Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dscottguitars on February 15, 2014, 04:29:31 pm
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Hi, I have a question about the resistor used in this mid boost circuit and if there is any reason it can be eliminated in mine. I took the circuit from a Fender Concert I had, see the schematic. It uses a 10 meg resistor across the switch, but I can't see any reason for it being there. I also have my preamp schematic with and without the resistor and would like to know if it can be used without it. It seems to me I am just switching in another capacitor in parallel with the one on the treble pot. It would make the total capacitance 2270pF vs 2000pF.
Thanks,
Daniel
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You often see large resistor across switches to minimize the 'pop' that can occur when engaging or disengaging the switch. Discharges the adjacent capacitor. If you don't need it--you don't need it. You can get away with lower value--4.7M if you need though. Regards
dennis
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Didn't think of that, thanks...
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... It would make the total capacitance 2270pF vs 2000pF.
It makes the total capacitance 2270pF vs 250pF. Which is what gives the impression of mid-boost, as upper mids are passed along with treble.
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I use this midboost for all 3 of my amps. And I like it ALOT!
You can calculate the values here: http://www.kusashi.com/series-capacitors.php (http://www.kusashi.com/series-capacitors.php)
With respect, Tubenit
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typo...