Tube socket tension

maddnotez

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Well-known member
Is this something any noob can check? If so how do you check?

I've been hearing much talk from the Bogner users that it is ok to use KT88's with the Rev 2 (EL34 amp) as long as they're low to mid bias range tubes.

Wanted to confirm with Bogner and this was the reply:

"We have been using Sovtek KT88s, but these are no longer available. You need to adjust the bias range, but if the tubes are too hot, they may be above the possible range. Try to find some low to mid range tubes. Also, your tech should check the tension on the tube socket pins, as this can be an issue on older amps with the heavier tubes.
Thanks CP"

So now I'm curious about the socket tension. I really want to use the KT88's and I know others do so it should be ok but I don't want to break anything.
 
what charlie is referring to is the fact that over the years, the pins have gotten smaller in diameter on new tubes. older amps with older tubes and big pins would expand the sockets. as was mentioned above, an awl or even a small flat screwdriver will suffice to tighten them up. they are split bushings, so just dig in and tighten them up. one reason why bogner and others default to JJEL34's is because they still have the larger OD pins on them and are more stable in the sockets. Not because they are cheap as some people insist. Compare EL34's to E34L's and you will see. Some Ruby and TAD tubes also have the large pins.

i can assure you that your amp will not bias up going from 34's to 88's. there won''t be enough bias range. you will need to piggy back another 22k (if i remember right) resistor on top of the current bias resistor to get into range. also, they generate a lot of heat. if it is an amp that you treasure, i wouldn't do it.
 
steve_k":wo3ekdvr said:
if it is an amp that you treasure, i wouldn't do it.

Thanks for the tips.

When you say you wouldn't do it, do you mean run KT88 without the resistor swap? Or that you wouldn't mod the amp to run KT88?

Mine sounds really good but I played a buddies that had the KT88 mod and it sounded amazing.
 
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