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RE: DCR of plate choke

1.) AC requirements

At the lowest frequency (for example 25Hz), you need -at least- four times greater load, than tube's output impedance. In this case it is 1960R.

If this "R loading" is correct, your tube's output impedance about 1/4 of load (Ri= 1960/4), about 500R.

At 25Hz the minimum required inductance is:
L=1960 /(2*pi*25) about 12.8H.

This inductance at higher frequencies generates higher value load, so distortion will be better there.

2.) DC requirements

Your "R loaded" tube DC operating point depends of cathode-grid voltage: Ua, Ia.

Sample Ua:150V Ia:20mA

The B+ voltage is larger, than Ua + required swing/2.
In this case the 1960R at 20mA 39.2V, so B+ =189.2V, half swing is 39.2V, the max swing is 78.4Vpp.

If you use plate choke, the B+ would be 150V+ (Ia*Rdcr).
At choke DCR -for example- 500R it's about 160V.

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  • RE: DCR of plate choke - euro21 02:15:28 03/09/17 (0)


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