Earlier this year, Finn Corvin Gallowsky and I introduced you to Ferrum's first-ever product: the Hypsos power supply, which provides voltages ranging from five to 30 volts and won us over with its flexibility and sonic impact on connected devices. The headphone amplifier OOR is Ferrum's second product.

By the way, our enthusiasm for the universally applicable power supply - it covers a very wide voltage and power range - led to the consequence that we conferred the Hypsos a Statement-in-High-Fidelity award in cooperation with our Polish colleagues. Until now we haven’t yet dispatched the award, because we hope to get the chance to hand it over personally later this year and to seize this opportunity to take a closer look at Ferrum's new premises. That is to say, that HEM and Ferrum boss Marcin Hamerla and his team, which now consists of more than 20 people, have moved to a larger company building in Pruszków near Warsaw since our last visit seven years ago. And this is where Ferrum's products are now primarily developed and manufactured.

The designer responsible for the OOR, Maksymilian Matuszak, explained in a Skype conference and by means of a technical white paper made available in advance to Hifistatement what makes the OOR stand out of the crowd according to his opinion: "First of all, the OOR has a unique discrete output stage. It is a hybrid Class A and AB concept. The special circuitry never allows either of the two output transistors, which are polarized similarly to a Class AB arrangement, to turn off. The current of both transistors is monitored by independent circuits that prevent the current from dropping below a certain threshold. In this way, distortion is much lower because the transistors do not go through the most non-linear part of their characteristic curve. This circuit is quite different from the well-known "Sliding Bias" and was therefore named "Gapless Current Transistor Bias" or "GCTB" for short by Ferrum.