What is the consequence of pulling 2 tubes on amps with 4 power tubes?
First let’s explain a bit about how your tube amp works. The transformer of your tube amp may be considered as a simple ‘gearbox’ for electrical voltage and current between tubes (motor) and loudspeaker (wheels). The ratio in this ‘gearbox’ is very important and it has a fixed value. When ‘pulling’ the tubes, the internal impedance of the tube amp is doubled. Because the ratio of the transformer is fixed, the impedance is also doubled on the loudspeaker-side of the transformer. For example: your 4 Ohm output connector of your amp changes into 8 Ohm and 8 Ohm changes into 16 Ohm etc. So if you pull one tube from each pair, you reduce the power of the amp by 50%. However, due to the way we hear, this isn’t much of a volume reduction. Because mistakes are easily made and because it does not really give you a bennefit, our advise would be to not do this. However, as long as you match your speaker impedance to your amp, it will not hurt your amp.
