TWIN PEAKS TREMOLO

Build Guide for v2.1

Revision 2.1 David Rolo 2014

The build consists of 2 boards that were designed to fit in a BB enclosure with top mounted open jacks. PCB1 holds the pcb mounted pots and rotary switch. PCB2 holds the main circuit.

The 2 boards are connected together like this:

The pots best suited are Alpha 16mm Right-angle PCB mount Pots:

And one mini rotary 2P4T switch like these:

Of course you can use other parts and not mount them on the PCB. Then you will probably need a bigger enclosure.

They can be ordered in batches from different places like: http://www.befr.ebay.be/itm/300881322642 http://www.aliexpress.com/item/Free-Shipping-20-x-Plastic-Band-Switch-2P4T-Rotary-Switch/996781872.html

Here is a wiring diagram:

Twin Peaks Tremolo Bill of Materials

Reference Quantity Name Description CAPS C14,C15 2 22p Capacitor C4 1 4n7 Capacitor C3 1 6n8 Capacitor C1,C12,C17,C18,C19,C20,C21,C22,C6,C9 10 100n Capacitor C16,C2 2 470n Capacitor C5 1 10u Capacitor Electrolytic C13,C8 2 47u Capacitor Electrolytic C10,C11,C7 3 100u Capacitor Electrolytic

RESISTORS R10,R11,R12 3 33R Resistor R31,R32 2 100R Resistor R20,R21,R22,R23,R24 5 1k Resistor R25 1 3k6 Resistor R17,R18,R19,R26,R27,R28,R29,R30 8 10k Resistor R3,R4,R5,R6 4 15k Resistor R7,R8 2 51k Resistor R13,R14,R15,R16 4 100k Resistor R1,R2,R9 3 1M Resistor POTS P1 1 10k lin Tone P2 1 10k lin Rate P3 1 10k lin Shape P4 1 10k lin Multiplier P5 1 10k lin Depth P6 1 10k lin Symmetry

TRIMPOTS TR3 1 5k Lo Pass TR4 1 5k Hi Pass TR2 1 25k Offset TR1 1 50k Volume

IC's U1 1 TL074 OpAmp U2 1 NE5532 OpAmp U3 1 TAPLFO Microchip

VOLTAGE REGULATORS T1,T2 2 78L05 Fixed Voltage Reg. DIODES/LEDS D1 1 1n4001 Diode LED1,LED2,Bypass LED 3 LED Light Emitting Diode

SWITCHES SW1A,SW1B 1 2P4T Four position Rotary Tap Switch 1 Momentary Switch Normally Off Bypass Switch 1 3PDT

OTHER XTAL 1 20MHz Crystal Oscillator VTL5C1/NSL32 2 VTL5C1/NSL32 Optocoupler

Here are the steps I would recommend to assemble the boards:

1) Populate the boards with all parts, starting with the smallest to the tallest. Solder in the pots and rotary switch last.

Notes: Use sockets for the IC’s, at least for the TAPLFO Depending on the kind of caps you use, you may need to lay down your electrolytics flat on the board to

gain space. I made sure to leave enough space on the board to accommodate the lying caps. R18 is the current limiting resistor for the Tempo indicating LED. The indicated value of 10k is what I am

using with white super-bright LED’s. Choose the value that will be best for your particular LED. I would recommend a super-bright as they will draw less current and reduce the chances of inducing ticking.

C22 is used to smooth out the sharp corners of the LFO signal and remove some spikes that can produce audible clicks especially with sharper edged wave shapes. You might not necessarily need it. It depends on your particular Optocoupler and whether you like the signal to be chopped real hard or not. I suggest socketing that cap, trying without it first and then start with a low value like 20n until you find a value that removes the tick but does not round off the square wave too much.

C3 and C4 define the High Pass and Low pass cut off frequency. If my calculations are right, with the values indicated in this document, the Low pass cuts at 664.3 Hz and the Hi pass at 780.6 Hz. You can of course experiment with other values.

LED1 is there to increase the output of the voltage regulator (5V + the Forward voltage of the LED). Try to find a LED with no more than 2V FWD voltage to make sure the voltage regulator still has enough drop out voltage to operate correctly. Note: the silkscreen shows the flat side the wrong way around. Follow the – and + signs for correct orientation.

C14 – one of the 22p caps next to the Crystal are labeled wrong. On the PCB it shows C16, when it should be C14:

Once soldered, cut the components’ leads as short as possible to minimize the space needed between the

two boards

2) When you have finished populating the boards, solder all needed outboard wires (not the ones connecting the 2

boards together) already in place leaving enough length to connect to their destination later on.

3) Fit the 2 boards back to back with a piece of cardboard or other insulator between them.

Don’t use anything too thick but also not too thin that component leads could poke through and cause a short. There are 3 holes where you can fit screws (M2.5 or M3, preferably plastic) that will secure the boards together with spacers between them.

4) Now connect each opposing hole of the 2 PCB’s together with some wire. I prefer solid core wire but twisted stranded wire will be OK too. Just watch out for loose strands that could cause a short.

5) Now you can fit the boards inside your enclosure and connect the outboard wires to their corresponding points, the bypass and Tap switches, LED’s, jacks etc

Now that you have finished assembling the pedal, you can bias it:

1) Turn the DEPTH pot fully counterclockwise, SYMMETRY and TONE in middle position

2) Set T3 and T4 fully counterclockwise

3) Start by measuring the supply voltage at bias point B1

4) Adjust the Offset trimpot T2 until you get the same voltage (about half of the voltage of B1) on bias points B2 and B3. This action will center the LFO signal (originally 0-5V) around the bias voltage of U2.

5) Now adjust T3 and T4 to have a good balance between bass and treble. As you turn clockwise, the optocoupler

gets more current and the signal gets louder. But increasing the current also increases the chance of getting audible clicks, especially with sharp wave shapes. So it’s best to be conservative and compensate for the volume with T1.

6) Adjust the volume trim pot T1 to have the same level between effect OFF and effect ON (or any level you like).

That’s it! Now trem’ away ;-)

Controls: Rotating from CCW to CW, the rotary switch selects the tremolo modes:

Bass and treble modulated in phase (normal tremolo) Bass and treble modulated out of phase (Harmonic tremolo) Bass modulation only, with fix treble Treble modulation only, with fix bass

Pots:

Tone : adjusts the balance between the bass and treble portions. Turn it fully CCW and only the bass comes out. Turn it fully CW and you get only treble. In the middle you get both. If you turn down the depth completely you can use the tone knob as a sort of EQ

Depth: Allows setting the depth of the modulation

Rate: Sets the speed of the modulation

Symmetry: Allows changing the ratio between the upper and lower wave of the LFO signal For

example, when using the square wave, you can set whether the “off” or the “on” periods are the longest.

This diagram shows the effect of the symmetry pot on some wave shapes:

Source: http://www.electricdruid.net/datasheets/TAPLFO2Datasheet.pdf

Shape: This knob allows selecting one of the 8 available modulation wave shapes:

Source: http://www.electricdruid.net/datasheets/TAPLFO2Datasheet.pdf

Multiplier: allows to select the multiplier that will be applied to the tapped tempo Source: http://www.electricdruid.net/datasheets/TAPLFO2Datasheet.pdf

This is a drill template I have been using but take your own measurements to make sure everything fits (before committing to drilling your box … ;-)