Choke- vs. Resistive loads

RC loaded stages

Input grid resistor (Rg in)
This has no influence on the tube behind it, only on the stage in front. It forms the load for the previous stage since the resistance between grid and ground (without grid resistor) is very high and does not form a real load for the previous stage besides for high frequencies where the inter-electrode capacity starts to play a role. Try to avoid using an output grid resistor and an input grid resistor in the stage behind it. Most power amps have an input resistor as shown in the image above. The output grid resistor of the first stage would be paralleled by the input grid resistor of the next stage.

Anode resistor (Ra)
Higher value means more amplification but earlier roll-off in the high frequencies and higher output impedance.
Lower value means less amplification but extended high frequency range and lower output impedance.

Output capacitor (C out)
Higher value means extended low frequency range but also higher price.
Lower value means early roll-off of low frequencies but lower price.
This can be compensated with a different value for Rg out.

Output grid resistor (Rg out)
Higher value means higher signal level and more low range frequencies
Lower value means lower signal level and earlier roll-off in the low frequencies.
This can be compensated with higher capacity value, but this increases pricing for the capacitors.

Cathode resistor (Rc)
Higher value means lower current but also higher plate impedance and earlier roll-off of high frequencies.
Lower value means higher current and lower plate impedance, extended high frequency range.

Conclusion: Keep resistor values as low as possible or otherwise chose a tube with a higher mu if you need the amplification.

LC loaded stages

As RC loaded above but:

A choke forms a different kind of load than a resistor does. The choke has a very low DC resistance value compared to RC loading but it also has an added AC resistance (impedance). This impedance is frequency dependant. A choke has the property of having a lower resistance for lower frequencies and vice versa. This means that a choke will not form the same load for the tube at lower frequencies as it will for higher frequencies. Amplification will thus be lower in the low range. To allow sufficient low frequency response the induction value of the choke will have to be chosen carefully.

A higher induction means extended low-range response but due to the many windings and bigger core there will also be a capacity between windings that will result in early roll-off in the high frequency range. This roll-off varies greatly with the materials used and the method of winding the choke. Layered windings are a must due to lower capacity between windings. A higher induction value also means a larger size for the choke.

Conclusion: A choke offers a very low voltage drop compared to RC loading due to the low DC resistance which allows for a smaller, less costly power supply and lower energy loss. The value of the choke has to be chosen carefully to get the widest bandwidth. Choke loading is best done with tubes that have a plate impedance (Rp) of less than 8K. Anything above this requires very high induction values which makes producing a good choke very difficult, expensive and large. At 8K you are looking at 250H or more...