Amplifier Mods

Fender Blues Jr. Mods
— Gain & Character

— Tone & Frequency Response

— Features

— Architectural

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Gain & Character

Tone

Features

Architectural

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The Fender Blues Jr.

The Blues Jr. is probably one of the better low-priced amps in the Fender line. It is capable of a nice Bluesy tone and flexible enough to become quite an impressive amplifier with a few mods.

Stock the amp has a very flat midrangy tone and an edgy crunch. There are several options for the Blues Jr to open up the tone and bring this amp into the class of a Fender Deluxe and other similar amps. The most-common least expensive "must-have" is the Twin/Tone-Stack mod made popular by BillM to improve on that flat midrangey tone. I implement a variant of this and can customize the stack for your tastes.

If you want a fairly low priced entry into the traditional tone of a Fender Amp, get a Blues Jr. and mod it with the 6V6 conversion and the tone-stack mod. You'll be impressed with the difference.

If you had a mod in mind that you don't find here, just email me and we can get it done.

Blues Jr. Gain & Character Mods

Overdrive - I

$30

w/ miniature panel-mounted switch

This mod provides a gentle gain boost of about 2-3X, roughly equivalent to that of the FAT switch currently in the design. It can be tailored for a Bright boost or a FAT/Full boost. For just that bit of additional Crunch this might be the ovedrive level for you.

Overdrive - II

$50

w/ miniature panel-mounted switch

With this innovative mod design the gain is boosted to screaming levels utilizing allmost all of the gain this amp has to offer. The result is amazing pick harmonics, with a screaming and full smooth distortion character that you wouldn't normally expect from the Blues Jr. When cranked the amp goes into a nice grid-overdrive compression like a Vintage Tube Amp should. The gain boost can be customized, and is VERY complimentary to the Mid-Boost mod.

Blues Jr. Tone Mods

Twin / Tone-Stack

$35

This is the inexpensive mod to resolve the "Boxy" sounding flat tone of the stock Blues Jr. This mod is often combined with the Output Transformer Upgrade or the 6V6 conversion as well as it increases the flexibility and range of the tonestack. The midrange control is rewired like that on the Fender Twin to allow for deep midrange scoop when zeroed. — The basic component values I use in this conversion differ slightly from those in use elsewhere, as I have found that shifting up the treble frequency knee and shifting down the bass frequency knee opens up the tone a bit more; somewhat of a hybrid of the BillM and Torres tone-stack values. I can adjust this to your taste though.

Mid Boost

$35

w/ miniture panel-mounted switch

This is a modification of the tone stack similar to that implemented in several old Fender designs which provides a tight and punchy midrange boost with the flip of a switch. Much of the tone-stack signal is routed around the stack to provide this boost, so an increase in signal gain also occurs providing a bit of overdrive boost. When this is combined with one of the Overdrive Mods the amp really starts to have a character beyond what anyone expects with awesome harmonics and tone.

Heyboer Output Transformer

$85

email for cost w/other transformers

This is a natural mod for the Blues Jr. The stock output transformer is a bit light in the low end, lacking warmth and openness. Replacing this with a Heyboer transformer really adds a warmth and rounding out of the tone to the amp. I do recommend adding the tone-stack mod at the same time -- these are quite complimentary. The Heyboer transformer has an outstanding tone, comparable to the much more expensive Mercury Magnetics transformer. If you want a different tranformer, like Mercury or Hammond, however; I will put whatever you prefer in there {Hammond $100, Mercury $150 — no need for the extra cost, trust me, you'll love the Heyboer}.

Blues Jr. Features Mods

Standby : STBY-OFF-ON

$35

replaces Power Switch

A Three-way DPDT ON-OFF-ON full-size toggle-switch is wired into the Power-Switch panel hole, wired for Standby-OFF-ON. I now use this configuration rather than an additional switch due to panel-space on the Blues Jr. This also retains the look of the front panel. Black labeling can optionally be applied.

External Speaker Jack

$35

This is one of the very common requests from Blues Jr owners — add another jack so I can connect up to an external cab. No Problem. — The mod consists of an additional jack next to the existing one. A cable must be plugged into the internal jack to activate both jacks. The Blues Jr can drive down to 4 ohms stock, so an external 8 ohm cab added with the internal speaker will work fine.

Buffered Send / Return Jack

$75

w/ Stereo-Jack -- { add $20 for dual-jacks }

This is a classic tube-buffered Send port at line levels compatible with most any stompbox or line gear, and a matching Retrun port direct into the power amplifier ahead of the Master Volume. I utilize the unused half of the 12AX7 already in the Blues Jr and a Williams Vintage Amplification UniAmp™ Board for the Send port buffering, keeping the layout and design clean and neat.

Bias Adjust

$35

Very similar to the BillM simple bias adjust mod.

I/P Jack Shielding

Aluminum Foil based shielding wrapping the Input Jack for improved noise immunity. This seems particularly important for the green board models.

Reverb Upgrade {for Green Board Models}

$35

Based on the BillM green-board reverb mod, but with increased reverb drive levels if desired.

Blues Jr. Architectural Mods

6V6 Conversion

$100 + 6V6 Tubes

$140 w/TAD 6V6s

This is probably the most amazing conversion mod yet for the Blues Jr. It turns this reasonably priced amplifier into something quite similar to the Fender Deluxe. I use a hybrid cathode/fixed bias that provides a very nice smooth tone that just isn't possible with the EL84s. The low end is opened up and the highs are crisper and sweeter. It totally changes the amp with tone you'd expect from an Amp at least twice the price. — Also — with the 6V6 mod, I have found that the existing output transformer is perfect. The 6V6s more than make up for the shortcomings of the stock OPT.

PowerDrive™

$120

to <1W w/continuous control {add $30 for <100mW}