Errata/ Notes on Revision 0.3.3

[jbeyerstedt]

Loose collection of things which I noticed when using prototype 2 (v0.3.3) for the first time:

Positive:

• Microphone and headphones noise floor seems to be quite a lot lower than at prototype 1
• vu meter low-pass filtering is not really noticeable (I like the quite snappy response)
• It still works

To improve:

• vu meter does not reach the top LED before the microphone clips at the headphones and line output
  • TODO: Increase amplification or change reference voltages
• low-pass filter of vu meter amplifier/ rectifier has a DC offset. Lowest LED is always lit, bottom 5 LEDs when microphone is "on"
• headphones have a bit too harsh high-end for my taste
• muting delay is too long (takes about 1 second to fade down, should be more like 100 ms max)
• microphone gain might be a bit too high (1/8 turn (should be about 10 dB) is fine for SM58 and HMD660)

[jbeyerstedt]

Also: Replace line input trim with a 10k resistor (empirical value for 0 dBu) or just make the op-amp stage unity gain