New Build
Moderators: pompeiisneaks, Colossal
Re: New Build
This is my first cathode bias build. I've noticed some designs include a huge cap across the bias resistor. Can somebody educate me as to the +/- of doing this? Does it make the PA compress more like a fixed bias design or...just the opposite?
Steve
Re: New Build
It helps in stabilizing the cathode voltage (e.g., bias) and to maintain gain.
It passes AC to ground around the bias resistor. Thus, that current it isn't available to raise the cathode voltage and mess with the bias.
A common trick is to put the capacitor on a switch in a tube in the pre amp section. When engaged, you get a very nice "little" boost in volume.
It is also a nice place to shape tone at the tube plate. Higher values=more low frequency content in the output. Lower=a higher frequency content in the ouput.
Dave O.
It passes AC to ground around the bias resistor. Thus, that current it isn't available to raise the cathode voltage and mess with the bias.
A common trick is to put the capacitor on a switch in a tube in the pre amp section. When engaged, you get a very nice "little" boost in volume.
It is also a nice place to shape tone at the tube plate. Higher values=more low frequency content in the output. Lower=a higher frequency content in the ouput.
Dave O.