On Fri, 2008-02-15 at 05:36 +0000, clae wrote:

> An unregulated supply can pass a mains spike as I understand it,
> proportionally. Could be wrong.

What would happen is that an unregulated supply will pass a proportion
of the RMS input voltage. In other words if you've got a 12V
transformer (not power supply, just the transformer) and you increase
the input to 260V, you'd get 13V out - not much of a difference.

This isn't the whole story though. When you rectify and smooth the AC
from the transformer (the important bit of the PSU, unless you're using
Alesis gear which takes AC) then the output voltage is the peak, not RMS
voltage.

So, for your 12V transformer, that would give you 16.97V, and if you
increased the incoming mains from 240 to 260V, 18.38V - well, look at
that, an increase of around 1.4V!

A typical 9V power supply has a transformer that puts out around 7v.
Increasing the mains as before, we'd get an output in the region of 10V.

So, small fluctuations in power won't affect your wallwart-driven
equipment particularly, unless they're not really that small (the power
company where my Mum lives once managed to deliver 320V to the town
instead of 240V. They had to pay for a lot of new radios, fridges,
answering machines and other such things...) because the internal
regulator in the equipment takes care of it. Regulated power supplies
won't do anything at all about mains spikes though, and if you're
gigging you're going to have extremely dirty power. The only way to
solve that is to use a spike suppressor strip.

You *are* using a spike suppressor, aren't you

Gordon