crackles using ASIO4ALL and a Zoom H4n as audio interface


I am using Cubase LE version 8, and trying to record some audio. Therefore I use my Zoom H4n recorder as audio interface, via the USB.
Further I am running Windows 7 on a HP ELite laptop: 8 GB RAM, 2.8 GHz, Intel Core i& CPU. Powerfull enough, I would say. But I don’t use an external audio card.

I am using the ASIO4ALL driver. But I get crackles, latency… I tried all combinations of settings: Multi processing, extnernal clock and Audio Power scheme on/off. And in the control panel I’ve experimented with many combinations: ASIO bufer size, Harware buffer (different buffer offset values)… I found a combination that gives me the less crackles.

Great! But still I hear crackles. So my question is: is there something I am missing? I begin to think that the only solution I have is to use an external sound card. If you think this is indeed the case: which card (as cheap as possible: I need it only for one project) would you recommend me? Or perhaps just another ASIO driver?

Thank you in advance! I am quite desperate after days of trying things and reading in the forum…