Build Your Own Clone Message Board

My first amp build ever was this Champlifier. After modding my Blues Jr. successfully, I figured...why not build an amp? It's just some resistors & capacitors & tubes & transformers....how hard can it be??

Read a bunch. Asked a few questions. Then dove in this week....

Impressed overall by the quality of the parts, and the clarity of the instructions. That being said, there were a couple of small snags. The board went together smoothly...not one bit of trouble on the assembly. Read an earlier post about making the leads 1/4" longer than instructed....that was helpful in most cases. When mounting the OT, found that one of the 6/32 nuts was actually 8/32. Oops. Had an 8/32 screw handy, so I enlarged one of the mounting holes and used that. Then found the screws on the standoffs were too long...fixed that with some small washers outside the chassis. For some reason the 7" (plus 1/4") white wire in step 13 came up a bit short. Wound up pulling the board, cutting the wire in the middle, and adding another 1 1/2" or so underneath the board.

Toughest part to wire up was the 12ax7 socket. The leads coming off the board were way too short to run as instructed in step 20. But by rotating the socket 180, pins 6, 7, and 8 were now within reach. Just had to keep re-checking to be sure the leads were going to the correct pins. Since the connections were in such close proximity, I used a bit of heat shrink as a precaution. (Also used heat shrink on the power switch, fuse, and non-ground part of the volume pot.)

Another change I made was to the grounding, per some of the discussion in another topic in this forum. Basically added a point using an existing hole in the chassis nearer the inputs. Slightly changed the layout of the inputs to accommodate the changes in grounding, but the circuit's still the same.

When it was time to power up, I ran through a power strip for extra protection (maybe?) and super quick disconnect in case of an "OH NO!" And, well...there were no "OH NO!"s. Everything appeared to function normally through all steps. No sparks. No smoke. No weird smells. No unusual hum or buzz or squeal. No shocks!! Plugged in the Tele, and let 'er rip!

I don't have any experience with these smaller amps, so I don't really know what "correct" Champ tone is. But low on the volume knob is clean and Fendery, and dimed it has that Derek and the Dominoes vibe on input 1. Input 2 is, as expected, less volume and less distortion.

As for actual volume...it's definitely less loud than the Blues Jr. But I can also imagine the wife asking me to turn it down too. To be fair, it's not yet in a cabinet. That's a couple weeks out....being built by Mather Amp Cabinet in Nashville. I read some post somewhere about a Champ keeping up with a drummer. Should a Champ be that loud??

So aside from not knowing how loud this thing should really be, the other thing I'm unsure about is the indicator light. It tends to fluctuate in brightness.....is this normal??

Meant to put in a screen resistor, but I forgot.....dang! I'll add that this week. Probably gonna make the negative feedback switchable as well.

That's pretty! But your light shouldn't fluctuate.

Awesome work man and nice thread run down of what you did. I can't imagine that light dimming being normal? I have not read anyone mentioning that though. Can't help with your questions as I have not played through one...yet. Just wanted to mention clean guts and looks great.

A little follow-up. Regarding volume....perhaps I was mistaken. This amp is plenty loud. It'll be groovy to see how the cabinet shapes the tone.

The indicator light still intermittently fluctuates in brightness. I'll have to take a reading on the socket and see if there's any variance there....unless someone has a clearer idea what's up.

Added the screen resistor. Didn't affect tone as far as I could hear. Seems like a safety of sorts....

Played with R10, the negative feedback resistor. That's kinda fun! With the Les Paul dimed on Input 1, and the white lead disconnected from the speaker jack, this thing was howling! Had a kind of early-Stones-fuzz kinda feel. Crazy loud for 5 watts too. Rolled back the tone knob on the fiddle to keep it from getting too shrill. Think I'm gonna put that on a small pot with a pull-up disconnect....same thing I added in a couple places on the Blues Jr.

Using a 4-ohm speaker. Seems a shame to cap the 8-ohm lead. I'll mess around in the coming weeks to add an impedance selector switch. Seems do-able.

Does anyone know how they do the half-power switch on the new EC VibroChamp?? Seems like that could be useful. Also, how specifically should a cathode bypass cap switch be rigged so that it doesn't pop. Could it be done with a pot instead??

My bulb fluctuates as well. I've tried like hell to determine what it is. I've played with the enclosure with the amp on and it seems to affect the bulb brightness; my best guess is that's it's the bulb enclosure. It fluctuates even while I'm not playing or without a guitar plugged in, so I don't think it has anything to do with the voltage or power. No problems with the amp, no cutting in and out, so I've left it alone.

I see a bit of the bulb brightness fluctuation on mine, too. Not sure what causes it, though I know the connections are all solid. In any case, it doesn't seem to affect the amp's tone any!

Half power switch may be a triode/pentode switch.
Basically the amp runs in pentode stock. This means the screen (pin 4) has it's own power node. When you hook it up triode the screen connects to the plate. It doesn't reduce volume all that much. It does change tone and mine (and others I've seen do the mod) hummed a lot when in triode.

Cabinet arrived a few days ago. Decided to go with one from The Mather Amp Cabinet Company in Nashville (http://www.mathercab.com/). Went for a slightly customized lacquered tweed Champ cabinet. Went with Mather based on the quality of their work, as well as their ability and willingness to do custom work. Some of the nicer appointments include through dovetail joints, vintage furniture glides, and a raised leather handle. Took just under 9 weeks to take delivery. Not bad considering every piece is made to order. Reasonably priced too...although slightly higher than Mojo / Marsh.

Went with a 4 ohm Weber Special Design 8" Alnico speaker after trying out the 8" ceramic Jensen that's pictured above. Wonderfully touch sensitive and glassy when the amp is cranked and the guitar's volume rolled off ('52 Tele RI with mods that include treble bleed and Fralin Big-T neck pickup). Haven't run wide open enough to make an assessment yet.....more on that later in the week.

I've got a couple mods planned, and also waiting for an impossible-to-get-but-somehow-I've-probably-pulled-it-off part to arrive. Once all that's done, I'll post photos....