I need new tubes... make some recommendations!

  • Thread starter Thread starter jndietz
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jndietz

The Way It Moves
Hey everyone... I own a B-52 ST6012 amplifier with Vintage 30s. I am interested in changing the tubes because 1) I bought the amp used and still has the same tubes and 2) right now I feel the amp has entirely too much gain. What do you guys recommend for all of the following:

Power: 2 – 6L6 / 5881
Preamp: 5 – 12AX7
Reverb: 1 – 12AT7
Rectifier: 1 – 5AR4

Thanks in advance everyone...
 
jndietz said:
Hey everyone... I own a B-52 ST6012 amplifier with Vintage 30s. I am interested in changing the tubes because 1) I bought the amp used and still has the same tubes and 2) right now I feel the amp has entirely too much gain. What do you guys recommend for all of the following:

Power: 2 – 6L6 / 5881
Preamp: 5 – 12AX7
Reverb: 1 – 12AT7
Rectifier: 1 – 5AR4

Thanks in advance everyone...
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I would try buying 2 or three 12AT7s or 12AU7s and subbing them in different spots in the preamp. You'll have to try them in different spots, to see where they make the change you want. These have somewhat less gain than the 12AX7s, and will be a direct replacement for you. I wouldn't worry about the power tubes; those 6L6s won't distort until your ears bleed.

Peace!

~Shawn
 
eyema_believer said:
I would try buying 2 or three 12AT7s or 12AU7s and subbing them in different spots in the preamp. You'll have to try them in different spots, to see where they make the change you want. These have somewhat less gain than the 12AX7s, and will be a direct replacement for you. I wouldn't worry about the power tubes; those 6L6s won't distort until your ears bleed.

Peace!

~Shawn
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+1...


trying at's or au's is a great idea here... as to the output tubes... if there's a degredation from age as you suggest... then the outputs are the ones to change... the pre-tubes can last for ages.... and check into rebiasing if you do change the outputs....
 
eyema_believer said:
I would try buying 2 or three 12AT7s or 12AU7s and subbing them in different spots in the preamp.
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12AT7s and 12AU7s draw more current and are NOT direct replacements for 12AX7s in all amps. Also it's not always immediately apparent that the amp is being damaged.
 
ocnor said:
12AT7s and 12AU7s draw more current and are NOT direct replacements for 12AX7s in all amps. Also it's not always immediately apparent that the amp is being damaged.
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Which explains why they have more headroom, I suppose. I will edit my post. Thanks for the heads-up.
Sorry to the original poster for making a recommendation that had been made to me and worked fine for me, but potentially could damage an amp. :o

Peace!

~Shawn
 
Look Here Look Here Look Here Look Here!!!!!!!!

Well, for some reason I can't edit my previous post about 12AU7s and 12AT7s. If someone in the future reads this shaky advice, PLEASE read this entire thread before proceeding, paying careful attention to this warning:
12AT7s and 12AU7s draw more current and are NOT direct replacements for 12AX7s in all amps. Also it's not always immediately apparent that the amp is being damaged.
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ocnor said:
12AT7s and 12AU7s draw more current and are NOT direct replacements for 12AX7s in all amps. Also it's not always immediately apparent that the amp is being damaged.
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and yet it seems the book i have here lists them as lower than ax7's... even if we assume that there's some varience from brand to brand one would still wonder what problems you experienced...
 
dementedchord said:
and yet it seems the book i have here lists them as lower than ax7's... even if we assume that there's some varience from brand to brand one would still wonder what problems you experienced...
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I don't think that there is a direct correlation between the gain of a tube and the current it consumes. That said, it's kind of hard to imagine that a preamp tube drawing a little more current could hurt (I presume) the power transformer, since the current consumed by a preamp tube (I'm pretty sure) is small compared to that drawn by the power tubes. In most/all tube amps, the preamp and power tubes pull their current from the same tap on the power tranny.
 
ggunn said:
I don't think that there is a direct correlation between the gain of a tube and the current it consumes. That said, it's kind of hard to imagine that a preamp tube drawing a little more current could hurt (I presume) the power transformer, since the current consumed by a preamp tube (I'm pretty sure) is small compared to that drawn by the power tubes. In most/all tube amps, the preamp and power tubes pull their current from the same tap on the power tranny.
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agreed... though he seemed worried about the current handling of the heater tranny specificlly... or did i miss read something again???
 
Over at the Carvin boards, some guys with way more knowledge than I have, stated that certain resistors in some amps may not be rated for the extra current draw. They also showed pictures of toasted resistors and circuit boards which resulted from using 12at7s. Another person stated that his amp fried when he substituted 12au7s in place of 12ax7s. Some amps may be fine with the substitutions but just make sure before you do it.
 
I swapped out the 12at7 for a 12ax7 in my '77 Fender Super Twin...is that bad??? I never trusted anything with tits or tubes.
 
Corndog said:
I swapped out the 12at7 for a 12ax7 in my '77 Fender Super Twin...is that bad??? I never trusted anything with tits or tubes.
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If you put a 12ax7 in a circuit designed for a 12at7 then you had better keep the fire extinguisher handy.


FireExtinguisher.gif
 
How about this question... where can I get myself a good multimeter?
 
ocnor said:
If you put a 12ax7 in a circuit designed for a 12at7 then you had better keep the fire extinguisher handy.
So you're saying that if you put a tube that draws less current in place of one that draws more current you're creating a distressful situation inside the amp? Not that I know anything about anything.....but usually stuff only gets too hot when you draw more current than a circuit is designed for....dunnit?
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I use a 12AT7 in my 1965(ish) Epi 101 single EL84 amp. All the 12AX7s I tried tended to overpower the EL84 and it got farty sounding. Much better with the 12AT7 -- is it as simple as burning up a resistor? I can fix that :)
 
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