We proudly present Ianus Protos - the XXX in the new Ianus Series

“Debuting at Munich High End May 2023, the new Ianus Protos Stereo power amplifier uses TriodeFet technology and has features that make it unique in the already innovative Ianus range.



Single Ended Single Stage?

The Ianus Protos integrated amplifier and its amplifier siblings in the Ianus range, uses TriodeFet technology, and it is based on it’s bigger brother, the Aperio.

Just like the amplifier based in,and contrary to the bigger Geminae model, the Protos is using the TriodeFet active element in a very different topology, as this is a Single Ended design It goes a step beyond to be the only integrated amplifier which is Single Stage as well. One stage from input to output posts.

The Design Concept

The Ianus Protos amplifier is not only Single Ended, it is also a Single Stage! Like the bigger Essentia model, incredibly, there is no driver stage and no input stage! However this is not just an amplifier but a complete integrated amplifier.That means that from the input to the speaker outputs, there is only one stage of amplification.

This extremely simple topology we feel is a breakthrough in amplifier design, and is an elusive design goal for many, including our lab. This feat was only possible to execute after the breakthrough of our TriodeFet technology, and now we are finally able to use an active element that has the needed specifications for the purpose: Extremely high linearity, high voltage gain, high current gain and very high input impedance. All in a single stage.

The Aperio and Protos integrated amplifiers use a common circuit core but with many differences in PSU design and part design.

The Protos means, the First. The Protos started as an exercise as to how small and simple we can make an amplifier out of lessons learned developing our bigger TriodeFet amplifiers. We strongly believe this is smallest sample of the technology, as the Minimum Complexity principles dictate how simple things can be designed and implemented. The Protos is indeed the Frist, the smallest offspring of our TriodeFet technology.

The volume control is implemented by  R2R relay-switched resistor array , instead of the complex (TVC) multitap input transformer used in our bigger models.



Practically maintenance free

The TriodeFet technology, in contrast to a SET amplifier design that is using big output tubes, is essentially maintenance free as the internal tubes used for curve creation are rated at more than 10,000 hours lifespan. Its unique single stage nature means that it is as sonically transparent as it can get. The amplifier power delivery is 20W (8ohm) full class A.

Triode or solid state?

Neither. TriodeFet technology does not sound like hybrid, tube or solid state amplifier. It sounds how an ideal tube amplifier should sound..

The triode-like transfer curves of the TriodeFet means the Ianus Protos ,like the bigger brother Aperio and Essentia, sounds very much like the very best Single Ended tube amplifier. A superb midrange and treble, accurate timbre and the huge soundstage we expect from big bottle tube amplification.

Technical Specifications



Single stage, Single Ended, TriodeFet technology

Gain stages:

Single stage amplifier, from input to output posts

Power output:

20W @8ohms

Tube compliment:

2 x 6j11p-e, compatible with: E280F / E282F / E810F / E180F, D3A

Volume control:

61 step Resistor ladder, relay switched volume control technology


Less than 0.1% THD at 20V rms


5 x RCA

Headphone output:

4-pin xlr output, directly driven by output stage.

Full power available for HP output / no Impedance matching required

Power bandwidth:

full power at 5Hz -3db

Maximum gain:

18db (tube dependent)

Noise floor:

-90db ref 1V RMS


Main unit: 500mm W x 490mm D X 170mm H. 60kg
PSU(tranformer unit/soft start) unit: 190mm W x 310mm D x 70mm H. 5kg