power amp/pre amp input and output impedence question
Hello, im in the process of researching a new system, low and behold my limited knowledge has led me to try understanding the input and output impedences to better assemble my new system as to the power amp and preamp.
in all of my years as a Hometheater guy I've avoided such topic because with "most" HT gear it all works together just fine.......
Hear I am many years later "catching up" on terms I should know, I was gonna just google and read, but most of the time well versed members can get to the meat better than random google replies
Thank you KG
kgveteranWhat yogi said is correct, the ratio of 1:10 or more. EG: CD or dac output impedance = 100 ohms, preamp input impedance should be 1000ohms (1Kohm) or more. Same for preamp to poweramp Same for poweramp to speaker. Cheers George |
what effect can be expected from a miss match.If the ratio is less than 10:1 you might have less headroom before the preamp makes distortion. There would also be more overall distortion so less detail and probably harsher sound. An output impedance of 1.2K ohms isn't bad. You can drive amps with 20K or higher input impedance no worries. The thing to look at is the output impedance at 20Hz. Many preamps have acceptable output impedance at 1KHz but at only 20Hz their impedance can be quite a bit higher. If at this frequency its less than the 10:1 rule of thumb you might experience less impact in the bass. |
"Same for poweramp to speaker." Yes "damping factor", stretching this one a little, but the lowest impedance of the speakers curve can also have the 1:10 rule applied to it that the amp is 10 lower than it or even better. So if the speaker is 2ohms in the bass the amps output impedance "should" be 0.2ohm or better lower at that frequency also. Then in there’s the capacitor coupled components, these need to be looked at first to see if the cap is big enough to maintain the 1:10 rule, if not there could roll offs at the frequency extreme |
