If cathode bias each EL34 has a resistor going to ground. Too low of a resistor value and the output tube anode (plate) will draw too much current and get red-hot. Bad! Is that what happened to some of the EL34's? The same thing will happen in fixed bias if the bias voltage is too low.
Blown tube issue
So one of my Tung Sol EL34s blew last weekend after 6 months and I’m not running them constantly. Manley is replacing for me.
My question is : is it ok to pop in a random EL34 in the interim and how does that affect sound ? Same brand better ? These tubes I bought from Manley are all bias numbered . Not sure if there is an exact slot order to the numeration .
Another thing that concerns me is I bought the snappers used from some Agon user who replaced/upgraded the caps . I’ve been told depending on his work this could be the reason I’ve already blown 2 power tubes in 1.5 years ? Anything I can be aware of appreciated !
my setup :
manley snappers
Manley jumbo shrimp pre
VPI super prime scout
allnic h1202 phonostage
My question is : is it ok to pop in a random EL34 in the interim and how does that affect sound ? Same brand better ? These tubes I bought from Manley are all bias numbered . Not sure if there is an exact slot order to the numeration .
Another thing that concerns me is I bought the snappers used from some Agon user who replaced/upgraded the caps . I’ve been told depending on his work this could be the reason I’ve already blown 2 power tubes in 1.5 years ? Anything I can be aware of appreciated !
my setup :
manley snappers
Manley jumbo shrimp pre
VPI super prime scout
allnic h1202 phonostage
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- 14 posts total
jasonbourne52 Manley and other tube amp companies should always provide information for proper bias adjustment.They do. Tube amps do need this done when output tubes are changed.A cathode-biased tube amplifier may also require periodic re-biasing as the output tubes age. |
What everyone else said. Also, if you bought the amps used with used tubes installed, it may not be unusual at all to have lost two tubes over a period of 1.5 years. The fact that you do not use the amps so much is neither here nor there. Tubes are most stressed during turn on and warm up.. Just like an electric lightbulb, they are most apt to blow at start up. Especially if you have never checked and adjusted bias during your period of ownership. As tubes age, the bias must be periodically adjusted. However, the tendency during the aging process is to lose transconductance, which means that as the bias stays the same the current through the tube will go down. That per se would not stress the tube; it would cause the sound to grow dull and lifeless. |
- 14 posts total