Kit Review: The Trill Tremolo Pedal

I was in the market for a two knob Tremolo kit and was about to suggest to MOD kits that they offer one. It was only a few days later that Guitar Kit Builder was asked to try out the brand new Trill Tremolo, so this worked out perfectly for me. In my guitar playing I have always favored the "Dynamic Duo" of a basic single-knob reverb and a two-knob tremolo.

I was already building a reverb kit (a future story here) when The Trill Tremolo arrived, and I'm looking forward to trying them both together when I finish the reverb.

Before I go over the kit building I'm going to toss it over to Jeff from Guitar Kit Builder to cover how the circuit works.

CIRCUIT DESCRIPTION

If you've ever played with the volume knob on your amplifier you know that a tremolo effect can be created by rapidly turning the knob back and forth, causing the volume to rapidly rise and fall. That's what a tremolo pedal does as well, using an oscillator to change the volume up and down at a steady rate.

An oscillator is just a circuit that creates a changing signal of a given frequency, such as a sine wave or a square wave. With that in mind, let's take a look at the schematic (click on the image to see a larger version).

The Trill Tremolo Schematic (Click to Enlarge)

In this design, transistor Q3 is the oscillator. To make a transistor oscillate we need to feed some of it's output signal back to the input, and have the feedback be in phase with the input signal. The Trill circuit uses a series of capacitors (C1, C2, C3) and resistors (R1, R2, R3) to phase shift the output signal. The potentiometer R2 allows the phase shift to be adjusted, which adjusts the frequency of oscillation and therefore the rate of the tremolo.

The oscillating signal is fed from the collector (C) of Q3 through the 10 ufd capacitor and R4 to the base of transistor Q2. This transistor operates as part of a voltage-controlled volume control.

To see this, look at how the signal from the input jack goes through the foot switch, through a .1ufd cap and then into a voltage divider consisting of R5, R6 and R7. The voltage divider is tapped at the junction of R5 and R6, and feeds the output amplifier, transistor Q1. In this arrangement, if R7 is reduced in value, the voltage feeding Q1 will also be lower. This is done by the collector-emitter part of transistor Q2, which is in parallel with R7. As the oscillator Q3 generates its varying voltage signal, it causes the resistance across Q2 to vary, which raises and lowers the signal across the voltage divider feeding Q1. Thus we get the tremolo effect, with the amplifier Q1 making up for the loss in the divider and providing a good output impedance.

OK, back over to Casey for his kit review.

The kit parts (Photo 2) all came in one plastic bag inside the enclosure. The detailed instructions are impeccable, which is as usual from my experience with other kits from this maker. The step by step illustrated instruction pages include several detailed drawings which were very easy to follow and I would rate this as a kit suitable for beginners.

When I inventory the parts (Photo 3) I like to take a minute and test each resistor with a meter, then tape them to the inventory sheet to make assembly faster later on. I did find a misprint on this page - it says that both types of capacitors are valued at 0.1ufd. In fact the fourth item is actually 3 each of 0.22ufd. The dark green caps are 0.1ufd and the gold foil caps are .22ufd (blue circle).

Photo 3 - Parts Inventory and Checking

The first step is installing the hardware (Photo 4).

Photo 4 - Mounting the Hardware Components

Next we run the jumper wires (Photo 5) between the jacks, terminals and posts. It will be about two hours more to finish adding the small components.

Photo 5 - Jumper Wires Installed

With all the small components in place (Photo 6) the building work is done.

Photo 6 - Small Components Soldered In Place

Finally we add the 9 volt battery (it comes with no AC adapter port) and we're ready to test.

Photo 7 - Completed Kit, Ready to Test

After installing the battery and plugging it into my new MOD 102 amplifier I gave it a short test drive and I was indeed impressed. It reminds me, on this amp, of an early Fender Princeton "bias-vary" tremolo. The Trill utilizes three NPN transistors at low voltage so there is no need for the old style opto-devices used in many vintage amplifiers. The controls were useful and predictable and offer a wide range of tremolo voices. It sure seems like a winner to me and lived up to my hopes when I was shopping for a tremolo.

I took it our local School of Rock to shoot a video demo so you can hear it for yourself.