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Looking to build a tone control for a SE champ style amp. I want to use a 100k A pot. Had a look at Adams amps site , and think that the moonlight or the garnet might be the way to go , however , in the case of the moonlight , i'm not sure if the other resistors need to be varied , to compensate for the lower pot value. The volume pot is 500k A , any advice would be great.
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Other then maybe that 100K pot is all you have and there is no way to get a 500K or 1M pot, .... why 100K?Originally posted by walkman View Post
That will probably lead to a poor tone control choice when coupled to a high impedance vacuum tube amp. -
They way I look at it.....the guitar already has a tone control on it...why add another one to the amp?Comment
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hi, Bruce
the radio chassis i've converted has a 100k A and 500k A they have thin shafts and the original knobs won't fit on replacement pots , though i could just use some new chicken head knobs..... and different pots.
The 500k A is suitable for 6av6? in between two halves of a 12ax7, currently 1.5k / 22 uf on the first and 1.5 / 1 uf on the second with a 0.022 coupling caps, and 270k grid stopper. Both have 100k resistors and the voltage is 162v , current 1.35 & 1.27.
the tone control is .0022 & 560pf , i had a .0068 in before and it seems that .0047 will be right on the mark when i get one. The 100k is the original pot that was used in the radio.
6AQ5 is the output tube , with a 1.5k grid stopper , 330 ohm / 22 uf cathode , 1 k on screen. Voltages are 12.5 cathode 261 screen, 262 plate. The Screen current is 2.4ma and the plate current is 36ma, the 6AQ5 has a max of 45ma? & 4 ma for screen so i'm well under at about 9w not sure what the transformer is but its the original one for the chassis. 6x4 recto is followed by 47uf , and two 22uf electros separated by 3k & 4k7, to drop the voltages to whats needed.
Initially i had it running with out a tone control , sounded great. However i was using a eq pedal to give a notch at the lower mid , bit of high boost.
I wanted to be able to use the amp without having the pedal , but didn't want to change the look of the amp. The first tone control i tried was more of a variable brite pass... signal split to the wiper of both volume and tone pots .1uf to ground and .0056 to one leg of the volume ... had a very small usable range where it sounded deep & full and loud at low levels of volume , and made the tone more into an overdrive control. realize now i could have just reduced the .1uf to something less.
the second tone control i tried was wired the correct way i think , but had .047 to ground and 500pf bak to the signal. To me this sounded really toneful it had a useable range and had a character that was really different to the previous tone control, however it sounded thin at low volume and overdrive at much lower on the volume pot and all together lower in output level . I considered keeping it as it was good for bedroom levels.
the way it is currently wired probably sounds the best though.... it could be a little louder , it does not seem as loud as with the first tone / brite control
how does the value of the 100k affect the impedance? does the next tube see the 100k and 500k in parallel ?Last edited by walkman; 08-03-2007, 08:13 AM.Comment
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