How do I determine the 'Z' of an Output Transformer (OT)
The 'reflected impedance' of an output transformer is determined by calculating it's 'turns ratio'
To find the turns ratio one applies a known (low) voltage AC supply to the primary tap and measure the voltage seen at the secondary (speaker).
As an example if 20V AC is applied across the primary and the speaker tap gives 1V out the ratio is 20:1 ...
The reflected impedance is the speaker load times the ratio squared, so for an 8 ohm speaker and the above ratio:
8 x 20 x 20 = 3200 or 3.2K
If the speaker was 16 Ohms, the OT load would be 6.4K
This site is run by unpaid, volunteer moderators, some of which have commercial interests in the guitar amplification business. They will all attempt to the best of their abilities to not interfere with commercial discussions. All messages on this forum express the views of the author and do not necessarily reflect the opinions of the site and (or) its administrators. This site will not be held responsible for the content of any messages posted on this forum. The operation of this site is supported financially by its members as a 501(c)(3) tax-exempt organization under section 170 of the IRS code.