stutter trem

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STUTTER TREMOLO BUILD INSTRUCTIONS By FF_Pedals 2011 Layout by Culturejam 2011 There are two ways to build this effect. The JFET can be used in series or shunt. The board was designed for series connection (original youtube demo). I tried modding it for a shunt connection and it sounds even better (signal based noise occurs in series mode as signal builds charge on C2). I will give the instructions for the shunt version. I highly recommend you build it like this. It sounds very good. See Appendix for original schematic and bill of materials. In the shunt version you do not need a switch for smooth mode, just a 100kB pot. You will also need a 1M resistor, 2 x 47k and a 330k resistor (compared to original BOM). Follow these instructions carefully. This is a SQUARE WAVE tremolo, make sure you twist all your offboard wiring for best noise performance. How it works: Q4 is the LFO from the EA Tremolo. Q5 is a BJT inverter that creates a square wave. R15, R21 and the “Cycle” pot set the DC bias on the base of Q5 which adjust the threshold voltage of the inverter to vary the duty cycle (off/on time of pulses). Q1 is an amplifier with a pre-gain cut volume pot. You could increase the gain by decreasing R4. You could eliminate the pre-gain volume and put a volume on the output (R23) if you prefer. R5, R6 and C3 set the signal ground and DC bias for the JFET. Q3 is an output buffer. In shunt mode the JFET dumps the signal between C2 and C4 to the signal

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Page 1: Stutter Trem

STUTTER TREMOLO BUILD

INSTRUCTIONS

By FF_Pedals 2011

Layout by Culturejam 2011

There are two ways to build this effect. The JFET can be

used in series or shunt. The board was designed for series

connection (original youtube demo). I tried modding it for a

shunt connection and it sounds even better (signal based

noise occurs in series mode as signal builds charge on C2). I

will give the instructions for the shunt version. I highly

recommend you build it like this. It sounds very good. See

Appendix for original schematic and bill of materials. In the

shunt version you do not need a switch for smooth mode,

just a 100kB pot. You will also need a 1M resistor, 2 x 47k

and a 330k resistor (compared to original BOM). Follow

these instructions carefully. This is a SQUARE WAVE

tremolo, make sure you twist all your offboard wiring for

best noise performance.

How it works:

Q4 is the LFO from the EA Tremolo. Q5 is a BJT inverter that

creates a square wave. R15, R21 and the “Cycle” pot set the

DC bias on the base of Q5 which adjust the threshold voltage

of the inverter to vary the duty cycle (off/on time of pulses).

Q1 is an amplifier with a pre-gain cut volume pot. You could

increase the gain by decreasing R4. You could eliminate the

pre-gain volume and put a volume on the output (R23) if

you prefer. R5, R6 and C3 set the signal ground and DC bias

for the JFET. Q3 is an output buffer. In shunt mode the

JFET dumps the signal between C2 and C4 to the signal

Page 2: Stutter Trem

ground (4.5V DC) through the low impedance path to

ground of C3. When the depth pot is cranked (0 ohms) it is

in full stutter mode. Increasing the resistance between the

JFET source and the signal ground increases the “off”

volume and gives a smoother more normal sounding trem,

even though it is hard switching between two volumes. By

adjusting the duty cycle in smooth mode some great trem

sounds can be made. Compared to series mode, in shunt

mode there is a little signal bleed through during the “off”

cycle which is combated by adding in the 100k resistor in

series with C2.

SHUNT Schematic:

Page 3: Stutter Trem

There are MANY ways to mod this effect. These values are

just my suggestions to get you going. Experiment and have

fun.

Parts list:

C1 100n

C2 100n

C3 100u

C4 10n

C5 39n

C6 100n

C7 100u

C8 100u

C9 1u

C10 1u

C11 1u

C12 10u

CYCLE 1M B (linear)

D1 1N914 or 1N4148

D2 4001 or other 1N400x

D3 LED Standard red diffused

Q1 2N3904

Q2 J201

Q3 2N3904

Q4 2N5088

Page 4: Stutter Trem

Q5 2N3904

R1 1M

R2 470K

R3 10K

R4 2K7

R5 47k

R6 47k

R7 1M

R8 100k B Depth pot

R9 1M

R10 1M

R11 1M

R12 10K

R13 100R

R14 10K

R15 1M

R16 10K

R17 2M2

R18 100K

R19 1K

R20 15K

R21 330K

R23 1M

RATE 100K C Rev. log

VOL 500K A log

Page 5: Stutter Trem

Shunt Build Instructions (highly suggested)

1. Locate the trace from the bottom of C4 to the source

(middle pin) of the JFET. Cut it with a utility blade

right under R11 so it’s hidden. Should be very easy.

Check with multimeter to make sure you have broken

the connection:

2. Install all of the resistors and diodes EXCEPT R8 and

R22. Put a 100k resistor standing up where the switch

SW1 was supposed to go. (ignore my 330k resistor

standing up, I had to use a 1/2W...)

Page 6: Stutter Trem

3. Install C2 from the top hole of C2 to the left hole where

R22 was supposed to go. Make sure the lead does not

short against the bottom hole of C2. Steps 2 and 3 let us

install that 100k resistor between C2 and the JFET

drain...

4. Install C4 but DO NOT CLIP THE LOWER LEAD. Bend

the lower lead of C4 towards the drain of the JFET (top

hole) do not solder it to anything yet.

Page 7: Stutter Trem

5. Install the rest of the caps.

6. Put the JFET in and wrap that lower lead of C4 around

the drain before soldering.

Page 8: Stutter Trem

7. Solder in the transistors or transistor sockets,

whatever you feel comfortable with.

8. Wire the pots, they are all variable resistors and you

can just use lugs 2 and 3 if you want, they are all the

same configuration. The depth pot goes where R8 was.

Twist the wires and put them in where R8 was

supposed to go, the order does not matter. Wire the

volume, and rate to the appropriate holes (Volume 2

and 3, Rate 2 and 3...). In shunt mode the duty cycle

works backwards so you have to connect lug 3 where

lug 1 was supposed to go.

9. Install the LED on the board.

10. Do your offboard wiring, available online

elsewhere. For a bypass indicator, solder a current

limiting resistor and length of wire to the longer leg of

an LED and heat-shrink it. Solder a length of lead to the

shorter end of the LED and heat-shrink. Connect the

side with the resistor to the 9V lug of the DC jack

(center lug) and the other lead goes to the 3PDT (see

offboard wiring diagrams online).

Page 9: Stutter Trem

Here’s how I drilled and built my Stutter Trem:

Appendix

Original schematic. JFET is used in series. Small signal based

charge builds on C2 and gives a little bit of ticking. Not

always noticeable but annoying when it happens.

Page 10: Stutter Trem

Original Bill Of Materials:

-Enclosure

-3PDT stomp switch

-SPST toggle (Smooth mode)

-DC Jack

-9V Battery clip

-9V Battery

-1 1/4" Stereo Jack

-1 1/4" Mono Jack

-1 Red diffused LED (Rate indicator)

-1 LED of your choice with appropriate resistor (Bypass indicator)

-1 1N914 or 1N4148 Diode

-1 1N4001 or equivalent 1N400x series Diode

-2 1M B Linear Potentiometer (one for optional smooth depth control)

-1 500k A Log Potentiometer

-1 100k C Reverse Log Potentiometer (50k C optional faster speed)

-1 2N5088 BJT Transistor

-3 2N3904 BJT Transistor

-1 J201 JFET Transistor

Page 11: Stutter Trem

RESISTORS:

-1 100ohm

-1 1kohm

-1 2.7kohm

-1 4.7kohm (optional faster speed mod)

-4 10kohm

-1 15kohm

-3 100kohm

-3 470kohm

-6 1Mohm

-3 2.2Mohm (2 of these were changed to 47kohms R5 and R6)

CAPACITORS:

-1 0.039uF (0.033uF could be substituted)

-1 0.01uF

-3 0.1uF

-3 1uF 16V Electrolytic Radial

-1 10uF 16V Electrolytic Radial

-3 100uF 16V Electrolytic Radial