A dramatic amp mod as well as the simplest in the Epiphone Valve Junior Head Tube Guitar Amplifier is known as the “JP1 Mod”. The name derived from the jumper labeled JP1 on the board.
It basically morphs the tone of the guitar amp from one with no definition, dark, to an instant edgy and more present tone. To my ears things came to life using the Fender Telecaster compared to the raw un-modded amp I had.
And all this without even replacing the tubes that the amp is shipped with (Sovteks). I suggest replacing the tubes, to a JJ (former Tesla) set. From there things get serious. But at least now for the sake of seeing how much a simple mod like the JP1 can boost your Epiphone Valve Junior tone character.
Snip It!
That’s all it comes down to - snipping a jumper. Technically eliminating the C3 (22uF) electrolytic cathode capacitor from the circuit on the second half of the pre-amp tube (12AX7). Simple as that! The amp will start singing - but not in falsetto.
All the tool you need is a simple wire cutter (preferably a flat one). No soldering iron, no soldering skillz, NOTHING! You can do it! If you can clip your nails, you can snip the JP1 labelled jumper on your Epiphone Valve Junior.
Follow the steps in the video and report back with comments on your impressions. Good luck!
on Dec 29th, 2008 at 6:34 pm
Hi Gabi,About the JP1 mod?..Did you not say somthing about a Presence switch?..and/or..what would happen if i added a switch to the JP1 jumper or a pot or a dpdt switch and a pot?yhanks..Mark
on Jan 1st, 2009 at 11:05 pm
hey, i had done the the JP1 mod and it mad the the sound so much better thanks for your tip. i was woundering if you would post a video up on making the epiphone have more power buy adding more tubes or adding a slave out put to run in to different head or for recording. thanks for your time.
brandon