new (old) amp day
- Thread starter dbw
- Start date
O
OzziePete
Guest
What speakers in that box? EVs would be crystal clear in that rig, but I'm guessing you went for Celestions or Webers?
There were two (or three) versions of the BF Bassman. All have some sort of interstage negative feedback - a way of "compressing" the signal a bit to avoid clipping...er... overdrive.<smiles>
This can be modified, or removed.... for one kick ass blues machine if you so desire. When you do that, depending on how you do it, and the extent, you'll have to reverse the output transformer leads on the tube sockets or its gonna squeal like nothing you ever heard before, and once heard will never, ever forget. The squeal is caused by the resultant positive feedback in the output. Reversing the leads makes it negative again, and the squeal goes away. The same thing happens when you put a transformer in any push-pull amp build, you have to go at it and make sure you've got it right by trial and squeal method.
I've found with the big iron, the 50w Bassman loves the big envelope KT-66 tubes with the metal bases. You'll have to remove the bear traps and add spring covers to keep the big bases connected (bear traps work with 6L6 or similar bases). Other than that - the KT-66 in the big "coke bottle" work great in those.
This can be modified, or removed.... for one kick ass blues machine if you so desire. When you do that, depending on how you do it, and the extent, you'll have to reverse the output transformer leads on the tube sockets or its gonna squeal like nothing you ever heard before, and once heard will never, ever forget. The squeal is caused by the resultant positive feedback in the output. Reversing the leads makes it negative again, and the squeal goes away. The same thing happens when you put a transformer in any push-pull amp build, you have to go at it and make sure you've got it right by trial and squeal method.
I've found with the big iron, the 50w Bassman loves the big envelope KT-66 tubes with the metal bases. You'll have to remove the bear traps and add spring covers to keep the big bases connected (bear traps work with 6L6 or similar bases). Other than that - the KT-66 in the big "coke bottle" work great in those.
Superlizard
Hero Member
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- 2,514
D00d... you went and got that when you could've got an amp modeler? :icon_jokercolor:
SCORE! :icon_thumright:
SCORE! :icon_thumright:
Superlizard
Hero Member
- Messages
- 2,514
I recommend Valve Art KT66s for current production:
New logo:
Old logo:
For NOS, go with Genalex (GEC) or any M.O. (Marconi-Osram) valve.
I hear there's a repro of the Gold Lion, but ain't tried them yet.
New logo:
Old logo:
For NOS, go with Genalex (GEC) or any M.O. (Marconi-Osram) valve.
I hear there's a repro of the Gold Lion, but ain't tried them yet.
It's a real '65... I don't think they reissued this amp anyway.
Cracked it open tonight and it's not all-original like I thought... I assumed it was because of the 2-prong cord and stock bias. It's got new filter caps and the screen resistors have been upgraded, so that's nice. There are a few new electrolytics and Orange Drops inside but also many original caps.
Tube chart says AA165 but it's definitely a AB165 circuit.
It is a 100% stock circuit though, including negative feedback, "balance" bias, and "death cap" (which is the original!
)
Gee, I wonder where it was last serviced
I will change the bias circuit to the sane kind, add 1-ohm resistors for biasing, get rid of the death cap and add a 3-prong cord. Then I will play it for a while before I do any "real" mods...
arty07:
Cracked it open tonight and it's not all-original like I thought... I assumed it was because of the 2-prong cord and stock bias. It's got new filter caps and the screen resistors have been upgraded, so that's nice. There are a few new electrolytics and Orange Drops inside but also many original caps.
Tube chart says AA165 but it's definitely a AB165 circuit.
It is a 100% stock circuit though, including negative feedback, "balance" bias, and "death cap" (which is the original!
)
Gee, I wonder where it was last serviced
I will change the bias circuit to the sane kind, add 1-ohm resistors for biasing, get rid of the death cap and add a 3-prong cord. Then I will play it for a while before I do any "real" mods...
arty07:http://books.google.com/books?id=bmeE_HNkAV0C&pg=PA34&lpg=PA34&dq=fender+bassman+mods&source=bl&ots=bgVb7vOEoh&sig=oapyOTu2cKyV7req1GIepuH1T8E&hl=en&ei=ZjLJSp-HI87RlAfLppiSAw&sa=X&oi=book_result&ct=result&resnum=10#v=onepage&q=&f=false
Nice collection of mods. Anybody else have others? Half power mod, maybe.
Nice collection of mods. Anybody else have others? Half power mod, maybe.
mayfly
Epic Member
- Messages
- 8,972
Yep that's the real thing all right. Nice and clean as well. The cap job is fine, and those two orange drops replace the two caps in the phase splitter, which are common failure points for this amp.
Yea, I'd get rid of the death cap :icon_biggrin:
Looks very nice!
Yea, I'd get rid of the death cap :icon_biggrin:
Looks very nice!
