MicTester's 1969 Fuzz Box

Her's a unique fuzz circuit from MicTester for your #FuzzFriday. Here's what he had to say about it:

Way back in 1969, I heard "Inna Gadda Da Vida" for the first time. I realized quickly after building some simple transistor stages that didn't work properly that "the" sound was coming from abused transistors! Experimentation over some weeks led to [this circuit]! Just two pots give an amazing range of distorted sounds and none of the components are critical. 

Please tweak away until you find the sound you want! Alter capacitors, change the transistors–experiment!

The original FSB thread with the schematic can be found here.

MicTester's Guitar Compressor

Here's a compressor design from MicTester. Here's what he had to say about it over on FSB:

Do you remember the old-fashioned way of doing bass compression? It used an LDR across the volume control illuminated by an incandescent lamp across the speaker terminals! It was a simple method back in the 60s....

This compressor is almost that simple! It uses a handful of cheap components (I built one for £9 including hardware!), but works really well. Guitarists who've tried it often ask "Is it on?", but miss it when it's off! It's quiet, and has good "squeeze" without the gain-change artifacts you frequently get with transconductance amplifiers or FETs.

The LDR should be ~1M in the dark, but almost anything will do.

Some of the component values are quite carefully chosen. The input capacitor (15nF - made up of a 10 and a 4.7 if the 15 is unavailable) is chosen to give some frequency shaping, and the interstage capacitor prevents handling noise affecting the compression. Green LEDs are chosen because they most closely match the response of the LDR, but yellow works almost as well. Obviously, the LDR / LED combination should be facing each other, and must be in a light-tight enclosure.

I've set up the board with pads for both 10nF and 4.7nF in parallel if you don't have a 15nF cap.

MicTester Hot Silicon Tonebender

Here's another one of MicTester's creation/adaptions. The Hot Silicon Tonebender is based on the classic SolaSound Tonebender Professional Mk II, but with silicon transistors and an added tone stack. Pretty much any medium to high gain transistors will work, so socket and try a few different ones out (BC109, 2N5088, MPSA18, etc). 

MicTester Buzz-Alike

Like many of the old germanium fuzzes, the Burns Buzzaround can be difficult to get right. It also uses 3 sometimes costly germanium transistors, and unless you also build a power inverter or use NPN transistors, you can't daisy chain it with other negative ground effects. To get around these hurtles, Mictester designed a work-a-like of the Buzzaround using only one (NPN) germanium transistor and germanium diode alongside a dual op-amp. Here's mictester's description of this circuit:

"The original consisted of two stages - a two-transistor amplifier and a distortion stage that could have both the amount of signal sent to it and the bias point adjusted by external controls. The third control was a crude tone control which fed the output. Originally, the output was unbuffered, and the leads and amplifier following would load the unit, and the top end would be rolled off, and often the tone control would have little effect. 

The first stage in the sound-alike is just a high input impedance op-amp gain stage. You may wish to increase the gain by increasing the value of the feedback resistor, but it sounds pretty good as shown. In the original, the first stage didn't really have much effect on the sound - it just amplified it enough to drive the following stage into conduction.

The heart of the beast is the germanium transistor stage. Apart from using an NPN transistor, this remains true to the original (why screw up a classic?), and still gives a wide range of sounds from the thin toppy fuzz beloved of sixties bands through to gated spluttery farts, with smooth warm distortion sounds in between!

The final stage is just a buffer - it isolates the tone circuit from the outside world, and allows a full range of control from muffled to glass-shattering!"

Simple Transistor Compressor

FSB member Mictester came up with this design a couple years ago. Utilizes 4 transistors, 1 PNP and 3 NPN, though you could probably use an NPN in place of the PNP. Best to socket and try a few different transistors. The schematic says BC213L for Q1 and BC183L for Q2-4, but any medium gain transistors should work okay (2N2222, 2N2907, 2N3904, 2N3906). I added some of the mods suggested in the FSB thread for higher input impedance and noise reduction.