Home   Shop   Cart  
Log InSign Up

This is the New Metal Marshmallow

Buy One on Etsy


Marshmallow is a piezo disc contact microphone with a nice high-impedance preamplifier. It is used to pick up sound waves traveling through solid objects, without also picking up sounds travelling through the air. Archival information about the discontinued Original and Burnt models is here, along with a product comparison.


Frequency Response

Bode Plot Details about how I measured this are on my blog.


Images of Marshmallow with different parts labelled Images of Marshmallow with different parts labelled
  1. Sensor: The actual audio sensor (piezo disc) is inside of the metal housing, on the flat side that is closest to where the audio cable enters the housing. This side should normally be mounted to whatever you are trying to record.
  2. USB Charging Receptacle: Metal Marshmallow has a builtin preamp, which is powered by a builtin rechargable battery. USB is used to charge the internal battery. The recptacle accepts a standard micro-USB charge cable, such as is used to charge many cell-phones. The charge time is about one hour, after which it will stay charged for about 10 days before it needs to be charged again, whether or not you are using the microphone. Note that Marshmallow does not use USB for audio, only for charging.
  3. Charge Status Light: This light will come on while Marhsmallow is charging, and will turn off once the battery is full.
  4. Audio Cable: This is standard shielded instrument cable.
  5. Audio Connector: This is a standard 1/4 inch mono (TS) female receptacle, which accepts a standard instrument cable. Marshmallow can then be plugged into any regular audio interface or mixer.


Images of Marshmallow showing how to install batteries Metal Marshmallow has a built-in rechargeable battery that powers its awesome preamp. It will ship with the battery drained. Prior to use you must charge it via a standard micro-usb charging cable. The charge-status light will come on when it starts to charge, and turn off when it is done charging. It takes about 1 hour to charge, and will last for at least 10 days of continuous operation. To reduce noise, Metal Marshmallow does not have a power switch; It is on all of the time until the battery drains. It is possible to use the microphone while it is charging.

Tech Specs

  Metal Marshmallow
Gain 14dB (white), 24dB (red), 34dB (black)
Housing Color Silver
Housing Material Milled Aluminum
Housing Diameter 39mm
Housing Height 32mm
Battery Type Rechargeable
Battery Life 10 days
Recharge Time ~1 Hour
Charge Indicator White LED (on while charging, off when done)
Hum Protection Built-In
USB Connector For Charging Only
Audio Connector 1/4" Female Unbalanced TS


Images of Marshmallows showing different variations

Marshmallow is available in a few different gain variaions. The standard model has red heat-shrink on the audio connector. This mic is good for most things and corresponds to the discontinued burnt marshmallow. There is additionally a low-gain variant with white heat-shrink that is better for recording loud sounds, like percussion, and this corresponds to the discontinued original marshmallow. Finally, there is a black heat-shrink model with high gain, that is good for recording very, very quiet sounds. If you watch closely, in the video above, you can see which variant I have used to record different things, which should give you a general idea of how they behave, although in many cases any of the mics would work just fine for a moderate sound source.

  Color Gain Decibles
  WHITE 4.7x +14 dB
  RED 15x +24 dB
  BLACK 47x +34 dB

Plug It In

Images of Marshmallow showing how to plug it in to an audio device

Origin Story

Hi, I'm Michael Krzyzaniak, creator of Marshmallow. While I was getting my PhD, I was building robots that played music. I needed the robots to listen to themselves while blocking out other sounds, so I thought I'd use a contact mic. Unfortunatly, due to questionable engineering, electromagenetic radiation spewed out of the robots' out of every pore. In retrospect, I was probably violating FCC regulations every time I turned it on, and people driving by probalby just heard "KSSSSHHHHHHH" on their radios. Needless to say I had considerable difficulty getting a clean signal through a contact mic; it was mostly hum. I ordered every single comercially available mic and built every DIY one I could find on the internet. None of them could withstand the hum, and furthermore, most had very poor bass response, making them unsuitable for the spectral analysis I was doing in my research. So I went on a quest to design a contact mic that could withstand massive hum and had good bass response, so I could complete my dissertation. The result is Marshmallow. It is the best contact Mic I have heard, so I decided to share it!