The change from the SendyAudio Peacock to the significantly cheaper Aiva is easy to bear after having the level adjusted, yet no serious differences in quality come to light - at least that's my first impression. After a longer listening and some toggling between the two headphones, it is noticeable that the spatial image during the drum intro seems to be larger with the Peacock in play, at the same time giving the double bass a bit more volume. Even though the OOR incites the headphones to sonic excellence, it does not equalize the differences between them.

So I commit myself to the Peacock again and enjoy the airy and dynamically exciting playback of Shostakovich's Symphony No. 15 by fully immerging in warm timbres. Although I don't find fault with the sonic performance in the slightest, I connect the OOR to the Hypsos instead of the supplied external switching power supply, which of course lists the company's own headphone amplifier already in its shortlist. Therefore a few movements of the combined rotary and push control knob are sufficient to set the correct voltage and polarity for the OOR: Thanks to the much more elaborate power supply, even more air surrounds the instrument groups, the spatial information appears to be more precise, and the fortissimo passages gain a bit more of dramatic impact. In comparison, I rate the added sonic value offered by the Hypsos a bit higher than that when swapping from the SendyAudio Aiva to the Peacock.

Needless to say, that I give the initial two tracks of Changing Places also a comparative listen via the big SendyAudio on the SPL Phonitor x, whereby its matrix circuitry stays deactivated for the time being: Dynamically, the Phonitor is even a little more convincing, but the subtleties in the transient and dying-out oscillation of individual tones become clearer through the OOR. It is almost impossible for me to assign a hi-fi criterion to what fascinates me so much about the Ferrum’s performance. In all individual disciplines, the headphone amplifiers perform at a similar level, but there is something delicate, tingling about the way the OOR presents itself sonically, which the neutral, rational sounding SPL is lacking. As might be expected, these differences are all the more pronounced when the OOR is powered by the Hypsos. Even when listening to Symphony No. 15, the Polish duo stays my favourite: The musicians seem to be playing in a slightly larger, airier room. With the matrix circuit influencing the sound of the Phonitor, the imaging doesn't get any more spacious, but to my ears it sounds a touch more coherent. Nevertheless, when it's not exactly about large-scale orchestral music, I simply enjoy the Hypsos and OOR combo more.

Not to give the OOR an edge, but simply because I can't stop listening to one of my latest discoveries on Qobuz, Houston Person and Ron Carter's lyrical duo album Remember Love, I start off with "My One And Only Love" with the Peacock connected to the Phonitor, and then repeat it with Hypsos and OOR taking care of the amplification. Even with the SPL, you can get infatuated by the old familiar, but excitingly interpreted melody. However, the Ferrum combo does this a bit better thanks to the airier performance and an emotionally stronger approach. Yes, my previous enormous appreciation for OOR and his fellow mate still remains unchanged with this track.