Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: J Rindt on June 28, 2011, 06:29:15 pm
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On the bass channel, I would like to use the unused triode for a cat follower. Is it as simple as just doing it.? Can I simply make the unused triode into a CF, and insert it between V1a and the present tone stack.? Then follow that with the same gain stage (that now follows the tone stack) that is on the stock schematic.?
That is to say...turn that unused triode into a CF, put it after the first gain stage, and before the tone stack, and continue with the stock schem.?
Thank You
http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_AB165.pdf (http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_AB165.pdf)
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If i got your question right, check the ampeg svt preamp on the library. Bright channel shows something close to your describe, as I understood it. However, there is a passive network with fixed values instead of pots. I believe you can insert a tonestack here.
Will it have a gain recovery stage after tonestack?
Hope this helps.
With respect.
Rzenc
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My question is....literally....the AB165 schem......bass channel....can I take the unused triode, turn it into a CF and insert it between the first gain stage and the tonestack.?.....everything else stays the as is.
Is it that simple.?
Thank You
If i got your question right, check the ampeg svt preamp on the library. Bright channel shows something close to your describe, as I understood it. However, there is a passive network with fixed values instead of pots. I believe you can insert a tonestack here.
Will it have a gain recovery stage after tonestack?
Hope this helps.
With respect.
Rzenc
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At a glance, I see no reason why you shouldn't be able to add the CF as proposed...........G
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At a glance, I see no reason why you shouldn't be able to add the CF as proposed...........G
OK.....thanks.
But I guess I am just turning V1b into a CF. I still have the unused triode, which is OK.
So I would still have One unused triode, and now the CF is operating off the B+ line without a 100k plate resistor. Not sure if that will have an effect or not.
FWIW, I guess I could parallel V1a and V1b, and then make a CF out of that unused triode. But I am not sure what that would get me. Just trying to do something different with the bass channel to make it better for guitar.
Perhaps the amp is fine without the added gain of activating that unused triode.
Thanks
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meow...
:icon_biggrin:
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I'd scrap the entire bass preamp and put a 5F6A (http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_5F6A.pdf) preamp in it's place. Or build a Plexi JMP 1987 (http://www.el34world.com/charts/Schematics/files/marshall/jmp_lead_50w_1987.pdf) preamp, which is very close to the 5F6A. Or build the November (http://home.comcast.net/~seluckey/amps/november/november.pdf) preamp which is a hard wired single input jumped channel Plexi preamp. Any of those three suggestions will use 4 triodes and sound good for guitar.
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Tweed would be fine, I just need to be able to fit the circuit on the existing eyelet board and existing face plate. I thought maybe, with the switchable cathode, 220k plate resistor, and the CF in front of the smaller value cap tone stack, it would be much more usable for guitar and different enough from the Normal Channel to make it worth the effort.
There are probably 20 different possibilities you guys could come up with. I just need something that more or less fits the board/face plate, a bit different than the other channel, and is not too high gain.
Thanks
I'd scrap the entire bass preamp and put a 5F6A (http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_5F6A.pdf) preamp in it's place. Or build a Plexi JMP 1987 (http://www.el34world.com/charts/Schematics/files/marshall/jmp_lead_50w_1987.pdf) preamp, which is very close to the 5F6A. Or build the November (http://home.comcast.net/~seluckey/amps/november/november.pdf) preamp which is a hard wired single input jumped channel Plexi preamp. Any of those three suggestions will use 4 triodes and sound good for guitar.
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...to fit the circuit on the existing eyelet board and existing face plate.
The bass channel faceplate has holes for 2 jacks, 1 slide switch, and 3 pots. That pretty much eliminates all my suggestions. Sorry...
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Nothing to be sorry for. Your suggestions are probably what the Bassman really needs, but I do not have the room unfortunately. I will just go with what I have, at this point, and see how it goes.
Thank You