Project · Boosters & Volume
Alembic™ Stratoblaster™ Booster
The J1 is a replica of the Alembic™ Stratoblaster™, the single-JFET boost from 1970s Alembic™ guitars that pushes a tube amp or drive pedal into warm overdrive without colouring your tone. At $31 for the complete kit and about a dozen parts, it is the easiest pedal we sell and our usual recommendation for a first build; layouts for a stompbox and for mounting inside a guitar are both below.
This is a nice little booster that can fit inside your guitar or can be mounted in a small stompbox. It is a classic Booster that provides that excellent single stage JFET sound. It drives a tube amp or distortion stompbox into awesome overdrive sounds! Any trademarks mentioned here belong to their owners and not to General Guitar Gadgets.
The story
About the circuit
Alembic™, the Northern California company that built instruments and electronics for the Grateful Dead, sold the Stratoblaster™ in the 1970s as an onboard preamp: a single JFET gain stage, small enough to fit inside a Stratocaster™, with a switch for the amount of boost. It adds no colour of its own. What it does is hit the front of a tube amp, or the next pedal, harder, so a clean amp starts to break up and a drive pedal gets thicker. A JFET stage behaves a lot like a tube stage, which is why this tiny circuit sounds warmer than its parts count suggests.
This project at GGG
JD posted the Stratoblaster™ in February 2002, and it was one of the very first projects to have a ready-to-solder board for sale on the same day it went up. With about a dozen parts it is the easiest build we sell, and the one we recommend when someone asks what to build first; the kit is $31, and the page has layouts both for a stompbox and for mounting the board inside a guitar, the way Alembic™ intended. A lot of first pedals built from this site were Stratoblasters, and a lot of those builders went on to a Fuzz Face™ or a Tube Screamer™ next.
Project files
Everything you need to build it
Alembic™ Stratoblaster™ Booster Ready-For-Transfer Printed Circuit Board Layout - For use only if you are a complete DIY person who wants to etch and drill your own PCB. Otherwise, we recommend you ignore this PCB mask and buy the Ready-to-Solder Printed Circuit Board or Complete Kit.
Schematic
Schematic
Parts layout
Parts Layout / Wiring Diagram
What you will need
Bill of Materials
Version 2010June13 · Copyright 2007 JD Sleep · Permission refused for posting/serving this file from any site other than www.generalguitargadgets.com · Trademarks are property of their owners
Resistors
| Resistor ID | Value | 3-band Marking | 4-band Marking |
|---|---|---|---|
| R1 | 100 ohm | ||
| (GGG Value) | brown-black-brown | brown-black-black-black | |
| R1 | 68k | ||
| (Original Value) | blue-gray-orange | blue-gray-black-red | |
| R2 | 22k | red-red-orange | red-red-black-red |
| R3 | 12k | brown-red-orange | brown-red-black-red |
| R4 | Boost Volume Potentiometer (50k C) | ||
| R5 | 100k | brown-black-yellow | brown-black-black-orange |
| R6 (Optional) | 1M5 | brown-green-green | brown-green-black-yellow |
| R11 | 1k | brown-black-red | brown-black-black-brown |
Potentiometers
| Part ID | Value | Type |
|---|---|---|
| R4 - Volume Control | 50k | Reverse Log Taper |
Capacitors
| Capacitor ID | Value | Type | Possible Marking |
|---|---|---|---|
| C1 | 10µF | Tantalum | 10µF or 106 |
| C2 | 1.5µF | Tantalum | 1.5µF or 155 |
| C3 | 100µF | Aluminum Electrolytic | 100µF |
Other
| Part ID | Part Name |
|---|---|
| Q1 | 2N5457, J201 or other FET |
| J1 | Stereo quarter-inch jack |
| J2 | Mono quarter-inch jack |
| J3 | DC Jack |
| B1 | 9 volt battery (not included in the Kit) |
| Sw1 | Heavy Duty 3PDT footswitch 9v battery snap, Printed Circuit Board, 24 gauge stranded wire, Enclosure, knobs |
How to build it
Instructions
Version 2014January03 · Copyright 2013 JD Sleep · Permission refused for posting/serving this file from any site other than www.generalguitargadgets.com · Trademarks are property of their owners
This is the SBB booster kit. It is a replica of the AlembicTM StratoblasterTM. This booster is an easy-to-build project that will produce a good clean boost and "fatness" to your guitar signal. The booster has many applications, including driving the tube preamp in your amplifier into nice distortion, driving other effects into new sonic territory or simply bringing up the volume of an effects loop when needed for lead guitar solos. The circuit is a single transistor stage that will give the signal some amplification. Clean and transparent for the most part. Use the project documents provided, starting with the General Build Instructions. Note that all the capacitors, including the tantalum caps C1 and C2 are polarized and need to be installed with the correct polarity. The long lead of the capacitors go in the square holes. The kit includes the parts to build it with the original values and also the parts for the updated version.
Here's an inside view of the unit we built to give you a real view of our construction.
Here is a chart of voltages taken at the transistor pins. Use these voltages as a guideline. You may not get the exact readings listed, but should be somewhere in this general range.
Component
Location
9 volt power supply Q1
Voltage
9v
Drain
6.9v
Source
1.0v
Gate
0v
Questions
Frequently asked questions
Is this a good first project?
Yes, the best one we have: one transistor, one pot, a dozen parts, and an hour's work. Every later kit uses the same skills.
Can I fit it inside my guitar?
Yes. The guitar-mount layout fits a Strat™ control cavity with a 9 V battery; the boost pot can replace a tone control.
How much boost?
Up to about 20 dB of clean gain, set by the Boost Volume pot. It sounds transparent until the amp or next pedal starts to break up.
Which transistor?
The kit includes a 2N5457; a J201 or similar JFET also works and changes the gain slightly.
More about this project
Notes, sounds and related links
YouTube Video of the Stratoblaster™ Replica Kit
Ready to build? We have the kit.
Buy a Alembic™ Stratoblaster™ Booster Replica Complete Kit. Includes all the parts and materials you need to build one, all for about the price you would pay for a PCB and parts.
Would you like a Ready to Solder Circuit Board for this project? Note: If you buy the kit, the Ready-to-Solder Printed Circuit Board (RTS PCB) is included in the kit. You do not need to purchase this Ready to Solder Circuit Printed Board if you buy the kit.