Integrated amp powered with 5881/EL-34 tubes

I am wondering how an auto-biased integrated amp can use, according to the manufacturer, 5881 or EL-34 output tubes, given that they are different electrically?
By your question, I'm not sure if you're asking for a technical explanation or wondering if it's really possible. If it's the latter the answer is yes. I have an auto-biasing AES AE-25 SuperAmp and have used 5881, 6P3S, EL-34, KT-88, 6550 and KT-66 tubes in it.
Clear. Then my amp just could not cope with it and blew a fuse when I installed EL-34 tubes instead of 5881. Also, it did not "like" NOS TungSol 5881 tubes (perhaps, because they have a lower plate current than, for instance, Sovtek or Chinese 5881 tubes).
Because the AE-25 accepts such a large number of tube types without any problem and there's no effort involved in biasing I've accumulated an embarrassingly large number of output tube sets. The NOS Tung Sol 5881's are some of my favorites and I tend to alternate them with EL-34's, either NOS Tesla or Siemens/RFT. I've spent less time listening to the KT-88's and 6550's but they also sound very good in the amp.