Overhaul of Carl Thompson Bass

Tony Senatore, full-time professional bassist extraordinaire and proud owner of this incredible Carl Thompson bass has been growing disenchanted with active electronics in general and felt it was time for a change. Tony wanted to remove the active EMG pickups, and try a great set of hand wound Kent Armstrong pickups using only passive electronics, and specifically to employ a varitone or multi-tone. In addition, he wanted ability to switch between pickups via some kind of toggle switch.

It is not every day that I have the opportunity to work on such a masterpiece as a genuine CT bass so there were two really important ground rules I wanted to adhere to.

1. I did NOT want to drill into the instrument in any way shape or form, so we had 4 controls to work with.
2. I wanted to keep this really intuitive from a live playing standpoint, so I didn't want to make unnecessarily complex.

Given these parameters, I suggested the following configuration to Tony:

• 3-way on-on-on mini-switch to select between the following pickup combinations:
  1. neck pickup alone
  2. neck/bridge in parallel
  3. bridge pickup alone
• Master volume (250 K), with volume kit (680 pf cap in series with a 150 K resistor) to prevent the loss of highs experienced when lowering the volume.

• Master tone (500 K) which will be driven by a separate 5 way rotary switch used to feed 5 different tone caps into the tone control. A push pull on the tone pot will be used to engage/disengage an 1.5 H hand wound inductor at the tail end of the varitone so the end result is 10 tones (5 without the inductor and 5 with). The 5 selected cap values were:

  • .015 uf
  • .022 uf
  • .039 uf
  • .047 uf
  • .1 uf

  I then drew up this schematic:

Here is a picture of the original bass. It is truly a work of art.

The original EMG active pickups.

Close up view of control cavity.

First the pickups and all electronic components were removed.

Rear view

Next the control cavity was lined with conductive copper tape for shielding purposes. Note: this tape is conductive through the glue ensuring a a good electrical connection, even for overlapping tape.

All wiring was first done outside the instrument on an MDF template to prevent any possible damage (no matter how remote) to the instrument's finish. The strange looking black round control is a hand wound inductor by Kent Armstrong....way cool!!

The prewired harness was then installed in the instrument.

Brand new Kent Armstrong Hand Wound p-bass pickups.

A happy customer picks up his bass!

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