How to specify K cluster in Hierarchical clustering with noisy data?

I’m new in Mining and Clustering and I wonder how to cut off the hierarchical clustering Dendrogram to obtain a specific number of clusters. The problem is here that the data is noisy and the SLINK algorithm consider these noises as a cluster and when I cut off the Dendrogram to obtain exactly K cluster, it gives me some noisy cluster and so ignores all or some of K expected clusters. So I think there should be some techniques to cut the Dendrogram without considering the noisy clusters.

Note that I know the number of K and it’s not a problem how to specify this number!

Thanks.