QRK-MNR - FX Loop Controller + more


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QRK-MNR is the "heart" of London Power's QRK-MINI amp switching system - the 'MN' in MNR - designed to provide complete control and bypassing of a series/mixing effects loop, synchronised with the channel selection of a 2-ch preamp. This amp configuration is the most popular form of 4-voice guitar amp. Relays are used to perform the audio switching - the 'R' in MNR.

QRK-MNR is also the most sophisticated effects loop controller available. It accommodates series/mixing operation and can be used to select send/return levels for instrument or line devices.

Combining QRK-MNR with QRK-LATCH and three or four RLYs provides a complete switching solution for a 4-voice system, where the voices are: A, A+FX, B. B+FX. How these voices are grouped is up to the installer, easily programmed by soldering diodes onto the PCB. Four diodes are supplied to satisfy the voices described - the most common application.

The preamp control portion of QRK-MNR could easily be a single output, inasmuch as mechanical relays provide an exclusive 1-of-2 choice switching between their non-powered and powered states. For many preamp configurations, this would suffice. For greater versatility, QRK-MNR provides two relay controls for symmetric relay functions. This means one relay group is 'on' while the other is 'off', allowing positive selection of features, as your application may require.

Effects loops can be simple or complex, transparent or tone-changing, series or mixing or switchable. To accommodate the best loops, like our own BFX, requires two relays: one for the series/mix function and one for enabling the loop. Both functions interact when the loop is set for 'series' operation when active, but must then be bypassed when 'off'. QRK-MNR handles this with ease and can be used just for loop control if that is really the issue of your switching application.

When QRK-MNR is used solely to control an effects loop, the RLY1 and RLY2 outputs can be used to control 'send' and 'return' levels and gain, for optimisation of the loop signal-to-noise for instrument level and line level devices. This capability greatly expands the possibilities for stand-alone effects loop controllers.

LEDs indicate the preamp status with separate LEDs for Ch.A and Ch.B. A LED also indicates when the 'series' mode is selected, and a fourth LED shows when the FX loop is active. Any or all of these LEDs can be on the front panel. In a system where QRK-LATCH is mounted remotely in a footswitch, then QRK-MNR's LEDs are welcome on the amp front panel.

QRK-MNR can also be used to interface a single panel switch (se our PSW) and/or foot switch (FSW) for easy single-switch selection of the two preamp channels and the loop status.

A plus or minus 12Vdc supply can be used. 

PCB construction makes assembly quick and easy.

PCB size: 3.7 x 1.5" (94 x 38mm)

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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