Ok - checked with a 20mV, 1kHz, sine and the ratio is still the same.But I checked the input transformer mentioned above... the signal is strongly attenuated on the secondary and since it is a step up transformer I guess that the signal should be amplified... no? best regards/John
If I have a tube preamp and want to measure the overall gain I have read that I send a 1kHz tone to the input... connect the ch1 probe to the same spot and connect the ch2 probe to the output and measure the ratio between the two.Then I should have number for calculating the gain (dBu???)... but I also have read that when calculating dBm I need the Resistance. But I do not know if it is the DCR of the input transformer or what?
Maybe I don't understand my calculator or I might be slow :/ but I give you the figures here and it would be interesting to see what you get out of it? V in = 20mV ppV out = 56mV pp