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so I bought a used YBA200 bass amp head yesterday from long and mcquade here in Winnipeg. Played it for about an hour and then pop, squeal, burning smell...I stop playing and check the back of the amp. One of the power tubes is not glowing (I don't know that it was glowing before this happened). So I take it to L&M and they try to give me just one tube. I tell them I'm pretty sure I need a matching pair because the tubes work in pairs and if they're too far off it would be bad. The guy tells me they don't come in matched pairs. So I get him to talk to the amp tech there to see if he can measure them to see if they're close. The amp tech tells him those tubes don't come in matched pairs and the amp doesn't need matched pairs. So I take the tube and go.

So, am I wrong in thinking I need matched pairs? These are 6550 power tubes BTW...4 of them.
 

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"All hail Pete Traynor!"

Marcus0000 said:
So, am I wrong in thinking I need matched pairs? These are 6550 power tubes BTW...4 of them.

It's ok, Marcus. Traynor seems to favour an "autobias" circuit in their new amps. I checked the schematic for the YBA200 and you don't need matched pairs at all. The amp will compensate.

It seems more to go wrong and extra cost to me but I'm just an old guy.None
 
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