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I mean the impedance between pres and amps, sources and pres, speakers and amps, etc....
And how do I maximize it correctly?
One example: I have a NAD amp with a switchable 10K / 100K. Just one preamps findings are with the 10k the bass is wicked boomy and the top end is muddled and diminished. With the 100k setting the bass is tight and the top end clear and well balanced.
charles
Follow Ups:
You would need to understand Ohm's law, capacitive reactance, inductive reactance, frequency, and their relationship. ELI the ICE man can also be helpful.
It's not far off to think of impedance as "A/C resistance." It's similar to resistance in DC circuits, but with the addition of a phase component. The Wiki pages on impedance and output impedance are pretty good.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
With regard to the relationship of preamps and amps, this is one area where Stereophile measurements are pretty useful. For almost every preamp they review there is a view of frequency response curves that show how challenged (lack of a flat curve from very low to very high frequencies) the preamp is when mated against different amp impedances.
When I examined my tube preamp's measurements in Stereophile I saw that I would be better off with an amp that had tube-amp-like (100k or higher) input impedance than the McIntosh SS amp (20k) I had at the time. They showed a curve at 10k that was awful, and the 100k curve being really flat. SS preamps are generally so low in their output impedances that mating to amps is much less challenging. Using a tube preamp requires that you do a little matchup work before buying.
I've been playing with passives these past few weeks, and the question of impedance matching (especially of the amp) always comes up.
(Seems that "fairly high" (about 100kOhms) is good with a passive, but very high and very low are not.)
I'm finding the same thing. At 100k a passive works great. At 10k or 470k (tube amps) they don't work very well at all.
charles
Did you try looking up "impedance" on the internet? Just about any question you have can be answered with a Google search.
Good luck,
John Elison
Impedance (Z) is the sum-total of Resistance (R), Capacitance (C) and Inductance (L), usually expressed in Ohms, though it may vary with frequency due to the L and C components.
Lower output impedances are usually better, especially at the amplifier outputs. There, you'll tend to get flatter frequency response. And in the case of preamps outputs, better ability to drive longer runs of cable.
Input impedances are another matter. Not sure why your power amp would have switchable settings there, but you can probably just leave it in the 100K position and forget about it.
Phono inputs are a special case: There, you want to start with the manufacturer's recommended Resistance and Capacitance settings.
Fixed (normal) input is 10k.
Variable input (100k) useful for matching multi-amp use cases or padding down high preamp output levels.
It has a fixed 10k and a variable 100k. I guess it's used for matching or biamping.
charles
Amps with higher input impedance are "easier" to drive. A 10k load is pretty challenging and not well suited to passive attenuators or even many tube preamps.
My ARC SP-9 MKIII recommends a minimum of 20k ohms - it drives VTL amps with 137k ohms.
There's output impedance from the preamp and input impedance in the amplifier.The input impedance of your amplifier can be considered the "load" placed on your premap. If the load on your preamp is too low, distortion will go up, and potentially the frequency response on the bottom end will be compromised.
As the load on the preamp increases (amp inmput impedance goes up), you will actually lose less signal from the preamp, and the distortion that the preamp produces will drop drastically.
As a general rule of thumb, we like to see an input impedance that is at least 10X the output impedance of the preamp driving it. So for a preamp with a 1K output impedance, 10K would be a recommended minimum. Generally, there isn't any harm in going much higher (100X).
Edits: 04/07/14
You might have it backwards. The term "load" refers to conductance rather than resistance. In other words, a heavy load equates to low resistance or impedance. Therefore, as the load increases, the resistance or impedance is reduced. For example, 10k-ohms input impedance represents a greater load than 100k-ohms.
Best regards,
John Elison
Thanks for pointing that out, I amended my post for clarification.
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