what's the tip? inside or outside?

Fazer

with an ac/dc power adapter (for an older portable keyboard), what is 'tip negative'?
is the tip the centre/inside or the outside?

thermionic

Tip is the inside, sleeve is the outside.

Tip is usually the terminology for a jack plug through, which has an obvious tip; "centre negative" is how I'd expect a barrel connector to be described.

Fazer

yeah, that was how it was described in the manual i found online (im sorting it out for someone else and dont have the keyboard with me)