Depending on how the algorithm is built, the ratio parameter should indicate the amount of dBs of delay signal attenuation for 1dB over the threshold for the straight guitar signal. In simpler words a 7:1 attenuates delay level more that a 2:1 ratio.
If you don't hear much actual difference, your input signal may not correctly match the input impedance of the pedal. If you are connecting a guitar directly to the TF, set the in/out levels switches on GUITAR. If the pedal is connected to an amp/preamp FX loop, then flip those switches on AMP and make sure a SEND pot (if available) is turned up enough to provide a beefy signal to the unit).
Also, if you set a Speed/Release time setting, like 200/300 ms. and play with the ratio, you should hear a difference in the delay level coming up while you don't play. Try a 500 ms delay with a good feedback…like 50 or 60%.
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