Noob question: Output impedance of interface

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guitarguy12387

Well-known member
Joined
Jul 17, 2008
Messages
302
Location
Boulder, Co
Hey everyone,

Quick noob question here. I'm messing with some amplifier simulations. I'm wondering what i should use as the source resistance. That is... say i'm feeding my amplifier with a line out from my interface... what should i use for the source impedance (output impedance of interface) in my sims?

Hopefully what i mean is clear. Thanks in advance!
 
600-ohms is reasonable. If the source is differential output, 300-ohms per phase. In the real world, a balanced output is usually 50-ohms per phase or less, depending on the value of the build-out resistor. Try 500 or 600 ohms. 1k may be alright too. I think yer gonna' have to experiment a bit. DW.
 
IIRC the 8903 (?) HP bench analyzer had 600 ohm and 50 ohm options.  I suspect less than 50 ohm is pretty rare. More than 600 ohm may be found in some consumer and low end gear. The only piece of test equipment I ever designed used 50 ohm source. 

I would be inclined to test for stability at extremes (say 1 ohm and 2k ohm), then characterize for performance at 50 and/or 600.

JR
 
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