Core Saturation Measurements In 70.7 Volt Line Transformers Used For SE or PP Tube Output Stage
4,970 views · Published 16 January 2018 · 11:23 · Indexed 9 October 2026
Channel: ElPaso TubeAmps · 2018 · Entertainment
Edit: It looks like after much back-and-forth and further research, this method is very flawed and the results are incorrect. I sometimes leave flawed videos posted as it documents what does not work so others don't have to try it. I am working with other viewers to find a better method. ........After many measurements on the small 70.7 volt line transformers where inductance and impedance values were turning out so good, I made a measurement of inductance with DC current flowing in the primary and found that even just a few mA (7 mA or less) would reduce the primary inductance from 6H to 20 mH or basically no primary inductance at all. The conclusion is these transformers can not be used directly in a single ended (SE) vacuum tube amplifier. There may be another method of shunt feeding the output tube with a second inductor and isolating the 70.7 volt line transformer with a capacitor that might work. I doubt these transformers can be used in push-pull amplifiers either as any plate current imbalance in the push-pull stage will likely saturate the core of these transformers.
