Thursday, December 22

All I want for Christmas is a modded Valve Jr.

Ok. So. Sorry about disappearing for all of November. And like most of December. On the plus side, it means that I've been really busy playing and working retreats and finding as many jobs as I possibly could and could not be bothered to do anything else. Certainly not much drinking and writing about it. I'm way behind on that project, and so it might scale itself to a life-long goal, rather than a scant year or two....

But it wasn't all work! Gear has moved around, as it is wont to do. The biggest changes include some trades: I traded my Musicmaster amp for a 1981 TS9 and a cmatmods Signa Drive, and I traded my Gretsch for a Strat. I've updated my pedalboard that I used for leading (which I'll show you guys in a later post) and I picked up, modded, and am now in love with, another Epiphone Valve Jr.

If you remember way back, I had a head/cab Valve Jr. back in the beginning of my guitar-playing days. I mostly got frustrated with it because of the fact that it is a head/cab which for whatever reason just seems like a big hassle to me. But then I found a little Valve Jr. combo on Craigslist for $75, and I thought to myself, why not?

Pictured: the most cumbersome 5 watts ever.

I figured, worst case, it will teach me a lot about amps and soldering and general electronics work, and if I screw it up, I'm only out a little. So I grabbed this little guy and a soldering iron and got to work.

I used the kit from Watts Tube Audio, choosing to go with the "Voxy" mod simply because I like AC30s but am almost never in a situation where I can crank one to get power tube distortion. I also planned on adding a "bright" switch because I like that. So I drilled a nice hole for the switch. Note to self: no matter how much of a pain it is, REMOVE THE CIRCUIT BOARD BEFORE DRILLING IN THE CHASSIS. I drilled right through a little capacitor on the stock board, which I was going to remove anyway, but it kind of gave me a wake-up call. Don't do that.

For the bright switch, I did a lot of research to figure out the best way to do it. One of the easiest ways to do it is to wire a small capacitor (in the order of pico-farads) across the volume pot and give it a switch. It's the same idea as a "treble bleed" mod that a lot of people will do to their amps or even their guitars, just with a switch. The idea there is that the resistance in the volume pot at any position other than wide-open sucks some of the highs out, so the treble bleed switch just adds those back in. The effect is lessened the more the amp is turned up, but that's just because those frequencies start to poke back through anyway. The first capacitor I used was apparently not rated for high-voltage applications. It was promptly destroyed and fuzzed out. So that was fun. Lesson learned, I got a 100pf capacitor rated at 250v, and it's been working fine.

So I got to soldering the board up. That all went well enough until I plugged it in and turned it on and promptly fried a power tube. To this day, I'm not sure if it was just a tube that was on it's way out or what, but it started sparking and generally doing a lot of scary things that you don't want to see in an amp. I triple-checked my wiring, reflowed some solder on some sketchy joints, installed a new power tube, and this time brought it up to full-voltage slowly (using a variac), and it seemed to fix the problem. I left it at full voltage for a while to make sure nothing died, and when I was satisfied, I screwed everything back in.

The only other major change I made to the amp was installing a 12ay7 tube in the pre-amp slot, rather than the stock 12ax7. If you don't know anything about tubes, that's okay. Basically, 12a_7 tubes are all electrically compatible. The important part is that a 12ay7 tube has a lesser gain structure than a 12ax7, meaning that an amp with one in it doesn't get quite as dirty as it would normally. I did the same thing with my Blues Jr. and it expanded the amount of control that I had over the volume. And also, the tube I used was a nicer NOS tube, so it just sounds better (and smoother) in general, since a lot of the distortion you're getting, even full-out, is preamp tube distortion. But now I get more use out of the volume knob, and can actually get a clean tone out of humbuckers, something that was all but impossible with a 12ax7.

Here's a quick video. It's just a really simple showcasing of what the amp can do, just my Tele straight in (or rather, through the JHS buffer and my pedal board, but with no other effects on). I play the same phrase on the bridge, middle and neck position, with me toggling the bright switch and turning the volume up. Since the amp is only 5 watts, I can turn it all the way up and not get things hurled at me. It's still loud, mind you, but it's not uncomfortable to be in the same room with.

I took it out to a Mass last weekend, and my sound guy was blown away at the clarity. I played it with the bright switch engaged, and used my Tele and Strat, and we put a '57 in that taped-off square, pointing towards the center of the speaker. When I went to plug it back in afterwards, I noticed that it kind of stopped working. Or, more specifically, that the tubes weren't glowing. So I made sure to go over the connection between the power transformer and the tubes (kind of a sketch one anyway) with a lot of solder, and now it's nice, clean, and reliable.

I should probably do a proper demo, putting some effects and stuff on there, but I just wanted to get a baseline tone out there. That's not even my clean tone, since 99.7% of the time I also have a Dynacomp and a BBE Sonic Stomp going. But expect more videos in the future, since this was way easier to do than I would have thought....

No comments:

Post a Comment