LM13600

[Haible Juergen]

	>Excuse my ignorance, but is 13600 so much beter than 13700?

Just different.
In a Vocoder, a 13700 is much better than a 13600, and in
a filter the 13600 is much better.
Why that ? Both are direct conclusions from the fact that the 
13600's buffer impedance is is changed by the Iabc current of the OTA,
and the 13700's is not.
If you're using the internal buffers, that is. If you don't use them, or put
a FET in front of them, the difference can be neglected. 

JH.