[cobaltmute]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif the noisier one masks the lower one. sucks but its true. you can't 'pre clean' the voltage supply any better than the downstream guys are going to treat it.

Well that only assumes that the TPS can remove all the noise of the upstream supply.

In a perfect world, with a perfect DC source, you'll only have the noise of the TPS reg on the output.

In the real world, you'll have the noise generated by the TPS plus all the noise that it lets through.

 

[linuxworks]

wouldn't the higher volume of noise in one freq band mask the lower volume (level) in the same band?

it would be additive if there was noise in one band by the source PS that was not attenuated at the board-level reg stages. but 'like for like', the higher will mask the lower and you don't add the two together.

if the noise was on the input stage of the amp, then the output would be magnified (in noise) since there is gain involved. but on the PSU rails, I'm not sure that noise is additive like you say.

 

[cobaltmute]

It's not necessarily in the same band though.

TPS and three terminal regs are supposedly very bad at rejecting high frequency noise. So if the noise is there, it is not dealt with by the reg.

So you get a situation of dirty source power, some of the noise removed by the TPS reg, some noise that passes through the reg because it doesn't filter it, and some noise added by the reg by its self noise.

I've never tested this - it's theory, but some people claim to hear the difference.

 

[CodeToad]

I guess it's safe to say that the sigma11 is less noisy than the wallwart and the difference is audible. It's overkill compared to a sigma25 but it's a reasonable overkill compared to something, say, like running 2 gauge power cables from the wall socket to the back of the amp.