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Preamp-Power amp Impedance matching?

rabbitfyter

rabbitfyter

Member
I've had many integrated amplifiers in my home, but never have used a preamp/power amp setup and I'm a little confused about impedance matching in that situation.

I'm trying to match an NAD C-165BEE Preamp to a Power Amp with a 4 ohm output (because the speakers are 4 ohm).The manual says the NAD is 75 ohm output impedance:

https://nadelectronics.com/wp-conte...165BEE-Stereo-Preamplifier-English-Manual.pdf

For a 4 ohm load, I keep finding things that have input impedances of 12k ohms and 25k ohms. Something like this:
https://www.stereophile.com/content/bk-st-140-power-amplifier-specifications

How important is it to observe this impedance between the preamp and the power amp? If this is incompatible, are there any suggestions for something I can look for? I don't need the highest quality for this setup, so I'm not going to be going audiophile for this, just good enough and ideally 100 watts per channel into 4 ohms.

Thanks in advance
 
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The amp's abilities regarding speaker impedance are a completely different consideration, not related at all to pre out impedance and amp input impedance.
 
rf: Well in fact it wouldn't even have to be 10:1. That's just a pretty sensible rule of thumb, as it ensures, that 10/11 of the output voltage will drop at the sink and only 1/11 at the source, so that there only is a pretty negligible level loss of not quite 0.83 dB. So less that 10:1 can still be ok, if one can live with a higher level loss.

However, in practice one of course has to keep the capabilities of the sources in mind. I.e., the output stages of pre-amps (and also of line-level sources (tuners, CD players, whatever...)) typically aren't designed to really be juicy in terms of output power, so if the source output impedance is very low, the sink input impedance shouldn't drop to 10 times of that just to fit to the rule, simply in order to keep the power demand within a reasonable limit.

Greetings from Munich!

Manfred / lini
 
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