Resistor values at supply to anodes

[cr0wl3y]

Hi there,

I am looking for help in changing resistance values in various circuits to get the right voltage at anodes. Advice on the specifics of the design I am working on and/or suggested sources where I can read a bit and understand the basics (which I am clearly lacking) would both be very much appreciated.

I'm "designing" (in reality patching different circuits together) a tube driven mixer. This will comprise phono stages which will feed into the line-level pre-amp which I have posted below, with the addition of a summing circuit in the box that is labelled "MIX". For the summing circuit, I am planning to use the "Feedback simple tube mixer" design in the following page (it's the third schematic):

The Tube CAD Journal: Vacuum tube mixers

You may note that the schematic asks for 200 volts DC supply, whereas the line-level pre needs 250. In addition, the phono stage needs a 300 volt supply. To my understanding, I therefore need to work with a 300 volt supply and:

A. Add a resistor to the power supply input for the line level pre so that voltage drops to 250 V
B. Change the value of the 10K resistor in the mixer circuit, so that instead of dropping 200V -> 100V as shown in the schematic it allows for a 300V -> 200V drop.

How do I calculate the correct values for the resistors I need for A and B?

Thanks a lot,
Nikos

[Arnulf]

How to design valve guitar amplifiers

More specifically:

The Valve Wizard

and

The Valve Wizard

[bob91343]

Read the section on resistance coupled amplifiers in the back of any RCA tube manual. It's pretty good and even if your specific parameters aren't covered, you can learn enough to do it yourself.