Headphone amplifiers – apart from DACs with a USB input – have been the hit of the last two years. As you can easily imagine, their popularity is related to the popularity of other media, such as the computer as a sound source and the undisputed supremacy of Apple and its iPod / iPhone / iPad in the role of a sound source. These two components – the computer and the portable player (and more recently the tablet) forced the manufacturers to return to products that seemed history (DACs – Digital to Analog Converters) or that seemed doomed to forever stay a niche (headphones and headphone amplifiers). That is one of the examples of how the audio industry can be revived. Maybe not quite the way the majority of us would have imagined, but fresh blood in the industry is fresh blood after all and we should enjoy it – even if we expected a different blood type…
With the renaissance of headphones came an opportunity for many tiny or even micro-manufacturers; often companies with just one full-time employee – their owner. In Poland, there are a lot of businesses of that type, one of which I have recently discovered – White Bird Amplification. Its first amplifier that I came across was the Virtus-01, using KT88 tubes in the output stage, coupled directly with headphones (OTL design - Output Transformerless). It was a very successful amplifier, becoming also a new reference for the manufacturer.
Not for long. During my review of the Virtus-01 Mr. Piotr Bocianek, the WBA owner, let me know that he was working on an even better design, based on the ‘cult’ tubes, the directly heated 300B triodes operating as a SET (Single-Ended Triode), that is with a single active component in the output stage, operating in class A.

The amplifier arrived in an identical packaging as the Virtus-01, i.e. in a large Styrofoam box closed at the top. Its enclosure is larger than that of the Virtus-01 and at first glance it looks as if it were adapted from the Grand Twin Pro design. But it is not – the Grand Twin Pro is a lot smaller than the Virtus 300B. The latter measures 347 x 70 x 250 mm and thus has a little narrower front panel and is slightly lower (in case of the GTP I rely on its description on the manufacturer’s website; I measured the Virtus 300B myself).
Mr. Bocianek’s new amplifier has an enclosure made of bent steel and aluminum sheets. The front panel is made of an acrylic plate imprinted from behind. The Virtus-01 had a gray front; here it is black. The headphone output is also different than that of the Virtus-01. The 300B features two separate outputs – one to drive headphones with an impedance of 100 to 300 Ω, and the other for 300-600 Ω headphones. Theoretically, that excludes all designs with a 32 Ω impedance, such as the new, limited edition Beyerdynamic DT-770 Pro (32 Ω), as well as Grado models and the HiFiMAN HE-4 (38 Ω, see HERE), the HE-500 and the HE-6 (respectively - 38 and 50 Ω, see HERE)., We will see if it is true, connecting to the WBA amplifier the HE-500s and the HE-6s. And probably also the Beyerdynamics.
For this review the amplifier has been equipped with the Electro-Harmonix 300B EHG tubes. The tube driving the 300B, the 6H30Pi “super twin triode,” also comes from Electro-Harmonix. However, for comparison Mr. Bocianek put in the box another classic tube – the gold pin version of Tesla E88CC. We will also give it a listen.

SOUND

The Virtus 300B amplifier in terms of fit the specific earphones reminds me very much another headphone amplifier reviewed in the April issue of HF (No. 96). It is the Funk Tonstudiotechnik LAP-2.V3 (see HERE) solid state amp. Both devices have similar sonic color, but that’s not the main point.
The thing is that the Polish amplifier works significantly better with high impedance headphones. And it sounds much better with headphones designed for recording studios. Just as the LAP-2.V3 does. Now, why is that? Damn if I know. I thought about that during the Funk Tonstudiotechnik review and I found no reasonable answer, either. There is no magic to it; it’s all physics, hence there must be some specific correlation between the changes in impedance, efficiency and frequency response. But what particular relations are involved, I do not know.
One thing is certain – the headphones that usually sound well or very well with a wide range of amplifiers, the Sennheiser HD800, the AKG K701 and the HiFiMAN HE-500, in this case did not sound as well as I would have liked. OK, I’ll say it, what the heck: I did not like that sound. While I could bear what I got from the HE-500, despite their low impedance, I could not listen too long to either the Sennheisers or the AKGs.
The sound was thin and distant with not very high dynamic range. Midrange resolution was fantastic, especially with the Sennheisers, but in the long run it was not listenable – at least I could not listen to it. Nevertheless, I cannot exclude the possibility that it has to do with my personal listening preferences; that my private war against sound sharpening and brightness, in the name of which I am able to accept or even to like a slight weighting of midrange, spreads to include the amplifier.
It’s just that while the head tells me just such a scenario, my heart dictates something else. Namely, that we cannot get used to light or bright sound, that there is some fundamental error to it, which makes us tired instead of deriving pleasure from music. And that a slight weighting of sound is much more acceptable, and you can even make friends with it; it may grow on us over time and become another aspect of our look at music.

And such was the sound, incredibly saturated, very close, slightly weighted in lower midrange, that I received from the Virtus 300B paired with my over ten years old Beyerdynamic DT-990 Pro (600 Ω). It was a bit like listening to my Leben with the “Bass Boost” knob at +3 dB, which I use quite often. I repeated that to a large extent with the 32 Ω (!) Beyerdynamic DT-770 Pro Limited Edition and it would be worth listening to their “regular” high-impedance version. It should sound really good.
But, as I said, it was my old Beyers that sounded so well that I happily listened to them for a few days, without feeling the need to return to my own system. Despite the fact that, in the end, it was better.
The reason for that is that the Virtus 300B amplifier has certain sonic characteristics that we look for in tube amps, especially the 300B. It is incredible three-dimensionality, great resolution and selectiveness. There really is something to that tube and even if you do not “feel” it, it’s worth listening to such system so that you know what others talk about.
What we get is very close and saturated sound. It makes you feel like sitting among the musicians, right where the microphones stand. Midrange is thick and palpable. No matter what the recording. I think it’s the “inventory benefit” of the accentuated lower midrange. The HiFiMAN HE-500 performed even better in that range but – as I said – the presentation was too distant, somewhat “lacking balls”, hence my preference for the Beyers.
The thickness, density I mention was contagious; once you hear it you look for it everywhere. Even a single instrument in an old recording – the violin of Henryk Szeryng in Bach’s partitas – was able to fill the space in our head, to permeate it, to show what we are waiting for, i.e. playing technique, composition, emotions, presentation.
But that is not a system “dedicated” to this kind of music – not at all! It coped very well with the rendition of low bass on Portishead’s album Dummy and the energy and drive on Depeche Mode CDs. The sound was dynamic and had an internal “drive” propelling everything forward.

I mentioned the bass – I had no idea that my DT-990 Pro can go that low. The presentation was not super-coherent, but that is something these headphones cannot do (hence my suggestion about the DT-770 Pro). Despite that, the bass was within my tolerance limits and did not disturb the presentation. And it was really low and saturated!

Tube comparison - Electro-Harmonix 6H30Pi vs Tesla E88CC

I said in the introduction that in addition to the 6H30Pi I found in the box from Mr. Bocianek the Tesla E88CC. The former, as far as I understand, is standard. However, as always with tube amps, tube rolling is an integral part of the whole fun. The review was conducted with the 6H30Pi and then I swapped it for the Tesla.
That has not changed much the amplifier tonal balance. While treble slightly weakens as does bass, the changes are, however, so small in that they can be disregarded in the final assessment. Much larger differences that can influence our choice concern the resolution of various sonic ranges and their presentation. In the end, it is a different sound.
The Tesla brings more peace, better vividness and better resolution in midrange. Vocals were a bit fuller, but above all better positioned in the three-dimensional (within limits) soundstage. Also, their bodies were better defined. A slight hardening of higher midrange– only audible in this perspective – disappeared; to achieve that with the 6H30Pi it required a careful headphones selection. Let me repeat – it was much more vivid and smoother sound, with nicer midrange.
However, I would not write off the Elecro-Harmonix tubes. What’s more, I come to the conclusion that they are two EQUIVALENT tubes, differing only in their character. The “Super-triode” is more selective and has better resolution at both ends of the sonic range. Bass is better articulated and defined. Also treble is shown stronger, more precisely. The higher bass is clearer and more contoured.
After several hours of tube rolling – which is not healthiest for them; you should wait for the tube to cool down, otherwise you shorten its life significantly – I could not decide which I would choose for myself. Each of these tubes, and there are still more to choose from, has something in itself and each of them offers a competent, comprehensive presentation. Maybe, just maybe, I would have gone with the Tesla, were it not for the fact that the 6H30Pi so beautifully fills the bass of the Beyerdynamic DT-990 Pro.
And how about the 300B replacement? In this case, the Electro-Harmonix sounded better than the Create Audio, i.e. fit better the sonic character of the amplifier. If I were to swap them for something else, it would be carbon tubes, such as Sophie. But it will not bring about as significant change as the input stage tube.

Conclusion

The top and low end of the amplifier, regardless of the input tube, seem to sound differently than midrange. It’s not even so much the tonal balance, although the lowest bass and high treble (more so with the Tesla than the EH) seem slightly withdrawn, but really just a bit. It concerns the resolution and selectivity of these ranges. I have no doubt – midrange with any of the two test tubes is simply outstanding, and perhaps that is why both ends of the sonic range seem to be inferior in this respect. Treble is a bit dull (compared with midrange), and the low end is not as selective as, e.g., with the Leben or – not mentioned before – with another headphone amp reviewed in the same issue of HF, the Ear Stream Sonic Pearl. The latter did not have such saturated midrange, such strong bass, but had better treble, cleaner, with more resolution. What is interesting is that the Sonic Pearl is a solid state amp; the Virtus 300B being a tube amp should actually be the king of treble.
The amplifier averages various recordings to some degree. They all sound strong, deep and full. Yet not all have been recorded in such a manner.

But maybe that is the strength of this unit. What do we expect from listening to music at home? I for one look for moments when my suspicion, my disbelief is temporarily suspended, the moments when I am taken “there”, when all that surrounds me disappears. It is easier to achieve on headphones than on speakers, as headphones physically cut us off from the outside world. However, to be able at the same time to convey emotions, mood, to evoke emotion in the listener the presentation must be coherent. The Virtus 300B, although not being perfect, can provide that. It is able to draw us into its world if we just allow it to do so.
The choice of headphones is, however, critical and may be unacceptable to many. In my opinion, pairing the Virtus 300B with top models from AKG, Sennheiser or HiFiMAN will not be the best choice. Your opinion may be different but I’m not “buying” that. In that respect, the Virtus-01 proved to be a better, much more versatile amplifier. On the other hand, the Beyerdynamic DT-990 Pro (and the DT-770 Pro) are an ideal match, as if they were designed for the 300B.
The amplifier is really inexpensive when you consider the cost of tubes alone. Its finish quality is not as refined as the above mentioned Sonic Pearl, but it is much cheaper. I will not sound equally well with all headphones and in this case first you need to buy the amplifier, then to choose matching headphones.

Testing methodology

The White Bird Amplifications Virtus 300B amplifier was tested in an A-B comparison, with the A and B known. Music samples were 2 minutes long; whole albums were also auditioned. The reference point was the Leben CS-300 XS [Custom Version] modified amplifier (push-pull EL84), and the Ear Stream Sonic Pearl amplifier (solid state). The following headphones have been used during auditions: the Sennheiser HD800, the AKG K701, the HiFiMAN HE-6 and the HE-500, the Beyerdynamic DT-770 Pro Limited Edition 32 Ohm and the DT-990 Pro (Vintage). The Sennheiser and the HiFiMAN headphones were connected via the Entreq Konstantin 2010 cables (reviewed HERE).
During the testing the amplifier was connected to CD players – my Ancient Audio Lektor AIR V-edition and Human Audio Libretto HD as well as a turntable – the Goldenote Valore Italian Job (Limited Edition # 014 ) with the Babele MM and Miyajima Laboratory Kansui cartridges. I used a power cord and interconnect from Ear Stream. The amplifier sat on its own feet, placed on a wooden shelf of the BaseSolid VI [Custom Version] rack from Base Audio.
I first used the Electro-Harmonix tubes that normally come with the amplifier but later I swapped them for the Tesla E88CC in the input stage, and the Create Audio Golden Jazz Series 300B in the output (see HERE for the comparison of the Electro-Harmonix and Create Audio tubes).

DESIGN

The Virtus 300B from White Bird Amplifications is a tube headphone amplifier with a solid state power supply. The input stage employs the Electro-Harmonix 6H30PiEH gold pin dual triode; the output stage is based on the 300B Gold power triode from the same manufacturer.

Front and back panel

The unit is quite large. Its enclosure is made of bent steel sheets and the front panel of an acrylic plate. The plate is imprinted from behind with knobs descriptions, the manufacturer’s logo and the name of the product. There are two knobs – a volume control and a power switch. Two headphone jacks are located on the far left and right sides – the left one for 100-300 Ω and the right one for 300-600 Ω impedance. In the center, between the knobs there is a small LED indicating power-on. The back only features an IEC mains socket and two pairs of RCA connectors – input and output (pass-through).
On the upper panel we have sockets for the three tubes and two round plastic ventilation grilles. In my opinion they look a bit out of place - the whole housing is very solid, sensibly designed, and these are so… plasticky. Next to the 300B sockets we can see small LEDs to indicate a tube failure. Underneath, there is another vent, covered with a prettier, but not particularly impressive plastic mesh. The unit stands on four sharp cones with the accompanying spacers lined with thick rubber pads.
Mr. Bocianek makes the following comment on the LED indicators for the 300B tubes:

"The amplifier is equipped with two electronic breakers with the response time of about 2 microseconds, serving as short circuit protectors in the event of a crack or burn of the 300B triode cathode filaments, usually resulting in a full short circuit. A tripped breaker cuts off power from the power supply which is indicated by the red LED, located in front of each 300B tube socket. The breaker can also be tripped on heavy overload which is harmful to directly heated cathodes. The open breaker resets on powering off the amplifier but not sooner than 15 seconds, when the cathodes cool down. Naturally, if either of the tubes is faulty in the manner described above, the breaker will trip again.
This protection is to prevent damage to the headphones in the event of a short circuit between the cathode and anode in the 300B tube, which does happen, although admittedly very rarely.
It is possible to listen with two pairs of headphones but there will be a marked decrease in the output voltage. Of course, it can be increased, but always at the expense of signal to noise ratio.”

Interior

All circuits are mounted on a few PCBs. Four of them comprise the power supply, one houses amplifier components. The power supply features two toroid transformers – separately for the anode voltage and the filament voltage. Tube heater filaments are powered by regulated DC supplies, separate for the left and right channel. The supplies feature numerous filter capacitors from different manufacturers. The anode voltage appears to be rectified and pre-filtered for all tubes. There is a bridge rectifier and several capacitors.
The amplifier PCB is small; a ceramic socket for the input/driver tube is soldered to it. We can also see metal and ceramic resistors and Wima capacitors, as well as large Nichicon Muse capacitors, soldered from the bottom side. They serve as coupling capacitors between the output stage tube and the headphones (blocking the DC at output stage). Power tubes sockets are mounted to the bottom plate on long spacing bolts. Alps “Blue Velvet” potentiometer is used for volume control. The interior houses many cables and the whole looks like a well-made prototype.