Realtime Audio Modification

Hey Guys,

I am looking into building an Arduino-powered Voice modulator.
I found this page: http://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/
I tried to implement the hardware for the input and output stage.

I have a few questions about this.
It's one of those projects that have to be done yesterday - so all knowledge and expertise is much appreciated.

First question.
The sound that get's output from the arduino is very quiet.
As far as I am able to understand - this is to be expected.
The output and input signals are supposed to be amplified for this to work well.
When I try the loopback sketch - It works, but I get a whole lot of hiss and noise in my signal.

The strange thing is - when I remove the 4.7 nF capacitor from the input stage, this seems to be fixed.
Am I using the wrong capacitor? I added a picture to this post of the capacitor I'm using. (See below)

Second Question.
Like I said before - I can get the loopback to work.
However, the "ringmodulator" sketch (which would be interesting to implement for my project)
only seems to generate (mostlu uninteresting) noise.

I'm also quite intrigued by the Bitcrush / Bitshift effects as described here: http://www.instructables.com/id/Lo-fi-Arduino-Guitar-Pedal/
But the code provided does not work with this hardware setup I'm affraid.
Could I do something similar with the setup that I have built now?

Third Question
Would It be possible to generate and manipulate feedback-like effects with the Arduino?
(As in - guitar amp output plugged into input)

Thanks in advance guys,
Jim

I don't have time myself to get into another project especially 8-bit audio processing.

Were you able to find this thread in the old forum with discussion from the original author?

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1224777046/0

Loopback would be better if you had gain on the input side, give you more signal to work with. You're ony getting 256 samples, don't cheat yourself.
There is discussion that Analog inputs 0 & 1 are swapped too, that may be part of it.