Jitter measurements
Contents
We also did some phase noise measurements with the Aeroflex. We focused on Allan Variance because we believe it has more impact than pure jitter. Allan Variance indicates variation in jitter. And our theory is that we are more sensitive to that.
Allan Variance is a way of measuring the stability of a clock signal over a period of time (we measure over 1ms). In good dacs, a stable clock is extremely important. Any small deviation in this stability – also called jitter – can be audible as a loss of detail, less spatiality or a somewhat “fuzzy” reproduction. A few picoseconds of jitter is already audible. Sometimes even less than 1ps. This is why stable clocks with low Allan Variance are important in a high-quality system.
We measure on the well-known Volumio Primo. We measure with an active probe directly on the 100 MHz clock in the Primo. The probe sends the signal to the Aeroflex PN9000. As a reference, we use the Axtal 100 MHz clock.
Allan Variance
As you can see, a good power supply and also decent filtering directly affects lower Allan Variance and – our opinion – better playback. The cleaner the power supply, the lower the Allan Variance. And this is also reflected in our listening test: more blackness, more flow, more depth.
Sir,
Thank you!
Sean
Sirs,
Trying to follow your D-Link advice but cannot distinguish DGS-108 Version 3 from 4.
D-link does not assist and email to D-Link not returned.
Mine also says on Box: 8 port Gigabit desktop switch. One light on each port.
On bottom says: H/W Ver.:E1.
Very much enjoy your testing!
Best!
Sean
Hi Sean. Version E1 is version 4. Version 3 is indicated as C6.
I’ve used an iFi SupaNova (included filter) power cable in the network box + an IEC C14 to Schucko female before the distributor for switches. This way all the equipment (router, switches, media converters) benefit from the power filtering.
For grounding the switches (better said, EMI/RFI draining) one can also use the ToughCable Connector Ground from Ubiquiti which can be plugged in one free Ethernet port. I prefer padding the interior of metal casing of the switch with copper adhesive foil and insert a drain copper wire or screw and then plug it (with a regular banana connector) to the special jack in the iFi / SilentPower AC iPurifier (that can be plugged in a free Schucko outlet).
a question: what kind of filters did you use?
It is a filter between the power supply and the switch.
the question was more related to brand and model
Can you elaborate bit more on this?
“What we clearly see with all switches is that it is crucial to ground things properly: that significantly reduces the noise floor. “
What else do you need to know? Grounding the switch – for example the casing – lowers noise.
There’s no ground connectors on normal switches so I o wondering how you go about this. Entreq for example have ground RJ45 connectors connected to ground boxes. But as I understand you you mean adding a cable to the chassis somewhere and connect to mains ground or?
The D-Link switch has a grounding screw on the case, for instance. Connect a wire from the case, with the D-Link from the screw, to the earth connection of an earthed plug and put that plug into an earthed socket. We tested it like that a few times, and it is clearly audible.
Only do so when you know what you are doing.