Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: zambo on December 17, 2011, 03:10:37 pm
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I posted this at ax84 as well. I figure it should be of use here as well. I did an experiment and measured the ma draw of my pp amp by putting my meter across the standby switch( in off position) using the ma setting ( effectivley putting it in series with the b+ supply). it meusured 52 ma with a guitar plugged in and ringing. I had the vvr on the amp cranked down a little over halfway. with guitar volume knob all the way off I measured 204 volts from plate to ground. its a cathode biased amp btw using a 260R non bypassed. I guess my question is can I use a 269ex PT rated at 65ma and a 125c OT rated at 8 watts 60ma If I bias the tubes cold enough to only draw around 50 ma? Would I do that by raising the cathode R therefore raising the bias voltage and dropping the plate voltage ( plate to cathode voltage) to around 200 volts? I know the voltage is kind of not as important so I am mainly concerned with the possible current draw issues.Sorry if I am not being clear enough, cough syrup is taking effect.