VCA IV: Quad OTA VCA - Complete DIY Eurorack Kit

The VCA IV is a high-density, four-channel voltage-controlled amplifier designed for precision signal shaping and high-fidelity mixing. This Complete DIY Eurorack Kit offers a streamlined building experience, combining the precision of factory-assembled SMD components with the satisfaction of a hand-built module.

Versatile Quad Architecture & Stereo Pairing

The VCA IV is fundamentally designed as four individual OTA-based VCAs, each featuring its own signal input, CV input, and offset control. This makes it an ideal utility for managing four separate audio or CV sources simultaneously.

Beyond its standard quad operation, the module is intelligently normalled to be used as two stereo pairs (VCA 1 & 2 and VCA 3 & 4). This architecture significantly simplifies complex stereo patching:

• Stereo Signal Normalization: Input 1 is connected to Input 2 via a switched jack (and Input 3 to 4). Patching a signal into Input 1 automatically sends it to Input 2, allowing for easy signal splitting or stereo processing.
• Dual-CV Normalization: CV 1 is connected to CV 2 (and CV 3 to 4) via a switched jack. This allows a single CV source—such as an envelope or LFO—to control both VCAs in the pair simultaneously, ensuring perfectly synced level changes for stereo images.
• Precision Balancing: Each channel retains its own Offset knob, allowing you to fine-tune the balance between VCAs or "center" of a stereo image even when the CV control is shared.

Voltage-Controlled Mixing & Signal Control

All four channels are summed at the Mix Out, allowing the module to function as a compact voltage-controlled mixer.

• Switched Outputs: Plugging a cable into an individual VCA output removes that specific channel from the Mix Out.
• Clean Mixing Pro-Tip: Because of the internal normalizations, unused channels can sometimes bleed into the Mix Out. To keep your mix clean, simply turn the Offset pot all the way down for any channel not currently in use to avoid unwanted signal bleed.

Effortless DIY Build: No Calibration Required

The VCA IV is one of the most accessible Eurorack DIY kits on the market. It is very easy to build, as all surface-mount (SMD) components are pre-assembled at the factory.

You only need to solder the through-hole (THT) parts, such as the jack sockets, potentiometers, and the power socket. Best of all, the circuit is designed for immediate "plug and play" use - no calibration or trimming is needed once the soldering is complete.

Key Features & Specifications

• 4 Independent OTA VCAs: Optimized for audio and fast modulation.
• Stereo Ready: Normalled inputs and CV for VCA pairs 1/2 and 3/4.
• Built-in Summing: Dedicated Mix Output for sub-mixing.
• Aesthetic Design: Black PCB front panel with white and gold-plated copper artwork.
• Beginner Friendly: Pre-soldered SMD; only THT components required.

What’s in the Box?

• VCA IV PCB (Factory-assembled SMD)
• Front Panel (Black, White, and Gold artwork)
• Complete THT Component Set (Jack sockets, Potentiometers, Power socket)
• 10-to-16 pin Ribbon Power Cable
• M3 Mounting Screws

Technical Specifications

• Format: Eurorack
• Width: 10HP
• Depth: 25mm (Skiff Friendly)