During the testing phase, we tweeked the various effects and sampling rate to achieve a nice sounding output.
Initially, we used the function generator and the oscilloscope to test the output from the Effects Processor. From the oscilloscope, we could see if the signal we got out of the device matched the input from the function generator (without any effects). This allowed us to ensure that our input and output stages were correct.
The sampling rate was increased to 12 kHz from the initial 6 kHz. We noted the sound obtained was distinctly better. However, because of the doubled sampling rate, the time data could be stored for in the limited memory was halved. As a result, the reverb effect suffers: a once distinct double echo is now barely detectable.
The hardware input stage suffers from noise. We inserted a noise gate which zeros the output when the input amplitude is small, but the noise is apparent when the signal exceeds the gate level.
Another possible source of noise is external. There was an afternoon we were working in the lab and the output signal was extremely noisy. The signal cleared up to it's usual noise level later in the day. It is uncertain what the actual souce of the noise was, but we suspect it was interference caused by some other electronics running in the lab.
We tried different input sources: a guitar and a CD player. We were able to get satisfactory output on both inputs.