S-PRE - London Power Spectum Bass Preamp Kit


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The S-PRE is based on the preamp sections of London Power's SPECTRUM bass amps. The front end is gain controlled and accommodates high-output active basses as well as low-output passives - and even piezo pickups. Clean sustain or overdriven sounds can be achieved, or just natural tube compression as the player desires.

The three-way EQ has a traditional and familiar feel. The second stage adds warmth and provides another means to achieve modern and traditional tonal textures. The output buffer assures that the tone generated will not be altered driving long cables.

Two 12A_7s (not included) can be used to provide an all-tube path. The front-end is optimized for 12AT7 but accepts any type. Local supply decoupling is included.

The board has silk-screening on both sides which allows you to stuff the components appropriately for INTERNAL or EXTERNAL TUBES. For INTERNAL, all the components are on the same side of the board; for EXTERNAL the components are on the opposite side from the tube sockets.

• Gain
• High
• Mid
• Low
• Volume
• Output

Power requirements: 12V-300mA; 320V-4mA
Use PSU-PRE or similar to build a stand-alone bass preamp.

Combine with AMP-10, AMP-25 or AMP-50 to build an integrated bass amp.

This item includes PCB, tube sockets, resistors, and caps. Also includes installation instructions including schematic and layout diagrams of the kit.

S-PRE requires assembly. If you wish to receive S-PRE pre-assembled, add PRE2-BLT to your order. Let us knowif you want it assembled for INTERNAL or EXTERNAL TUBES.


For more info on London Power Preamp Kits, see our Selecting a Preamp Kit page.

Need a chassis for your preamp project? See our Rack-Mount Chassis page, or browse under Building Supplies.


PCB size: 5.9" x 1.5" (150mm x 38mm)

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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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