Acepilot71 4-27-2018
May I ask guys with The Ear to describe or qualify the difference you notice depending on the Ethernat cable?
I suggest two categories:
- Quality of a music
- Quality of a sound
First one relates to the purity of the instruments, voices, etc.
Second - presence/absence of parasite noises, distortions etc.
IMHO you should notice only second one.
That’s an excellent question, IMO, Acepilot. However I have my doubts that we will be able to infer much in the way of a conclusion from the answers that may be provided.
As I stated in my earlier posts in this thread, what seems to me to be a plausible technical explanation for some or many of the reported cable differences is that RF noise whose amplitude and spectral characteristics are cable dependent is to an audibly significant extent finding its way around the ethernet interface and buffer memories in the receiving device, thereby potentially affecting timing jitter at the point of D/A conversion. And perhaps affecting analog circuitry further downstream as well.
If that explanation does in fact account for some or many of the cable differences that have been reported it seems to me that the audible consequences of those effects would be just as likely to subjectively manifest themselves in the first of your two categories as in the second. For example, regarding the audible consequences of jitter the following statement appears in
this paper by Professor Malcolm Hawksford, a noted academician and researcher in this and other audio-related areas:
One of the major difficulties in quantifying and explaining the consequences of jitter is that there are many sources of jitter. Also, jitter can be classed into three basic forms (all can coexist) where there can be periodic, correlated to audio and uncorrelated artifacts. Periodic jitter-related artifacts are further complicated as they can be linked, for example, to mains hum as well as the various clock signals present within equipment. Also, there can be correlated elements with the actual digital signals carrying the audio information. All these inter-related dependencies complicate the interpretation of jitter making it difficult for a simple jitter estimate or spectrum to be interpreted in terms of its subjective consequences. As well as the numerous sources of error, the system architecture itself can influence the way jitter affects the resultant audio signal. For example, the use of noise shaping and up-sampling [10] with linear pulse code modulation (LPCM) alters the spectrum of the jitter induced distortion. Whilst, as suggested in an earlier paper [11], the use of a multiplying digital-to-analogue converter (DAC) with a raised cosine reference signal can in certain circumstances reduce distortion and augment interpolation between samples prior to the low-pass filter reconstruction filter. There are also analogue amplifiers which when processing a sampled-data signal can produce distortion akin to correlated distortion [12]. Finally, the choice of 1-bit sigma-delta modulation (SDM) code [13], pulse-width modulation (PWM) code [14] or multi-level LPCM code [15] changes the nature of jitter distortion.
And as stated in the paper’s conclusion:
Jitter is an important aspect of digital audio system design and as suggested by the simulations described, it can result in distortion that has a relatively complicated form. As stated, there are several mechanisms that give rise to jitter where in practice it is the relationship between jitter and signal that is critical.
Finally, regarding the potential effects of RF noise on analog circuitry, the sonic character of whatever audible consequences may result from effects such as intermodulation of that noise with the audio signal, and demodulation of AM (amplitude modulation) spectral components of the noise, it seems to me could very well manifest themselves in either or both of the two categories you defined.
As you aptly said in an earlier post, there are "too many variables in this equation." :-)
Best regards,
-- Al
