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Headphone amplifier
Erzetich Audio PERFIDUS

Price: 479 euro

Manufacturer: Erzetich Audio

Erzetich Audio | Blaž Erzetič s. p.
Voglarji 21 | SI-5252 Trnovo pri Gorici | Slovenia


Manufacturer's webpage:

Country of origin: Slovenia

Text: Wojciech Pacuła
Photos: Wojciech Pacuła

Published: 2. March 2013, No. 106

How do we find new brands, original devices from interesting manufacturers? (“We”, meaning audio reviewers). Well, we search the Web, we observe what other reviewers test, or sometimes we get information from those manufacturers. In this particular case of Erzetich Audio from Slovenia two methods worked together. First, I found a picture of an interesting device on the Web and soon after that I found it in the Newsroom. So I contacted the owner, Mr. Blaž Erzetič (hence the explanation for the manufacturer’s name), and asked him to send me the device for a review. Mr. Erzetič answered immediately and promised to send me a review unit but suggested that I first have a look at his newest product, the Perfidus that was just getting ready for being manufactured.
Slovenian and Polish brands have something in common in that you can hardly find their reviews in international audio magazines. I think it will change soon as the 21st century is an age of web-based magazines, which gives small manufacturers a much better chance to get their products reviewed. Web-based magazines don't really need an audio distributor in their country of origin, nor do they need to be paid for ads or in any other way; all they need is a product for a review. Their strength are the Readers who require honest, reliable and prompt reviews of novelties that just came to the market. A magazine is responsible for the first three; the last one lies in the hands of a Manufacturer. Erzetich Audio would be rather unlikely to get a review in a print magazine as their operation is based on direct sales – no distributors or dealers. What you're reading here is in fact an international debut of this interesting brand.

Despite I have studied electronics and been involved in sound for almost 25 years, my professional path went mainly into visual direction. Since 1998 I've been working as a designer, illustrator and photographer.
Those were also (beside the sound) topics that I've been teaching at two Slovene universities: University of Arts and University of Natural Sciences. As a musician I have released 4 albums: one with US label Wampus Multimedia, two with German label Black Rain and one with my own label Neversun. That got me even more in touch not only with music, but also with sound engineering in studio, on-stage and off-stage. I work as a freelancer designer since 1999, but in the February 2012 I have expanded also into production of electronic devices under brand Erzetich.

Merging my knowledge of electronics, acoustics and design I have created three headphone amplifiers that, for their timeless and unobtrusive design, were featured on plenty of design webzines and blogs around the world (USA, China, Greece, Russia, Poland, ...), including Yanko Design and Delood.
Bacillus is a AD8066 op-amp based amplifier with 250 mA current buffer at the end. That means that op-amp feels no load and therefore no non-linearities. Input capacitors are Wima KPT. Sound is slightly bright.
Bacillus tilia is OPA627 op-amp based amplifier, also with current buffer. It uses Obbligato Gold Premium input capacitors. This combination makes it sound smooth and neutral.
Perfidus is class-a amplifier with transistor based current buffer, while at the input stage uses OPA627 op-amp and Wima input capacitor.

Headphone amplifiers are not as popular as they should be. I find absurd people buying studio headphones for, let's say, 500 EUR and plugging them straight into portable MP3 player. That's like buying a Ferrari and driving it on a gravel road. Big studio headphones need power that a portable player (not even soundcard or built-in headphone outputs on CD player) doesn't have. Difference is obvious when using dedicated headphone amplifier: thick bass, clear sound, less distortion, good soundstage, etc. .

Erzetich headphone amplifiers are practically small power amplifiers: they have double power supply and only one high quality (input) capacitor in the signal path. Power supplies are also embedded into the chassis, making amplifier compact and simple to carry around if needed. If you see a single power supply headphone amplifier (usually with an external on-wall-socket transformer), that's trouble, because it needs a big output capacitor, which means quite some undesirable signal shaping. I wish that more people would be aware of that.
All of the components are of great quality: Alps potentiometer, WIMA or Obbligato input capacitors, Burr-Brown integrated circuits, OFC silver plated wiring, etc. All units are also individually handcrafted and tested which gives additional value to these devices. Since we sell our amplifiers directly from the website, we can keep prices more than reasonable for that kind of quality.

There is a fourth, hybrid, headphone amplifier on the way that is based on tubes and solid state output. It's not sure yet when it will be in production. Hopefully this year. Since we are at our beginnings, we must first let people know about our brand and our products, always keeping in mind great quality for good price.


A selection of recording used during auditions

  • Debussy. Complete Piano Works, wyk. Walter Gieseking, "Signature Collection", EMI, 55917 2, 4 x SACD/CD (2012).
  • Random Trip, Nowe Nagrania, 005, CD + FLAC 24/44,1 (2012).
  • Allan Taylor, Old Friends – New Roads, Stockfisch, SFR 357.6047.2, CD (2007).
  • Barbara Lea, Woman In Love, Riverside/Sinatra Society of Japan, XQAM-160, CD (1955/2007).
  • Dead Can Dance, Anastasis, [PIAS] Entertainment Group, PIASR311CDX, "Special Edition Hardbound Box Set", CD+USB drive 24/44,1 WAV (2012);
  • Depeche Mode, Singles 13-18, Mute, 6 x SP CD (1991).
  • Handel, La Maga Abbandonata, Simone Kermes, Maite Baumont, Il Complesso Barocco, dyr. Alan Curtis, Deutsche Harmonia Mundi/Sony Music Entertainment, CD 88697846212, CD (2003/2011).
  • Jethro Tull, Thick As a Brick, "40th Anniversary Set", Chrisalis/EMI 461923, CD + DVD PCM 24/96 (1972/2012).
  • Józef Skrzek, "Pamiętnik Karoliny", Polskie Nagrania/Metal Mind Productions, MMP CD 0535 DG, CD (1978/2009).
  • Megadeth, Countdown to Extinction, Capitol/Mobile Fidelity Sound Lab, UDCD 765, gold-CD (1992/2006).
  • Muse, The Resistance, Warner Music Japan, WPZR-30355-6, CD+DVD (2009).
  • Porcupine Tree, Deadwing, Lava, 93437, CD (2005).
  • Portishead, Third, Go! Disc/Universal Music K.K. (Japan), UICI-1069, CD (2008).
  • Tadeusz Woźniak, Tadeusz Woźniak, MUZA Polskie Nagrania /Polskie Nagrania, PNCD 1289, CD (1974/2010).
  • Warne Marsh Quartet, Music For Pracing, Mode/Muzak, MZCS-1111, „Mode Paper Sleeve Collection vol.1”, CD (1957/2006).
Japanese versions available at

I must say that finding the best matching headphones for this amplifier was quite a challenge. If you just plug in any pair of not too expensive cans, they will, most likely, sound rather poorly, emphasizing upper midrange that might become a bit unpleasant. While its undeniable purity and transparency will surely sound attractive, the longer listen will result in a rather fast material fatigue. The material in this case being us, the listeners.
I started with the old and actually not all that inexpensive AKG K271 Studio that often work very well with class A amps (see HERE). I also wanted to check out the Oyaide HPC-X62 headphone cable, dedicated to these cans. Unfortunately it didn't work – the sound was rather shrill and plastic. The top and bottom end are not the strongest points of the K271, but in this setup all their problems with saturation and differentiation came right up so distinctly that I couldn't simply ignore them. I wasn't too happy with the Beyerdynamic DT770 Pro Limited Edition 32 Ω, either, nor with the HiFiMAN HE-500. The former sounded a lot like the AKG and the HE-500 delivered too limited, too distant sound to consider them seriously.
The Slovenian amplifier proves how careful we must be to voice our opinions. Imagine a short audition of this amp in an audio salon with poorly matched headphones or listening to it at home with our usual one or maybe two pairs – most likely you'd send it back as quickly as possible. That is a good example of audio magazines raison d'être, as we are able to advice our readers a possible direction of quest. The final verdict would be thus a secondary goal of a review. If most audio salons are gone we will need to trust the manufacturer and/or opinions expressed on some audio forum, and these may often be the same people. Buying directly from the manufacturer you can always send the product back if you don't like it, but it takes time and it’s a hassle, plus it doesn't solve your problem as you still don't have a product that you need. Nowadays it is the reviewers that often act as some sort of 'pre-selectors', taking the role previously handled by audio shops. The greater the responsibility that rests on us.

So I did my best in this review, like I always do, trying to dig deeper and not letting myself get discouraged by the first setbacks. After some time I arrived at some very interesting setups and conclusions.
After a time-consuming process of selection I was left with three pairs of headphones: the HiFiMAN HE-300, the AKG K701 and the Beyerdynamic DT-990 Pro (the older, 600 Ω version). The order is based on how long ago they were introduced to the market – from the 'youngest' to the 'oldest' – and hence their availability, although my preference of how well they paired with the Perfidus would be exactly reversed: I liked the DT-990 Pro the most, followed by the K701 and the HE-300. But what's important is that all three sounded really good with this amplifier and I could easily live with any of them paired with the Perfidus.

To find a reference point for a given product constitutes probably half of a successful review. Such a comparison explains many things that would be hard to clarify otherwise, either because of lack of time or proper vocabulary to describe it. In this particular case I'd have no doubts to choose the Ear Stream Pearl, a Polish headphone amplifier, as the “soulmate” reference (see HERE).
The key sonic characteristics with the Perfidus in the audio path are good resolution and selectivity, speed and high dynamics. Especially the latter is a bit surprising considering that this device doesn't seem to have too much headroom. And it was mostly the dynamics that made the described 'incompatibility' with some cans so irritating. When I listened to an old Walter Gieseking solo piano recording, the upper octaves were immediately emphasized with each instrument’s crescendo. This amp was able to present tonal differences between individual key strokes. This 'effect' was obvious not only with the piano that delivers plenty of high harmonics, but also with some older recordings like Music For Prancing by Warne Marsh Quartet. The album, originally released by Mode and now wonderfully restored from vinyl LP by Japanese Muzak, has a rather limited frequency response, with almost no treble. The Perfidus played it with much care, clearly showing, especially with the HiFiMan cans, the weaknesses of this recording but mainly presenting a slightly warm although not slowed down music, with emphasized lower midrange, yet without making the sound syrupy. Usually with a warm amplifier the dynamics would be averaged, but the Slovenian device somehow emphasized it.

The tonal balance might be described as gently lit up but also with a solid low end base. The latter was most obvious with the HE-300 and this setup offered the most 'modern' sound, in the sense of widest frequency range, great dynamics and slightly dull upper midrange, somewhere above 900 Hz – 1 kHz. It was a pure pleasure to listen to Depeche Mode recordings from their singles box No. 3, or to dense, meaty sounds from the Random Trip album and to the beautiful, deep voice of Allan Taylor on Old Friends – New Roads. The sound was deep but open and fast at the same time. The last characteristic repeats itself a lot in my review and seems to be a key feature of the Perfidus presentation. It might even 'push up' its selectivity a bit, helping to differentiate the cymbals so nicely which in turn makes the recordings such as Anabasis by Dead Can Dance and the latest release of Thick As A Brick breathe and flow, with the instruments having proper acoustics, and it structures the whole recording really well.
Selectivity is quite impressive, allowing us to 'see' the sound images spread wide and deep on the soundstage. The volume of sound might not be as big as from high-end headphone amplifiers but that should not come as a surprise considering the price. What might be surprising is the amount of small details, previously hidden somewhere in the mix and now presented more openly, although still merging into the bigger picture. You can clearly hear both the foreground and the backstage. The presentation is clean, distinct, with some tendency to brightness, as also stated by the manufacturer himself. With the Beyerdynamics and the AKGs the sound will be creamier, with less accented both frequency response extremes. I liked it more that way as it’s the coherence and depth of the presentation that I value more and these were slightly better here. But it is each listener’s individual preferences that will decide in finding the best headphones for the Perfidus. I hope I gave you some helpful clues.


One of the most interesting pieces of information one can get from audio manufacturers is what devices/systems they use when auditioning their prototypes and working on the final sound of their products. The idea is (usually) to create an all-rounder, a device that would be a good match for most systems, but eventually the manufacturer has to audition it in a particular system/systems. It is easiest to obtain such information from smaller manufacturers, as it is obvious for them that their product will work better in some systems than it will in others. These guys don't just calculate their own profit and loss account but they also take into consideration a prospective customer. In other words, these guys also think of us, the audiophiles. Blaž Erzetič is one of 'these guys'. When asked about the cans he used he named them: Grado SR325, Beyerdynamic DT770 Pro, Sennheiser HD600, Sennheiser HD280 Pro and some smaller models like: AKG K450, AKG K44, Koss K/6X plus.
Before I received his e-mail with this information I assumed that high-impedance cans would sound best with the Perfidus – so I thought of the Sennheiser HD800 (300 Ω), and as next choices: the Beyerdynamic DT990 Pro (900 Ω), the AKG K701 (71 Ω) and, kind of an exception, the HiFiMAN HE-300 (50 Ω). The AKG offer quite warm, creamy sound which I thought would fit this system nicely, and the HE-300 bring high sensitivity to the table, which could also be a benefit here.
But most headphones named by Blaž were rather low-impedance ones, which suggested that something else was at play here. It seemed that it was rather a combination of impedance, sensitivity and frequency range. When it comes to matching cans with an amplifier it is about matching the amp’s output and the load – it is that simple. The Perfidus will allow you to build a reasonably priced system that will deliver a very satisfying performance. Each pair of headphones I mentioned in my review will do very well with this amp. You might also think about a moderately warm source.
The specification available on the manufacturer's website reads: “character – bright and quick”. I can only concur – this gentleman knows his device. He created a nice looking, well-built headphone amplifier that will bring lots of joy to its owners.


The test was an A-B comparison with the A and B known. Music samples were 2 minutes long; whole albums were also auditioned. The reference devices were my Leben CS-300XS [Custom Edition] amplifier and the headphone output of the Arcam FMJ A19 amplifier. Apart from my reference CD player, as a source I also used the Arcam rDAC with the Bakoon SATRI BPS-02 battery power supply, and the Restek Epos CD Player.
There are two obvious weaknesses of this amps design – its feet and the power cord. I couldn't do anything about the latter but I did what I could about the former. The amplifier sat on the Acoustic Revive RIQ-5010 quartz discs, with the fo.Q G-53FS damping spacer in between, and I placed the whole on the Acoustic Revive TB-38 isolation platform. I decided to put two more quartz discs on top of the device – it couldn't hurt, right? And it made me feel better… Especially that I had a chance to hear the influence of Acoustic Revive accessories during Audio Show 2012, when Mr. Ken Ishiguro personally set these up for two systems, with the Dynaudio Xeo active speakers and electronics from Octave. Since then I'm not just a 'believer', now I'm rather a 'follower'.


Headphone amplifiers, as a specific kind of amps, follow a rather specific design. Especially when it comes to reasonably priced devices. The smallest among them are really tiny and can fit in your palm. The bigger ones usually look similar to the Perfidus.
The Perfidus is a solid-state headphone amplifier, with an output stage working in class A. The casing has an elongated shape, with a small front panel that sports a volume knob, a headphone socket, and a small, red LED that acts as a dot over the 'i' in the device’s name. The on/off switch sits on the back panel next to the power cord. The latter is bad news as it is permanently fixed and judging by its looks I'd rather replace it with some high quality cable. There is also an analogue input – a pair of solid RCA connectors. I haven't mentioned that before but the front panel looks really nice – it is an acrylic plate with lettering on its inner side (see White Bird Virtis-01). The letters were chosen to add some modern and professional look to the device’s fascia. There are two company's logos – one around the headphone socket and the other on the top panel. The logo is a circle with *ahem* little horns…
The device is housed in a rigid, aluminum casing. There are two main parts – the top and the bottom bolted together – all one needs to do is to slide in the PCB and then fix the front and back panel – it's a simple solution used also for many much more expensive devices. The Perfidus sits on four feet used to hide the screws nuts.

The whole circuit is mounted on one PCB occupying the whole unit’s interior. It's divided into two parts. The back is occupied by a chamber with the power supply – a small toroidal transformer and four Rubycon capacitors. The power supply section is separated from the amplification circuit by a thick aluminum plate with voltage regulators bolted to it.
The signal runs from the inputs via long shielded cables to the front of the device where it is connected to PCB right next to a nice Alps potentiometer. The pot is coupled by nice, large Wima capacitors. Right next is a TL072 chip. It's a DC-Servo to maintain DC 0V on the output. According to Blaž Erzetič headphone amps working in class A, after warming up have a tendency to increase DC offset drift which might be dangerous to the headphones. The DC-Servo detects DC-offset voltage and corrects it.
The gain stage is really interesting. In the input there is a Burr Brown OPA627 surface mount on a tiny board with pins which plugs into a classic socket. The second stage is solid-state, push-pull Class A. It employs the STMicroelectronics BD139+BD140 bipolar transistors. Mr. Blaž informed me that this is not a typical gain stage but rather a current buffer, meaning a circuit with gain equal 1. All the voltage is delivered by the first gain stage. The transistors are mounted to both side walls that are thicker in this area (additional aluminum plates are added). All passive components seem to be of high quality – precise resistors and polypropylene capacitors. All electrolytic caps are from Elna. The headphone socket isn’t gold plated.

Even though it is an inexpensive device, inside you'll find some fine, carefully selected components – capacitors, resistors, potentiometer, power supply, but also the casing itself is of a high quality. The two problematic, from my point of view, components are the non-detachable power cord and the long signal cables running right next to the power transformer. The whole rest is very good indeed.

Specifications (according to the manufacturer)

Headphone impedance: 8-600 Ω
Frequency response: 4 Hz - 40 kHz (-1 dB)
Power consumption: 15 W
Dimensions (W x H x D): 110 mm x 64 mm x 280 mm
Weight: 1325 g
Character: bright and quick


  • CD player: Ancient Audio Lektor Air V-edition, review HERE
  • Phono preamplifier: RCM Audio Sensor Prelude IC, review HERE
  • Cartridges: Miyajima Laboratory SHILABE, review HERE), Miyajima Laboratory KANSUI, review HERE
  • Preamplifier: Ayon Audio Polaris III [Signature Version] with Re-generator Power Supply
  • Power amplifier: Soulution 710
  • Integrated amplifier/headphone amplifier: Leben CS300 XS Custom Version, review HERE
  • Loudspeakers: Harbeth M40.1 Domestic, review HERE
  • Headphones: Sennheiser HD800, AKG K701, Ultrasone PROLine 2500, Beyerdynamic DT-990 Pro; 600 Ω version, review HERE, HERE, and HERE
  • Interconnect: CD-preamp: Acrolink Mexcel 7N-DA6300 (article HERE, preamp-power amp: Acrolink 8N-A2080III Evo, review HERE
  • Speaker cable: Tara Labs Omega Onyx, review HERE
  • Power cables AC (all equipment): Acrolink Mexcel 7N-PC9300
  • Power strip: Acoustic Revive RTP-4eu ULTIMATE
  • Stand: Base; under all components
  • Resonance control: Finite Elemente Ceraball under the CD, Audio Revive RAF-48 platform under the CD and preamplifier
  • Pro Audio Bono PAB SE platform under Leben CS300 XS [Custom Version]; review HERE