In all cases, the defendant and the attorney for the Commonwealth may waive a jury trial with approval by a judge of the court in which the case is pending, and elect to have the judge try the case without a jury. The judge shall ascertain from the defendant whether this is a knowing and intelligent waiver, and such colloquy shall appear on the record. The waiver shall be in writing, made a part of the record, and signed by the defendant, the attorney for the Commonwealth, the judge, and the defendant’s attorney as a witness.