Negative swing with a DAC

[pedja089]

Just add high pass filter

[The Master]

Sorry, I should mention that I only have 24V DC available from a switching PSU and the amplifier is single supply (not split).

I could potentially move the entire amplifier ground up by 1.5V as 22.5V would still be enough to power it.
A potential divider won't be suitable to hold the ground of a 100W amp though.

[pedja089]

Did you see my post?
That is common way to remove dc offset and center signal around 0V.

[Dave]

If it were me, I would vary the signal between 1 and 4 volts with the PIC, 2.5 volts being your artificial ground (bias) and then cap couple it to the amplifier. I have done this before with our radio repeater for the courtesy tone's.

[HenrikOlsson]

I'm not sure why you're ignoring the idea of simply AC-coupling the signal into the amplifier but if that doesn't work for whatever reason it might be possible to use the PIC to generate a negative supply rail for the DAC using a chargepump circuit and the CCP module in PWM mode. It'll add circuitry though.

[The Master]

pedja089:-
I did see your post. Are you suggesting to use that circuit on the output from the DAC? I thought the sine wave was representing an AC supply.

Dave/Henrik:-
I've just done a bit of reading and it looks like "cap coupling", "AC-coupling" and pedja089's schematic are all the same thing. I will give that a go and see what happens.

Henrik:-
I have plenty of board space for once so if I do need to add extra stuff it won't be a problem.

[pedja089]

Yes, that circuit should be on output of DAC. And it is just first image from WEB.