Edward Bartolo <edbarx@???> wrote:

> What you wrote reminded me of a dangerous filter that consists of two
> high voltage series-connected capacitors connected in parallel with
> the mains with their middle point earthed. Since these capacitors are
> almost certainly the same value they will devide the mains voltage by
> two. This fact can be verified with a high impedance voltmeter
> connected with the disconnected earth connector and one terminal of
> the mains supply.

Yes. Doesn't need to be that high an impedance meter either, a while ago (as part of a discussion in another forum) I just did a quick check with a basic digital multimeter and measured about 95V on my Macbook Pro. And as I mentioned, there's enough current there to be able to feel it.

> I want to avoid using a dangerous circuit like this.

Good luck with that, you will struggle to find any equipment without such a filter - unless it's cheap Chinese s**t where you find places on the board for them, but once "certified" they omit them to knock a couple of pennys off the price.

> With it, my death would only be a dielectric failure away.

They are supposed to be X (or is it Y ?) rated - supposed to fail open-circuit rather than closed, but your point is valid. But given how much equipment has exactly this setup, and how few incidents we hear about (I can't recall hearing of any), it doesn't seem to be that big of a problem.

But yes, it does seem odd that it's allowed to connect the chassis of equipment (weakly unless a cap fails) to the mains 8-O


> One way to solve this problem may be to use a pair of isolating
> transformers for the audio signals ...

Or use an optical connection and convert to analogue outside of the computer ? Not sure how many laptops have optical outputs these days, or whether a USB device would have low and stable enough latency/jitter for the job ...