Richyieee
Head-Fier
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- Apr 10, 2012
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When warming up a tube amp do you need to run a signal through it or is it effective just to turn it on.
Running a signal through it and rubbing it like a Genie's lamp usually does the trick for me
As for running a signal through - as soon as the cathode is initially heated (30 seconds, give or take) - the tube is going to amplify and reproduce the music signal. Whether or not a signal is present before or after makes no difference......
As for running a signal through - as soon as the cathode is initially heated (30 seconds, give or take) - the tube is going to amplify and reproduce the music signal. Whether or not a signal is present before or after makes no difference......
I beg to differ about the "before" part.
It will only make no difference safety wise if the tube amp's volume knob is set to the minimum at initial startup.
Can you imagine what will happen if you do a cold start on a tube amp with an input signal already present at maximum volume?
The caps or resistors in the tube amp will give way.
This is why most tube amp manufacturers recommend setting the volume knob to the minimum before the amp is turned on.
Despite the silliness of many posts in this thread, the real answer has to do with the nature of tubes. They need heat to allow the cathode part of the tube to "boil off electrons." It is these "free" electrons, that are added to the signal applied at the grid, that produce amplification. The free electrons are "added" to the signal coming through the grid. The "plate" of the tube accepts the addition of the signal from the grid with the added electrons coming from the heated cathode. The result of the output at the plate is a much stronger, amplified signal.
All that depends on the heating of the cathode, however. To reach a thermal equilibrium takes time. Thermal equilibrium is an inexact condition, usually brought about by the passage of time that is much greater than a few musical songs. Think how long it takes to boil a pot of water or heat an oven to 400 degrees to cook your pizza. For a tube to be dependably linear (minimal distortion), that elevated thermal equilibrium must be achieved and it takes time.
As for running a signal through - as soon as the cathode is initially heated (30 seconds, give or take) - the tube is going to amplify and reproduce the music signal. Whether or not a signal is present before or after makes no difference. It will either produce sound or not. The best sound will be reached when that thermal equilibrium has been achieved, however.
P.S. There is an initial state, depending on the amplifier design, where the accompanying parts of an amplifier (DC-blocking capacitors) have not charged enough to block the DC needed to bias a tube. That DC, if passed through the circuit, could damage your headphones. Those things only last a half-minute or so, though, so as long as you don't attempt to listen to a signal in that brief moment after turn-on, everything stated above applies. Many OTL tube amps are built with a relay-delay to take care of this specific, turn-on condition.
Some amps - output transformer-coupled amps, for instance - need no cautions about power turn-on spikes.
As for running a signal through - as soon as the cathode is initially heated (30 seconds, give or take) - the tube is going to amplify and reproduce the music signal. Whether or not a signal is present before or after makes no difference. It will either produce sound or not. The best sound will be reached when that thermal equilibrium has been achieved, however.