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Forum Home > Layout Gallery - GuitarPCB Build Documents, Mods and Tips > EMEXAR 2

Site Owner
Posts: 8793

Thanks to Bruce R. for an excellent board design, you will have the ability to build any one of (3) classic pedal style designs including a work-alike of the Dist+™, DOD250™, or Micro Amp™. Even a YJM308™ .



Importantly, you will also have the ability to Mod these to your delight, in typical GuitarPCB fashion.



Emexar 2 - Build Document

Latest Build Document Update 7/17/14 at 9:00AM EST

Delete older versions prior to building.


Always check here: The Layout Gallery for any updates or new Mods, before building any project.

New mods will be recorded here, once members and moderators have built some up to see what they have tried and like.

Tone Mods for DIST™ and DOD250™

  • Under the “socket and see” approach try different clipping diode options in the Dist+ or 250 such as Germanium, Silicon and LED. For example, populating D1 and D2 with Germanium and Silicon "in series" will produce a unique tone with more available volume or gain. Try adding a Diode or LED at D3 for Asymmetrical clipping. DPDT Wiring Boards make this a real simple mod, with on-board switch pads.

  • To smooth out the distortion on the Dist+ or 250, you can change the clipping diodes. Use (2 or 3) 1n4148 diodes (substitute an LED in D3 for a bit more crunch).

  • Use a DPDT Switching Board to switch between your favorite clipping choices by connecting common leads to the pads for D1. Leave D2 and D3 unpopulated with this option. This will make it easy to populate diodes in series, as well.

  • For the Dist+ or 250 builds, you can open up the bass response, by changing C4 to 220nF, or use a DPDT Wiring board to switch between stock and a “fat boost” capacitor. If you want to use with bass guitar, try 680n in C4.

Testimonial from Moderator Wilkie1 regarding the MicroAmp style build.

The MicroAmp™ has tremendous gain! I put in a 500mv sine wave and the output went from unity gain up to almost 6V!


The response was the same from 25 Hz to over 3KHz., NO DISTORTION observed anywhere. Totally clean.


Sonically it was totally transparent on guitar. The o’scope looked just fine throughout the freq range of a bass or standard guitar.

A few of the many DPDT Wiring Board options!



Recommended accessories:

1. Barry's Famous Pot Condoms™ .

2. 3PDT Wiring Boards .

3. Barry's Best Pedal Hookup Wire.

4. DPDT Wiring Boards - Perfect for Mods

5. DC Power Jacks 2.1mm

6. Common Anode LED (Optional to Standard LED)

7. Plastic Bezels for Common Anode LEDs

8. Pot Condoms for mounting in tight quarters over potentiometers

9. GPCB Secure Mounts - For mounting with room to spare

June 27, 2014 at 3:56 PM Flag Quote & Reply

Site Owner
Posts: 8793

The build document for the EMEXAR 2 has been updated. 7/17/14

This is the basic info change or update:

• For the MicroAmp™, the resistor at R1 (the original value 22M) this is not a common value, a 10M which will be fine. Also when populating C4 you may use an Electrolytic, or Tantalum Capacitor. The North side, or Top Pad of C4 looking at the board would be the Positive leg. Note: If using a Tantalum for fit, you must orient it correctly, or risk damage!

• For the MicroAmp™, the resistor at R10 is replaced with a diode, 1N4001 (D5 on the schematic).  The diode must be oriented with the cathode side (white band) to the top pad of R10.

• The MicroAmp™ only has a single Level control. If you wish to keep your build true to the original, we suggest using a wired solder lug potentiometer connected to the "Gain" pads so you can center the single knob on your enclosure. If you do this, you will need to solder a fixed 10k resistor between "Volume" pads 1 and 2, and a jumper between pads 2 and 3.

• Below, you will see a section from the schematic, as well as the same section below it, which is slightly modified. In the MicroAmp™, R3 connects from VB to the left side of R2, whereas in the other builds, it connects to the right side of R2. An additional pad named MA has been added to the board to allow for R3 to be connected as in the original MicroAmp™ circuit. At the right of the schematic images, you will see part of the circuit board (some traces have been removed for clarity). All builds use the right pad of R3, and the left side of R3 will connect as shown in this image, depending on which project you are building.


Emexar 2 - Build Document

Finished Custom Emexar Build Thread

July 17, 2014 at 1:03 PM Flag Quote & Reply

Site Owner
Posts: 8793

Make an Ultimate Boost Box!

Here is some sample wiring options courtesy of Trom

November 3, 2016 at 11:16 AM Flag Quote & Reply

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