Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Digital Drive ]

---

[ Alert Moderator ]

---

RE: It would be a deal-breaker for me indeed.....to this reviewers credibility.

Posted by Thorsten (M) on January 2, 2015 at 19:22:16

In Reply to: RE: It would be a deal-breaker for me indeed.....to this reviewers credibility. posted by dave789 on January 2, 2015 at 15:09:05:

Hi,

> There can be product by product variation within the same model,
> V90.

The serial numbers and production dates are very close.

> I do not know why the person who connected things should be blamed.

I am not blaming the person for connecting things. But for publishing test results with insufficient fact checking. I for one would have tried to eliminate these mains related components from my measurements much harder and likely would have succeeded.

I guess that is the difference between a consummate professional who desires to understand what really goes on and an Amateur bend on panning products.

> Connecting a DAC to an analyzer or an amp is not aerospace
> engineering. For an ordinary audiophile to use V90 jitter free,
> what do yo suggest?

Use as is. As I remarked,all I see are mains related side-bands which are NOT jitter, just hum. And at a very low level. If the hum bothers you, find the source.

> With a power supply without ground prong, there is no ground loop.

For a power supply without an earth connection there is still a ground somewhere. In the kind of plug-top SMPS as used in this review it is via a low value capacitor, called a "Y" capacitor. Values of 10nF are common. Similar capacitors are also found inside mains powered gear without an earth connection, simply because you HAVE TO HAVE A GROUND somewhere, even if this one is not obvious.

This capacitor is usually connected to one blade of the Power plug only. If this side is connected to the neutral line of the mains (which should be the same as earth), all is well. If it is connected to the life connector (a 50% chance) then 115V/60Hz will applied across this capacitor in the USA and 230V/50Hz in Europe.

As a result 50/60Hz currents of up to around 1mA will flow through this capacitor, into the ground of the DAC and from there into the ULP analyser used to test. Now if there is any inductance and resistance in the cabling used and in the connectors (rest assured there is plenty), you can easily get fault voltages of a few 100 microvolt, more then enough to bollox up the test results.

> There can be of course ground noise. Anyway, if that V90 needs
> aerospace engineering level care to avoid "power supply related
> jitter," it just indicates poor quality control or poor design by
> Musical Fidelity.

It indicates neither. It indicates a lack of competence in the person performing and interpreting the the tests. There is a reason why only licensed and competent professionals are allowed to practice law and medicine, sadly similar restrictions do not apply to audio measurements.

You may argue that the published test indicates the real world hum noise performance of the DAC in a careless set-up with the wrong AC Plug polarity (if my guess is any good), but what he measured is still not jitter, just hum and normally these levels of hum should be a warning sign to the performing the tests that something in the test set-up is amiss.

Anyway, I see no point in defending competitors products, Imerely wanted to point out that just because "A measured K and claims it is X" does not mean that K is real and really represents X.

And as said, it happens often enough that K is not "real" and that it does not represent X.

Only last week I had one of my junior Engineers chasing instrument ghosts for two days trying to find noise that did not originate in the device where he supposedly measured the noise. And this feller did press the school bench for 3 years to get his EE degree...

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

This post is made possible by the generous support of people like you and our sponsors:

VH Audio

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---