Need Schematic reading help

[ItysNotMe]

Hello again folks! I have come across a neat design on-line that I am trying to make an etch-able circuit board from , and I have a question about it! It is rated for 24 volts.

I am wanting to drop the voltage to about 5 volts to bias two electret mics while keeping it at the right voltage of 24 volts at the chip.

Is there a way to do this with resistors or should I feed my mics from a separate circuit and plug them into the inputs of the amplifier? The site and design is at https://schematics.circuitdiagram.net/viewer.php?id=jdv1335145437w.gif

Thank you very much in advance for your help in this!

 

[throbscottle]

You need to build a little voltage regulator using a 78L05 or similar - there are tons of designs out there. Connect the input of the regulator to your 24v line, use the 5v output to bias your mics.

You could use a potential divider - ie two resistors in series - instead to give you the 5v off the 24v supply, but you risk getting feedback from the amp back into the mics 5v supply via the 24v line, and also the voltage won't be as stable as with a regulator. Also it wastes some power as current is flowing through the resistors all the time. You would need maybe 10 times the mics combined bias current flowing through the resistors.

 

[ItysNotMe]

I may just go ahead and avoid all that and just build a separate circuit and power source to plug the mics into the amplifier's inputs instead! I do not want to chance the feedback issue! Thanks!!!

 

[throbscottle]

Really, it's a very small issue - as long as the 5v is decoupled you should have no problem - especially with the 78L05 option, which is really a separate power supply anyway, just that it gets its supply from your 24v line rather than the mains.

If you really must have a separate supply, if the mics will run at 4.5v, you could run them from 3x AAA batteries (or 4x if the mics will run at 6v), or even a stack of button cells. The mics will draw hardly any power so they should last a long time. Better than building a separate mains power supply.

 

[ItysNotMe]

Now that sounds like a worth while plan! I am not new at electronics ; but I am new at designing and building my own! I really appreciate your help in this! Have a great evening! I will keep you updated! Thanks!