A really weird thing is happening with the crystal mic. I do NOT understand this.
The same circuit board taken from another box and put in this box is much noisier. Like, 15-20db noiser. Both boxes are metal or metal-lined, and I’ve checked – repeatedly -the metal lining on this one is grounding.
This is true even with no crystal element attached.
Also, any board put in this box is quieter – less signal. This makes even less sense.
I’m so confused.
This is part of a collection of posts on building microphones and microphone-related kit, such as mic pre-amps.</p>