For Fuzz Friday, here's another Big Muff based circuit to add to the collection. The Iron Bell is a variation of the Skreddy P19, the schematic of which was graciously posted by Marc from Skreddy a few years back. It's not based on any one classic Muff, but is Marc's unique blend of custom values, and features a boosted mids tone stack, with a switch to increase the mids. Shortly thereafter, the Iron Bell came out with a few mods, the biggest of which is the replacement of the Mids switch with a potentiometer and a few value changes. The layout below reflects the MojoHand iteration of the circuit, but the P19 can be built on the same board (see below for component changes). It's laid out for board mounted pots and should fit in a 1590B.
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To make the Skreddy P19, made the following changes:
- Replace the Colour pot with an SPST on/off switch
- Change Q2-4 to BC550
- Change the following components indicated on the layout:
* 200Ω
** 10k
• 47nF
•• 2.7k
‡ 6.8nF