Tube Amp Archive

Hey I just finished my first build and it does a similar thing when I turn the
power switch to off position, it makes a thump sound with a slight whistle in the speaker.

I would like to know what causes it, I guess it could be a switching transient
when the switch is opened.

Hi Everyone, Anyone out there besides me that puts on Rubber Gloves (besides the one hand in the pocket, etc) when working on amps? Best Regards Steve I just finished my first build and always(most of the time) use rubber gloves and eye protection when testing, but as I approached the end of my bui...

Thanks for the reply guys... @ Phil_S My power tube bias current was calculated like this: Pa = maximum plate dissipation of tube Va = anode(plate) Voltage Pa(max) = 25W (EL34) ; Va = 450V I(bias) = 0.7*Pa(max)/Va = 0.7*25/450 = 38.9mA My preamp tube bias was calculated like this: Pa(max) = 1W (12AX...

Hi All. I have recently completed my first build a 100w push-pull type amp with 3 preamp gain stages a cathode follower, phase spliter/inverter stage with a quad el34(Electo Harmonix) output stage fixed biased with each output tube biased at 32mA @ 450VDC(plate). The amp design is a combination of t...

Thanks for sharing, cool post!