I was reading " An approach to audio frequency amplifier design" by the British firm GEC from 1957.
In the appendix, it gave a table to define the properties of transformers that I thought might be of interest to the forum.
This applies to the top end and the amount of Henries will define the bottom end.
Ian's formula is very useful here, as it defines the source resistance required to allow the transformer to operate at -1dB at the frequency of interest:-
Most of the vintage transformer plots I've seen, seem to have less high end response than modern types. I guess this sweetens up the digital music we have nowadays.
DaveP
In the appendix, it gave a table to define the properties of transformers that I thought might be of interest to the forum.
This applies to the top end and the amount of Henries will define the bottom end.
Ian's formula is very useful here, as it defines the source resistance required to allow the transformer to operate at -1dB at the frequency of interest:-
https://groupdiy.com/index.php?topic=43026.0 from 2011First you need to know the impedance of your driving source. Let's say is is a microphone with a source impedance of 150 ohms.
The low frequency response limit of the transformer is determined the primary winding inductance of the transformer at the lowest frequency of interest. For a 1dB drop at the lowest frequency you want the impedance of the transformer to be twice the source resistance at that frequency. So for a 150 ohm source and 1dB down at 20Hz we need:
2*pi*20*L (transformer impedance at 20Hz) = 300 (twice 150) so L = 300/(40*pi) = 2.4 Henries
Most of the vintage transformer plots I've seen, seem to have less high end response than modern types. I guess this sweetens up the digital music we have nowadays.
DaveP