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Output stage idea - secondary in cathode circuit
On Sep 27, 5:06*pm, Morris Slutsky wrote:
Output stage schematic: *http://img14.imageshack.us/img14/8218/pseudootl.jpg Been playing around with this in SPICE. *This is sort of inspired by Brosie's single ended "power buffer" circuit, only it's push-pull. Maybe it's sort of like a McIntosh output stage, except that it doesn't use a separate feedback winding. What I like about this idea is that it seems like a very easy way to apply a bit of damping right at the output stage, without worrying about low-frequency rolloffs and phase shifts during preceding stages. *Might be an easy way to tame the low-frequency high-impedance resonance of a loudspeaker. *While it might be difficult to get sufficient drive with low-gain triode or beam tetrode tubes, it doesn't look like a difficult problem to drive this circuit using EL84 or EL34 pentodes. It's also an elegant looking circuit - to actually hook a speaker right to the tube cathodes, almost looks like an OTL! *I could even pretend that some of the tube milliamps were directly driving the speaker, assisted by the transformer secondary. I wonder why I've never seen this circuit before. *Is there some reason that this hasn't been used? I'm a little concerned about stability, about high resonance frequencies where the transformer induces a 180 degree shift. *Any ideas how to be safe about this? Thanks, I look forward to any suggestions or advice. I have drawn 4 and 16 ohm taps on the secondary, as I imagine that a 4 ohm tap would be a center tap between 0 and 16 due to the square law of impedance. I hope this is correct. |
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