DACS & EMI, and EMI contamination in general?

[brucew268]

I'm not sure where this belongs... I've heard that DACS are the equipment having the most issues with EMI, other than cheaply made equipemnt, but am a little unclear, both on DACS and on EMI contamination.


Is contamination more by EMI radiated through the air into the wires (or equipment)?
Is contamination more by EMI transmitted down the wires?
Are DACS more a source or a recipient of contamination?
How are these issues effected by a linear PSU place away from both the DAC and the distribution block?

Since the earth wire is in common with the neutral rail in most house mains, would not contamination work into the system through contaminated rails, regardless of grounding or shielding? Shielding would be against radiated EMI, not wire-transmitted EMI, and earthing is in common with a possibly contaminated neutral wire.

Have I got this all wrong? I'm airing my ignorance in the wind here.

[StanleyB]

Where did you hear these things? Let's step back a bit and first inspect what you have heard for accuracy, before attempting to give it the homeopathic treatment.

[brucew268]

Hm. Well in general, I've read many people say that a shielded cable is best for a DAC or CDP. And I know I've read more than once about either EMI or RFI.

... here is one quote from this forum:


...There seems to be a fashion for screened cables in mains leads, but as screening raises capacitance which can and does have an effect on impedance and power supplies, I'd only recommend screening for devices which are high EMI emitters such as DACs and CDPs. For all other applications, a low capacitance low impedance lead seems to work best IMHO.

Of course, these things can be very kit dependant, and others may have different views, but I thought I'd share my tuppenceworth anyway.

[StanleyB]

Except for speaker leads I can't recall having seen an unscreened audio, video, or PC lead on sale for years. The earthing wires are also used as a screen as part of the lead design.

[AlexM]

In a shielded mains cable, is the screen tied to the plug earth or the equipment earth?.

[Reid Malenfant]

Plug earth hopefully :)