Blues junior modifications


the super switch

    Take control of the FAT circuit from anywhere on stage or the studio with clear visual feedback of what the FAT circuit is up to with B5 Amps FAT Pill. 

    One of the main complaints from Blues Junior owners is the lack of visual status for the FAT circuit.  I thought it was pretty lame the FAT circuit is engaged by a small flimsy plastic button.  However, it can also be engaged via a foot switch, but the foot switches Fender makes are a poor crop at best.  Even worse, they provide no visual indication of what state the FAT circuit is in.  So after a few design concepts I was kicking around, the “FAT PILL” was born.  I built a few of these for Blues Junior owners and they seem to really love them!  Now, I seem to build a lot of them. 

    The FAT PILL’s small footprint can fit into the most densely crowded of pedal boards.  It sports a small rugged enclosure, a bright blue LED that can be seen in any environment and can interface with the amplifier with any standard guitar cable.  Best of all... it does NOT require batteries to operate!  It integrates with the Blues Junior perfectly.  You just plug and play and engage the FAT circuit to your tone’s content, fully knowing what state the FAT circuit is in via the bright blue LED.  You never have to worry about having enough battery life to get you through your gig.

    Granted it cost a little more, but compared to what Fender is charging for a flimsy foot switch with no visual indication and requires NO batteries to operate, its money well spent!  Please e-mail: to have a FAT PILL custom built for your Blues Junior.  Some people like having more mass under their foot, so a FAT PILL circuit can be built into a bigger enclosure if desired. Check out the Price List for pricing.

the easy bias module

  More and more guitarist are really starting to take notice how their tube amp are biased.  It’s yet another variable that plays a big part in one’s tone.  If you own a Blues Junior... you definitely should take notice!  Why?  For reasons nobody can explain, Fender decided to bias the Blues Junior way too hot, pushing the envelope of the max plate dissipation of the EL-84 power tubes.  An additional kick in the teeth to the Blues Junior owner is this “hot” bias scheme is not adjustable.  It’s essentially fixed by a resistor network, leaving the Blues Junior to run in what I like to call “Chernobyl mode.”  Like the ill-fated reactor in the Ukraine, the power tubes run too hot, significantly reducing tube life and performance.  Not to mention the unwanted BTUs causing the amp to run thermally hotter to further degrade the components inside the chassis.  Electronic’s mortal enemy is heat and the stock Blues Junior generates plenty of it!  Regardless of where you might like your bias set for, the stock approach is “shut up and love it.”

  There are a two modifications out there to remedy this problem.  However, they are at both extremes.  One involves drilling holes into the amp’s rather frail Printed Circuit Board (PCB) to make way for a potentiometer.  Which certainly works, but some people don’t feel comfortable drilling into the fragile PCB.  Additionally,  if one is not cognizant of the adjusted value of the potentiometer there could be little or no bias voltage and then the power tubes start to “red plate” and once again you presented with a Chernobyl problem.  Not good!  The other is pretty much a waste of time.  It involves replacing the fixed resistors with fixed resistors of different values.  Yes, it does cool the bias for the power tubes, but it’s still fixed.  Meaning, there is no way to adjust the bias as the the tubes start to wear.  Personally, I would rather have the capability of adjusting the bias via a potentiometer to get the most out of the power tubes and having better control of the power tube’s bias circuit than the fixed resistor scheme.  Drilling is a hassle and difficult on the Blues Junior PCB and just replacing resistors is almost counterproductive.


  Take control of the Blues Junior’s Reverb and FAT circuit from anywhere on stage or the studio with clear visual feedback of what these circuits are up to with B5 Amps Super Switch.

The Blues Junior featured above sports the Super Switch mod and other key mods that elevates this Blues Junior to “Deluxe” status.  Finally, total control with silent illuminated switching!

The Blues Junior footswitch family:  The Super Switch Standard, Super Switch Compact, and the popular FAT Pill.

The Super Switch Compact is perfect for densely populated pedal boards or if you are just looking for a compact streamlined footswitch with detachable patch cable.

  One of my goals when designing and developing modifications for low-power tube amps is to try to incorporate big amp features to make these mighty tone machines as flexible as possible while preserving tone.  The Blues Junior stands for more improvement.

  Out of the box, the guitarist has little control over the stock Blues Junior.  The guitarist simply sets the desired gain, EQ, and reverb and off he or she goes, and that works if your in a studio environment or just practicing.  But, most of the customers I modify and repair this amp for use it as staple for giging, and the Blues Junior is not very interactive in a gig environment.  Now you can finally take control of this great amp’s features on the stage or in any situation with this truly unique modification.  Enter the B5 Amps “Super Switch.”

The custom built Super Switch Standard’s rugged steel construction is perfect for those who want to feel some mass under their feet and is the perfect footswitch for the Blues Junior.

  The Super Switch is a hybrid footswitch that has DNA from the FAT PILL (featured below) and the long awaited “quiet” reverb switching solution in a custom made footswitch.  The footswitch interfaces with a switching module that resides inside the amp and boast natural reverb decay.  Meaning, the reverb will naturally decay as the note subsides, not abruptly cutting off the reverb during mid-note, ideal for the performing guitarist. 

  The switching module performs all of its switching duties within the sanctuary of the shielded chassis.  The fragile reverb signal is highly susceptible to noise and interference and never leaves the confines of the amp as other reverb switching modifications do.  The primitive method of sending the reverb signal to the footswitch severely limits footswitch cable length and invites noise.  Plus, some of these primitive mods have some pretty unsavory things happing to the reverb tank to make it switchable.  Believe it or not, the reverb tank is pretty fragile too.  It does reside in a very hostile environment after all.

  The other great features I like about this unique mod is the footswitch sports bright LED indicators for both the FAT and Reverb functions and absolutely requires No Batteries to operate!  The switching is silent with no annoying pops.  Gone are the days having to stop playing to turn down the reverb to make way for your favorite time-based effect, or stepping on a blind footswitch and not really knowing what state the desired function is in due to lack of visual feedback, and dealing with unreliable, expensive, and caustic batteries that will eventually find there way into a landfill and possibly into the water supply.

  The Super Switch when combined with power supply stiffing, tone stack mods, and adjustable fixed-bias elevate this amp to “Deluxe” status in my humble opinion.  Hence my version of the Blues Junior Deluxe.  I perform this package of mods in house along with a host of other Blues Junior mods.  Please e-mail: to arrange to have your Blues Junior elevated to “Deluxe” status or any other modification for that matter.  I am in the process of developing a modification kit for the Super Switch to be released very soon.


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Compact and no drilling required into the delicate PCB!

  Enter the B5 Amps Easy Bias Module.  It’s simple, yet very effective!  No drilling into the fragile PCB and a cinch to install.  The module attaches to the PCB via an existing screw.  The insulated material on the bottom of the module prevents noise from vibration.  The module has a wide bias voltage range to accommodate the freshest to the softest of EL-84s that might reside in the amp.  The module also has a built-in resistance buffer to prevent a Chernobyl incident in the event of confusion when setting the amp’s bias.  And best of all, it’s adjustable!  So, as the power tubes start to wear, you can tweak in the proper bias voltage and still maintain the amp’s tone while getting your money’s worth out of the power tubes.        

blues junior modifications prices

  1. -Super Switch kit: $100 plus $12 shipping, includes standard footswitch.  In shop installation: $175.

  1. -FAT Pill: $50 plus $7.50 shipping.  Custom color: $65 plus $7.50 shipping.

  1. -Easy Bias Module: $22 plus 4.50 shipping.

  I also perform all of the “standard modifications:” Tone stack mods, power stiffing, standby switches, adjustable fixed-bias etc.  I always recommend to have the standard mods installed during the Super Switch installation, it saves time and money when installed at the same time.

  I have modified and repaired a lot of these now iconic amps and there is much room for some significant improvements.  There have already been some great mods developed.  Check back here frequently, as I am always developing new mods for this great amp. 

To order, E-mail: to inquire about Blues Junior B5 Amps modifications or repair.