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Re: Limiting the bass

The reason for the 'funny slope' of the RC network formed by the cathode resistor and it's bypass cap, as compared to the RC network formed by the coupling cap and the grid resistor, can be explained as follows. At a very low frequency, the attenuation of the RC blocking network at the grid is close to infinite; not true of the RC cathode bypass network, because the cathode resistor has a very finite resistance at DC. So at very low frequencies, the gain of the output tube is reduced by the fact that the cathode impedance is equal to the cathode resistor, but it does NOT go to 'zero'.

Take the cathode bypass cap away and the amp will still work; take the coupling cap away and it will not make a sound.

So if you goal is to 'roll off' the low frequency response, a suitable coupling RC network will be much more effective than the cathode bypass network.


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  • Re: Limiting the bass - mikeyb 14:31:19 04/10/07 (1)


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