Hi Pietro,
the Shure WH20
QTR has a 6.3 mm
TS plug, so actually the right plug to connect to the unbalanced MIC Input of the SX900.
BUT: It is not possible to
professionally extend the cable of this microphone: A 6.3 mm cable socket of a corresponding extension cable can very easily cause noises or crackling. In addition, the WH20
QTR can only be operated
unbalanced, which is a major disadvantage if the mic is connected to a standard XLR microphone input (e.g. external Mixer or keyboard XLR Mic Input) should be connected and / or if a relatively long cable should be used).
That's why I recommend buying the WH20
XLR. To connect it to the SX900, you additonally need an unbalanced
extension cable (preferably as short as possible) "XLR female connector to 6.3 mm TS plug":
Best regards,
Chris