Phono Box DS3 B output impedance

I am not sure why you prefer Pro-ject phono box over other brands. The xlr output imp on Schiit Skoll is only 10 ohms. Fully discrete, true balanced output and more dynamic. The SINAD from the 3rd party (asr) rated 78 for DS3 but 81 for Skoll.

Oh, you save a bunch of green.

1.66K divided by 200 = ~8/1, so not quite 10/1, but the difference is trivial. There is nothing magic about the 10X rule of thumb.

The fraction of signal voltage transferred is defined by the fraction Zi/Zo+Zi. When the ratio of output to input Z is 1/10, that fraction says 92% of signal voltage is available to the driven device. When it’s a ratio of 1/8, about 89% of the signal voltage is transferred. No big deal.

@lanx0003, I considered the Skoll indeed but Schiit products are hard to find here in France so I had no opportunity to listen to it first. I was offered a good deal for a demo DS3 B so I went for it as I was very satisfied with sound and flexibility.

+1 @boozendormi  Now knowing you are in Europe, I could relate to your situation.

+1 @lewm but forget not that the 110-ohm impedance of an XLR cable also plays a role. Suddenly, you have 1660/(1660 + 200 + 110) = 84.3%. No big deal? I’m afraid not. I believe this should have some impact, at the very least, on the conversion quality of an ADC.

For impedance matching, I usually aim for a much higher ratio than 1:10—often by another order of magnitude. That said, there are exceptions in the market, such as Denafrips DACs, which have a relatively high output impedance. Even with an output impedance of 5000 ohms, their strong current delivery allows them to drive most (pre-)amplifiers effectively. Additionally, their transformer-coupled output stage provides a degree of impedance matching.

Where on earth do you get the idea that "an XLR cable" has a 110 ohm impedance? And even if it did, do you count that as part of the output Z or does it add to the input Z? That choice would drastically affect the calculation. Of course, the higher the ratio above 1:10, the better the numbers look, but it usually makes no audible difference so long as the gain structure is sufficient. What may matter is input capacitance, which when the impedance match gets much less favorable (much below the 10X "minimum", approaching 1:1) begins to cause a high frequency roll off in the audible range. At a ratio of 1:8, that should not be a problem, either.

Re the Denafrips DAC, about which I know very little, if its output Z is 5000 ohms and if it is driving in voltage mode, no amount of current is going to help if the input Z of the driven component is much below the 10X rule. No matter what, if the input Z of the driven component is 5000 ohms, equal to the output Z of the Denafrips (1:1), then you would lose 50% of signal voltage to ground. The calculation for voltage remains the same regardless of current, in voltage drive. In a DAC, even that poor impedance match may not be noticeable, absent an effect of C on frequency response, because DACs make so much signal voltage, they can usually drive an amplifier even without a linestage.  All you need is an attenuator.