I have been given an amp from an organ built in the 50s with huge power and o/p transformers and filter choke (twice the size of those on the 100w Marshal amp I also have on the bench). Valves are 2x6SN7 and 2xEL34 in a Williamson-style design. Plate voltage is 900 volts. The o/p transformer has 2 separate speaker windings of unknown impedance. By running a known ac voltage through the HT winding and measuring the voltage on the speaker windings I was able to determine that the winding ratios were 23:1 and 76:1. These seem much lower than I expected. Does anyone have any idea what are the output impedances of the o/p transformer are then? Thanks for any suggestions.
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