2013 Munich High End Show: Erzetich Audio Headphone Amplifiers

One of many cool and unusual features of the Munich High End show was a "Newcomer" area. Upstart firms have a hard time affording the big room rates, so a budget display area is a great idea. Arranged radiating in a circle, about eight chest high counters (each about 6'x2') gave Newcomer exhibitors the opportunity to reach out to show-goers. There, introducing themselves to the audio world, was Slovenian headphone amp maker Erzetich Audio. CEO Blaz Erzetich started the company last September but has been working in audio for almost 25 years, and it shows in his gear. And I'm not talking about the outside—though the gear looked dandy to me. Erzetich amps use a current drive output, that quite a bit different than a normal voltage drive amplifier. The input voltage signal goes through an op-amp gain stage, but the output of the amplifiers converts the voltage signal to a current signal. That means that the output voltage of the amplifier will do anything it needs to to deliver a current signal that matches the audio input to the amp to the voice coil of the drivers. It's the current in the voice coils that actually drive the diaphragms, so this type of amplifier creates a very linear relationship between the input audio signal and the driver's physical response. I'll forewarn you that current drive amps seem to be a coming phenomenon in the world of headphones, and you'll be hearing more and more about them over time. I very much like the idea personally.

The are three amps in the Erzetich line-up: the Bacillus (€449); the Bacillus Tilia; and the Perfidus. Sorry, had troubles connecting to the their website and couldn't get pricing.)

Cami's picture

Great concept indeed! I hope you can stay in touch with Blaz and get a couple of his Amps to try out in the future, looks like a really solid and interesting newcomer.
Liked the aged wood detail a lot, and it would look awesome with other woods too, really nice detail. The devilish Perfidus in the middle looks like something I'd love to get my hands on.
Of all the hundreds of pictures and some videos some friends attending the show have shared, these little Amps look really nice and tempting.
I ran into some trouble trying to open the Erzetich website, the connection times out and no matter how much I wait it just doesn't open up. I hope Blaz takes care of that soon, because I'm really curious on the specs of his Amps.
Did you get to listen to the Amps? With that background noise it has to be darn difficult to form an impression, though.

Great one, waiting for the next booth.


John Grandberg's picture

I've chatted with Blaz a few times and he's a cool guy - very laid back, proud but not overly boastful about his gear. We will definitely have to check out the Perfidus. 

I can't recall the pricing other than it seemed reasonable. Less than $1k for sure. 

Cami's picture

to get your impressions, John, since I mostly share your taste in gear and thorough reviews.

I found a review at 6moons, but it is rather confusing, as the listening experience of the reviewer deals a lot with finding the right headphone match. My hunch is the matching problem has to do with impedance, but there was no mention to any measurements so it ultimately played out as a game of trial and error.

I also found a price reference in dollars: $973 USD.

I hope the Erzetich website is back and running as soon as possible, cause these Amps and the current drive concept sure got my attention.

OJneg's picture

Hey Tyll.

Blaz didn't seem to understand what you meant by transconductance amplifier. I'm wondering if he meant that it was actually a true transconductance amp, or just a buffer implemented in the output stage. I imagine that the opamps would constitute the input and gain stage, and he used some sort of discrete buffer that would keep unity (voltage) gain, but source extra current to drive the load. This is all speculation but I'm guessing that's what he meant by "current amplifier".

xnor's picture

I guess he (Blaz) confused current source with current gain and an amplifier that outputs current for low impedance loads with current amplifier.

John Grandberg's picture

I don't know all that much about the design, but I do recall output impedance being very low (less than 1 ohm). So whatever that reviewer was having issues with, it wouldn't be impedance related. 

Tyll Hertsens's picture

You know, I think you guys may be right. I pressed him about it off camera before I shot the video and he kept saying it was a current drive output.  Guess there's a little homework to do here.

And if John is correct about the output impedance that would sort of nail it.  True transconductance amps have high output impedances as current sources are stiff.  It's one case where a high output impedance isn't a problem.

Cami's picture

I found a review that was featured at 6moons but which was originally written in Polish by Wojciech Pacula for the Polish High Fidelity magazine earlier this year (This time I read it more thoroughly.). As Blaz puts it in that article:

"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."

In the minimalistic specs listed by Wojciech, the headphone impedances recommended are 8-600 Ω, so I guess the impedance is likely to be 1Ohm or less. The issues in matching of headphones apparently have more to do with the specific quality and characteristics of the headphones Wojchiech tried with the Perfidius, than with a possible impedance mismatch.

Wojchiech also writes:

"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."

Transconductance Amp or not, I'm still interested.

As I read at Erzetich's FB page, there are some more detailed specs available at the website now, but I guess Blaz is updating the website after the High End show, because I still can't get it to load. Anyway, I hope there will be more news, specs and reviews of the Perfidus around soon.


Erzetich's picture

Website is now on and running. Provider was under attack and servers have been down for some time.

Regarding output... it is a bit tricky to say what exactly it is. Yes, it is a current buffer, but it adapts to the load, so it doesn't work in a classic way. For example, if you put on 10 ohm headphones or 600 ohm headphones they will have same power on them (around 150 mW/channel), not 60 times different power.

Although 6moons reviewer from Poland is a cool guy (I met him personally), I find his review at some parts confusing, too. Anyway, there will be another review online soon, so we'll be able to hear a different perspective.

Tyll Hertsens's picture

Would you be willing to let us know what the output device is? What is the output impedance? Sorry about all this confusion. 

Erzetich's picture

In Bacilluses it is Burr-Brown's BUF634T set to maximum speed. In Perfidus it's a class-A transistor based amplifier. Output impedance is about 56 ohm, but don't be alarmed about it, because it works in a bit different regime.

Tyll Hertsens's picture

As I mentioned in a post above, a current drive amp is indeed a different kind of beast, and output impedance doesn't matter at all in the way it does with a voltage drive amp. Really looking forward to the chance to hear one of these amps. Keep up the good work!

Erzetich's picture

When you asked me if it was transconductance amp, I said yes, because I roughly knew the technology. I know it has some similarities, but I am still keeping that definition in the air.

Anyway, it's a machine to enjoy music with, not a muscle car. :)

Cami's picture

I still have some trouble loading the Erzetich website. I had it online this morning, but I got up for a some coffee and when I came back to my laptop the server was down again. 
I got to see several articles contained in a section entitled "knowledge base", addressing various audio and tech topics, and anyone can sign up to receive the articles by mail. I found that feature really nice and interesting. .
I found a couple of videos on youtube presenting the Bacilus Amps (Bacillus & Bacillus Tilia), that show the inside of the Amps and generally detail components and design.
It would be great to see the Erzetich Amps featured in a future review and have them added to Innefidelity's Amp measurements database.


Erzetich's picture

It works fine with me. Try again.

John Grandberg's picture

Sorry about the output impedance thing - I could have sworn it was .5 ohm or something like that. I must be remembering a completely different product. It's rough getting old....

pbee's picture

just what you dont need when the amps are getting good publicity - i am very interested in this new current drive amp technology -  could be a versatile and useful amp for my desktop and the pricing seems reasonable. I want to listen to one but New Zealand is a long  long way from slovenia to ship so guess will have to wait for more reviews

Erzetich's picture

We ship worldwide, that's not a problem. Problem becomes if the unit stops working, because of costly shipping back and forth. You either take a risk and buy it online or wait if those units will be distributed in New Zealand.

About the website: yes, seems down again. As mentioned before, provider was attacked by hackers today and they're still setting up their machines. Chill out for the weekend and get back to it Monday.