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[AT 1 SEPT 2008]
PRE-AMPS AND PUPS
A rough outline subject to amendment.
Pre-EB and EB BASSES
Pre-EB STING RAY (1976 - 1984)
PICKUPS AND ROUTING
1976 up to, and including, circa early 1978
Pickup from Sting Ray Bass dated Jan/Feb 1977.
Note that the pole pieces extend below the bottom of the pickup casing. All Pre-EB pickups are wired in parallel.
Pickup cavity routing and Pickup from Sting Ray Bass. Body date 17 June 1977.
(Pics courtesy of "calzone")
The main pickup cavity is routed deeper at the bottom to accomodate the extended length of the pole pieces.
In relation to the pickup itself, two seperate coils are wired together in parallel to cancel the hum that would otherwise be present should only a single coil be used for the pickup. Thus the term "Humbucker". Coil resistances for this style pickup are not known at this stage.
Throughout the Pre-EB period, pickups are passive (not active), the coils are wired in parallel and pole pieces are Alnico. This is also the case with current Ernie Ball Sting Ray Basses. The battery powers the pre-amp only.
Circa early 1978 to end of Pre-EB period (1984)
Pickup from a late 1978/79 Bass. Pole pieces are now shorter and flush with the
bottom of the pickup casing. Each coil has a resistance of approx 3,900 Ohms.
Resistance of the 2 coils in parallel gives an overall approx resistance
of 1,950 Ohms.
Underneath view of same pickup.
Top view of the pickup and pickup routing.
As the pole pieces are now shorter, the pickup cavity is a single routing.
Towards the end of the Pre-EB period (circa 1983?), the pickup routing
outline took on the shape of the pickup itself. It is thought that this
may have co-incided with the introduction of clear pickguards.
A Carey Nordstrand pickup type "MM 4.2" with alnico pole pieces.
The Nordstrand pickup is designed on the 1978 Pre-EB pickups and will fit all Sting Rays from 1976 to present date EXCEPT for the new optional twin pickup Sting Rays introduced in 2005 (with pickup covers similar to the Bongo Bases). Resistance measurements are the same as for the Pre-EB pickup above with the shorter pole pieces.
PRE-AMPS
Introduction
Although the Treble and Bass controls have no centre detent position, the pre-amps appear to be CUT and BOOST with respect to the treble control . On the other hand, the pre-amp is boost only with respect to the bass control.
The Pre-EB pre-amps use an Audio (Log) taper pot for the Volume control which tends to bunch up the volume adjustment to the upper limit of the pot rotation. The Ernie Ball 2 Band EQ pre-amps (same as the Pre-EBs) correct this by using a Linear tapered Volume control pot to allow for a smoother adjustment throughout the whole pot rotation. The EB pot values remain the same.
All Pre-EB pre-amps use a "LM4250CN" IC chip. The same chip is also used on all Ernie Ball 2EQ pre-amps to current date. However, the 3EQ option introduced by Ernie Ball in 1987 uses a "TL062" chip.
1979 pot with code dating on the side.
Volume, Treble and Bass pots are code dated on all pre-amps during the Pre-EB period. For example "1377626". The "137" component identifies the type of pot (a single pot rather than a stacked pot). The next two numbers identify the year ("76" indicates 1976 as the year of manufacture). The remaining two numbers identify the week of the year ("26" indicates the 26th week of 1976 which is June). The code example "1377626" therefore identifies the pot as being manufactured in June 1976. Pot dates may, or may not, identify the date of the pre-amp. As Music Man purchased them in large quantities, it's not unusual to find pots that are one to two years older than the pre-amp itself.
1976 to early 1977 (Black Epoxy)
 1976 pre-amp.
From 1976 to early 1977 a red/orange coloured capacitor is located on the treble pot rather than being included on the circuit board itself.
Pre-amps are sealed in black epoxy. The IC chip is soldered direct to the circuit board. The sequence of lead-out wires from the board is completely different to subsequent Pre-EB pre-amps boards.
Schematic pre-amp wiring for 1976 and early 1977 Basses.
1977 to 1978 (Black Epoxy)
There appears to be three types of pre-amps used during this period.
Type 1
Pics courtesy of David.
Type 2
Normally, pre-amps are attached to the pots (at each end of the board), with
material similar to that used for the string mute pads. In the above picture,
the webmaster has rebuilt the control plate. In order to mount the pre-amp
board, a whole piece of computer mouse pad material has been used.
Note that the leadout wires to the bass pot (on right) are now yellow instead of violet
and have been reduced from three to two. The bottom lug of this pot is now unsoldered
(as opposed to Type 1 above). Note also that the two leadout wires to the volume pot
have had their colours reversed as opposed to Type 1. White now goes to
the centre lug of the volume pot and black to the bottom lug.
Type 3
Note that the leadout wires to the bass pot revert back to being violet. This pre-amp
appears to be the main one used towards the end of 1978.
1979 (Epoxy Deleted)
1979 pre-amp. (Pics courtesy of "freedok"). Note the red and blue
coloured Tantalum capacitors. Green and maroon Tantalums
were often used aswell. On latter pre-amps, Electrolytic
capacitors become standard.
From 1979 to the end of the Pre-EB period, the epoxy coating was deleted. The IC chip was now mounted to the board via an IC socket rather than soldered directly to the board itself. However, from 1985 (beginning of the Ernie Ball period) all ICs returned to being soldered directly to the circuit board.
Schematic pre-amp wiring for Basses from 1979 to 1984 (end of EB period).
Although the epoxy is now deleted, note that the colour coding of the lead-out wires is the same as for the Type 3 pre-amp used during the 1977-1978 period above. Because of this, it's presumed that the 1979 non-epoxy pre-amp is the same. The same colour coding is found on Ernie Ball 2 Band EQ pre-amps from 1985 up to circa 1990. There after, the Ernie Ball 2 Band EQ pre-amp board changed from rectangular to a crescent moon shape but the circuit remains the same.
With respect to Cutlass 1 Basses (introduced in 1979), the pre-amps are the same as for the Sting Rays.
Circa late 1979 or early 1980
At left is the non-switchable jack first used on Sting Rays.
The jack (right), introduced late 1979 (early 1980),
disconnects the battery when the guitar
lead is removed.
Initially, all pre-amps remained permanently turned on. Removal of the guitar lead did not disconnect the battery. Current drain was considered to be low enough for the battery to last its normal shelf life whether left connected or not. A newer jack was introduced late 1979 (or 1980) to disconnect the battery. This is the position to current date.
Circa late 1981 or early 1982
"LM4250CN" chip (left), Electrolytic capacitor (centre)
and a Tantalum capacitor (right).
Electrolytic (as opposed to Tantalum) capacitors appear on non-epoxied pre-amps from circa late 1981 (or early 1982) onwards. Audiophiles would argue that the electrolytic has a more mellow and pleasing tone to the ear.
A 1983 pre-amp with Electrolytic capacitors.
1982 to end of the Pre-EB period (1984)
1982 schematic reproduced with permission.
The IC chip can be damaged should the guitar lead become short-circuited. In circa 1982, the addition of an out-board 1K ohm protection resistor was recommended to save the IC chip from destruction.
At the beginning of the Ernie Ball period the resistor remaind an out-board addition. From circa 1986, it was included on the circuit board.
An Ernie Ball replacement pre-amp for Pre-EB and Ernie Ball Sting Rays up to
circa 1990 (there-after the board changes to a crescent moon shape).
The protection resistor has been included on the circuit board.
EB STING RAY (1985 - Current)
PICKUPS
Intro
Pre-EB pickups (above) varied individually due to winding techniques adopted at that time. Ernie Ball automated the windings to make the pickups a more consistent product. All pickups are wired in parallel.
As with the Pre-EB Sting Ray pickups, Ernie Ball Sting Ray pickups are passive, the coils are wired in parallel and pole pieces are Alnico. The battery powers the pre-amp only.
1985-mid 2003
Pickup from a 1989 Sting Ray.
As with Pre-EB pickups, the pole pieces are Alnico. Underneath wiring changes from Green and Yellow (Pre-EB) to Green and Orange. The coil windings are now finished with a winding of tape. All pickups (both Pre-EB and EB) are wired in parallel. The black leadout wire is "Ground". The white leadout goes to the pre-amp.
Mid 2003-Current
SR4 Pickup with rounded-edge Alnico pole pieces. Introduced mid 2003.
(Picture "Davtran").
2005-Current
2005 Sting Ray with two Humbucker pickups (Picture "Steve Dude Barr").
Close-up view of the two Humbuckers. (Picture "hmagman").
The new two-pickup Sting Ray Basses were introduced at the July 2005 NAMM Show. Pole pieces remain Alnico with rounded edges. However, the black plastic pickup casing differs slightly to that of the standard Sting Ray and is similar to the pickup outline featured on the Bongo Bass.
Aswell as two Humbuckers (HH) above, the Sting Ray is also available with one Humbucker plus a Single coil pickup (HS). Both are offered with 3 band pre-amps only (no 2 band).
As to pickup configurations:
HH Click Here
HS Click Here
(both are links to the Ernie Ball website)
PRE-AMPS
Introduction
The Ernie Ball 2 Band EQ pre-amp (to current date) is the same circuit as the Pre-EB non-epoxy pre-amp introduced in 1979 except for the subsequent inclusion of a protection resistor which was a Pre-EB modification in circa 1982. In 1985, EB included it as an outboard modification (as with the Pre-EB pre-amps from 1982) but in circa 1986, the resistor was relocated the board. Also the Pre-EB pre-amps use an Audio (Log) taper pot for the Volume control which tends to bunch up the volume control adjustment to the upper limit of the pot rotation. The Ernie Ball 2 Band EQ pre-amp corrects this by using a Linear tapered Volume pot to allow for a smoother adjustment throughout the pot rotation. However, all pot values remain the same as the Pre-EB pre-amps.
Wiring of the pre-amp board to the pots pickup and jack remains the same as the Pre-EB non-epoxy pre-amp introduced in 1979. The sequence of lead-outs from the pre-amp board also remains the same.
The board changed from rectangular to a crescent moon shape in circa 1990 but the circuit remains electrically the same.
1985
1985 pre-amp. A protection resistor has been added as per the 1982 Pre-EB
schematic (pictured previously) and is located within the plastic sleeving to
the right. Note that, from this point on, the IC socket is now deleted and
the chip is soldered directly onto the circuit board.
Circa 1986 to circa 1990
Pre-amp as found from circa 1986 to circa 1990. The protection resistor is
now relocated on the circuit board.
The EB replacement pre-amp for Pre-EB and EB Sting Rays up to circa 1990.
Reproduced with permission. A schematic wiring diagram for the M05400
replacement board directly above. Note the violet lead-out wire on left
hand side as opposed to the normal three yellow lead-outs. However
this is the generall schematic for all EB 2 band pre-amps from 1985
to circa 1990. Note that this is the same layout as
for the Pre-EB schematics.
To this point, pots have been of the "lug" type (above left). From Circa 1990,
direct mount pots (above centre) have been used exclusively for 2 band
pre-amps due to the circuit board design (see below). As the pot values
remain the same, the direct mount pots can be modified for use in the
earlier pre-amps by bending and cutting the pins (Above right).
Circa 1987 to circa 1990
Although the 2 band is still available at current date, Ernie Ball introduced the
optional 3 band pre-amp in 1987. (Picture from a 1989 Sting Ray Bass). Note
that, although the two outer pots are hook-up wiring (lug pots), the two inner
pots are soldered to the circuit board by pins attached to the pots. Also
note that the pre-amps are dated (yellow sticker on rear of bass pot).
Reproduced with permission. Schematic wiring for 3 band
pre-amps up to circa 1990.
Circa 1990-Current (2 band)
From circa 1990, the 2 band pre-amp circuit board changed from rectangular to
a crescent moon shape. Note that the lug pots are replaced with direct mount
pots that solder direct to the circuit board with pins. The circuit remains the
same as the earlier pre-amps.
Reproduced with permission. Schematic wiring for 2 band pre-amps from
circa 1990 to date.
Circa 1990-Current (3 band)
From circa 1990, the 3 band pre-amp circuit board changed from rectangular to
a crescent moon shape. Note that the two outer lug pots are replaced with
direct mount pots to match the two centre pots that solder direct to the
circuit board with pins. The circuit remains the
same as the earlier 3 band pre-amp.
2005-Current (3 band with two pickups)
From a 2006 SR4 HH (two pickup) 3 band Sting Ray. The pre-amp board is
the same as for the single pickup 3 band Sting Ray (courtesy "Goldsie").
Reproduced with permission. Schematic wiring for 3 band pre-amps
from circa 1990 to date.
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