Boscoe MMSA78 - Music Man Sabre Bass Preamp Replica

Note: This preamp is a replica of the late 1970s and early 1980s Music Man Sabre preamp. If you have one of the later Sabre basses (the ones with the blade switch) it instead uses a StingRay preamp. You can use this preamp as it has a very similar voice to the StingRay but includes the bright switch, or you can use my StingRay preamp replica instead, which can be found at: https://reverb.com/item/78583151

Overview:

This is a reproduction of the classic late 1970s Pre-Ernie Ball Music Man Sabre 2-band preamp. This preamp recreates the exact tone of a late 1970s Sabre but is made with modern manufacturing methods and uses screw terminals to easily attach connections without soldering.

I'm a bass player and computer geek and I'm a huge fan of Leo Fender's late work, so I decided to design this preamp to recreate the vintage late 1970s Sabre sound - but modernize it and make it easier to work with.

Design goals:

• Must reproduce the exact circuit used in late 1970s Music Man Sabres. This includes support for the bright switch which was only present for a few of the early years.
• Must use the original, now discontinued LM4250CN opamp that's key to the distinctive sound and phenomenal battery life. I've installed the opamp in a socket so it was never exposed to the heat of a soldering iron. This also allows one to experiment with alternative opamps should you desire.
• Use screw terminals instead of soldered on wires to make installation easier
• Incorporate modern surface mounted electronics
• Attractive silk screening with clearly labeled terminals
• Incorporate a 1kΩ protection resister between the output jack and the LM4250CN opamp. Music Man attached this in between the output jack and the opamp to protect it from shorts that in rare circumstances could fry it. Other reproductions do NOT include this and it must be soldered on separately.

Installation notes:

This is an unusually designed preamp as Leo Fender designed it to obtain a particular sound. Thus, to recreate the late 1970s sound exactly the preamp needs to be paired with the following:

• 25kΩ audio (log) taper potentiometer (A25K). I recommend Alpha RV16AF-10-15K-A25K-3LA. You can substitute a linear taper potentiometer (B25K) if you like as it won't affect the sound.
• 1MΩ reverse audio (log) taper potentiometer (C1M). I recommend Alpha RV16AF-10-15K-C1M-3LA.
• 100kΩ audio (log) taper potentiometer (A100K). I recommend Alpha RV16AF-10-15K-A100K-3LA.
• A SPST or SPDT switch (any kind) if you want to utilize the bright function.

Note that vintage-style Sabre bass pickups are not readily available. You can either buy used ones sold online at places like eBay or Reverb or buy StingRay vintage-style Alnico humbucking pickups wired in parallel with around 1800Ω resistance. Suggestions that work well are Nordstrand MM4.2, Seymour Duncan SMB-4A, and Aguilar AG-4M. You can use this preamp with just one or multiple pickups.

There are other replica pickups around, and the circuit will still sound good if you use a higher resistance pickup as found in Sterling by Music Man basses, but it won't necessarily have the exact sound.

To use the bright functionality you will need to use a SPST or SPDT switch or a push-pull potentiometer. You will want to wire the common pin to ground and one side of the switch to the BRIGHT screw terminal on the preamp.

Modern Sterling by Music Man Ray4, Ray5, Ray24, and Ray25 basses should use B25K volume pots, A100K bass pots, and C1M treble pots so if you have one of those basses you may be able to reuse your potentiometers.

When wiring, see attached image for which lug on the potentiometer is the wiper, CW (clockwise), and CCW (counter clockwise). Do not attach a battery until all components have been attached.

This preamp should fit easily into basses with large control cavities or rear cavities (such as 5 string StingRays, StingRays with double humbuckers, and others). It will be a tighter fit in 4 string StingRays with crescent shaped control cavities, though it should still fit. 16mm potentiometers (like the ones suggested above) are recommended as they're more compact. Due to slight differences in routing between different models you may have more or less room.

Dimensions: 50mm x 18mm x 11mm

Final notes:

Unfortunately I do not accept returns or refund requests as it's easy to damage the preamp if you're careless or don't know what you're doing. This preamp was designed to be as durable as possible and each one is individually tested before shipment. I want your project to be a success so if you have any issues please let me know and I will do my best to help you.

This includes only the preamp. You will need to provide potentiometers, a three prong TRS audio jack (stereo), an on/on/on switch (if you want to use the bright function), and a pickup (if you don't have one already). Screw terminals on the preamp require a 1.5mm precision flathead screwdriver to tighten. Message me if you need any help sourcing parts.

In regards to the bright function - the bright switch on this bass was designed to boost the treble in the area of 10,000Hz. This is a very subtle effect and is mostly noticeable when slapping and popping. Music Man eventually discontinued this and Sabre basses made in the 1980s used StingRay preamps. See my other listings if you're looking for those.

Shipping is free via USPS with tracking to the United States. Please contact me with any questions. Thanks!