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In Reply to: My horn pics and SET 45 amp question ? posted by Les Hudson on March 2, 2007 at 13:29:59:
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).
Follow Ups:
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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