Eldaford - if they affect digital pulse characteristics (different bandwidth) then they produce different amount of jitter. Shielding also affects the jitter since noise causes changes in threshold levels. Some DACs are not sensitive to jitter (like Benchmark DAC1)at all but others are. Impedance matching also plays a part. Many cables ends-up with an RCA connector that is not 75 ohm. |
Juanpablocuervo -
Electric current is not a "travell of electrons" - they move only about 1/2" per second and is also not a charge moved from electron to electron (wave) since they are spaced 10000 time their size apart. One theory says that electrons emit photons but this doesn't work either. Check Wikipedia!!!
While you describe properties of the cables why don't you mention inductance of the cable? It would be nice to mention characteristic impedance.
"in extreme capacitance, cuts more, making holes from the tiny bits&Bytes traveling at 3Mhz. and then paste on top of other bits, creating dissorder, or a blurr effect , creating digital errors, micro data lost. clock sync lost." - You must be kidding!!!! |
Added bits would be extreme case of impedance mismatch. It's more to preserve shape of the pulses to avoid crossing threshols at different times causing jitter. Jitter creates sidebands not harmonically related to root frequency (audible). Even double Phase lock Loop cannot compensate for fast changes. |
Palerider - if you cannot understand just read more.
Myself, if I cannot hear the difference I modestly admit it without saying that everybody else only "THINK" they hear a difference (that would be an arogance on my part). |
Rja - Cable itself does not have jitter. It creates jitter by reflecting fast transitions on impedance boundaries or allows slower transitions to be contaminated by less than perfect shielding. It is impossible to test it without standard ambient noise source (and location) and standard output transitions (each transport is different). |
Rja
Question has been answered many times. Digital cables introduce jitter. Jitter creates sidebands at very small level not harmonically related to root frequency. It is basically noise in time domain. Noise is reducing resolution, imaging, clarity etc.
Jitter is induced in coaxial cables by external noise or characteristic impedance mismatch (signal reflects on impedance boundaries). In Toslink jiiter is induced by system noise in presence of slow rise/fall time (slow transmitters and receivers). |
Eldartford - assuming ideal square pulses spikes/distortions will happen to every pulse, but in reality signal has jiiter all the way thru with electrical noise etc. Imagine signal with slightly different rise time from bit to bit and cable with mismatched characteristic impedance. This will result in creation of staircases (transmission line efect) different at different bits since slew rate is different. Different shapes of different bits will be converted to jitter. Cable with perfectly matched characteristic impedance won't produce jitter in this scenario.
Second possibility is noise. Imagine shielded digital cable in the presence of electrical noise. Amount of jitter (caused by limited slew rate + noise) will depend on quality of shielding and will be different for different cables.
Third possibility - limited bandwidth. There is inherent noise on the top of digital signal (power supplies etc). Cable with limited bandwidth will reduce rise time and make this noise "visible" to receiver (gate will recognize level at different times on the slope of rising signal). Perfect cable with very high bandwitdh won't reduce slew rate and noise won't be visible.
I suspect that cable experts might bring many more explanations - I'm not an expert. It is, in my opinion, much more difficult to explain why power cables help with imaging but I don't question that they do. Audio is very subjective thing. How one knows that other person only "thinks" he hears difference? Trying to find scientific reasoning is a noble thing but we shouldn't question experience of others. |
Lightminer - If DAC reclocks like Benchmark (asynchronous upsampling) then quality of the cable is not of importance. Benchmark tested it with thousand feet of CAT5 network cable and it did not show any audible effect. The reason for that is few Hz jitter bandwidth of the Benchmark providing suppression in order of -100dB at the frequencies of interest (kHz) on the top of already low level of jitter (order of -80dB).
For traditional non-upsampling DACs I would look for 1.5m coax (Toslink gives about 2x jitter) double or even triple shielded with high quality connectors. I would also look for the transport with slew rate in order of 5ns instead of typical 25ns and very good power supply (to minimize system noise induced jitter). |
Rja - AFAIK jitter is the only difference between digital cables. I don't know of anything else that can affect the sound. Jitter can be measured but many factors can change it - like level of electrical noise around, amount of system noise etc.
One cable might work very well, having perfect impedance matching, with fast slew rate outputs while the other might offer perfect shielding - important with slower transitions especially in noisy environment. In addition there are preferences of flexibility, color and overall quality. There are, of course, identical performance cables offered by different companies - same as with analog interconnects.
Why do you want to establish absolutely the best ($$$$)? My system and my ears are perhaps not good enough to appreciate the best cables (analog or digital).
I would still trust my ears or reviews more than measurements. Don't spend money if you cannot hear the difference. |
10 out of 10 on spoiled milk test ain't bad - I got 6/10 on the milk and 7/10 on rotten eggs. |
Marc258 - I wonder if you read anything on this thread before posting. Toslink is not superior. Toslink is not more expensive. All is system dependent. |
Lvhjr1, Optical cables don't have problem of jitter cause by reflections on impedance boundaries but rather from jitter being result of system noise affecting slow transitions (inherent to low slew rate of transmitters). Noise also affects transition of signal thru receiver's threshold (causing jitter) in coaxial cables, but much less because transitions are faster. |
Some people, convinced that digital cables cannot make any difference, claim that people who can have to be under influence of placebo effect. They don't realize that their strong conviction makes them unable to hear the difference because of negative placebo effect. |
Mceljo, there are only 3 non-overlaping channels in 2.4GHz WiFi. My microwave operates on one of the channels interrupting my music while neighbors operate on two other channels with routers most likely set to max power. I switched to 5GHz. It gives me 23 non-overlaping channels, practically nobody uses it (not very popular), no sources of interference, and poor penetration thru the walls keeping offending signals (if any) away.
I bough 5GHz WiFi USB adaptor for my old MacMini and dual band Linksys router. Receiver (Airport Express) can receive both 2.4GHz and 5GHz. No more dropouts. |
Mapman, I couldn't hear any difference between CDP (coax) and Airport Express (Toslink). I've never tried different brands but compared very short (<1') and 2m long generic coax (self made) and couldn't hear any difference.
Now my CDP is a cheap Blu-ray player wired thru my TV (HDMI) to Benchmark (Toslink) and I still cannot hear any difference switching to AE. It is possible that Benchmark's jitter supression is good, but unfortunately it can also mean that my hearing is not that good. Either way sound is very clean and smooth suggesting no jitter presence. |
It is a system thing. Cable that works perfect in one system might be bad in another. It comes to characteristic impedance matching and quality of the shielding. Characteristic impedance is affected not only by geometry of the cable but also materials. Anything that changes inductance or capacitance of the cable might change characteristic impedance resulting in reflections on impedance boundaries producing jitter - adding noise to music. |
Knownothing, Imagine that you play clean 1kHz sinewave but digital stream jiters in time back and forth at 60Hz. It will result on analog side in expected 1kHz signal and two other signals (sidebands) at 940Hz and 1060Hz. Their amplitude will depend on the amplitude of time jitter. These sidebands will be at very low level, in order od -50dB but still audible since they have no harmonic relation (like overtones do) with original 1kHz tone. It is form of modulation (similar to FSK). While music has many frequencies time vibration (jitter) of the signal appears at many frequencies, together causing whole bunch of new frequencies - a hash. This has has amplitude proportional to sound level and is inaudible without signal. It will make music less clean, imaging less precise etc.
Mapman, very short coax should be free from reflections. Rule of thumb says that to avoid transmission line effectes (reflections) use cable so short that propagation one way thru it is less than 1/8 of transition time. Assuming average transition at 25ns it will be <3.125ns equivalent to about 2ft of the cable (propagation = 5ns/m). Since it should include internal connections in transport and the DAC I would not risk putting more than 1ft. Longer cable might cause reflections and to avoid first reflection affecting first transition cable has to be longer than about half (threshold point) of this transition 25ns/2=12.5ns. At 5ns/m it will be 2.5m and since it is both ways 2.5m/2=1.25
It shows that 1.5m or even 2m cable might be better than 1m.
I said might because nobody knows exactly what transition time is so it is pretty much trial and error. If your fancy transport outputs 5ns transition it will give you great immunity from electrical noise affecting transition time, but will require well matched characteristic impedance to avoid reflections. Toslink is immune to ambient electrical noise and does not produce transmission line effects but driver transitions are slow making it more sensitive to system noise (on both sides). |
I second Mapman's recommendation of network streaming. Computer speed, amount of RAM, playback program, file format etc. make no difference since timing is recreated on the other side of the bridge (saves a lot of money). Sound still can be affected by ambient electrical noise but in this respect slow computer might be better than the fast one.
Asynchronous USB should be good as well since, as name suggests, it does not use noisy/jittery timing from computer by buffering the data and requesting different amount of samples each frame to keep buffer between underflow and overflow. |
