#1
Hello,

Id like to ask, would it be possible and if, how hard and expensive to mod the 5Watt Epiphone valve junior for each of the folowing

- Adding a reverb
- Adding an EQ (including presence)
- Adding another channel
- Adding master volume
- Increasing the wattage by adding tubes
- Adding external FX loop send/return


Now, to avoid being flamed, I don't plan to apply all mods to the amp, I will probably just hot rod the circuit (found some sites with that), or more precisely, I will ask my friend to do it, since I am not too good with electronics.

I just want to know what possibilities there are, just to know.
#2
adding an eq would be the only thing you could do with simplicity as this would be connected directly to the jack input and would be the first thing in the signal path between your guitar signal and the rest of the amp, but then with the same effort you could just make yourself a pedal eq, or even by one if you're thatway inclined.

the rest of the projects involve desoldering certain parts of the amp and taking it apart. I believe that there is no preamp, ie the 5w junior is a power amp full stop (this is what i have heard) and therefore an fx loop (which sits between the pre and the power amp) wouldn't be doable.

A real reverb requires constructing one using a reverb tank (you can get them at smallbearelec.com) and is supposed to be easy, but i dunno, requires a bit of workmanship rather than electrical knowledge.
#3
thanks a lot!


if it doesnt have a pre amp stage, wouldn't it be a good idea to build in one (tube of course)? it could have two channels + an EQ. I've heard that this amp has a lot of free space in the chassis, so it could be inside. Plus it could have a true bypass for the preamp...
Hm, would it be possible to add a preamp and make it lets say 20 watts?
#5
Quote by Klayy
thanks a lot!


if it doesnt have a pre amp stage, wouldn't it be a good idea to build in one (tube of course)? it could have two channels + an EQ. I've heard that this amp has a lot of free space in the chassis, so it could be inside. Plus it could have a true bypass for the preamp...
Hm, would it be possible to add a preamp and make it lets say 20 watts?


from here i can only forward you on to this website: http://www.ax84.com/. sign up to their discussion forum and ask away. this is a website and community dedicated to building small tube amps so they should be quite knowledgeable with the valve junior and any mods that you can do with it.
#6
It has a preamp and power amp, but they're just incredibly simple.
EDIT: And to awnser your question, all of those mods, except the tone stack maybe, would be more work than it was worth. But I know a few people have done simple things like change out some caps to increase the gain.
If you could blow up the world with a flick of a switch,
Would you do it?

If you could make everybody poor just so you could be rich,
Would you do it?

With all your power,
What would you do?
Last edited by Wayward_Son at Jul 27, 2006,
#7
Typically the most single expensive parts in a tube amp are the transformers. That's why this amp is such a good deal, they're very cheap. To add wattage you'd have to put in higher grade trannies, which rather defeats the purpose of modding the amp...

For the other issues though, you could add a 12ax7 driven reverb and EQ crap quite easily.

I don't think making a whole new channel would really be worth it, I'd personally just have a toggle to switch in another preamp gainstage.


I've been thinking about buying a VJ too, just to mod. Seems to me it would be a great platform to mess with. I'd probably chuck all the PCB stuff and just rebuild the guts on eyelet board or something else easy to mess with.
I'm not very active here on UG currently.
I'm a retired Supermod off to the greener pastures of the real world.
#8
Yeah, I dont want to mod it to save money or something, but that amp is so simple, that you can do about anything with it
Thanks for the posts, guys
#9
hey i've got an idea for the 2 channel thing. it's sometihng i'm gonna do with my single channel laney gh50 when i get it.

make a volume pedal, keep the volume of the amp at the stage where it distorts and activate the volume pedal (which is a passive device that limits the volume to whatever you set the volume to) to lower the output of the guitar and lower the distortion. however your cleans will be a lot quieter, and your distortion will just explode and kinda be to much. but hey experiment!
#10
Quote by Klayy
Hello,

Id like to ask, would it be possible and if, how hard and expensive to mod the 5Watt Epiphone valve junior for each of the folowing

- Adding a reverb
- Adding an EQ (including presence)
- Adding another channel
- Adding master volume
- Increasing the wattage by adding tubes
- Adding external FX loop send/return


Now, to avoid being flamed, I don't plan to apply all mods to the amp, I will probably just hot rod the circuit (found some sites with that), or more precisely, I will ask my friend to do it, since I am not too good with electronics.

I just want to know what possibilities there are, just to know.


None of them are worth it, really, IMO.

I've just had a look at the schematic:

Adding a tone stack could be done, thats the only one I can think how to do effectively. A presence control can't be implemented as the amp is SE and has no negative feedback loop, and the only other way I can think of of adding a presence control relies on a tube-powered Bax stack.

That brings us on to the next point...the PT (power transformer) in the Valve Junior is just too small to add any more tubes, really. It has next to no headroom in terms of current..I suppose another 12AX7 could be done for something. Another channel would take a whole bunch more tubes (unless you wanted to add a switchable gain boost which could be bypassed...that could be done with another AX7 stage).

Master volume would be a no-no, as the poweramp distortion adds so much to the Valve Junior's sound that little crunch would be present at low master volume levels as the input to the poweramp wouldn't drive it, IMO. I guess it could be added between V1B and the power valve.

More valves/power would need a bigger PT/OT, so no. A FX loop would also need more tube stages if it's meant to handle line-level stuff...again, not worth it for such a simple circuit.

One mod that CAN be done is to add a gain switch by adding a switch which shorts out R6 (the 1 meg resistor before the volume pot). This might do the "2 channel" thing. Also, you can rip out the resistor in series with the input jack, replace it with a 22k (from 68k) and rip out the resistor from input jack to ground to add some input gain.