Late 60's guild thunderbass

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i have a late 60's thunderbass head and would love to change the 8417's to 6l6's. anyone have a schematic for this mod?
 

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Prowess has all the schematics that we know of. You need to double the negative voltage for the bias supply. 8417s were designed to run on -17 volts, 6L6gts need about -35 volts in the bias supply.
Good luck with the conversion, shouldn't be too difficult for an experienced amp tech.
 

AcornHouse

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I know this is a somewhat common mod (if I can use that term with a not common amp), but what is your purpose? I know 8417 tubes are not common, but they are available and not outrageously expensive (like 6bk11s). I love the sound of my 8417 Thunderbass and feel it's well worth the trouble to keep it as spec'd.

Of course, anyone is free to mod their own equipment as they see fit. I just think it's become a go to fix that doesn't need to be.

8417ers unite!
 
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it's for a customer, he just thinks $65 and up for a used tube is a bit much. thanks for the replies. =)
 

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He is going to lose volume. The fifty watt 8417 T-basses only needed 400 volts on the plates.
 
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