Capricorn - Violet Ram's Head (1973 #4) Clone

[PedalBuilder]

In the latest installment of my Big Muff binge, I built a Violet Ram's Head. Takeaway here is that you should build one, too, if you haven't already. Build it right and you get a smooth and articulate muff that sounds good all the way through the tone control's rotation.

I'm generally a proponent of breadboarding before you build, and that's especially true for circuits like the Big Muff that can be middling or magical depending on which component values you choose. I breadboarded half a dozen of the different Ram's Head variations listed on Kit Rae's site before settling on the 1973 #4 circuit (the schematic is at the bottom of this post). It sounded almost perfect, but slightly darker than I liked. Kit Rae notes that the actual values on the 1973 Big Muffs that he measured tended to differ from the printed values:

[T]he real tonal differences are from the mix of the individual component values. These differences are what give each Muff its own unique character. The older the Muff, the more those values seem to be different from one unit to another, and the newer the Muff, the more they are the same from unit to unit.

For example, here are some general measurements from a few 1973 era violet Big Muffs, versus what the printed values show.

470pF ceramic disk caps usually measure in the 545-565pF range. Never 470
0.1µF poly caps usually measure in the 0.08-0.09µF range
470k carbon comp resistor measurements range from 530-560k. Never 470
100k carbon comp resistors usually measure 10-20k larger. Same with the 100Ω
10k and 12k carbon comp resistors almost always measure 1-2k larger
33k resistors usually measure accurate to the printed value. Those appear to be metal film, not carbon.

That is just for the specific component types used in that specific circuit from that year, not necessarily typical of other component types. How much of that variance was there from the start, happened in the first few years of burn in, or happened in 40 years since is anyone's guess.

Based on that suggestion, I experimented with swapping out some of the 100n coupling caps for 82n caps. I had the best results were with C4 (C3 on the Muffin Fuzz) and C2 (C13 on the Muffin Fuzz), but now it sounded slightly too thin. I added parallel capacitors to increase C4 to 90n and C2 to 88n—perfection. Other changes—I used pairs of silver mica capacitors for the feedback caps; each pair measured 490pF.

Transistors are modern, low-noise devices. Transistor gains are as follows (numbering follows the schematic below): Q1 - 239; Q2 - 179; Q3: 212; Q4 - 159. I usually build my pedals with an I/O PCB that uses MOSFETs and zener diodes to provide reverse polarity and over-voltage protection. Because everything in this build is rated for at least 30v, I skipped the I/O PCB and wired a heatshrinked 1N5817 from the power jack to the PCB. Rather than using a hole for the DC jack, I used Tayda's line cutting feature to create a shape that matched the shape of the DC jack so that it can't turn in the hole and stress the joints.

The enclosure is a winked silver 125B from Tayda, UV printed with a double pass of white and matte varnish.