Phono Box DS3 B output impedance

+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.

How can you not know this and still spout all kinds of technical details here? The nominal impedance of an XLR cable used in professional studios is typically 110 ohms, while an RCA cable has 75 ohms. Also, when determining effective voltage gain, damping factor, and so on, the cable impedance is considered on the source side, not the load side.

If you are not familiar with Denafrips gear, I suggest you avoid making assumptions, such as "driving on the voltage mode," that you need to verify first before continuing the discussion.

Thanks a lot for those explanations, guys.

I'm reaching my limits in terms of understanding resistance and electricity but I will slowly learn and then understand what you're talking about.

As far as the sound quality is concerned, it's fine the way I'm going now. But you know, it's always better to match what you hear with the good figures so you are sure that everything is fine. Want to be sure that I made nothing wrong that could have an undesirable effect later...

What I was concerned about mostly is: I wondered if there could be damages if input Z is too low and output Z too high. From what I read it seems that it's not the case, but better to be sure.

"How can you not know this and still spout all kinds of technical details here?" Because I only write what I think is correct.  However, I am not an engineer, not infallible, and I can make mistakes.  When I am in the wrong, I like to be corrected, because I will have learned something. Your point about cable impedance is making me think again about what I thought I knew.  I thought cable impedance enters into the calculation only at RF level frequencies. I thought that at audio frequencies, we need only worry about cable resistance, which in this case is only a few ohms, at most. Cable resistance (not impedance) can be ignored in this instance, or so I thought. If I was putting out incorrect information, I apologize to the OP, and thanks for correcting me. I'd like it if someone else can comment on this particular point.