Apogee Duet & Aggregate Device

[usw]

Hi folks,

I am a first time user here. Congratulations for this great forum.

I need some advice about getting my Apogee Duet to work as an aggregate device.

I had bought a TC Konnekt24D about a year ago with which I had horrible driver problems on my MBP in Logic Studio. However one thin I really loved about the Konnekt is its ability to have some realtime FX and a decent compressor. I need to record Vocals and one stereo keyboard at the same time.

A month ago I decided to get a new interface. My plan was to get a better interface (better A/D) for recording vocals & guitar and use it together with the Konnekt as an aggregate device. I bought an Apogee Duet which has great pre's and A/D and aggregated it together with my TC Konnekt. During recording sessions I use the Duet only for the vocals. The Duet's analog output (carrying only the singer's voice) is connected to the Konnekt's stereo input (channel 1/2) just to give the vocalist some realtime FX from the Konnekt. At the same time I record my stereo keyboard which is connected to the Konnekt's 3/4 input. The complete Mix can be heard through the Konnekt's main output.

Now comes the weirdness:
When I record vocals & keyborad together, the keyboard track is not in sync with the recorded vocals. After several minutes of recording some digital noise appears and I have to restart the whole MBP to get it working again (just for another 5-10 minutes).

My question now is:
Am I doing something wrong in my setup? I have read that Apogee doesn't support aggregating the Duet (though my dealer told me it will work). Would aggregating the Konnekt with a MH ULN2 work better for me?
I am open to sell the whole stuff and get something else that meets at least the following requirements:

1. Two high quality pres and A/D channels
2. Two additional channels for recording a stereo keyboard
3. Realtime FX (comp. & reverb) for the vocalist for monitoring

Any ideas or hints how to get this setup working and stable (either change my configuration or buy somethin new)?

Thanks a lot in advance and best regards.
Udo