Impedance matching with tube amp


I have a Mccormack DNA 0.5 which has an input impedance of 100kohm. I'd like to get the Schiit Saga preamp, which has an output impedance of 180 ohms. Now, I've read about the 10:1-100:1 ratio of input:output impedance for power amps and preamps, so this wouldn't quite fit that range of ratios. Would this still be a good option, and if not, what other (<$500) tube preamp options do I have?

Thanks!
muffinhead123
@bdp24 So you're saying that the nominal impedance is a measurement of output impedance at some chosen reference frequency? Is it typical for there to be large enough fluctuations in impedance across the frequency spectrum so that problems occur? From what others have said, I feel like the large input impedance coefficient of the power amp provides me with a lot of headroom to tolerate preamp output variations, but maybe I'm wrong.

Exactly muffinhead123. Not that problems WILL occur because of the input impedance varying with frequency, but that they can. For instance, a tube pre-amp may have an output impedance of 600 ohms at 1kHz---which is probably fine for an amp with an input impedance of, say, 20k ohms. But the pre’s output may jump up to 2000 ohms at either a higher or lower frequency than the 1kHz figure---which would be marginally acceptable for the amp’s 20k ohm input impedance, causing a noticeable roll-off in bass. But 100k is about as high an input impedance in a power amp as I’ve seen. By the way, when I said the ratio "should be" 10 to 1 or 100 to 1, depending on whom you ask, I inadvertently left out the words "at least"---should be at least 10 to 1 or 100 to 1.

In a lot of amps, the designer’s chosen input impedance, which could be within a range of values, is a balance chosen between a couple of competing factors---a couple of dB of noise being sacrificed to get a higher input impedance, for example. I think it was Nelson Pass who said that a lower input impedance (10k to 20k) makes possible a better amp, but that a figure that low results in greater demands being placed on the drive capability of the pre feeding the amp. Perhaps Audiogoners atmasphere or Al, experts in these technical matters, will provide more complete info.

I owned a ARC REF 3 pre amp , output imp 100 K , poweramp Sphinx PJ26 , input imp 600 Ohm , at the balanced input . I had a lack of the lower registers , finaly I bought two BAT VK1000 poweramps , marriage in heaven !
ARC Ref3 output impedance is 300 ohms SE and 600 balanced. Anyone designing a preamp with a 100K ohms output impedance is in the wrong business...
hello Kalali ,
You are right  about the 600 Ohm , sorry fellow audiogonners  for the wrong figure I give . When I got the Sphinx poweramps I thought 600 Ohm to 600 Ohm  no problem , but ARC poweramps all have 100 k input imp to be sure about the lower registers .