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Re: Unbalanced double triode creates unbalanced speaker output?

Posted by Jim McShane (D) on September 6, 2003 at 08:07:47

In Reply to: Re: Unbalanced double triode creates unbalanced speaker output? posted by steve oda on September 5, 2003 at 20:31:30:

This is another common misconception - that the "phase splitter" actually divides the signal. Not true! Actually, both tube sections drive the entire sine wave - one just does it 180 degrees out of phase to the other. Here's a quote from noted amp designer Randall Aiken:

"Common misconception #1: A phase splitter splits the signal into two halves, each half feeding one output tube so each output tube amplifies only half the signal.

The truth: A phase splitter produces (ideally) two equal amplitude sine waves, each inverted with respect to the other, not two "half sines". Both power tubes get driven with a full, complete sine wave at all points of the input cycle in any class of operation."

The long-talied pair (due to the "tail" resistor) tends to be self-balancing also.

Keep in mind too, that the gain is different between the two triode sections because while one half of the tube has signal applied to the grid, the second half signal is applied to the tube's cathode. This means the gain will be different by the nature of the circuits.

Given all this, it's hard to see how anything but gross mismatching (one section normal, one section near death) could have any effect.

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