The output impedance of your signal generator adds to R1 which reduces the low cutoff frequency of the highpass filter.
It also reduces the input level of your circuit.

 

I know that the instrument impedance adds to the input impedance but without an actual voltage divider why would it decrease the input voltage? Have the signal part of the module done but still need to add power terminals, GND and the bypass grounding caps at the +/-V input chip socket pins. Looks like I might get it done today anyways.

 

Your bandpass circuit has an input resistor that is 1k and a feedback resistor that is 100k so the gain is 100k/1k= 100 times.
If your signal generator has an output impedance of 1k then the gain of your circuit is 100k/(1k + 1k)= 50 times.
You can also look at is as the generator resistance and the input resistor of your circuit are a voltage divider.

 

Yep, I understand that. I thought you meant the input signal level. Went ahead and finished it up. You're making a believer out of me, it WORKS now!

TL071CP @0.1Vpp for all. Nice phase shift @ center freq.



And for comparison a LM301AN Identical to the TL071

Still lots of low-end noise but only a small bump ~60Hz.