Effects of Input Impedance

Most amps have input impedances listed in their specifications. I personally have gear with 10kΩ, 20kΩ, and 50kΩ values. I know good electrical design dictates that these should be high, but do these different values affect the sound signature of DACs? Do they use these values to dial in their gain multipliers maybe?

The main reason for asking is that I want to A/B my Atom and Rebel amps, but their output impedances are very different (10k and 50k respectively). Should I be breaking out the switch box, or will RCA splitters do the job?

It’s probably fine, 10K is on the lower side, but unless you are using a DAC that doesn’t have an output buffer (yes there are some) it really shouldn’t matter.

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Either one will work just fine for the most part as long as they are decent quality

TLDR: for subjective A/B, I think your fine.

Impedance is important for any analog signal transfer, but is especially so when talking about power transfer. That’s why headphones and speaker impedance is something widely discussed, as impedance matching is something important when you want to transfer power at a somewhat broad frequency range (40 to 40k and the likes) to a device that needs this power to produce the air pressure, a.k.a. sensitivity (roughly).

In DACs when are mostly dealing with signal voltage more than power, and therefore matching impedances isn’t as important. As long as you don’t clip your signal or put a load the DAC can’t drive, like if it was something like 200 ohms, there shouldn’t be any signal loss or distortion.

One thing you can found with a great disparity in input impedance is a difference in volume, as the “signal gain” of the DAC may be at an specific impedance rating. But I would say separating this from any amp related aspectd by ear on a A/B comparison is very hard to say the least. So go ahead, make your comparison and maybe consider sharing with us afterwards. =)

High input impedance is necessary because there are a lot op Op-Amps that can not handle much current (less than 1mA).
So even 4 10k Ohm input impedance amps on a very low current DAC will be fine.

Some resistor types could influence sound in the high frequencies (>15k Hz), unlikely that is more than mesureable though.