     /// Four letter unique description of the node
     public static let ComponentDescription = AudioComponentDescription(appleEffect: kAudioUnitSubType_HighPassFilter)
 
-    private var mixer: AKMixer
+    private var mixer = AKMixer()
     private var au: AUWrapper
 
     /// Cutoff Frequency (Hz) ranges from 10 to 22050 (Default: 6900)

    public var dryWetMix: AUValue = 1 {
        didSet {
            dryWetMix = (0...1).clamp(dryWetMix)
            inputGain?.volume = 1 - dryWetMix
            effectGain?.volume = dryWetMix
        }
    }

    private var lastKnownMix: AUValue = 1
    private var inputGain: AKMixer?
    private var effectGain: AKMixer?
    var inputMixer = AKMixer()

    // Store the internal effect

        self.cutoffFrequency = cutoffFrequency
        self.resonance = resonance

        let effect = _Self.effect
        internalEffect = effect
        au = AUWrapper(effect)

        super.init(avAudioNode: mixer.avAudioNode)

        inputGain.volume = 0
        effectGain.volume = 1

        if let input = input {
            input >>> inputMixer
            input >>> inputGain
            input >>> effectGain
        }
        effectGain >>> effect >>> mixer
        inputGain >>> mixer

        au[kHipassParam_CutoffFrequency] = cutoffFrequency
        au[kHipassParam_Resonance] = resonance
