Mixing Power Tube Brands OK?

Troy T. Blues

Comstock Station
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2,543
My bass player has an Ampeg SVT Classic head. It uses 6ea 6550 tubes and one is blown. Don't know how long that was the case. They are Sovtek 6550WE's. Due to availability and time concerns, can he sub with another brand? Any potential issues with that? I know that it's quite costly to retube all. We have a big gig next weekend.....Thanks!
 

Floyd Eye

Member
Messages
13,879
My bass player has an Ampeg SVT Classic head. It uses 6ea 6550 tubes and one is blown. Don't know how long that was the case. They are Sovtek 6550WE's. Due to availability and time concerns, can he sub with another brand? Any potential issues with that? I know that it's quite costly to retube all. We have a big gig next weekend.....Thanks!

SVTs run in matched triplets. While replacing a single tube MAY get you through a gig, I highly recommend you don't leave your amp in that condition for long. My suggestion is a matched triplet at a minimum.
 

Floyd Eye

Member
Messages
13,879
The odds of replacing a single power tube and getting the CL to bias are very slim. As I said, you may get through a gig ok, then again you may end up smoking some grid screen resistors or something else.

Personally, I would look for a loaner if I had to, then buy 6 matched 6550s ( or at least 2 matched triplets) and replace the tubes. If the amp doesn't bias properly, take it to a tech.
 

Troy T. Blues

Comstock Station
Messages
2,543
Thanks guys. We are all set. We found some and he's gonna replace the three tubes in that section. Thanks again!
 






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