Add DC Offset to Audio Signal After Amplifier Output

[Nigel Goodwin]

Thanks for pointing that out. Your figures are what I am seeing on the lab power supply read out. The present heatsink is probably too small, but I can fit a larger one.

The 22R resistor is 10W ceramic but it gets too hot to touch. Given that the current is less than one watt, is there an explanation for this?

10W is it's absolute maximum - it will get far too hot to touch at MUCH lower wattages.

 

[atferrari]

I was just trying to keep things small scale. Yes, I think you are right. Bigger heatsink and an aluminum clad load compensating resistor in series with the low resistance coils.

But it is always good to learn a few other techniques which I may try just for fun. I have seen a transformer used to add DC offset to function generator output. There is a Keysight publication that describes it.

https://www.keysight.com/au/en/assets/7018-06324/white-papers/5992-3310.pdf

Are you sure you signal generator cannot add and offset by design? My Siglent can be programmed to provide a signal with a + or - offset applied to the output. BTW it took me some time to program it right.

 

[unclejed613]

Audio frequency modulation of a steady state, unidirectional magnetic field.

you do realize that if you have something detecting the audio radiated by the coils, there will be no DC on the pickup side.