Abstract: The invention relates to a servovalve for regulating the flow or pressure of a fluid, comprising: a control stage comprising at least one permanent magnet, at least one coil and an armature (13) configured to be able to be driven in rotation around an axial direction; a power stage comprising a filler plate (23) and a drum (22) mounted rotatably in said filler plate (23); a slender mechanical transmission shaft (31) extending along said axial direction and having a first end (31a) connected to said armature (13) and an opposite end (31b) connected to said drum (22); characterized in that said control stage further comprises a slender torsionally flexible tube (32) extending along the axial direction (8) around said slender transmission shaft (31) and having a first end (32a) secured with said armature (13), shrunk onto said first end (31a) of said transmission shaft (31), and an opposite end (32b) clamped by a tube support (33) extending as far as said filler plate (23), so as to form a flexible mobile assemb