TELEFUNKEN KT88-TK Vacuum Tube Matched Quad

Product overview

The TELEFUNKEN KT88-TK Vacuum Tube Matched Quad is a newly manufactured, cryogenically treated version of the legendary KT88 beam-power tetrode, supplied here as a matched quad of KT88-TK tubes.

The KT88-TK shares similar applications with the 6L6 and EL34 and is one of the largest tubes in its class. Its characteristics of high power and low distortion make it ideal for guitar amplifier applications where the player is seeking a higher gain tone with less distortion than a 6550 provides.

Plate voltage, up to	800 V
KT88 introduced	1956
Tubes in this product	4
Treated, tested and burned‑in	Cryogenic

Key features

• KT88 beam-power tetrode, one of the largest tubes in its class
• Handles a plate voltage of up to 800 V
• High power and low distortion
• Classic KT88 mid-range with an expanded low end and very high end
• Shares applications with the 6L6 and EL34
• Black Diamond Series: rigorously tested, cryogenically treated and extensively burned-in

The KT88-TK sound

Tonally, the Black Diamond Series KT88-TK has the same characteristic mid-range as the original KT88, with an expanded low end and very high end. Its rigorous quality control and durable construction yield a dependable tube ready for the most demanding applications.

A power amplification favourite

Introduced in 1956, the KT88 offered an alternative to the 6550, and with the ability to handle a much higher plate voltage of up to 800 V it became a common choice for power amplification design.

Applications

• Hi-fi power amplifier: home audio power amplifiers designed around the KT88
• Guitar amplifier: guitarists seeking a higher gain tone with less distortion
• High-power amplifier with four tubes: amplifiers that run four KT88 power tubes
• Studio backline: studios keeping their KT88 amplifiers session-ready
• Live sound and touring spares: backline techs carrying replacement power tubes
• Rental inventory: rental stores retubing amplifiers between bookings

Black Diamond Series

TELEFUNKEN Elektroakustik Black Diamond Series vacuum tubes are new production tubes, manufactured in partnership with a specialist vacuum tube factory in Slovakia and designed to be harmonically rich and tonally balanced. Each tube is rigorously tested, cryogenically treated and extensively burned-in before it carries the Black Diamond name, so the KT88-TK arrives ready for the most demanding applications.

This configuration: Matched Quad

This product is a Matched Quad: four KT88-TK tubes matched by TELEFUNKEN and supplied together as one set. Keep a matched set together in the four positions of the same circuit.

Fitting and care

Always switch the equipment off, unplug it from the mains and let the tubes cool completely before removing or fitting a tube. Fit the KT88-TK only in a socket specified for the KT88, keep each tube in the position of the one it replaces, and press it straight and fully into the socket. Power sections hold high voltages, so leave any work inside the chassis, including any bias adjustment the amplifier requires, to a qualified technician. After fitting, let the equipment warm up and listen at low volume first. Store spare tubes in their packaging, protected from knocks and moisture.

What's included

Included	Four TELEFUNKEN KT88‑TK vacuum tubes (matched quad)
Not included	Amplifier or equipment, sockets and installation, bias adjustment

In the box

• Four TELEFUNKEN KT88-TK vacuum tubes (matched quad)

Vacuum tubes are glass components: handle them by the glass envelope, avoid knocks and keep them in their packaging until fitting.

TELEFUNKEN KT88-TK Vacuum Tube Matched Quad: frequently asked questions

What plate voltage can the KT88 handle?

TELEFUNKEN states that the KT88 can handle a plate voltage of up to 800 V.

How does it sound?

TELEFUNKEN describes the characteristic mid-range of the original KT88 with an expanded low end and very high end, plus high power and low distortion.

What does Black Diamond Series mean?

It is TELEFUNKEN Elektroakustik's range of new production vacuum tubes, designed to be harmonically rich and tonally balanced; each tube is rigorously tested, cryogenically treated and extensively burned-in.

Do I need a technician to fit it?

Fitting is a straight swap in the socket, but power sections and rectifier circuits hold high voltages. Where an amplifier has adjustable bias, have a qualified technician check it after fitting new power tubes, following the amplifier maker's instructions.

How many tubes are included?

Four tubes, matched by TELEFUNKEN and supplied as one set (Matched Quad).

Where can I buy the TELEFUNKEN KT88-TK Vacuum Tube Matched Quad in India?

The TELEFUNKEN KT88-TK Vacuum Tube Matched Quad is available from Shivansh Electronics, Kolkata, West Bengal, India, with delivery across India.

Workflow 1: Hi-fi power amplifier

Home audio power amplifiers designed around the KT88.

Connections

Connect	To
KT88‑TK	KT88 output sockets of the hi‑fi amplifier

Setup

1. Switch the amplifier off, unplug it from the mains and let the tubes cool completely; power sections hold high voltages, so leave work inside the chassis to a qualified technician.
2. Note each position, then gently rock the old KT88 tubes straight out of their sockets.
3. Fit the KT88-TK tubes with the pins or key aligned, pressing each fully home, and refit any retainers.
4. Power up and let the amplifier warm up; have the bias checked by a qualified technician where the amplifier requires it, then check the sound at low volume.

Tip: Keep the matched quad together in the same circuit.

Workflow 2: Guitar amplifier

Guitarists seeking a higher gain tone with less distortion.

Connections

Connect	To
KT88‑TK	KT88 power tube sockets of the guitar amplifier

Setup

1. Switch the amplifier off, unplug it from the mains and let the tubes cool completely; power sections hold high voltages, so leave work inside the chassis to a qualified technician.
2. Note each position, then gently rock the old KT88 tubes straight out of their sockets.
3. Fit the KT88-TK tubes with the pins or key aligned, pressing each fully home, and refit any retainers.
4. Power up and let the amplifier warm up; have the bias checked by a qualified technician where the amplifier requires it, then check the sound at low volume.

Workflow 3: High-power amplifier with four tubes

Amplifiers that run four KT88 power tubes.

Connections

Connect	To
KT88‑TK	The four KT88 power tube sockets

Setup

1. Switch the amplifier off, unplug it from the mains and let the tubes cool completely; power sections hold high voltages, so leave work inside the chassis to a qualified technician.
2. Note each position, then gently rock the old KT88 tubes straight out of their sockets.
3. Fit the KT88-TK tubes with the pins or key aligned, pressing each fully home, and refit any retainers.
4. Power up and let the amplifier warm up; have the bias checked by a qualified technician where the amplifier requires it, then check the sound at low volume.

Workflow 4: Studio backline

Studios keeping their KT88 amplifiers session-ready.

Connections

Connect	To
KT88‑TK	KT88 sockets of the studio amplifier

Setup

1. Switch the amplifier off, unplug it from the mains and let the tubes cool completely; power sections hold high voltages, so leave work inside the chassis to a qualified technician.
2. Note each position, then gently rock the old KT88 tubes straight out of their sockets.
3. Fit the KT88-TK tubes with the pins or key aligned, pressing each fully home, and refit any retainers.
4. Power up and let the amplifier warm up; have the bias checked by a qualified technician where the amplifier requires it, then check the sound at low volume.

Workflow 5: Live sound and touring spares

Backline techs carrying replacement power tubes.

Connections

Connect	To
KT88‑TK	Spares case, then the KT88 sockets of the touring amplifier

Setup

1. Switch the amplifier off, unplug it from the mains and let the tubes cool completely; power sections hold high voltages, so leave work inside the chassis to a qualified technician.
2. Note each position, then gently rock the old KT88 tubes straight out of their sockets.
3. Fit the KT88-TK tubes with the pins or key aligned, pressing each fully home, and refit any retainers.
4. Power up and let the amplifier warm up; have the bias checked by a qualified technician where the amplifier requires it, then check the sound at low volume.

Workflow 6: Rental inventory

Rental stores retubing amplifiers between bookings.

Connections

Connect	To
KT88‑TK	KT88 sockets of the rental amplifier

Setup

1. Switch the amplifier off, unplug it from the mains and let the tubes cool completely; power sections hold high voltages, so leave work inside the chassis to a qualified technician.
2. Note each position, then gently rock the old KT88 tubes straight out of their sockets.
3. Fit the KT88-TK tubes with the pins or key aligned, pressing each fully home, and refit any retainers.
4. Power up and let the amplifier warm up; have the bias checked by a qualified technician where the amplifier requires it, then check the sound at low volume.