Silicon Buzzarounds

[jrmy]

OH HELL YES!!!

Wasn't this supposed to be a PM?

Nah, the PM gushes even further!

[Chankgeez]

[jrmy]

Hey man, I'm too old to play coy anymore.

[digi2t]

Here's a little blurb on Buzzicon tuning. There are three trimmers in the unit, and if you wish, you could play with them, to alter the character of the circuit.

You may wish to save/print the info below for future reference.

Buzzicon tuning.

A decent quality digital multi meter (DMM) will be required to view the voltages. Clip the negative (black) probe to any ground point. You'll be using the positive (red) probe to take reading.


Before adjusting any of the trimmers, ensure that the pedal controls are all at their maximum positions, and the "Attack" switch is set to first position, "Bright".

The unit uses a stereo jack switching scheme on the input, so you need to insert a plug into it, or else the unit will not power on. I recommend plugging in your guitar, but SET THE GUITAR VOLUME TO ZERO TO TAKE YOUR VOLTAGE READINGS. You may plug the output into your amplifier. This way, you may make adjustments, and use the guitar to hear the effect of the adjustments. Turning the guitar volume to zero is important to get accurate readings of settings that please you, since any output from the guitar will raise the voltages in the Q3/Q4 area.

Here is a picture of the board, with the transistor and trimmer nomenclature;



The nice thing about the metal can transistors that I spec'd, are that the casings themselves are part of the collector, so simply touching the positive probe of the DMM to the transistor's metal casing, will give you your collector voltage. All the voltages I give below are for collector voltages.

For reference, the original unit demo'd in the HTC video is set to the following voltages;
(Guitar plugged in, guitar volume at zero, all pedal pots at max., Attack set to Bright)
- Power supply voltage = 8.93v (this may vary from power supply to another, and isn't really important.)
- Q1/Q2 collector voltage = 5.20v
- Q3/Q4 collector voltage = 0.75v
If you decide to go back to the original sound, set the unit to the above voltages. THE PROPER PROCEDURE FOR RETURNING THE UNIT TO ORIGINAL TUNING IS OUTLINE IN A SEPERATE SECTION BELOW.

WHAT THE TRIMMERS DO:

T1 sets the voltage for the Q1/Q2 Darlington pair collector voltage. These first stage transistors are basically amplifying the guitar input, overdriving Q4. You can set this anywhere in a 3v to 6v range, and sound-wise, it will vary from cleanly boosting the fuzz, gating, or fizziness. The higher the voltage, the more output, but keep in mind, that too much, or too little voltage will severely affect the sound of the unit.

T2 sets the voltage for Q4, which is responsible for the fuzz. 0.5v to 1.5v collector voltage is a decent range, again, more or less than that will start to really deteriorate the fuzz performance.

T3 is a special trimmer. It controls how much Q3 will affect Q4. Q3 and Q4 are in a "piggyback" arrangement, to try and emulate the characteristics of a single germanium transistor. In short, Q3 is used to reduce the gain of Q4 (the fuzz transistor), trying to copy the leakage character that germanium transistors are known for. It doesn't do it perfectly, but does help give this circuit it's own flavor. PLEASE NOTE THAT T2, AND T3 ARE INTERACTIVE!! Adjusting T3 will move Q4's collector voltage, so before adjusting Q4's collector voltage via T2, it will be important to set T3 to minimum resistance. This will increase Q4's voltage, and take Q3's impact on Q4 out of the equation temporarily. Once you adjust Q4's voltage with T2, you can then readjust T3 to reduce, or "soften" Q4's final output.

So if you wish to make adjustments, the typical procedure would be as follows;
- Adjust T1 to set the first stage output. Turn up the guitar volume if you wish, and tweak the trimmer, playing between adjustments to hear the difference. To record the voltage of Q1 collector, turn the guitar volume to zero, and touch the DMM positive probe to Q1's casing.
- To adjust the fuzz section, we need to first take Q3 out of the equation. Ensure that the guitar volume is at zero. Touch the DMM positive probe to Q4's casing, and at the same time, turn T3 trimmer. Watch to see the voltage increase. If it is decreasing, turn the trimmer in the opposite direction. Turn the trimmer until the voltage stops increasing. From stock form, it should top out at, or close to, 1.00v.
- Now play with T2 to vary the fuzz sound. You can turn up your guitar, play, and tweak the trimmer, until you find a fuzz sound that pleases you. Once your happy with the fuzz, return the guitar volume to zero, and record Q4 collector voltage for future reference.
- Finally, turn up the guitar volume again, and tweak T3 to soften the fuzz if you wish. Remember that you maxed out the trimmer in step 2, so you be going in the opposite direction now. There will be a slow reduction in the fuzz edge, but a slight increase in sustain as a benefit. Past a certain point, the volume will turn down substantially, as excessive "softening" will shut down Q4, so don't go too far. Turn the guitar's volume to zero, and record Q4's collector voltage again, for future reference.

Play with it, and have some fun. You can create a new Buzzicon sound.

If you get lost in the tuning, and wish to return the unit to it's original trim, the steps are;
- Guitar plugged in, volume at zero.
- All pedal controls at maximum, attack on bright.
- DMM probe on Q1 casing adjust T1 trimmer until Q1 collector (transistor casing) voltage reads 5.20v
- DMM probe on Q4 casing, adjust T3 trimmer watching which direction Q4's collector voltage goes. Turn the trimmer in the direction that increases the voltage, and turn the trimmer until the voltage stops increasing.
- Probe still on Q4 casing, adjust T2 trimmer to bring Q4's collector voltage to 1.00v.
- Probe still on Q4 casing, readjust T3 trimmer to bring Q4's collector voltage down to 0.75v (anywhere between 0.7v and 0.82v will be OK).
- Recheck Q1 and Q4 voltages again, to ensure that they are correct. Make any slight adjustments that may be necessary to get them spot on.

By playing with the trimmers, you can set the unit's character all the way from a gating fuzz, fizz fuzz, sparky fuzz, or very mellow, "closer to overdrive" type fuzz. Have fun with it.