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I'm using a pair of Tractrix 180hz Front Horns (see pic) full range 6.5" drivers (about 106db). This is powered by a homebrew SET 45. My question is - How can I determine the coupling cap needed (in the 45 amp) to help create a hi-pass filter at about 50 hz? I would prefer that the 45 tube , trannys , and 6.5" speaker never had to see anything below 50 hz without having to introduce a crossover.
Follow Ups:
if you are going to limit to 50hz, then you will have to mess with cathode bypass caps also, if any exist. biamping? what's that big ass woofer doing?
The horn is fullrange and the 15" Eminence is powered by a class D plate amp with active xover.
The cap between the driver tube and the 45 is now a 2uf poly. I know that I can change that to a smaller value to to get a 50hz cut off. Sorry I'm a speaker Geek and building tube amps is fairley new to me. Here is a link to all of my projects.http://gallery.audioasylum.com/cgi/view.mplUserImages=33876&session=
159000/(50cps*impedance) for a 6BD per octave filter. So if the input impedance of the 45 amp is 100K, you need a .0318uf cap in series to block the lows.Or, if you don't want to add a cap to the system and your amp does not use feedback, you could use the same math to change the value of the coupling cap between the drive and the 45 (based on the resistance value of the 45 grid resistor).
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Sorry I'm not sure that I understand. The coupling cap now is a 2uf poly. Here is my schematic.
http://gallery.AudioAsylum.com/cgi/gi.mpl?u=33876&f=se_glorya.jpg
OK the output tube grid resistor is 220K. So the 3db down point with the 2uf. cap is .36cps. 159000/(resistor in ohms times cap value in uf)= the freq. of the 3db down point.159000/(resistance times freq) = cap value in uf. So to get a 3db down point of 50cps, 159000/(220000*50cps)=.01445uf. Just change the 2uf. to a .015uf. That will work fine.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks so much , I'll give it a try.
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