Computer-generated noise and hi-fi systems don't mix
Quote:
An oscilloscope may measure some minor noise but it's well below the detection threshold of my ears.
Precisely - and Tim's, too, and everyone else's, but nevertheless the noise exists and you do hear it; just not as 'noise'.
Quote:
Early days reported detrimental performance before computers were even connected to audio systems, just like fridge freezers it was recommended you switch of any PC even if it was in the next room?
Steve, you are absolutely correct. It's not just noise in the mains supply itself; it's airborne interference such as RFI which things like mobile phones and computers generate that interferes with hi-fi systems. Quite simply, when you expose the room your hi-fi system lives in to the outside world (by having phone connections, modems, computers, and aerials for TVs, etc) installed in its vicinity, you're in turn exposing the sensitive circuitry in your hi-fi system to the forms of interference they attract or generate.
I have experimented quite extensively in the past with this and can clearly hear the detrimental sonic effect of having a PC (by which I mean a large stand-mounted computer, or these days my laptop) switched on in the same room where my hi-fi system is, especially when the PC or laptop are sharing the same mains supply. Separate circuits isolate things to an extent but ultimately you only have the one incoming household mains supply, so every appliance connected to it adds a detrimental effect in terms of noise, which is thus transmitted to all other items sharing the same supply, and this can be heard with sensitive audio equipment as degradation in sound quality, particularly in more revealing systems.
Quote:
All digital components go to one power strip, all analog to another. Each power strip is plugged into a separate circuit. Even through very sensitive Etymotic ear canal headphones, there is no noise.
Tim, there *will* be (measurable) noise present in your system as a result of your digital computer gear (it's the same with my CDP and DAC), but your ears won't hear it as such: it will be translated as distortion, manifesting itself on music signals, and thus the sound reproduced by your hi-fi system (heard through headphones or whatever) even if you don't realise it - there is no getting away from this unfortunately. That's why filters are designed for the purpose and these can be shown through measurements to demonstrably remove the noise created as described above, the only thing is that most filters in doing so remove some of the music, too, hence why I, for example, don't use them and simply optimise my room and my system in such a way that any noise generated by the aforementioned items is minimised as far as possible.
There is nothing in my listening room apart from my hi-fi system, all my music, a carpet, and a few comfy chairs! All the necessary everyday stuff which causes interference to the system is kept in the lounge downstairs :cool:
Mains supplies worldwide have never been as 'noisy' since the advent of all the paraphernalia digital or otherwise we use nowadays - mobile phones, computers, household appliances, entertainment media, fluorescent (and especially flashing Christmas tree) lights, you name it; they all chuck noise into the mains supply to the detriment of our hi-fi systems. You can address the problem to an extent but never fully cure it. One of the best ways of reducing its effect, though, is to use analogue equipment mainly and keep computers, and other items using SMPSUs, well away from hi-fi systems! ;)
Marco.
