WIP: Buffered Dual FX Blend Board

This one's more of a utility circuit, it combines two signals by blending the output and uses an gain recovery amp to reduce loss of volume. It's the expansion of a schematic included in an older Geofex PDF about panning circuits for use with guitar effects (1). The inputs are buffered to help with variations in output impedance from the circuits being blended. There was an extra opamp left on the IC so I buffered the power (2) and used a TL074 IC. Right now this is designed as a standalone circuit but can easily be integrated into a circuit that internally blends signals, like the MXR Blue Box (3)...actually, more on the Blue Box some other time.

Fig 1, schematic

1. The TL074 can be substituted with two TL072s. If you don't want the power buffered, you can do a TL072/TL071 combination as well.

2. The non-inverting amp (IC2_C in the schematic) has a gain of 11 dB (4), but can be adjusted according to your taste. There's a loss of volume after the B10K pot and this is what got my setup to unity volume. 

3. This circuit isn't supposed to color the sound too much and there are easy changes for mods. C1 and C3 have a big effect by filtering respective input, increasing the value will eventually dampen the sound while going lower (˜100pF) could result in more ground hiss. The R9-C12 R-C filter (R13-C13 as well) after the buffer can also be adjusted. R22 also has an impact on the output filtering and can be modified. 

 

BREADBOARD BUILD

It took some work but I got this circuit to fit on a 400pt breadboard. Both inputs work (can hear signal in output) when a guitar preamp is connected and the B10K pans nicely between the two sides.

 

 

Fig. 2, breadboard build

 

PERFBOARD LAYOUT

It took three versions to get this laid out on perfboard but I have not verified it yet. The Volume pot can be wired on-board to help you secure the circuit in the pedal build. I'll update this project when I get the build up and going.

 

Fig. 3, perfboard layout and B.O.M.

Guitar: Sound to Light Fuzz

This fuzz started out as as adaptation of a circuit I saw online that used a peizo mic for input to convert sound into light flashes. The schematic looked like it could easily be adapted to a guitar pedal with volume control, jacks, power filtering and polarity protection.

1. You can also use a 1N5817/100uF power filtering combo and will have a lower voltage drop across the 1N5817 in series (1). Be sure to not just sub the 5817 for the 4001 in this schematic, it won't work that way.

2. This fuzz is high gain, so one mod could be to add resistance to ground from Q2. This could roll back some of the harsh distortion with these high gain transistors. 330R-1K could be an option to start and you could also try adding a cap to ground - like at Q2 in the ToneBender - for extra crunch with the resistor in place(2). I am going to try this on a breadboard soon and will report back. 

3. Changing to input cap (C1) to a higher value like 470nF or 1uF will allow for more bass frequencies to come through. C2 and C3 are adjustable as well. 

4. Q1-3 can be almost anything with a higher gain - 2N5088, BC549C, etc. 

5. POT1 can be adjusted to taste, a B500K might roll off some of the treble if the circuit is too "bright" with the A100K (no pun intended).

 

Fig. 1, schematic

STRIPBOARD LAYOUT

This one is fairly simple, but depending on what enclosure you box it up in you may want to wire the LEDs off board. For my build I socketed them so I can just wire them up however I want in the end. 

 

 

Fig. 2, stripboard layout and BOM

 

STRIPBOARD BUILD

 

Fig. 3, stripboard build, unboxed

 

DEMO VID

Fig. 4, demo vid

Bass: GBS Fuzz

This is the GBS, it developed from a chat with JSA Effects (1) about adding some buffering in front of the Bazz Fuss, a simple but powerful-sounding fuzz circuit. I ended up adding a passive Muff-style tone control plus gain recovery stage for some EQ as I had an unused half of an opamp. Fatter coupling caps also make it more appropriate for bass frequencies.

1. The buffer is standard Klon-style (2) but the gain stage uses a BC549C instead of the 2N5088 seen in many Bazz Fuss builds and is biased by the 3.3M R5 resistor. This gives the fuzz more "growl" and saturation to my ear. I borrowed this from a Brazilian company called Epider Sound and their Heavy Metal pedal (3). The addition of the R5 doesn't seem to work with BC549Bs, so make sure you have the right transistor.

2. D1 can be swapped out with other types of diodes for different textures - other silicon (1S1588) or BAT41/46 are good starting points for more open vs compressed gain.

3. Right now, the gain recovery stage is set at 10 dB (470K/47K for the non-inverted second amp). A B500K pot could replace the 470K (R11) if you wanted the option to dial it back. I will definitely try this on the breadboard again, since this fuzz can get really saturated.  

4. The tone control has corner frequencies of 1540 and 800 Hz, but these are easily modified with standard BMP tone stack values (4).   

5. You may want to socket the 47nF cap C12, it's what worked best for a bass fuzz but can be customized for your own tastes. This cap has a big impact on the amount of background hiss.

Fig. 1, GBS Schematic

 

The perfboard layout is pretty straightforward and I managed to get it all together without any jumpers. As of right now, this exact layout is unverified. The one I used for the pedal build needed a few fixes so I worked in changes to clean up the wiring for this layout.

 

Fig. 2, Perf Layout and Mask (Reversed)

 

Here's a few pics of my build, since I used a DPDT switch there is a daughter board with the Millenium 2 bypass for the indicator LED. A 3PDT switch means you don't need this tiny board. 

 

Fig. 3, GBS Build Apr 2023

 

Demo vid:

 

Fig. 4, It's only 1 minute