power amp/pre amp input and output impedence question

I notice as i research amps and preamps, sometimes these specs are hidden away or non existent in the owners manual  :0/
 
Why would they not include these important numbers ? Is this kinda like when a manufacturer says an amp can put our 1000watts/ch @1Khz and not a full bandwidth watts/ch, not just a convenient 1Khz signal which is fairly easy for the amp

@kgveteran Yup! Sometimes the output impedance of some preamps isn't all that low (particularly tube preamps) even though on the right setup it can sound pretty nice. In some cases the manufacturer might not have even measured it.

We don't specify out output impedances either, but we **do** spec that they can drive a 600 ohm load and that the output impedance is flat with respect to frequency.

Gotcha

Hello all,

When looking at my ARC component specs the ratio is well beyond 10:1

My Classic 120 mono block amp has an input impedance of 100,000 Ohms
My LS3B preamp has an output impedance of 500 Ohms

That ratio is 200:1

My next amp will be a REF 75, which has an input impedance of 300,000 Ohms.

That ratio matched with my LS3B will be 600:1

Am I doing my math wrong here?  This seems to be so well beyond the 10:1 target to not be of any concern.

Wondering about mixing brands, I checked a Conrad Johnson preamp.  Its output impedance was 100 Ohms that would drive that ratio even higher.

Next I went to McIntosh's website and the C2600 preamp doesn't list the output impedance.....only input at 44,000 Ohms, while my LS3B is 50,000 Ohms.

Are there some extreme examples of mixing brands where this is a concern, but most often not at all?

As long as you are north of 10:1 you're good. The only issue you might run into with amps with a very high input impedance is you might want to keep the capacitance down with your interconnect cables so as to maintain high frequency bandwidth.