1. Use Blue and Yellow LEDs for Sine and Cosine
The Frequency Shifter is a fabulous module, but I found the three red LEDs to be a bit monotonous. I kept the red LED for the Input Level but replaced the Sine and Cosine LEDs with blue and yellow respectively (I find that blue and yellow provide a nice contrast). I used Digikey #67-1081-ND for the yellow LED and Digikey #67-1748-ND for the blue LED. I also had to change R72 on the Frequency Shifter motherboard from 330 ohm to 2.2K ohm to lower the brightness of the blue LED. The Frequency Shifter uses surface mount parts, but changing only one resistor is not too tough. The end result looks fantastic.