Retro Instruments OP-6 - Classic All-Tube Microphone Preamplifier
The Retro Instruments OP-6 is a meticulously hand-built recreation of the legendary RCA OP-6 preamp - one of the most iconic tube microphone amplifiers ever made.
Faithfully capturing the rich, open tone and musical saturation of the original 1940s broadcast and film preamps, Retro Instruments has brought this classic circuit back to life with enhanced reliability and modern studio functionality.
With its massive transformers, high-voltage Class A design, and precision-matched tubes, the OP-6 adds unmistakable vintage depth, warmth, and harmonic energy to any source.
Key Features
- Authentic all-tube circuit based on the original RCA OP-6 preamplifier design.
- High-voltage Class A topology with premium NOS tubes for authentic analogue tone.
- Up to +75 dB of gain - ideal for ribbons, dynamics, condensers, and line-level sources.
- Custom input and output transformers deliver musical saturation and extended frequency response.
- Front-panel Hi-Z instrument input for direct bass, guitar, or synth recording.
- Variable input pad and output trim for flexible drive and headroom control.
- Phase reverse and 48V phantom power for full microphone compatibility.
- Massive low-end response and smooth, silky high frequencies with natural compression.
- Hand-built in the USA using premium-grade components and matched tubes.
Applications
- Vocals: Adds stunning presence, tube saturation, and vintage harmonic warmth.
- Ribbon & Dynamic Mics: Provides plenty of clean gain with thick, musical colour.
- Bass & Guitar: Perfect for DI recording or re-amping through a tube front end.
- Drums & Room Mics: Captures body and natural compression with cinematic dimension.
- Mix Processing: Use as a tube line driver for mix bus weight and character.
Technical Specifications
| Unit Type | Single-Channel All-Tube Microphone Preamplifier |
|---|---|
| Circuit Type | Class A, high-voltage vacuum tube design (no starved-plate emulation) |
| Gain Range | Up to +75 dB |
| Tubes | Matched NOS dual-triode and pentode tubes |
| Inputs | XLR Microphone, ¼” Hi-Z Instrument Input |
| Outputs | Balanced XLR Line Output |
| Controls | Gain, Output Trim, Pad, Polarity, 48V Phantom Power |
| Input Impedance | 1.5 kΩ (Mic), 1 MΩ (Instrument) |
| Frequency Response | 20 Hz - 20 kHz ±0.5 dB |
| THD | 0.05% - 5% (variable depending on drive level) |
| Noise Floor | -125 dBu (A-weighted, 150 Ω source) |
| Power Supply | Internal universal power supply (100-240V AC) |
| Form Factor | 2U rackmount chassis |
| Weight | Approx. 6.8 kg |
| Build | Hand-built in the USA by Retro Instruments |
Why Choose the Retro Instruments OP-6?
The Retro Instruments OP-6 delivers the unmistakable character of vintage broadcast tube preamps - bold, warm, and harmonically rich.
Its unique combination of depth, clarity, and natural compression makes it an exceptional choice for vocals, acoustic instruments, and ribbon mics.
Whether used for tracking, re-amping, or mix colouration, the OP-6 brings timeless analogue tone and musical weight to any modern recording chain.