Inverting op amp input impedance?

[WGTP]

If I run a non-inverting op amp into an inverting op amp, the input impedance to the inverting op amp is set by the resistance before it?  If I use a small resistor like 1K am I rolling off highs because of the low impedance?   

[R.G.]

The output of an opamp is quite low impedance. It's apparently well under 1 ohm until you actually pull a lot of current out of it and start hitting internal limiting stuff.

The input impedance of any inverting opamp stage set up with Rf for feedback and Ri for input resistance is just Ri, because the feedback action makes the inverting input appear to be at ground, as long as the opamp output and freqeuncy response can shovel enough current in and out of the inverting input to make that come true.

The only problem with low Ri is that it's hard to put enough current into it. If you have an inverting stage driving it to supply the current, the input impedance of the inverting stage will be that 1K resistor. Many opamps are happy driving low impedances, such as the 600 ohm loads in line level audio, although some opamps don't like it.

You should be fine.

If what you're trying to do is get high input impedance (with that noninverting input stage) and high gain from an inverting stage (the 1K resistor) with low noise (trying to keep Rf on the inverting stage down), then you can do it that way just fine.

You can also get high input impedance, high gain and low(ish) resistor values on a single inverting stage by using a T network for the feedback from the output.

[WGTP]

Thanks.  I guess the treble roll off from low impedance is due to the effect on the guitar pickup.  That does not apply in this scenario.