The "Schoeps Mod" Kit – Transformerless Clarity meets Vintage JFET Tone.

Audiophile PCB Kit | Fits Standard U87 Donor Bodies | True 60V Polarization

The Concept:Most DIY kits force you to choose: Do you want the clinical detail of a modern transformerless mic, or the warmth of a vintage one?This kit gives you both.Based on the legendary Schoeps CMC5 topology, this circuit delivers incredible transient speed and open high-end. But we replaced the standard sterile transistors with a Vintage-Style 2SK30A Audio JFET, adding a touch of musical saturation and "tube-like" 2nd harmonics to the signal path.

Why This Build is Different:

  • 🔥 The "Secret Sauce" JFET: We swapped the standard BF245A for a 2SK30A-style Audio JFET (GR Rank). I hand-test every single transistor to ensure it hits the "Goldilocks" current range (3.0mA – 5.0mA). This smooths out the high frequencies, removing the "harshness" often associated with transformerless mics.

  • ⚡ True 60V Polarization: Many cheap "mod kits" starve the capsule with only 30-40V, killing your dynamic range. This circuit includes a precision DC-DC oscillator that generates a stable +60V rail, ensuring your capsule performs exactly as the manufacturer intended.

  • 🧩 Hybrid Design: The PCB is engineered with a Schoeps CMC5-style schematic but physically laid out to drop perfectly into standard "U87 Style" donor bodies (like the GT-2B, Alctron, etc.). You get the "big body" look with the "fast" sound of a Schoeps.

  • ⚖️ Hand-Matched for Silence: The output resistors (R10/R11) are the gatekeepers of noise rejection. I manually measure and hand-match these to <.1% tolerance. This ensures professional-grade Common Mode Rejection (no hum!).

What You Get in the Kit:

  • High-Quality PCB (custom U87-Body shape)

  • The "Vintage Voiced" 2SK30A JFET (Pre-tested)

  • Audio-Grade Capacitors (Panasonic/Wima Film & C0G Ceramics)

  • Hand-Matched <1% Metal Film Resistors

  • High-Voltage Inductors (Verified for instant oscillator startup)

  • Digital Guide: Includes a Troubleshooting Flowchart and a "Multimedia Biasing Guide" to help you dial in the JFET using just a multimeter.

Compatibility:

  • Body: Designed to fit standard large-diaphragm "U87 Clone" bodies (with the internal rail/spine system).

  • Capsule: Compatible with any standard 34mm Condenser Capsule (K67, K87, or CK12 Edge Terminated).

Buying Advice:This is not a toy; it is a professional recording tool. Intermediate soldering skills are recommended.