Looking for a way to do the following....

You link you ac signal via blocking capacitors and send you dc via the inter capacitor section this often done when a 48V Dc is required by audio equipment in studio locations (phantom) power circuit.

Unfortunately a phantom power system does this by virtue of having a balanced line and a 3rd lead to work with. In this case I don't have that 3rd lead, only an unbalanced line with 2.

You don't need three wires just share the neg or ground put the 12 volts on the signal line and isolate the dc using caps in the signals path to isolate you DC supply, it works I have used this method with no problems just make sure the dc is well smoothed.

You will need to establish 2 circuit paths, a DC circuit and a audio circuit. The telephone office puts a 48 volt signal on your telephone line at the central office and your voice (audio) is transmitted back over the same two wire circuit.

Remember, Capacitors transmit AC (audio) but will not pass Direct Current.

Inductors will pass direct current but offer impedance (AC resistance) to audio current flow.

The phone company applies the DC through chokes (inductors) and the Audio through capacitors. Sizing these components is a matter of the degree of isolation needed and the lowest frequency audio signal that you want to transmit.

In general the higher the choke inductance (henrys) and the lower the winding resistance (ohms) to DC, the better the isolation.

The size of the capacitors will also affect the frequency response. and in general the larger capacitor, the better the low frequency response but it will be at a cost of Power loss (loading). If the 1 volt audio signal is from a low impedance source (able to deliver current) then it is easier to design the system.

A computer circuit design program is the easiest way to select component sizes. because no math knowlege is required.

Note that in the above discussion the term repeat coils may be used in telephone applications. This is an application of inductances.

In short, couple your DC on and off the line through inductances and your Audio on and off the line with capacitors, and your incuctances (chokes) must be rated for the DC current. (swinging non saturating core air gap chokes preferred)

Put the 1Vp-p signal into a 1:1 transformer, if the secondary side has a center tap you can inject the 24V, 1A in there. At the other end do the reverse.

Naturally you'll need to make sure the DC doesn't saturate the tranny. Jeff

Look up "battery feed circuit". If you register at freepatentsonline.com you get to see circuit diagrams. Unfortunately most available circuits (like the LB1011) are for telecoms., and, you want much more current. As Snakers has said this is the "easy" way to do it:-

But if you want high performance it won't be small.

Snakers, Randall, thank you! I was going down the "telco path" and in my design, was trying to use a transistor gyrator as a replacement for L. However I keep finding when I run the sim in spice that I can't seem to get an amp to pass through no mater how I would spin the design. Any thoughts on a gyrator route?

Thanks again, Mike

I don't know why I bothered! It is simple you gave the answer in your own answer to me. Doh Bart where are my pills?

I'm sorry but no disrespect was or is intended. Your answer simply didn't meet the needs of the problem I am trying to solve. All I pointed out was that a "Phantom Power" set-up requires 3 wires. I don't know how making that observation is answering my own question, but, OK.... I appreciate the fact that you did answer, and I'm sorry that you are somehow feeling emotional about the subject. Maybe Bart's pills will help with that.

The only reasopnthey use 3 wires is bcause theybnuse a fully balnced tranformer coupled means od doing this because they are going into profressional equipment. What I was am suggesting is that DC isolaltion but AC signal passage can be easily achieved by the use of just two components thes are two capacitors in serries with the signal path so as to allow the intermediate section of you two wires to convey the DC and AC power and signal the ground or negative side is common to both with the DC and AC using the other you can further isolate the AC from the DC circuit by a choke or a diode network. I have worked with pro audio cicuits for many years and not had any problems, this is an industry accepted way to get over you problem. From what you have written you have never done this befor do not teach you grandfather to suck eggs!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Got those pills Bart.

You're absolutely right Brainwave...you shouldn't have bothered. Apparently no one is listening to you, and you should avoid replying to any other messages in the future. Except mine...because I like vague answers that omit huge amounts of information for me to continue searching for, and / or intermix terminolgy that really isn't applicable (I.E. Phantom Power Circuit).

Comment from Snakers

Randlls method is a much better way, because if the polarities are observed, the DC flux is cancelled and there will be no core saturation problem, however the size of the wire on the windings still must be considered in order to be able to carry the current.

DC Pass & Sig Blocking Coils & Signal inject & Pick on local & remote Ends are required

1. Connect Balanced-DC-Filters on output of DC Power-supply & Remote Equipment Input.

2. Inject Audio-Signal to feeder [Line] after the DC filter & pick signal before filter at Remote.

DC filter is network of Coils in series with both-lines to pass DC to the remote Equipment and aviod shunting of signal.

A capacitor may or may not be connected before the coils at Power-Supply output & after the coils at Remote Equipment across both-lines.