Fender Blues Junior Straight Six Modifications for MIM

Introducing the Fromel Blues Junior Straight Six mod! Finally, vintage black panel tones from your Blues Junior!

For Made in Mexico (MIM) Blues Juniors. A Made in USA version is coming soon. In the meantime we can do the mods on a Made in USA Blues Junior in house: send us your amp. The USA version isn't available as a kit.

The Straight Six mods literally transform the circuit of your Blues Junior to that of a 60s West Coast amplifier company in their glory days. All those classic, big, beautiful and expansive tones you love can now be yours!

The stock Blues Junior is a cool amp, sorta tweed-ish tones, and is a medium-volume grab-and-go workhorse, but I’ve always thought it could be so much more. The circuit has always bugged me: it’s really just a series of compromises to get it to do what it does, with each version that comes out fixing a problem that was there at the beginning. With the mods we get all of that out of the way for a simpler and classic signal path without the compromises the amp has stock. Less in the way and fewer compromises = cleaner, bigger and less noisy!

The Straight Six takes its name from the “Magic Six” settings on a black panel: Treble on 6, Mids on 3 and Bass on 2 (2 × 3 = 6!). After the mods your Blues Junior has very close to these same settings with the tone controls on noon, straight up, so Straight Six! But that’s not where they need to stay, because you’ll have more control overall over your EQ settings too.

The mods

• Replace the input jack with a high-quality chassis-mounted input jack. The stock PCB-mounted input jack is low quality and I couldn’t tell you how many broken ones I’ve seen!
• Cool the bias so your power tubes will last longer and be more reliable.
• Change the Fat switch to a full-frequency boost, still footswitchable!
• Change the tone stack to that of a vintage black panel amp, with more range on the knobs and the “Magic Six” settings straight up at noon.
• Change where the tone stack is in the signal path. This is the beating heart of these mods and what they share with every black panel amp.
• Change the circuit and raise the voltages of the phase inverter to that of a black panel amp: more clean headroom!
• Replace the power supply filter caps with different-value caps of much higher quality for tone, feel and reliability.
• Change the voicing on the reverb to sound like vintage black panel reverb, except usable through the whole range of the knob, from a little ambience to surf’s up! All while lowering the noise the reverb circuit adds to your amp. Big, beautiful and lush!

If you have the Supreme mod already, you’ll unfortunately need to buy the full Straight Six mod kit, as the two kits are completely different and only share a couple of small components. Though if you already installed those shared components, at least you won’t need to do it again!

If you have installed the Blues Junior Tube Board (or are planning to install one with the Straight Six), you’ll need to rewire it to work with the Straight Six, and the instructions cover that.

Your amp will sound amazing with just the Straight Six mod, but if you’re one of those folks who just can’t stop until your Blues Junior is absolutely all it can be, I have some modification recommendations in order of importance:

1. Straight Six mod (of course!)
2. Blues Junior Tube PCB
3. The Soursound BJR-OT2 output transformer, specifically designed by Soursound for the Straight Six mods
4. Eminence Alessandro GA-SC64 12” speaker
5. Mojotone Bluebird 15W 1x12 pine cabinet
6. Soursound SST-125C3A choke

I’ve been thinking about these mods for a couple of years now, and I’m very happy with how they turned out and so excited to share them with you. This is what I think the Blues Junior always should have been from the beginning!

Install instructions

Blues Jr Straight Six mods guide