The input stage of the OOR is realized with carefully selected, fast operational amplifiers featuring a special external compensation. Within this section, the adjustment of the gain and by means of a four-channel ALPS potentiometer also the volume can be performed, as the entire signal path is completely designed as a balanced circuitry. It is containing neither transformers nor coils. Unbalanced input signals are converted into balanced signals by the input amplifier section. Before reaching the unbalanced RCA output, the signal is converted back to single-ended.

The output power amplifiers are – as aforementioned – of completely discrete design and operate using low-noise bipolar transistors. There are four of these amplifiers, two for each channel, as is required for a balanced output topology. These amplifiers are DC-coupled, and there is a DC servo that features a three-decibel cutoff frequency at about 0.1 hertz. The available output power into 32 ohms is four watts at the 6.35-millimeter jack output, and 5.5 watts at the balanced four-pin XLR output. At 600 ohms, 200 and 800 milliwatts are available, respectively. The output impedance here is less than 0.3 ohms, regardless of load, while at the RCA preamp outputs, it's 22 ohms, and at the XLR connectors, 44 ohms.

Since the OOR undoubtedly belongs to the group of stationary headphone amplifiers due to the mains power it requires, I connect it therefore to the balanced outputs of Chord Electronics' DAVE and in a first glance to the supplied external 24-volt switching power supply. The OOR spends the approximately 40-hour break-in period - partly powered by its own power supply, partly by the Hypsos - with the Audeze LCD-X that I received back from repair. Since I've been working with the incredibly well-sounding and opulently equipped Weiss DAC502 with its special equalization for the LCD-X, I am nevertheless aware that the magnetostat isn't exactly blessed with an ultra-linear frequency response without it. However, it really offers a lot of fun paired to the OOR on the rather randomly selected album Changing Places performed by the Tord Gustavson Trio. On "Deep As Love", I especially like the accurate differentiation of double bass, grand piano, drums and cymbals. The transient and dying-out oscillation of single tones or chords is immensely detailed to follow without distracting the listener from the musical content. The inner dynamics of individual sound events are rendered in an equally remarkable way. "Graceful Touch" begins with a quiet intro on the drums, and in the process you get a very credible impression of the imaginary recording space. Generally speaking, the instruments don't stick on a flat plane between the ears, and although the OOR doesn't come with a cross-feed circuitry, the sonic image doesn't seem to be factitiously widened out: I really wouldn’t mind to become a headphone aficionado!

This impressive sound experience is not only feasible in conjunction with the Audeze: With the SendyAudio Peacock, I enjoy the first songs of the album at least as intensively - but in a slightly less spectacular way, being tonally somewhat more balanced and coherent. The three-stage gain control was initially set to the middle position, but already in combination with the LCD-X I reduced the gain by ten decibels, in order to allow the potentiometer to be now used in the range between eleven and one o'clock instead of between eight and ten o'clock. All headphones used are operated in balanced mode, since the OOR is conceived balanced throughout as well.