Manual bias easy question to answer.

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cheap-Jack

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Re: Manual bias easy question to answer.
« Reply #20 on: 27 Nov 2012, 06:40 pm »
Hi.

(1) The other kind of biasing is called cathode biasing. With cathode biasing, the grid has a leak resistor going to ground and no negative voltage is applied. The cathode is connected to a resistor which goes to ground. The potential across that resistor is what is considered the bias voltage.

(2) With DC biasing, a negative voltage is applied to the grid through something like a 100K resistor and the cathode is grounded.

(1) Yes, this old school type cathode bias using a resistor has been a historic classic after decades today.
     With HD audio equipment available todate, many find it sound not that pleasant.
     
     As posted above, battery bias to replace the cathode grounding resistor sounds so so much better, IME.

(2) Yes, this topology usually applies to O/P stage power tubes where high bias voltage, e.g. -32VDC is needed.

     For biasing of tubes used in phonostages & linestages, where the bias voltage is very low, e.g. 0.5V -2.5V, battery bias will be a much better alternative sonically.

     Needless to say, cathode biasing is far better than grid biasing under same conditions.

c-J