Adjustment mechanism for the variable adjustment of a compressor inlet of a compressor having an axis of rotation, wherein an axis of the compressor inlet is the same as the axis of rotation of the compressor, the adjustment mechanism comprising: a rotationally moveable adjustment ring around the axis of rotation of the compressor, a plurality of orifice plate elements which are rotatably mounted such that they have rotation axes parallel to the axis of rotation of the compressor, the plurality of orifice plate elements are operatively coupled to the adjustment ring; characterized in that the adjustment mechanism comprises an actuation device comprising: a housing part; and a lever assembly with a bearing section, an input section and an output section; wherein the output section is coupled to the adjustment ring of the adjustment mechanism on a first side of the housing part and in that the input section is configured to be coupled to an actuator rod on a second side of the housing part, wherein the lever assembly is rotatably mounted in the housing part via the bearing section on the compressor inlet side, wherein an axis of rotation of the bearing section is parallel to the axis of rotation of the compressor, wherein a joined assembly using a welded connection is formed through the bearing section and either the input section or the output section, and wherein the bearing section and the other of either the input section or the output section respectively are configured as one part, wherein the output section has a first lever arm with a first end region and a second opposite end region, wherein the first lever arm is welded to or configured as one part with the bearing section via the first end region; and wherein the second end region has a recess through which the output section is operatively coupled to and enters into operative engagement with a coupling elevation of the adjustment ring of the adjustment mechanism. a rotationally moveable adjustment ring around the axis of rotation of the compressor, a plurality of orifice plate elements which are rotatably mounted such that they have rotation axes parallel to the axis of rotation of the compressor, the plurality of orifice plate elements are operatively coupled to the adjustment ring; characterized in that the adjustment mechanism comprises an actuation device comprising: a housing part; and a lever assembly with a bearing section, an input section and an output section; wherein the output section is coupled to the adjustment ring of the adjustment mechanism on a first side of the housing part and in that the input section is configured to be coupled to an actuator rod on a second side of the housing part, wherein the lever assembly is rotatably mounted in the housing part via the bearing section on the compressor inlet side, wherein an axis of rotation of the bearing section is parallel to the axis of rotation of the compressor, wherein a joined assembly using a welded connection is formed through the bearing section and either the input section or the output section, and wherein the bearing section and the other of either the input section or the output section respectively are configured as one part, wherein the output section has a first lever arm with a first end region and a second opposite end region, wherein the first lever arm is welded to or configured as one part with the bearing section via the first end region; and wherein the second end region has a recess through which the output section is operatively coupled to and enters into operative engagement with a coupling elevation of the adjustment ring of the adjustment mechanism. a housing part; and a lever assembly with a bearing section, an input section and an output section; wherein the output section is coupled to the adjustment ring of the adjustment mechanism on a first side of the housing part and in that the input section is configured to be coupled to an actuator rod on a second side of the housing part, wherein the lever assembly is rotatably mounted in the housing part via the bearing section on the compressor inlet side, wherein an axis of rotation of the bearing section is parallel to the axis of rotation of the compressor, wherein a joined assembly using a welded connection is formed through the bearing section and either the input section or the output section, and wherein the bearing section and the other of either the input section or the output section respectively are configured as one part, wherein the output section has a first lever arm with a first end region and a second opposite end region, wherein the first lever arm is welded to or configured as one part with the bearing section via the first end region; and wherein the second end region has a recess through which the output section is operatively coupled to and enters into operative engagement with a coupling elevation of the adjustment ring of the adjustment mechanism.