INPUT/OUTPUT IMPEDANCE


Hello pro's,

I don't want to over think this, but I just pulled the trigger on a power amp rated at 10k(RCA) 15k(XLR) input impedance. Problem is I don't know the output impedance of my pre/pro(Marantz av7705). I looked everywhere and even called Marantz. My gut tells me all is ok...or is it!  I know you should be within the 1/10 ratio. So, does it make much difference whether your 1/10 or 1/100 ratio?

Thanks,
Anthony
128x128antho768
I love the way people remove posts after asserting something truly ridiculous creating "plausible deniability"...lol
Thanks everyone for your replies. So I'm wondering if I should return the amp and get the Parasound a52+. The amp I am receiving tomorrow is the Anthem MCA 525. I originally was waiting for the Parasound, but noticed this thing and was impressed with the build and specs. I know with Parasound, their impedance is in the 90's(k). 

What are your opinions.

Anthony
I have no knowledge as to how the Anthem and Parasound amps compare sonically.  But as I and George indicated earlier impedance compatibility is not an issue in this case.

Regards,
-- Al

Either is likely fine from an input impedance perspective. 

Usually it is tube pre-amps that have higher output impedance that some SS amps can handle better than others typically with input impedance ~ 40 to 60 Kohm or higher. 

Anthem amps are products I have heard recently that I would consider owning. Have not heard Parasound but those are also highly regarded in general. Either should work well and sound good it seems in your case.

If you think you would ever consider using a tube preamp with the amp you choose I would choose the amp with the higher input impedance which sounds like the Parasound, all other things being equal.
As George alluded to that is most likely to be an issue in the case of tube-based components, many of which use a coupling capacitor at their outputs. The impedance presented by a capacitor increases as frequency decreases, so the output impedance in the deep bass region can be much higher than the specified output impedance, which is usually based on a mid-range frequency such as 1 kHz.
In the old days tubes got around this problem (in balanced systems) by using an output transformer. This enabled the output to also not reference ground, something that is *very* tricky to do without a transformer! We developed a circuit that allows for direct-coupling of the output in the balanced domain but otherwise acts much the same way as an output transformer does, although wider bandwidth and less distortion. So there are tube preamps that can drive loads like this with flat frequency response; in fact can drive loads as low as 600 ohms.