SR4 PUPs AND PREAMPS
Pre-EB & EB (Part 2)
EB 3EQ PREAMPS (1987 - Current)
Beginning of 1987-Circa 1990 (3 band).
Pic of a 1988 3EQ Preamp.
As opposed to the 2EQ with its"treble" & "bass" controls, the 3EQ has an extra "mid" control in addition to the volume control. A "TL062" chip is used whereas the 2EQ uses a "LM4250CN" chip. Pot values for the three tone pots are each 50K ohms with a centre detent. The volume pot, as with the 2EQ, remains 25K ohms with a linear taper. All subsequent 3EQ preamps remain the same albeit with slightly different circuit boards.
The 3EQ was
introduced as an option to the 2EQ preamp in Jan 1987. However, the same 3EQ was standard for the new SR5 introduced latter in 1987. The 3EQ was also standard for the dual pickup
SR4HH and SR4HS Basses introduced in 2005 (no optional 2EQ for the SR5 nor for dual pickup SR4 Basses).
Note that, although the two outer pots have lugs for point to point wiring, the two inner pots are soldered directly to the circuit board with pins attached to the pots. Note also that the preamps are dated with a round sticker on the rear of a control pot from 1988 onwards. Prior to this some were dated with a black marker pen on the rear of the control plate.
Reproduced with permission. Schematic wiring for 3EQ
preamps from circa 1987 up to circa 1990.
Circa 1990-October 2006 (3 band).
Pic of a 1994 3EQ preamp.
Just like the 2EQ, the 3EQ circuit board also changed from rectangular to a crescent moon shape. Note that the two outer lug pots on the previous 3EQ version (above) are now soldered directly to the board. The circuit still remains the same as do pot resistance values.
Reproduced with permission. Schematic wiring for 3EQ preamps
from circa 1990 to Oct 2006.
October 2006-July 2018 (3 band).
Pic of an Oct 2006 3EQ preamp.
The circuit remains the same and continues to use the TL062 chip. Although pot resistance values remain the same, the previous larger pots are replaced by smaller "Noble" pots. [2EQ preamps change to Noble pots 3 years latter in Sept 2009].
Schematic wiring for 3EQ preamps from Oct 2006 to July 2018.
July 2018. Regular SR4 ceases to be offered. New Special Lightweight SR4 introduced with new re-voiced 3EQ 18 volt preamp & neodymium pickups. In general, no more 3EQ 9 volt nor alnico pickups.
The new "Special" SR4 18 volt re-voiced preamp
board for both the SR4H and HH.
New Neodymium pickup for the new 18 volt
With the next generation SR4H and HH Special Sting Ray Basses, introduced July 2018 and offered in place of the regular SR4, the previous 9 Volt 3EQ preamp is replaced with a new revoiced 3EQ 18 volt preamp (pictured above). The brass control plate is reolaced with aluminium (chrome or black). The pickups are now Neodymium rather than Alnico. In general, the older 3EQ 9 volt preamps and Alnico pickups are not an option. All pot values remain the same as with the previous 3EQ 9 volt preamps ie the three tone pots are each 50K ohms with a centre detent and the volume pot remains 25K ohms with a linear taper.
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