Dan Armstrong Bass - Electrical Specification & Wiring
Above right. The schematic on the back of the owner's manual shows the first version of the Dan Armstrong bass wiring (ARM B-1). Note the single capacitor used in the circuit. The volume and tone pot values are identical in the bass (200K, audio taper) and were often a shared part with the volume control on the Dan Armstrong guitar.
Although the electrical specification looks simple - just a single pickup and two knobs - in fact the wiring is very unusual. The pickup consists of two stacked single-coil pickups that terminate with a common ground lug. The 'tone' control then varies the mix between the two coils, while C1 acts as a ___ capacitor.
Although the electrical specification looks simple - just a single pickup and two knobs - in fact the wiring is very unusual. The pickup consists of two stacked single-coil pickups that terminate with a common ground lug. The 'tone' control then varies the mix between the two coils, while C1 acts as a ___ capacitor.
At right, a Dan Armstrong OEM bass pickup. These photos show the three outside termination lugs (center lug is ground for both coils), and also the metal base plate, presumably used for shielding.
Given the packaging constraints of trying to stack two single-coil pickups on top of one another, the potting material is necessarily thin on top and therefore prone to cracking and flaking. Various examples of this problem are shown at right. |
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The electrical spec for the earliest basses consists of two CTS potentiometers dated May 1969, and a bright blue tone capacitor (manufacturer unknown so far).
Shown at right are the volume and tone pots for bass D146A. The CTS volume pots are stamped with the electrical code 1376920. The first three digits (137) identify the manufacturer as CTS. The next two digits are the year of manufacture (here 1969) and the last two digits are the week of manufacture (20th week of 1969 or somewhere in the week beginning May 12). Although not precise, the May 1969 date on the early volume pots is consistent with a mid-1969 start date for production, as Dan Armstrong's were introduced to the dealer market at the NAMM show, which ran between June 22 - 26 in that year. This photo also shows the foil shielding that was applied to the pickguard on the very early basses. This feature was dropped along the way, either for cost or aesthetic reasons. |
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1971 Wiring Change. In March 1971, Ampeg published Product Bulletin # 17 which covered changes in the wiring of the guitar and introduced a switch for the DA bass. The change in the wiring spec prompted an update to the schematic in the Owner's Manual (above), which now refers to the guitar as model ARM G-2 and the bass as ARM B-2.
With respect to the bass, the wiring changes are significant - there are now 3 capacitors in the circuit along with a double-pole, single throw, switch.
With respect to the bass, the wiring changes are significant - there are now 3 capacitors in the circuit along with a double-pole, single throw, switch.
Shown at right are two photos from bass D2335A. This particular bass happens to be a fretless model, and sports a factory black pickguard and headstock. Pot codes are 1377036, which dates the pots to ____ 1970. This was the last batch of pots used in bass production, and lasted through to the end of the run. D2335A clearly shows the updated wiring package, so in fact this bass was produced sometime in the middle of 1971.
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