Sourcing a DC Power Supply

What are the requirements? DC voltage and current? AC voltage and current - frequency - wave form?and what accuracy is needed

Power Supply Electrical characteristics-

I think you are better off with 2 separate supplies: 1. Adjustable DC as required 2. A function generator or frequency generator. It seems that with the impedance loads you have a series circuit with resistors / or semiconductor circuit will take care of your modulation problem to join the supplies together

Might I suggest that what you need is a high-wattage audio amplifier, possibly removing any blocking capacitors between stages and at the speaker output? Peter

or DC amplifier or direct coupled amplifier as you mention. But still a function generator or audio generator too. A function generator has more extended settings to e.g. also preset the DC

Possibly you could use a transformer with the secondary in series with the power supply and drive the primary with your AC signal.

I think the tasformer will get saturated by the DC current.

the transformer doesn't get affected as long as the coil wire can handle the current.

A transformer (or an iron coil) will not be saturated as long as the current does not exceed I_sat (as given by the manufacturer). (I_sat generally is not the same as the I_{max ,} where I_max is the maximum current that the wire can handle.) The suggestion of Guest in #5 is, also, a solution. However a proper transformer is more expensive and difficult to be found. (It must be able to handle the dc current and it must be able to pass the frequency range of your ac signal efficiently.) On the other hand, an inductor is cheaper and easier to be found. (Moreover, you can use more inductors in series or you can make one by yourself. Or you can even make an "electronic coil" -with transistors and capacitors- which behaves like an inductor.)

I'm pretty new to this forum. What do you use to draw? and how you get it in your message? Tks