     /// 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

    public override func detach() {
        stop()

        let nodes = [inputMixer.avAudioNode,
                     mixer.avAudioNode,
                     internalEffect,
                     inputGain.avAudioNode,
                     effectGain.avAudioNode]

        AKManager.detach(nodes: nodes)
    }
