Sunday, July 27, 2008

Epiphone Valve Junior and the BitMo Trio Mod

My first Epiphone Valve Junior was one of the combos. Sounded OK but a little sloppy and very noisy. Sold it and never looked back. Since then, however, they've made a ton of improvements and now they are great little amps at any price.

Here's mine in original stock condition:

I got mine in like new condition for about a hundred dollars shipped from an online auction site. They go for that much give or take ten bucks all the time. It's a good deal. Buy one if you're considering it. Totally worth it. The sound to me is sort of Marshall-esque-good midrange bite and that crunchy AC/DC type of distortion. Doesn't get too terribly loud when you crank it either, which is a good thing. I can comfortably play it dimed for a while in the afternoon or evenings but not at night. It's a few degrees louder than a stereo at what I think of as normal listening volume if that helps you put it in perspective.

As I said, I like it a lot but I'm not one to leave well enough alone. It's a little dark sounding for my tastes sometimes (my cabs have kind of a dark sound to them, if you have some brighter Celestions or something this'd probably be great) and could deal w/ a little more names. After looking into mods for some time, I decided on the BitMo Trio mod, which you can get on the internets for about fifty bucks. It adds a tone knob, gain boost and three different gain voicings.

All of this looks like a few parts in a bag once you get it in the mail:

Now to install these mods, first thing you have to do is get in the amp. Valve Juniors have self-discharging power supply capacitors so they are relatively safe to work on. Don't be afraid to roll up your sleeves and get to work on this as a first amp project. The voltages that can build up in tube amps and knock you on your ugly ass should be rendered harmless. However, you can never be to sure so the standard advice still stands: don't be a retard.

To open it up, first you have to take off the back:

It's held on by screws. Turn them counter-clockwise to remove them. There are then some larger screws on top you need to remove. They're hidden under little plastic things, which I always thought were a bit tacky but, you know, if don't want little cost cutting measures like this, buy a more expensive amp:

The cab is designed such that the amp-part doesn't just fall down when you remove these screws. You have to slide it out. And it looks like this:

Note: I am not drinking whiskey but I do keep it on my workbench/kitchen table for emergency purposes. You never know when things are going to get too complicated to handle properly sober.

Next step is to drill the holes for the new controls. Don't rush this and wear safety glasses. The BitMo kit comes w/ a template to place the hole:

I just poked a hole and made a little mark w/ a sharpie. That one's for the tone knob/gain boost. The one for the three-way switch you just gotta guess on.

To drill these suckers, you need to be patient. Buy some good quality drill bits for drilling metal. You probably won't be able to get away w/ just buying a quarter inch and three-eighth inch bits. They're too big for one pass. You need to start w/ a smaller bit and work your way up. Go in about eighth inch increments maximum. Be careful and let the drill do the work. Don't try to push it though any faster than it wants to go. I put some tape over the marks to keep the drill from scratching up the faceplate if it slipped (and it did).

Here's the finished holes:

Now, from here, you have to actually install the mod. This is the frustrating part so I didn't end up getting all too many pictures. You're in luck though since GearScore has an excellent page on it. Between this and the very good instructions that BitMo sent w/ the mod, it was fairly simple to get it all up and running. I soldered everything to the pot and too the switch, installed them and then soldered them to the top of the circuit board. Easy.

The one trick, which I stole from that GearScore page I linked to, is to use a pair of vice grips to hold things while soldering them:

Holy crap! That makes life so much easier I'm embarrassed I didn't do it until now. Anyway, that up there is the gain voicing switch w/ all parts attached. The tone knob/gain boost looks about the same but I forgot to get a photo.

Here it is all installed:

I had a bit of trouble on the three-way gain voicing switch but other than that it was easy. It's easy to get turned around by the schematics BitMo includes so be careful. It's not necessarily the best way to do things but I just soldered the leads to the top of the board. Works but it is a little sloppy.

Here she is all put back together:

I didn't do the water slide decals because I screwed up all the practiced ones I tried. I guess it would look a little cooler w/ them.

As far as how it sounds, it's a big improvement over an already good tone. The gain voicing switch just gives you three levels of gain, really. The higher gain settings seem to get a bit more oomph in the high midrange as well. The tone knob is nice too. It's not the most versatile thing in the world and seems to work something like a high end filter though it does add a bunch more high end than is available stock just by being there. The gain boost, adds some lows back in and is what can really take you over the top when you got the thing cranked.

Overall, not a bad way to spend a Sunday afternoon. I used to use an OD pedal to really crank the Valve Junior into rocking distortion territory but now it's totally unnecessary and sounds better besides. I'd recommend this to anyone as an easy first mod or a way to get a killer small tube amp for the price of a decent distortion pedal.


Smitty said...

Nice job Frank. They make a bitmo mod for the Blackheart Little Giant, which I am considering at some point. I just get nervous tinkering with PCBs and soldering irons. I don't really know what I am doing

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Anonymous said...

Nice story as for me. I'd like to read a bit more about that theme. The only thing I would like to see here is a few photos of some gizmos.
Katherine Karver
Phone Blocker

Eli Noonan said...

What wattage soldering iron should I use for this?

Eli Noonan said...

What wattage soldering iron should I use for this?

Frank said...

My soldiering iron is switchable 15-30 watts, normally run it at 30. Kind of counter-intuitively, lower wattage can make you more likely to burn out components. Slower heating means the heat has more time to spread out over the component. What you want is one tiny area to heat very fast and then to take the iron away quickly and as soon as the joint is completed.