Relay Bypass Module Kit Installation Guide (Rev. 1.0)

General Description

The Relay Bypass Module Kit (RBM) is a clever circuit that enables you to have real true bypass switching in virtually any effect pedal! The RBM can be incorporated into new pedal designs or retrofitted into existing pedals that might not have true bypass switching. A lot of thought went into the design of this module and to make sure the switching operation is reliable and noiseless. On top of normal ON / OFF switching capability, there’s also a user programmable momentary mode which allows the use to insert the effect into the signal chain only while pressing down on the footswitch, upon release the effect is bypassed.

Difference Between This Kit And Pre-assembled RBM Modules

The most obvious difference between the products is that this is a kit! You get all the parts in through hole form and you need to assembled them on your own. Some experience in soldering is required. The benefit for you, as a customer, is that you get the lowest cost relay bypass module available on the market. Another difference that is worth mentioning is the program running on the micro-controller. The kit has a user programmable option for normal ON / OFF  operation and a momentary mode as mentioned earlier on this page. The default power on for the kit is always bypass mode. If this is something you would like to alter, you need to get one of our pre-assembled modules as they have user programmable power on default (you can see the complete description of these modules by clicking the appropriate link on the right sidebar).

Tools For Assembly

Assembly of the kit is simple if you have the right tools. It would be a good idea to go through the list and make sure you have all the tools and supplies.

  1. The RBM Kit (obviously)
  2. Soldering Iron (low wattage is perfect)
  3. Some solder
  4. Small Wire Cutter

RBM Kit Assembly

Before you start with the actual assembly. It’s quite obvious, but you should only try assembling the kit if you have some previous experience in soldering. If you don’t you might injure yourself by accident or perhaps burn some of the components in the kit rendering it useless. So onwards… Remove the components from the plastic bag and lay them out in front of you. It should look similar to what is shown in the picture below.

RBM Kit Content

RBM Kit Content

You should be able to identify the following components (from top right in clockwise direction):

  • RBM PCB
  • 0.33uF Electrolytic Capacitor (black cylinder)
  • 0.1uF Ceramic Capacitor (marked with “104″)
  • 0.01uF Ceramic Capacitor (marked with “103″)
  • 10k Resistor (5 band marking: brown – black – black – red – brown)
  • 1M Resistor (4 band marking: brown – black – green – gold)
  • Schottky Diode (marked with “4V3″)
  • Small Signal Diode (marked with “1N914″)
  • 5V Regulator (marked with “L78L05″)
  • MOSFET (marked with “2N7000″)
  • Relay (marked with “HFD31/5-L1″)
  • Pre-programmed MCU (marked with “ATTiny13A”)

Take the 1M resistor and insert it in C3 as shown below.

1M Resistor Inserted in C3

1M Resistor Inserted in C3

Bend the resistor’s leads on the bottom of the PCB and solder it in place, afterwards snip off the leads using the wire cutter.

1M Resistor With Ledas Bend And Soldered

1M Resistor With Ledas Bend And Soldered

Take the 0.01uF capacitor (marked with “103″) and insert its leads near the resistor’s leads as shown in the picture below. After that solder the capacitor and resistor leads together as shown.

1M Resistor and 0.01uF Capacitor

1M Resistor and 0.01uF Capacitor

After the leads are soldered together you can bend the capacitor upwards so it will be positioned closely together with the resistor and take up little room.

1M Resistor And 0.01uF Capacitor Bent Upwards

1M Resistor And 0.01uF Capacitor Bent Upwards

Next, insert the 10k resistor to R1 as shown below. After insertion you should bend its leads on the underside of the PCB, solder them and cut off the excess.

10k Resistor in R1

10k Resistor in R1

For the following step you should be careful. The diodes are similar looking so you need to recognize the marking on at least one of them to be able to tell the two apart. Look for the Schottky Diode with the marking “4V3″ on it. The writing is small, but I can read it without my glasses so you should be able to do the same :) After you’ve recognized the diode, insert it in the D2 position. Take extra care to make sure the black ring on the diode’s body is next to the hole with the ring marking. This is the Cathode, if you insert the diode the wrong way the circuit won’t blow up, but it won’t work.

The Schottky Diode Inserted In D2, The Bottom With The Black Ring Marker Is Flush With The PCB

The Schottky Diode Inserted In D2, The Bottom With The Black Ring Marker Is Flush With The PCB

Now it’s time for the other diode that is marked with with “1N914″. The directional feature is the same, you should insert the Cathode side of the diode into the hole with the ring marker in the D1 position in the PCB as shown below.

Small Signal Diode In The D1 Position

Small Signal Diode In The D1 Position

Next, grab the 0.1uF capacitor and insert it into the C2 position.

0.1uF Capacitor In C2 Position

0.1uF Capacitor In C2 Position

Now it’s time to insert the voltage regulator. The MOSFET comes in a similar package (TO-92) so make sure you can read the writing “L78L05″ otherwise you are inserting a wrong component! Finding the right orientation is easy as you need to follow the outline drawing on the PCB. Insert the regulator into the Q1 position. While you are at it, take the other device in similar package and insert it into the Q2 position. Please note: because of a last minute component change the pinout of this device is different than the original one that was supposed to be used so you need to insert it revered! You can see the outline on the PCB, don’t follow it – insert the device the other way around as shown below.

Regulator in Q1 And MOSFET In Q2 (Reversed)

Regulator in Q1 And MOSFET In Q2 (Reversed)

We’re almost done now… Take the relay and insert it in position K1 according to the directional line marker. It should be coincide with the line marking on the PCB.

Relay In K1, Note The Direction

Relay In K1, Note The Direction

Out last capacitor in next, insert the radial packaged device into the C1 position. Please take care to make sure you install it in the correct polarity. The long lead goes into the hole with the small cross marking next to it. Another marking is the white strip on the side the capacitor without should be found on the same side as the white marking in the capacitor’s footprint.

Capacitor In C1 Position

Capacitor In C1 Position

The last component you need to install is the MCU with the code that runs this board. Please observe the package, as shown in the picture below. You can spot a dot indicator in the plastic package. This should be on top of the dot marker on the PCB.

MCU Placed Next To PCB To Show Dot Markers

MCU Placed Next To PCB To Show Dot Markers

Insert the MCU into position U1 and solder all the leads. You are done assembling the board! If you followed all the steps you should have a board that looks like in the pictures below.

Completed RBM Kit PCB

Completed RBM Kit PCB

 

Programming Mode

The module has two operation modes. “Normal” is defined as the mode that is press “ON”, press “OFF” which is a direct replacement for a mechanical switch. In addition, there’s a “Momentary” mode which keeps the effect bypassed while the footswitch is not pressed and in active while held down. The user can enter programming mode by holding down the footswitch while connecting power to the module. After releasing the footswitch, any additional press will alter between the two operation modes. The LED indicates which mode is selected. LED = ON means Normal mode is selected and LED = OFF means Momentary mode is selected. To complete the selection the power should be removed from the unit. When the power is powered back up the chosen mode will be initiated automatically.

Module Connections

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Pre-Programmed RBM Micro-controllers

I’m now offering my code for integration into your product. This is the same code that is the heart of my RBM system. This means you only buy a pre-programmed micro-controller (DIP or SMD package) and get all the documentation needed to integrate it into your design. Needless to say, I’m always an email away for any tech. questions you might have.

Code revisions that are done to my RBM modules are also effective here, so if you want to know about the latest features please click on the latest RBM instillation guide on the side bar.

Schematic & Circuit Explanation

In the next few paragraphs I’ll explain the circuit that I’m suggesting as a standard application for my pre-programmed RBM micro-controllers. If you find this boring or unnecessary you can simply download the schematic and bill of materials. If there are remaining questions after reading the text below, please use the contact form on the right toolbar.

schematic

Schematic Of A Suggested Bypass Circuit Using an RBM Pre-Programmed MCU

The heart of the system is the micro-controller (U2). The maximum recommended supply voltage is 5V and I strongly recommend sticking to this recommendation. U2 is bypassed by two capacitors: C4 & C5, these are not mandatory however I do use them in my own circuits. If you want to keep your part count to a minimum you can leave these out. Pin 1 is connected to 5V using a 10k resistor, this is very important because if this pin is left floating a random reset might happen,

D4 is the indication LED. You can use most types of LEDs here and limit their current using Rled resistor (calculate using Ohm’s law, pin output is 5V when active, 0V otherwise). Please use LEDs with a maximum current draw of 20mA, higher than that might cause damage for the micro-controller.

S1 is a momentary “soft” foot-switch, you can hook a capacitor (C6) in parallel with it for improved noise immunity, however the algorithm in the micro-controlled should allow you to work with even the worst quality switches with no problem. So C6 can be omitted if you’re after a low part count.

The relay (K1) connections are showing in the schematic, input is the guitar dry input, output is the output from the apparatus to the amplifier or next guitar effect, send is hooked up to the effect’s input and return is the effect’s output. D2 & D3 are 5.1V Zener diodes which prevent back EMF pulses from the coil in the relay. The fact is that energizing time for the coil is kept so short that the coil is far from being fully charged so no back EMF is noticeable (and I have checked this with several relay models). These diodes can be omitted if you don’t think back EMF from the coil will be noticeable.

Q1, C3 & D1 are used as a muting circuit while switching the relay. It is important to use the recommended parts and values, otherwise performance might be compromised.

Off course you’ll need 5V supply to feed the circuit. The classic 7805 is a good standard choice, however better solutions exist. See Bill of materials for more options.

Layout Considerations

There are a few rules that I suggest you follow when laying out this circuit as part of your board. In general analog and digital ground separation is a good practice, although I’ve designed many audio freq. circuits not using this practice and everything worked fine. The idea is to hook up the ground of the MCU at a SINGLE POINT to the ground of your circuit, this point could be the ground of the output jack for example. This prevents “dirty” current from the digital side to interfere with your analog circuit.

Another idea would be to keep the MCU and other related components close to an edge of the board, this is done to prevent possible interaction between the circuits.

If you decide to use bypass capacitors on the MCU, keep them as close to the power pins as possible. At distances of even a few mm they become less effective.

Now this is an important one: do not run signals or ground under the relay. The coil might couple noise into your signal if you do! Keep in mind that the relays are housed in plastic cases and these do nothing to protect your circuit from interference from the coil which discharged and can introduce noise while doing so.

Last bit, if you decided to use protection Zener diodes on the relay coil leads, make sure they are physically close to the relay. These parts can actually be mounted under the relay on the other side of the PCB if you happen to use SMD components.

NEXT TO COME – BOM with suggestions for both TH and SMD components!

Power Consumption

The latest revision of my code was all about reducing power consumption. I hooked up the RBM micro-controller without an LED to a 5V bench power supply through a Fluke 8600A and got these results:

RBM2 current active

That’s 161.24 micro-amps in active mode.

RBM2 current bypass

And that’s 100.89 micro-amps in bypass mode.

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Relay Bypass Module (RBM) Installation Guide (Rev. 2.0)

Version 2.0 of the monomonster RBM module

General Description

The Relay Bypass Module (RBM) is a clever circuit that enables you to have real true bypass switching in virtually any effect pedal! The RBM can be incorporated into new pedal designs or retrofitted into existing pedals that might not have true bypass switching. A lot of thought went into the design of this module and to make sure the switching operation is reliable and noiseless.

Module Connections

All the electrical connections required for a successful installation are located on the top of the PCB. Let’s review the required connections (left to right):

  • Out – connection to the output jack
  • Return – to the output signal of the effect circuit
  • F & F – these connect to a momentary, normally open, switch
  • Voltage – positive supply voltage, like your battery for example
  • Ground – a good ground connection would be the output jack
  • LED – LED output, 5V when active 20mA abs. max.
  • Send – to the input of the effect circuit
  • In – input jack (dry signal)

Programming Mode

When your module is powered up (gets connected to a power source) it will go into factory default which is bypass, however you might want to change the default so the pedal will by on (active) immediately after power is applied. To change the current default you need to remove the power from the unit and hold down the bypass switch while you apply the power. After the power is applied, release the bypass button to active programming mode. Each additional push of the bypass button toggles the LED (and does not change the relay position). You can toggle between the two options with LED on meaning the power-up default will be active pedal and LED off meaning the power-up default will be bypass. After you selected the state you’re interested in, remove the power from the pedal, wait 5 seconds, and re-apply the power. You pedal will power-up to an operating mode according to what you have just selected.

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Smart Bypass Box – Retired

PLEASE NOTE – I’m glad to announce that I sold out my 2nd lot (30 pcs). Thank you for everyone who supported me and bought one. As of now the product is discontinued. If you are interested in custom solution based on my RBM system please get in touch with me.

The monomonster Bypass Box is the 1st pedal I’m starting to produce as standard. This is an advanced version of the external bypass boxes which are available from several manufacturers. My original intention was to offer much more functionality than just an ON/OFF box because many times I know I needed more than just that!

The Bypass Box is based around my popular RBM module, it also uses a high quality mechanical relay for true bypass switching as well as the ‘pop’ preventing circuitry from the RBM modules. The Bypass Box has 4 1/4″ mono jacks: input, output, send & return. The effect (or effects) to be bypassed is inserted between the send & return jacks with ‘send’ plugged into the effect’s input. Since real estate on your board is scarce and there aren’t any knobs on the device it made sense housing it in a small box that can be easily fitted almost anywhere on a pedal-board.

The Bypass Box has 3 operation modes:

  1. Click On / Click bypass – Standard bypass
  2. Normally On / Press & hold foot-switch for bypass
  3. Normally Bypassed / Press & hold foot-switch for On

The user  toggles between the above modes using a small button located on the side of the pedal. The dual color LED provides clear indication of the selected mode:

  1. LED on while active / LED off while bypassed in standard mode
  2. LED red while active / LED blue while bypassd in momentary modes

The user’s selection is stored in memory so the Bypass Box remembers in what mode you use it even if you unplug it from the power supply.

Extra Extra: It’s worth mentioning that if you select one of the momentary modes and connect no pedal in the loop you can use the Bypass Box as a kill switch or a reversed kill switch with no clicks – pretty cool!

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Texas Shuffle Overdrive / Distortion – Now Shipping



The Texas Shuffle is my take on the classic green-box overdrive pedal (you know the one…). The idea was simple: I wanted to make a limited edition yet affordable overdrive pedal that incorporates the mods I personally like which are, in part, different from what everyone else is doing. Setting up production for such a pedal is expensive and would end up being a $300+ pedal for such a small quantity and that’s not what I wanted.

Luckily, I’ve found a Chinese factory who makes very nice quality clones for a good price. Their product seemed like a good starting point to achieve what I want, so I bought 50+ pedals (a few for prototyping) with the intention of transforming them into something really really good. IMHO, the end result can be compared against any boutique pedal that costs double, triple or more.

Although this pedal is what you would call a ‘clone’ it’s actually about 30% different from the original circuit, and I’m not referring to just components of different values but rather to the tone stack which is entirely different and implements a different approach than the original circuit. For this I had to create a small PCB which sits on top of the original PCB and taps into it at strategic points. The end result is a pedal that can deliver classic screamer sounds with the gain turned very low (almost to a minimum) and beefy heavy distortion sounds on the rest of knob range. It also responds very well to the guitar’s volume knob.

So what’s going on in there you ask? I start with a stock screamer type pedal and apply the following alterations:

  • Remove all the tantalum caps and replace them with film caps
  • Replace a few resistor and capacitors for different values
  • Install higher voltage electrolytic caps so the pedal can run on 15V
  • Replace the input & output buffer transistors to low noise type devices
  • Replace the stock clipping diodes with non-identical LEDs
  • Disconnect the original tone-stack and hook-up my piggy-back PCB
  • Apply a sticker with some crazy monster graphics for your pleasure :)

Tone stack board mounted on top of the main board, it will be covered in a protective coat after testing

If you would like to buy one, use the link below. The price includes international shipping using insured registered airmail service (around 10 to 14 days delivery to most locations). I’ll guarantee these pedals to be free of manufacturing defects for a period of one year.

Buy Now Button with Credit Cards

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Relay Bypass Module (RBM) Installation Guide (Rev. 1.1)

Version 1.1 of the monomonster RBM module

General Description

The Relay Bypass Module (RBM) is a clever circuit that enables you to have real true bypass switching in virtually any effect pedal! The RBM can be incorporated into new pedal designs or retrofitted into existing pedals that might not have true bypass switching. A lot of thought went into the design of this module and to make sure the switching operation is reliable and noiseless.

Module Connections

When viewing from above (relay side), you’ll notice a total of 11 labeled wire connection pads. You can solder the lead wires to these pads directly or use the provided pin headers instead. Follow the connections listed in the table below, for a larger image click anywhere on the table.

RBM connections

Schematic

Here’s a generic schematic of an effect unit which is bypassed using the RBM. Notice the labels on the two “switches”, these are the same labels you’ll see on the RBM’s top side.

True Bypass with Grounded Input

Programming Mode

When your module is powered up (gets connected to a power source) it will go into factory default which is bypass, however you might want to change the default so the pedal will by on (active) immediately after power is applied. To change the current default you need to remove the power from the unit and hold down the bypass switch while you apply the power. After the power is applied, release the bypass button to active programming mode. Each additional push of the bypass button toggles the LED (and does not change the relay position). You can toggle between the two options with LED on meaning the power-up default will be active pedal and LED off meaning the power-up default will be bypass. After you selected the state you’re interested in, remove the power from the pedal, wait 5 seconds, and re-apply the power. You pedal will power-up to an operating mode according to what you have just selected.

The power-up default can be changed an unlimited number of times and the state you have set is stored indefinitely, or until you change it again.

Changes From Previous Revision

While all the connections to the pedal are exactly the same as the previous revision, the module had undergone changed both is software and hardware. These changes are the result of feedback from customers, I always welcome feedback and encourage it because it helps me build a better product for you!

Hardware-wise, I have changed the regulator to a better model which allows the module to consume a lot less current than the previous revision. Active mode is about 0.8mA and bypass mode is about 0.45mA (no LED). Just to put things in perspective, the previous revision draws about 4mA in active mode. Although this is a more expensive component, I did not change the price of the unit.

Software-wise, programming mode was added. This uses the EEPROM (electronically erasable read only memory) on board of the micro-controller to store a personal default power-on state which is saved indefinitely or until you change it again. Off course, even when you remove power from the unit.

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Relay Bypass Module (RBM) Installation Guide (Rev. 1.0)

Version 1 of the RBM module (newer version available)

Before we dive into all the technical stuff, I would like to thank you for choosing the RBM. Your support is highly appreciated

General Description

The Relay Bypass Module (RBM) is a clever circuit that enables you to have real true bypass switching in virtually any effect pedal! The RBM can be incorporated into new pedal designs or retrofitted into existing pedals that might not have true bypass switching. A lot of thought went into the design of this module and to make sure the switching operation is reliable and noiseless.

Module Connections

When viewing from above (relay side), you’ll notice a total of 11 labeled wire connection pads. You can solder the lead wires to these pads directly or use the provided pin headers instead. Follow the connections listed in the table below, for a larger image click anywhere on the table.

RBM connections

Schematic

Here’s a generic schematic of an effect unit which is bypassed using the RBM. Notice the labels on the two “switches”, these are the same labels you’ll see on the RBM’s top side.

True Bypass with Grounded Input

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