When Only the Best Will Do

The Ray Tubes RESERVE KT88 isn’t for everyone. It’s the distillation of decades of experience. With a bespoke design, small-batch production, and meticulous selection, the Ray Tubes RESERVE Collection reveals audio details you never knew were there.

Hand selected and tested, the Ray Tubes RESERVE KT88 is designed specifically for hi-fi audio applications. Featuring gold-plated pins and our monocrystalline carbon Magic Coating, the RESERVE Collection easily outperforms New Old Stock and new production alike. Fewer than 5% of production meets our standards.

The KT88 is a beam tetrode introduced in 1956 as a variant of its smaller cousin, the KT66. Its name is derived from kinkless tetrode, an earlier name for the beam tetrode, and it’s been popular in high-fidelity stereo systems since its introduction. Since New Old Stock of the KT88 is especially rare, Ray Tubes is proud to offer brand-new KT88 vacuum tubes.

Sound Characteristics

RESERVE KT88 is a vacuum tube that combines power and resolution, making it ideal for listeners who appreciate strong dynamics, a spacious soundstage, and well-controlled bass.

1. Bass Performance
   Solid and powerful with deep, well-controlled low frequencies. Ideal for music with large dynamics and complex arrangements, such as symphonies or rock music.
2. Midrange Performance
   Full-bodied and rich, reproducing vocals and instruments with excellent texture for a detailed and layered sound.
3. Treble Performance
   Clear and transparent without being overly aggressive. A key strength is its high resolution, ensuring clarity without sounding muddy.
4. Dynamics and Soundstage
   Outstanding dynamic range, well-suited for music with strong contrasts between soft and loud passages. Soundstage is large and well-defined with excellent spatial separation.

Technical Specifications

• Tube Type: KT88
• Tube Socket: 8-pin
• Max Anode Dissipation Power: 42 W
• Max Screen Dissipation Power: 8 W
• Max Anode + Screen Dissipation Power: 46 W
• Max Anode Voltage: 800 V
• Max Screen Voltage: 600 V
• Max Grid Voltage: ~200 V
• Max Cathode Current: 230 mA
• Heater Voltage: 6.3 V
• Heater Current: 1.6 A
• Transconductance: 12 mA/V
• Amplification Factor: 8

Tetrode Connection

• Screen Voltage: 250 V
• Anode Voltage: 250 V
• Anode Current: 140 mA
• Grid Voltage: 15 V
• Grid Current: 3 mA
• Internal Resistance: 12 kΩ
• Amplification Factor: 8

Triode Connection

• Anode Voltage: 250 V
• Anode Current: 143 mA
• Grid Voltage: 15 V
• Internal Resistance: 670 Ω
• Amplification Factor: 8

Package Contents

• Set of four, two, or single vacuum tube
• User handbook featuring burn-in guidelines
• Certificate of authenticity and warranty

Compatible Amps

Explore Ray Tubes' Tube Amp Compatibility List.

The Ray Tubes One Year Warranty

Most vacuum tubes are notoriously fickle. That’s why warranties are rare. But we trust our products and we’re proud to offer our One Year Warranty against manufacturing defects. For more details, check out our warranty page.