Leo-
100+ Head-Fier
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- Oct 20, 2007
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@pinnahertz very good words, RF is definitely the issue that gets transmitted through digital inputs. It's bad with USB, typically not that much with Ethernet (although badly constructed cables with shorted shields can ruin them) and optical inputs are typically immune to it (but one needs to watch out for bad transmitters problems though). I don't know much about Coax though, seems to be quite a mixed bag.
Regarding noise interference, there are basically two types of noise. I've already hinted at this before in the thread, which got lost in the noise (sic) of some other forum members who don't grasp the basic concepts of signal transmission. There is signal-independent noise - like mains hum that is basically AC signal that "leaks" due to magnetic effects on transformers and is of constant level and is simply amplified by the system. If you play jazz, classical or rock it will always be there with same intensity. This type of noise is not a big real issue since our brains are quite efficient in filtering out this sound, and the signal is not affected at all.
The bad noise is signal-correlated noise, which means that the analog signal gets affected by the noise injected in the system. This is typical of RF noise, which interfere with components like capacitors which get discharged at very high frequencies and this does indeed affect the signal. The RF noise itself is inaudible, however in the presence of RF noise the analog components will produce an altered signal which is then perceived as altered sound.
When you put a choke on a USB cable feeding a Dave, you reduce some RF frequencies that reach either Dave's PS or other analog parts. Dave should be insensitive to timing changes in the digital signal, however in theory the chokes affect the raise times of the digital signal (remember that the choke affects any current changes in the cable) which can adversely affect the timings of the signal, so folks avoid chokes if you can.
Regarding noise interference, there are basically two types of noise. I've already hinted at this before in the thread, which got lost in the noise (sic) of some other forum members who don't grasp the basic concepts of signal transmission. There is signal-independent noise - like mains hum that is basically AC signal that "leaks" due to magnetic effects on transformers and is of constant level and is simply amplified by the system. If you play jazz, classical or rock it will always be there with same intensity. This type of noise is not a big real issue since our brains are quite efficient in filtering out this sound, and the signal is not affected at all.
The bad noise is signal-correlated noise, which means that the analog signal gets affected by the noise injected in the system. This is typical of RF noise, which interfere with components like capacitors which get discharged at very high frequencies and this does indeed affect the signal. The RF noise itself is inaudible, however in the presence of RF noise the analog components will produce an altered signal which is then perceived as altered sound.
When you put a choke on a USB cable feeding a Dave, you reduce some RF frequencies that reach either Dave's PS or other analog parts. Dave should be insensitive to timing changes in the digital signal, however in theory the chokes affect the raise times of the digital signal (remember that the choke affects any current changes in the cable) which can adversely affect the timings of the signal, so folks avoid chokes if you can.