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RE: YES, It Makes a Difference

" '....the caps will be required to bypass more signal current to ground, rendering them less effective.'
What do you mean by that?"

When the cathode currents from the tubes are equal and opposite, such as when a single pair of push-pull tubes are in play, only a very small amount of the cathode current will flow through the bypass cap. This is small signal, Class A operation as JKT explained above, but it's only the first possible scenario.

A second scenario is that a bypass cap might be connected to two opposite phase cathodes as above, but not in the same channel of the amplifier. This works OK for monophonic sources, but if the program material differs between the right and left channels, the cathodes will no longer be equal and opposite. The difference current will now go through the caps, even in Class A.

Thirdly, and probably the worst situation, is that a bypass cap is connected only to cathodes that are in phase, either in the same channel or across the two channels. Now the cap must bypass virtually *all* the AC cathode current to ground. Even compared to large signal AB1 operation, a time during which the cathodes are not equal and opposite, there's still an advantage to connecting the cap to cathodes that are out of phase. Connecting it to cathodes that are in phase will require that it pass about twice the AC current during AB1 operation as would normally be the case.

The bottom line is that the more signal current the capacitor is required to pass, the more it will be heard.




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  • RE: YES, It Makes a Difference - Triode_Kingdom 21:10:23 07/13/15 (0)

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