So I have a Traynor YBA-200. It's got two pairs of 6550s in it. The tubes pairs inside are by different manufacturers. Is this a problem? They're all 6550s and it's been working without a hitch, but I just want to know if this could cause future problems. I don't really know how old they are, so I was thinking of getting new ones sooner or later anyways. Any advice would be appreciated. Thans!