A quick web search reveals many AI-written posts about contact mics with clickbait titles. Such posts claim that all contact micropohones are just piezo discs soldered onto guitar cables, and only differ in their casing. These sites then typically go on to 'review' some of the cheapest contact mics available, which are in fact just piezo discs soldered onto guitar cables. Of course, each review is accompanied by an affiliate link to Amazon, revealing the true purpose of the post.
Why these AI-generated sites are wrong
I have discussed several of the most promenent problems with these type of cheap microphones in previous posts. I have also given their solutions. It is not suprising then that a review of products with known problems and known but unimplemented solutions would conclude that they are all the same and none is the best. The issue is that some contact mics do have different stuff on the inside, and that stuff matters. It really does make some contact microphones measurably better than others.
Some contact mics do have different stuff inside
Metal Marshmallow contact mics don't differ from other contact mics just in the housing. They have builtin preamplifiers. These preamplifiers were designed specifically to address the fact that a piezo disc soldered directly to a guitar cable does not make a very good microphone. Metal Marshmallow II has an internal battery-powered preamplifier and a rechargable battery. Metal Marshmallow Pro has a built-in Phantom-Powered preamplifier with adjustable gain. This internal circutry gives them much better bass-reponse, lower noise, and higher sensitivity than any other contact microphone that I have measured. Figure 1 shows some of the internals of Metal Marshmallow contact microphones, so you can see for yourself that it isn't just the same old trash.
Figure 1: Part of Metal Marshmallow's Internal circuitry that sets it apart from cheap contact microphones.
In my opinion they are the the best contact mics!
Conclusion
Don't trust everything you read on the internet. Buy a Metal Marshmallow instead, they are the best contact mics :)
