important when listening to music with a lot of layers.

But even still, this to me is not enough to justify a 5 out of 5 score. Which leads me into my next section....

Full Bodied Sound
With transparency and definition in check, these by themselves would make the sound quite flat and not very exciting. But thanks to the full bodied nature of this DAC, every note has weight, impact and purpose. There isn't a single note that sounds just... "meh". Everything sounds like its meant to be there and with authority.

Another added perk of having such a full bodied sound make's everything sound very three dimensional. There's plenty of space here, and each note takes up every bit of that space - creating very pleasing note texture.

The other benefit of having such a full bodied sound is that it adds much needed thickness to thin sounding headphones.

Personally I have experienced this and is probably the reason why I fell in love with this device. It gave me something that I was lacking with all my other devices. I have the Thieaudio Monarch's which sound amazing by way of its tuning but is also known to sound somewhat thin in the upper bass and lower mids region. I have tried virtually everything in my arsenal of audio equipment to make these IEM''s sound fuller and add more mid bass impact. I've done everything from tip rolling, cable rolling, changing out sources and every possible permutation of the like, and I couldn't quite find that sweet spot.... until I tried the Signature.

As I mentioned earlier in this review; as soon as I got this device, I listened to it for about 2-3 hours straight. Just playing track after track, with no sign of OCD tendencies to "tweak this" or "switch out that". Just pure audio enjoyment and satisfaction. This was with the very same Monarch's that I've tried everything under the sun (well everything that I own anyway...) to realize its full potential, but nothing came close to what the Signature did for me with my Monarch's.

Another thing the Signature did for my Monarch's was that it cleared up some inconsistent coherency issues I had with the bass. The bass driver configuration uses a 10mm Dynamic Driver in conjunction with 4 BA woofers. The issue here is that the blending between the dynamic driver and BA's caused the bass to have inconsistent behavior when reproducing the sound from track to track. Sometimes it sounds amazing. And sometimes, not so amazing...

But with the transparent, defined and full bodied sound of the Signature, it reigned in the bass and made it sound extremely coherent and very well controlled on a consistent basis. Every track I threw at it, it reproduced the bass to sound full and whole - with no questioning about "what's going on down there?" or "Is that the bass or the lawn mower outside??".

Coherency here is simply brilliant.

Sound Add-Ons (Versatility)

In addition to the original sound of the Signature, it also includes a few add-ons that may alter the sound for better or for worse. Generally for the better, but depending on the technical capabilities of the headphones you're listening to, it might be too much for it to handle. iFi Audio has made their in-house technologies, xBass+ and 3D+ available on most of their DAC's.

xBass+
Personally, I'm a fan of the xBass technology. The beauty of this bass boost feature is that its not DSP, but instead it is ASP. This means that its analogue domain processing and provides sound processing that directly affects the frequency response instead of doing this in the digital realm.

The result are nothing short of impressive. It adds a generous amount of bass boost that sounds clear and natural from sub bass all the way up to the mid bass region.

However sometimes I feel like the xBass+ feature on the Signature can be a bit much at times. And what I mean by this is that if the sound signature of the headphones already have a generous amount of sub bass or mid bass respectively, xBass+ will correct for the entire spectrum and can make it sound a little muddy.

This is why I prefer the combo of the Signature with the xCAN. The xCAN features an enhanced and more versatile version of xBass since its xBassII instead of xBass+. By disabling xBass+ on the Signature and utilizing xBass II on the XCAN, you can set it to "Bass", "Presence" or "Bass + Presence". This gives you the flexibility to correct for sub bass ("Bass") alone without affecting the mid bass ("Presence") and vice versa, while still giving you the option to have both enabled if desired.

I would have loved to see iFi implement the xBassII feature on the Signature instead of xBass+ to allow for the versatility of setting what kind of bass boost you want, but xBass+ is still good in its own right and gets the job done quite well. However, its something that I would have to turn off altogether if it has a negative affect on my music, but most of the time it works well and is sufficient for my needs.

3D+
I don't have too much to say about the 3D+ feature, but from my experience, its a welcomed sound altering addition. To my ears, the 3D+ feature is a little more subtle in presentation than the xBass+ feature, but I do find it makes a difference when enabled. I've found that it adds more air up top, thus making the sound brighter and creating the effect of an enhanced soundstage. I generally just leave this setting turned on more times than not.

IEMatch
This really isn't a "sound add-on" per say, but it is a nifty little feature for super sensitive headphones that have a lot of background hiss or require more volume granularity than just throwing it on Eco mode. The point of IEMatch is to create a blacker background and improves the dynamic range, thus increasing the usable volume range.

Personally I don't own highly sensitive headphones such as the Campfire Andromeda to properly utilize this feature, but it hasn't stopped me from trying it out. Honestly, I've had mixed results with IEMatch. I understand the technology behind IEMatch with it attenuating the signal going to your headphones, allowing you to increase the volume and essentially change the tonality, but I've found that the overall sound was a little too muted for my tastes. Even with the volume cranked up, it just sounded like my music was veiled and slightly muffled. But again, for the headphones I own, I'm not the target audience for this feature.

So personally I just leave it off.

Versatility
So again, the whole point of this section is to show how versatile the Signature truly is. With the inclusion of 3 digital filters, 3 power stages, IEMatch (High and Ultra), xBass+ and 3D+, the Signature has a lot to offer in way of altering your sound to your listening preferences. Simply fantastic.

Conclusion

So to sum things up, I had a wonderful experience with the Signature and truly enjoyed every bit of it. It's a very well built piece of equipment and for the price, its a steal. I've spent hundreds (if not thousands) of dollars in total on various DAC's and this one by far exceeds my expectations and changed my perception of value for what you get in sound quality in this price bracket. I was always of the mind that I needed something in the $1000+ tier to get absolute top tier performance, but the Signature gave me what I was looking for and more.

I've spent a lot of time with the Signature and it is now my go to DAC for when I wanna hear my headphones at their best.

Unfortunately I haven't heard the Signatures other sibling - the micro iDSD BL, but for my tastes and musical preferences, the Signature just does it for me. I've even read other comparisons between the iDSD BL and the Signature saying that the Signature lacks "edginess" and "oompf" compared to the BL, and in relative terms, that may be true. But hearing what the Signature has to offer, I do not find that at all to be the case. From what I've experienced, the Signature is edgy, has tons of body and definition, and may even sound a bit forward at times.

So if you're looking for an all-rounder that has power to drive all your headphones and has an overall well balanced sound, the Signature checks off all the right boxes. I highly recommend!