Still not as good as we want, but that's not the only problem. Then we can get down something like 5 ps accuracy. They are much too slow, and too inaccurate. So using any normal oscilloscope is simply out of the question. We really want to measure in the picosecond range (ideally sub-picosecond). Let's ignore the really big mash jitter which is easy to measure. That information is only available inside the chip itself, where you have no way of reaching it.Īnd in any case, measuring the clock jitter on the clock input pin of the dac (which I assume is what you want to do) is far from trivial. Some dac chips have built in jitter reduction techniques yes, which means measuring the jitter on the clock input won't give you the actual jitter in the sample clock. But in many cases it's the only possible way. The method has limitations of course, like every other measurement method. How large a problem this is will depend on too many things so I wouldn't dare to give a strong opinion on whether it can ever be audible or not, but at least in theory the effect is clearly there.Ĭlick to expand. As soon as you have some nonlinearity somewhere in the chain (dac, amplifier, speaker.) you get all the intermodulation products, for example the pre-ringing togehter with a 20kHz signal gives a distorsion peak at a very audible 2050 Hz. This doesn't seem like a useful trade-off.Īnd I agree that removing a useless signal is a good thing, even if the useless signal in itself is inaudible.
This in practice turns the probably inaudible 22050 Hz signal into a high-frequency attenuation that we (or at least some of us) probably can hear. I think the only sure way to get rid of the pre-ringing, is to low-pass filter with a less steep filter, sacrificing some of the higher frequencies. Systemctl enable rvice (Activate at boot time, you can use it always)Ĭlick to expand.I realize that I didn't write that last part very well so it doesn't say what I actually meant. Systemctl start rvice (Simple activation, now you can use it) Systemctl daemon-reload (Load the created rvice) # Note: if start fails check with "systemctl status upmpdcli"ĮxecStart=/usr/bin/upmpdcli -c /etc/nfĨ. # (Reference)/lib/systemd/system/rvice settingĭescription=UPnP Renderer front-end to MPD Create a user named "upmpdcli" as it doesn't work as root. # Setting of /etc/mpd.conf (Added the following) Loglevel = 3 (It won't start if you get a level 1 error) Logfilename=/var/log/upmpdcli.log (Specifies that it should be logged) Install the upmpdcli related libraries.įriendlyname = SymphonicMPD (Any renderer name) Here is the way how to install upmpdcli in SMPD.Įdit /lib/systemd/system/mpd.socket as follows to enable port 6600.Ģ. The Raspberry Pi: Audio out through I2S | Dimdim's Blog It´s like measuring the THD of an amp by pointing a microphone at the speaker.ĪFAIK the frequency change in MASH mode is immediate, first you have a short pulse, thanĭimDim did an article about this back in the day, when the raspberry was new: Of jitter-reduction, you don´t even know if it reacts linear. Measure jitter by analyzing the sprectrum of an testsignal on the output of the dac.īut it´s a flawed method, because by measuring the analog signal you are introducing aĭevice to the chain which behaviour you can´t predict. yeah, i totally get what you are trying to do (did it in the firrst place), of course you can So definitions can sometimes gat a little fuzzy. (which i think is actually kind of awesome. i´m not an audio-engineer not even an EE, but i´m not illiterate, i work as anĮletrician in the maintenance in the automotive industrie for over 30 years.ĬNC machines are way more complicatet than any of the audio-stuff.Īnd you must keep in mind that none of us in this diskussion is a native english speaker Just enjoing listening to my beloved musik and i´m diy-ing my audio-gear for my wholeĪdult life. My intention was to simply ignore you, because the previous "diskussion" was pretty much pointless.īut maybe we can still have decent conversation.įirstly, a little bit about my background: i´m an "audiophie" in th literal sense of the word,
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