Frail and faltering follower of Jesus

7 string bass active to passive conversion - Fazley Mammoth

By Gavin Davies

How I converted my 7 string bass to passive, solved the buzz and hum, and fixed clashing tuners

I bought this bass in July 2022 for £233 - you can see my original review of the Fazley Mammoth 7 string bass here

Well, I finally did some work on it – I’ve:

  1. Replaced the active electronics with passive ones
  2. Fixed the grounding problem on 4 of the 7 strings
  3. Fixed the clashing tuners
  4. Shielded the electronics cavity

It works great now - the buzz is solved!

It would still need a lot of work to be a main bass - new pickups, new nut, fretwork, truss rod adjustments, weight fixes… etc.

Here’s the preamp that WAS in the bass - I was wrong about it taking 18v - Chris Cuthbertson on Youtube let me know that “Looks like the batteries are connected in parallel so 9V with twice the capacity instead of 18V” which makes sense, given the preamp takes 9v. Seems a bit unnecessary but there we go! Perhaps that circuit is known to eat batteries? Generally active bass batteries last aaaaages if you don’t leave them plugged in!

I found this chart online of roughly the effects of different caps on tone pots, sorry but I don’t recall what page it was on!

Here’s the bridge wire as-was, note how it doesn’t cover all bridges:

Here’s the only pickups I could find that seemed a suitable replacement (although they’d need a bit of hollowing out like the warm rodded gear4music chicago 6 string bass I modded ) - Bartolini 108g67j1.

Here’s all the left over bits I removed!