Samantha.pdfProduct Overview
The Samantha Microphone Kit is a complete electret condenser microphone solution built around a low-noise OPA-based impedance converter and a proven capsule design. It represents the starting point in the Sound Sleuth OPA microphone platform.
Samantha combines a JLI2555B electret capsule with a high-performance amplifier stage, delivering low noise, wide bandwidth, and high dynamic range in a simplified design that does not require an external polarization voltage.
Samantha is the simplest configuration in this series, using an electret capsule. This reduces system complexity and cost while still providing strong performance for a wide range of recording applications.
Design & Performance
Samantha was developed with a focus on low noise, low distortion, high bandwidth, and high headroom. This led to the use of the Texas Instruments OPA1642, which met these requirements while also maintaining low quiescent current suitable for phantom-powered operation.
The circuit was presented at the 153rd Audio Engineering Society meeting in the paper “Improved Microphone Impedance Converter Using an Operational Amplifier”, and Samantha was the first microphone to implement this design.
Self-noise measures <13 dBA, meaning that in most environments, ambient noise dominates over the microphone’s internal noise. The circuit is also capable of outputting signal levels high enough to exceed most microphone preamps, ensuring that the microphone electronics do not limit the signal chain.
With the OPA circuit, the microphone is effectively defined by the capsule. Samantha uses the JLI2555B, a 26mm electret condenser capsule used in both commercial and DIY microphones. It provides a neutral response and performs well across a wide range of sound sources.
Ever wanted to put a condenser microphone on a snare or hi-hat? Samantha is all ears. For high SPL applications such as close-miking drums, a 220pF capacitor can be added across the 1GΩ resistor on the PCB to reduce output by approximately 17dB. This allows the microphone to handle louder sources without overloading downstream equipment.
The JLI2555B is manufactured in an ISO9001-certified facility with tight quality control, resulting in consistent performance across capsules. Combined with a repeatable circuit that does not require hand-selected components, this enables consistent microphone builds without the need for matching.
Samantha is well suited for drum overheads, guitar amplifiers, voiceover work, and low-noise applications such as nature recording.
What’s Included
- Single Channel OPA PCB
- JLI-2555BXZ3-GP electret microphone capsule
- 3D printed microphone saddle
- Microphone body and headbasket
- Internal chassis
- Shockmount
- Hard case with custom foam cutouts
- All required connectors, wiring, and hardware
Key Features
- Complete microphone system with matched components
- Simplified electret design with no external polarization voltage required
- Low-noise OPA-based electronics for clean signal capture
- Compact and straightforward build process
Applications
- Studio recording (vocals, instruments)
- Voice and general-purpose microphone use
- DIY and custom microphone builds
Who This Kit Is For
Samantha is ideal for builders looking for a straightforward microphone project or those who want a complete solution without the added complexity of external polarization circuitry. It also serves as a strong foundation for understanding condenser microphone design.
Technical Description
The electret capsule used in Samantha contains a permanently charged diaphragm, allowing it to operate without a high-voltage polarization supply. This simplifies the electronics while maintaining a full-range audio response.
The included OPA-based impedance converter provides a low-noise interface between the capsule and downstream audio equipment, ensuring stable operation and compatibility with standard microphone preamps.
- Low Self-Noise
Suitable for general recording and voice applications. - Wide Frequency Response
Full-range audio capture for typical microphone use cases. - Simplified Power Requirements
No high-voltage polarization supply required.
Build & Demo Resources
Video Overview:
Samantha Microphone Demo
Build Guide:
Step-by-step build instructions
What Else Is Required
Assembly requires basic tools and soldering of a small number of connections. A compatible audio interface or mixer with phantom power is required for operation.
Helpful Pairings
For additional components and customization options, see our DIY microphone parts and accessories.
Frequently Asked Questions
What is an electret microphone?
An electret microphone uses a permanently charged diaphragm, eliminating the need for an external polarization voltage supply.
Is this a complete kit?
Yes. This kit includes the capsule, electronics, body, and all hardware required to build a complete microphone.
How difficult is assembly?
Assembly is straightforward and involves a small number of solder connections and mechanical assembly.
