Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: J Rindt on May 05, 2010, 02:08:50 am
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In the "bass channel" of this amp, there is a .02uf cap from one leg of the Treble Pot to ground. Does this shunt the higher frequencies to ground as the treble pot is increased? I would like to make this channel "better" for guitar, so I thought I might delete that from the amp when I build it.
I can follow the schematics, and build from them, but I do not understand what is happening to the signal at all parts. Are there some components I might want to leave off to maximize the bass channel for use with guitar?
Thank You
http://www.el34world.com/charts/Schematics/fender/BASSMAN_6G6A.pdf
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In the "bass channel" of this amp, there is a .02uf cap from one leg of the Treble Pot to ground. Does this shunt the higher frequencies to ground as the treble pot is increased? I would like to make this channel "better" for guitar, so I thought I might delete that from the amp when I build it.
I can follow the schematics, and build from them, but I do not understand what is happening to the signal at all parts. Are there some components I might want to leave off to maximize the bass channel for use with guitar?
Thank You
http://www.el34world.com/charts/Schematics/fender/BASSMAN_6G6A.pdf
you need to leave those tone control parts in place. That .02uF capacitor, in combination with the 100k potentiometer are what forms the functioning treble control. With the treble control turned up all the way, the signal is taken with less highs removed. The resistance of the pot combined with that .02uf Cap (forming a R-C filter) will have a higher cut-off frequency than with less resistance between where the signal is taken and that cap. It's kind of late for me here, (well, "kind of" is an understatement,) and the formula to show where those cut-off frequencies are eludes me at the moment. I'll let someone else explain that part for now, while hoping what I have said isn't confusing. Needless to say, with that specific value of cap there, it will make that channel dark with the treble control turned down. You may play around with that cap value though to change how dark it does get. (I would guess you'd probably not want to go any less than the .005uF found on the normal channel, and definately no more than what is there already (.02uF), but the exact value will depend on you and your ears.
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OK Thanks -
Maybe I have this back wards, but this is a Low Pass filter. So if I lower the uF value of that capacitor, there will be more bass frequency rolled off. A .002 cap will roll off more bass than a .02 does. Is that how it works?
Thank You
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...this is a Low Pass filter. So if I lower the uF value of that capacitor, there will be more bass frequency rolled off. A .002 cap will roll off more bass than a .02 does. Is that how it works?
No. That's backwards.
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...this is a Low Pass filter. So if I lower the uF value of that capacitor, there will be more bass frequency rolled off. A .002 cap will roll off more bass than a .02 does. Is that how it works?
No. That's backwards.
OK, now I've got it.
Thank You
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OK Thanks -
Maybe I have this back wards, but this is a Low Pass filter. So if I lower the uF value of that capacitor, there will be more bass frequency rolled off. A .002 cap will roll off more bass than a .02 does. Is that how it works?
Thank You
As slucky said, that is backwards. It would be true if the cap was like the .1uF cap just before the treble control, coming off the plate of that triode. But when it goes to ground, like it does in the treble (or tone) control, it will bleed off highs. The larger the value (aka .02uF or more,) the lower the frequency be when it starts to get bled off. The lower the value (aka .002uF or less) the higher that frequency will be before it gets bled off to ground.
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OK Thanks -
Maybe I have this back wards, but this is a Low Pass filter. So if I lower the uF value of that capacitor, there will be more bass frequency rolled off. A .002 cap will roll off more bass than a .02 does. Is that how it works?
Thank You
As slucky said, that is backwards. It would be true if the cap was like the .1uF cap just before the treble control, coming off the plate of that triode. But when it goes to ground, like it does in the treble (or tone) control, it will bleed off highs. The larger the value (aka .02uF or more,) the lower the frequency be when it starts to get bled off. The lower the value (aka .002uF or less) the higher that frequency will be before it gets bled off to ground.
Thank You. This stuff is all pretty new to me. I do a lot of reading, and try to retain as much of this knowledge as I can. But I really do appreciate all the help I get. I know this is pretty basic info for a lot of you guys, and it must all start to sound repetitive, so I appreciate you guys taking the time to go over the basics.
Thanks Again
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Thank You. This stuff is all pretty new to me. I do a lot of reading, and try to retain as much of this knowledge as I can. But I really do appreciate all the help I get. I know this is pretty basic info for a lot of you guys, and it must all start to sound repetitive, so I appreciate you guys taking the time to go over the basics.
Thanks Again
You are quite welcome. :smiley: