Ray Tubes Select KT88

Ray Tubes Select KT88 – the finest contemporary alternative to a rare classic

Only the top 4–5% make the cut

The Ray Tubes Select KT88 is a beam tetrode introduced in 1956 as a more powerful successor to the KT66. As an output valve in push-pull amplifiers, it delivers greater power output and deeper bass response than the EL34 — consequently making it the preferred choice for complex, large-scale music. Fewer than 5% of any production batch earn the Select designation. Furthermore, New Old Stock of the KT88 is exceptionally scarce, thereby making a high-quality new production tube the only sensible option for serious tube rolling.

Powerful dynamics and rich detail

The Select KT88 excels in low-frequency performance: bass is solid and powerful, with deep, well-controlled frequencies ideal for rock, symphonic music, and complex arrangements. Thanks to the careful hand-selection process by audio engineers, the midrange is full and layered — thereby rendering vocals and strings with particular naturalness and textural richness. Moreover, the treble is clear and detailed without any harshness. Consequently, the KT88 projects an exceptionally wide and well-defined soundstage with outstanding spatial separation. In PrimaLuna amplifiers such as the EVO 100 Tube Integrated, the KT88 is a popular alternative output valve — tube rolling with the Select KT88 therefore reveals the full dynamic capability of these amplifiers.

Ceramic collar and gold pins

Every Ray Tubes Select KT88 features gold pins for superior conductivity and oxidation resistance, alongside a ceramic collar that — above all — provides exceptional heat resistance for a valve that generates considerable warmth during operation. Each tube arrives in protective packaging with a user handbook covering burn-in guidelines and a certificate of authenticity. The 12-month warranty against manufacturing defects reflects Ray Tubes' confidence in the durability of their product.

Specifications

• Tube type: KT88 (beam tetrode)
• Socket: 8-pin (Octal)
• Amplification factor (µ): 8
• Transconductance: 12 mA/V
• Internal resistance: 12 kΩ
• Max. anode dissipation: 42 W
• Max. screen dissipation: 8 W
• Max. anode + screen dissipation: 46 W
• Max. anode voltage: 800 V
• Max. screen voltage: 600 V
• Max. cathode current: 230 mA
• Heater voltage: 6.3 V
• Heater current: 1.6 A
• Available as: single, matched pair, or matched quad
• Warranty: 12 months against manufacturing defects

Frequently asked questions

What is the difference between the KT88 and the EL34?

The KT88 is a beam tetrode with a higher maximum anode dissipation (42 W versus 25 W) and a greater maximum cathode current. It therefore delivers more output power and a more powerful bass response than the EL34. Furthermore, the KT88 is suited to amplifiers operating at higher supply voltages. The EL34 tends to sound slightly warmer and more vocal-forward, whereas the KT88 places greater emphasis on dynamics and low-frequency control.

Is the Ray Tubes Select KT88 compatible with my amplifier?

The KT88 is a standardised beam tetrode compatible with all KT88 valve amplifiers and push-pull output stages. In some amplifiers it can also be used as a drop-in replacement for the EL34, provided the bias is adjusted accordingly. Ray Tubes provides a comprehensive compatibility list on their website. Feel free to contact us for tailored advice on your specific amplifier.

How long does the Ray Tubes Select KT88 need to burn in?

Ray Tubes recommends a burn-in period of approximately 40 hours before the tube reaches its full sonic potential. The sound therefore continues to open up and fill out over the first days of use. Detailed burn-in guidelines are included in the user handbook supplied with every tube.