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DAC/amp impedance

andreasmaaan

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#1
Hi @amir, following a discussion in one thread in which a member described blind AB testing done with a range of DACs feeding a passive attenuator and a very low impedance power amp, it occurred to me that perhaps measurement of electronic components’ output and (if applicable) input impedance wouldn’t be a bad idea.

I googled the DACs that member had tested and was able to find published specs on only two thirds of them, and there the range was 1 to 500 Ohm output impedance, with no data re impedance vs frequency.

This is one metric where reliable data may actually be quite helpful to some, and also a metric that is not commonly even spec’d let alone measured.

In most cases I’m sure the results will be unremarkable, but it appears not in all cases..
 

March Audio

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#2
If the load connected to a dac (the amp) is purely resistive then any output resistance in the dac should have no effect on frequency response. It will however act as an attenuator reducing output voltage. The reduction dependant upon the output resistance and load resistance.

Most amps should be relatively high input impedance and primarily resistive in character so you shouldn't for the most part see major issues. However that may not be exclusively the case.

I would probably be less concerned about the output resistance and be more on the lookout for unusual amps that have very low input resistance/impedance. It's usually specefied
 
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andreasmaaan

andreasmaaan

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Thread Starter #3
Yeh, my thinking was more to catch outliers than because it might be at all interesting in 95% of cases.
 

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