QRK-LATCH - Quad Voice Controller for Guitar Amps


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 QRK-LATCH is the heart of the QRK Quad Relay Kit amp switching system.

  • provides a 1-of-4 voice selection
  • expandable to any number of voices
  • use as front-panel control
  • use as remote foot-switch control
  • use for multiple foot-switch stage locations
  • 2-way communication between all switch stations
  • voice LED driver (4 LEDs)
  • internally regulated voltages
  • operates from positive or negative 12Vdc

The QRK system allows for direct random access from any system voice to any other voice. The 'voice' of a guitar rig might be the combination of the preamp channel plus reverb plus other effects.  Each time you add one new feature or function, the number of combinations and thus the number of voices multiplies. For example, a two-channel preamp obviously only has two voices. Add reverb and now there are four voices; then add an effects loop and there are eight voices; add a third preamp channel and there are twelve voices.

Combine QRK-LATCH with QRK-SW to have a modern front-panel interface for up to four selections. Add QRK-LED to have a glowing indication of what has been selected, or mount the LEDs individually with LED mounting hardware.

Combine QRK-LATCH with QRK-FSW to create a sturdy interface for foot-actuated switches. The Switchcraft elements used here also make nice panel switches. Use a six-wire cable and connector to wire this to the amp.

QRK-LATCH can be combined with QRK-RLY, QRK-SR, QRK-SF and/or QRK-FET, in any quantity to control jfets, relays, voice LEDs and function LEDs. In such a system, QRK-LATCH can be inside the amp chassis or in a remote position. With QRK-LATCH mounted in a remote foot switch, the voice LED driver on the QRK-FET and/or QRK-RLY provide LEDs on the front panel of the amp.

Two or more QRK-LATCHes can be wired in remote locations with another QRK-LATCH inside the amp. The internal QRK-LATCH provides front-panel control, where the remotes may be two foot switches. Two-way communication ability means that hitting a button on one control panel changes the status indication on all the panels. Sophistication like this is rarely offered in production foot conrtollers or even system controllers.

When more than four voices are to be accessed, QRK-LATCHs can be ganged "sideways" using the LNK connection and lifting one resistor on each added QRK-LATCH. This allows the first QRK-LATCH to set the default and for all of the QRK-LATCHs to interact as required.

QRK-LATCH is quick to assemble with its high-quality PCB and kit notes.

Kit requires assembly. Kit requires assembly. If you would like this kit pre-assembled, add QLTCH-BLT to have the PCB pre-assembled, The assembled boards are bulkier than the loose parts, so shipping is slightly higher.

PCB size: 3.7 x 2", 94 x 51mm

For more information, download our informative PDF: London Power ERK, RLY & QRK-series Switching Kits Selection & Application (2.2 MB, 22 pages).


About London Power

London Power was founded in 1990 by Kevin O'Connor, after two decades of research into innovative audio amplification techniques. Kevin is an audio designer, author and speaker, known for his proprietary methodology called Power Scaling, and for his eleven books on audio subjects. Whether you seek amps, kits or information, you'll find useful answers here on not just the "how" but the "why" of audio amplifier design. Please enjoy the information on this site, and don't hesitate to contact us with questions.

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