11/19/2022 0 Comments Universal output transformer a 3880![]() ![]() €œNever attribute to malice that which can be adequately explained by stupidity.â€Īccording to the Riders spec sheet for the RCA 29K, the 12 inch electrodynamic speaker has a voice coil impedance of 2.2 ohms. Rather the 2.2 ohm speaker impeadance was converted by wrong taps on the output transformer to 10K*2.2/6.95 ohms or about 3.17K! Definitely NOT the correct impedance for his PP 6K6's!!! In Ed's case the wrong taps didn't convert the 10K P-P load across the tubes to 6.95 ohms at the speaker. ![]() If you use an output transformer that transforms the speaker impedance to the wrong plate (or plate-to-plate) load impedance, performance will suffer as Leigh pointed out. ![]() BUT, it's the SPEAKER impedance, TRANSFORMED BY THE OUTPUT TRANSFORMER, that determines the load resistance that those tubes "see". Sure, the data for tha output tube lists a plate (or plate-to-plate) load impedance for a given set of operating conditions (power output, distortion, required signal voltage input, etc.). The hard thing to understand about output transformers, output tubes and speakers, at least for me, was the fact that the output tube load resistance either for a single or push-pull hookup was NOT determined by the tube(s) plate voltage, grid bias, or anything about the tubes as such! ![]()
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