Musicman/Sterling S.U.B.

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars
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george giblet
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Post by george giblet »

Found some pics the other day a put this together.

Sterling SUB Ray4 Bass

The preamp seems to following the Tobias version of the HAZ Labs preamp.

Technically the Bass pot value is unverified but I can't imagine it not being 100kB.

The stock wiring uses a 500k A? volume pot.

Even for stock wiring there are three variations of wire colors.
On the web there's a version which has a 25kA volume pot
this seems to be a mod.

Someone mentioned a 250kA volume pot. That could be an error.
Stock Wiring Variants

Whatever the wire color variant the pots should be wired according
to the pot pin numbers on the overlay pic.

Vol pot 500k(A?)
Treble pot 100kB
Bass pot ? 100kB

The pickup is wired to the wiper of the volume pot (Vol pot 2)
Volume pot pin 3 is then wired to the preamp input.

The bass pot is soldered pcb (contacts along edge of pcb).

Even for stock wire there seems to be variations in the wire colors.

1) ** known good Sterling SUB Ray4 2013

Preamp Input/Vol 3 Green
Treble 1=Green, 2=Red, 3=Orange
Preamp Output/Jack Orange

2) 2013/2014

Preamp Input/Vol 3 Green
Treble 1=Green, 2=Orange, 3=Red
Preamp Output/Jack White

3) some others

Preamp Input/Vol 3 Green
Treble 1=Green, 2=Red, 3=White
Preamp Output/Jack White
PCB connections along edge of PCB.

1 Red +V
2 White/Orange Preamp Output
3 Black }
4 Black } one of these blacks might not be connect
5 Black }
6 Green Preamp Input
Stock wiring GRW_W posted 2012-10-17 13.52.55.jpg
MM Sterling Sub PCB markup.jpg
MM Sterling Sub SCH.gif

george giblet
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Post by george giblet »

FYI, Apparently there's a second revision of the PCB, perhaps from around 2018/2019.

Changes: The main change I can see to the circuit is the addition of a diode
across the power rails "D1" which is locate in the corner of the PCB. The
added diode D1 helps prevent damage to the preamp when the battery terminals
are reversed.

Reason: There's a few examples on the web where the 10uF/16V cap is totally
burnt and the preamp is faulty, probably due to reversed battery connections.

Second revision differences are identified by:
- Addition of diode D1 in the corner
- Different PCB which has a totally new layout.
- The PCB has designator text (R1, C1, D1 ... etc) on the component side.
- The wiring points around the board have changed.
- The treble pot wires connect to the edge of the board, not across the center.
- The treble wires have changed color: Orange, Violet, Gray

I have not re-traced this board as the pics aren't good enough to see the details.
The part values look the same as the first revision PCB, so there's little
reason to think the circuit is different.

Some additional info:

The second revision wires the pickup the pin 3 of the volume instead of pin 2.

Since about 2018 the SUBs are made in China. Apparently the preamp was changed then.
People on the web claim the preamp fixes the overly hot output signal on the earlier
Indonesian made SUBs. It's not clear that issue is fixed at all. It's not clear if that
issue is fixed by the preamp or simply the pickups aren't as hot.

To make things more confusing, since around 2018 Sterling released a "Stingray" series
which have 21 frets where as the SUB's have 22 frets. There's a Stingray Ray4 and a SUB Ray4.
So from now on the term "Ray4" is ambiguous.

If anyone comes across the new preamp see if you can spot any changes related to attenuators
on the input or output circuits.

george giblet
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Post by george giblet »

I just read a whole heap of posts:

The things mentioned in the thread are not consistent:
- "Made In China Ray4 and Ray5 have a redesigned circuit"
- "The preamp for China is voiced in the same manner, so that tonality will not be affected"
- "All China production have the newly redesigned preamp, which have zero volume spike issues. They are still hot on the output when all controls are maxed, but everything 'dials down' as you do so."
- "The volume circuit is now a complete "post" signal, so that it dials down smoothly."

The unit I saw did *not* have the volume control wired "post" preamp.

So my summary of reality is:
- The list I wrote above.
- The PCB is different but the circuit is the same except for the addition of diode D1.
- The wiring of the volume control was changed, which makes the volume control operate more normally.
- The output when the volume control is maxed out is still high.

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