gistfile1.swift

    let engine = AVAudioEngine()
    
    func setup() {
        let inputNode = engine.inputNode
        let outputNode = engine.outputNode
        
        NSLog("all: %@", AudioDevice.All().map{$0.name})
        NSLog("inputs: %@", AudioDevice.All().filter{$0.isInput}.map{$0.name})
        NSLog("outputs: %@", AudioDevice.All().filter{$0.isOutput}.map{$0.name})
        
        let inputDeviceName = "Logitech USB Headset"//"Soundflower (2ch)"
        let outputDeviceName = "USB Sound Device"//"USB Sound Device"
        
        let devices = AudioDevice.All()
        let inputDevices = devices.filter{$0.isInput}
        let outputDevices = devices.filter{$0.isOutput}
        
        let inputDevice = inputDevices.filter{$0.name == inputDeviceName}.first!
        let outputDevice = outputDevices.filter{$0.name == outputDeviceName}.first!
        
        func setCurrentDevice(node: AVAudioIONode, device: AudioDevice) {
            var id = device.id
            check(AudioUnitSetProperty(
                inputNode.audioUnit,
                AudioUnitPropertyID(kAudioOutputUnitProperty_CurrentDevice),
                AudioUnitScope(kAudioUnitScope_Global),
                AudioUnitElement(0),
                &id,
                UInt32(sizeofValue(device.id))))
        }
        setCurrentDevice(inputNode, inputDevice)
        setCurrentDevice(outputNode, outputDevice)
        
        let mixer = AVAudioMixerNode()
        mixer.renderingAlgorithm = .StereoPassThrough
        engine.attachNode(mixer)
        
        let format = AVAudioFormat(standardFormatWithSampleRate: 44100, channels: 6)
        
        engine.connect(inputNode, to: mixer, format: format)
        engine.connect(mixer, to: outputNode, format: format)
        
        let (success, error) = errorWrap{ self.engine.startAndReturnError($0) }
        println(success, error)
    }