Switching cap values --> Level loss?

[suryabeep]

Hi everyone, I made one these today and switched C7 for C6 by mistake. Now when I audio probe it, I get full signal at the output of IC1A , but nothing on the 'far' side of R8. I get a good signal on the output of IC1B, but it is much less in volume.
To be exact, I swapped C7 for a 1uf film cap and C6 for a 220nf (once I realized I mesed up C7 I tried to get as close as possible to the original value for C6).
I've built about 5 of these before without swapping the caps and they've all worked fine, which is what leads me to believe the caps are the issue.
Why is this happening? All the voltages look good, 1/2 Supply where it should be.

Edit: The schematic posted is just part of the whole schematic. The rest of the circuit is working fine, except for this part.

[Keppy]

Opamps do everything they can to make the inputs the same voltage. In a standard inverting stage like you have, that means the (-) input will be the same as the (+) input, just a steady voltage. That's exactly how it SHOULD be.

The gain of the opamp stage will be a ratio of the feedback resistor to the input resistor. That means that for unity gain, you need 6.8k feedback resistance, to match the resistance of R8. Since C5 shorts out the feedback path for high frequency AC voltage, there is much less than 6.8k resistance for those frequencies. C5 is meant to reduce/remove frequencies above the audible range, but by increasing C5's value, you've caused it to affect audio frequencies as well.

[suryabeep]

Keppy - C5 is still its original value, I'm not sure what you mean.
The weird thing is that there is no signal audible on the input of IC1B. I'm not sure why, and I've never seen anything like this before while debugging the numerous other builds that I've messed up.

[Keppy]

Sorry, I misread the cap numbers in your post. The point about the inverting opamp still stands. You shouldn't be able to get a voltage signal off either input in this configuration, because the output works to keep both inputs the same, and one of them is tied to a steady voltage.

Increasing C7 shouldn't change anything audibly. Reducing C6 should change the filter frequency of your bass control, so you'll probably want to fix that one. However, turning the bass control all the way up eliminates the effect of that cap. If you still have a level drop with the bass control maxed, then there's probably another error.

[antonis]

What Keppy said.. 

Both C6 & C7 form HPFs (one in the NFB loop of IC1B and the other on IC3A non-inverting Input) and their values have nothing to do with signal "loss"..
(at least at 1μF/100nF levels..)
Replacing C6 with C7 results to raising Bass cut-off frequency by a factor of 10..
(from about 23Hz to about 230Hz - with Bass pot all the way down..)

Unless your signal comes from first frets of low-E string (with Bass pot all the way down) you shouldn't notice any audible difference.. 

P.S.
IMHO, C7 could be safely scaled down 10 times (i.e. -3db point from 1.6Hz to 16Hz..)