MMSR77

Thank you for your recent purchase of a Boscoe MMSR77 preamp!  This is a replica of the vintage preamp used in late 1970s Music Man StingRay basses.  Each preamp has been individually tested before shipping and should help recreate the classic StingRay tone in your bass.

While this preamp will work great with many different kinds of pickups and wiring configurations, if you are looking to recreate a vintage StingRay tone the following components are important:

• Music Man style humbucker with 1750-1950Ω resistance and approximately 700mH inductance (early StingRays had varied winding counts) wired in parallel

• 25kΩ volume potentiometer (either taper, marked A25K or B25K)

• 100kΩ bass potentiometer (audio taper, marked A100K)

• 1MΩ treble potentiometer (reverse audio taper, marked C1M)

• 9V power supply

When assembling, make sure to complete all connections before attaching the battery.  The preamp may be a tight fit on some 4 string StingRay style basses with crescent control plates.  If so, make sure you have longer wires so you can move things around as needed to fit everything or route out some additional space.

Carefully attach wires to the screw terminals.  Tinning the ends of stranded wire with solder is recommended to ensure a good connection.  Make sure the pins on the bottom of the preamp aren't in contact with conductive paint or metal - cover with electrical tape as needed.

Should you encounter any noise in the circuit, make sure you have the potentiometers grounded and the bridge ground attached.  If you use a vintage humbucker like the Nordstrand MM4.2 note that it is built to the original spec and does not have its pole pieces grounded.  Extra shielding and grounding may be required.

This preamp includes as an extra feature the 1kΩ protection resistor that Music Man incorporated into its later basses.  This protects the LM4250CN opamp, which could become damaged should the guitar lead be shorted even momentarily.  It does not affect the tone, but if you're a purist and want to recreate the 1977 circuit exactly you can bypass the resistor by connecting the output jack directly to the volume wiper, skipping the screw terminals on the preamp.  However this puts your LM4250CN opamp in danger of being shorted out and it is not recommended.  There's a reason Music Man later added the resistor.

The preamp's connections match the layout of the late 70s preamps so they should be able to be a drop in replacement.  The back of the preamp has the connection points marked.

When wiring potentiometers to the preamp, make note of the nomenclature used.

• CCW - the counterclockwise lug, on the left when looking from the bottom

• Wiper - the middle lug

• CW - the clockwise lug, on the right when looking from the bottom

Here is a simple diagram for reference: