GGG Fuzzrite Build

I recently ordered a Fuzzrite kit from General Guitar Gadgets. I was originally going to build the pedal on vero board as part of a 3-in-1 fuzz pedal.

I used the included 2N3904 transistors, but socketed the Q1 and Q2 positions for when Smallbear reopens their online shop.

The kit came with 2 red Wima 0.0022uF capacitors, which were not great fits on the PCB.

7/15/20 - I received some 2N649 transistors from Smallbear and will do an A/B comparison one day.

Shure M67 Preamp Mod

I purchased a Shure M67 a few years ago with the idea of performing the individual direct out mod. I likely gave up after being overwhelmed by the messy stock wire layout.

I want to give the RodC M67 mods a try, to relocate the gain knob to use the preamp for louder sources. His website was now gone, with a few other sites preserving the information.

• Channel 1: gain control to be relocated; switchable unbalanced direct out to headphone jack chassis hole.
• Channel 2: gain control to be relocated; switchable unbalanced direct out to “2” banana jack chassis hole.
• Channel 3: stock gain; switchable unbalanced direct out to ”3” banana jack chassis hole.
• Channel 4: stock gain; stock mix bus connection intact.
• Line Output will be rewired to the Microphone Out XLR jack, with 600 ohms resistance across pins 2 and 3 if possible

I hastily yanked out the headphone jack before I started taking pictures to document the stock wiring.

Stock wiring on switches.

Headphone circuit removed. Balanced output remaining to be removed. 

Edit 6/2/20. I started to make the changes to the output section of the preamp. I spliced the line level tap of the output transformer to the Microphone Out jack. 

I have so far rewired the gain pot of channel 1 to come before the transistor stage. Next will be the wiring of the direct outs.

Edit 6/18/20. I completed performing the modifications to the M67.

The repurposed mix bus output has an 820 ohm and 2.2kohm resistor pair in parallel on pins 2 and 3 for an equivalent load of 597.35 ohms. I can directly connect the mix bus output to a balanced line input and load the preamp properly.

The direct outputs are lower in gain as expected, as the taps are before the final amplification stage. I can understand how relocating the gain pot to attenuate the signal into the transistors is useful for louder sources like drums. 

I currently have the new unbalanced direct outputs of the M67 hooked up to my the RCA inputs of the Roland VSR880 recorder as a few extra channels of mic preamps.

Rear panel with 3 Switchcraft 112BX connectors for channels 1-3 direct outs.

Overall view of chassis.

Direct out jack wiring (black & white twisted wires). 

Lo-cut switches rewired as switchable direct outputs.

Markup of schematic depicting my M67 modifications.