ARC VT Series amps

I own a VT 130SE, can I use KT 88 tubes or will the amp be harmed? It was designed for 6550 tubes.

For a time I used KT88s in a VT130 with no problems. Some prefer them to 6550s, but I found they sounded a bit sterile.
That's the second time I heard the same thing said, about being sterile. Thanks Dgarretson