Allen Amps Class Act Kit

[-CM-]

Before I had even gotten the Old Flame kit I recently completed (http://forums.birdsandmoons.com/forum/showthread.php?t=189), I ordered a Class Act kit from Dave Allen of Allen amps. During a conversation about the Old Flame, I mentioned that I would probably want to get a Class Act in the future. He informed me that there were only 2 left, one head, and one combo, and that he wasn't going have anymore. So I decided to go ahead and get it. This thread, then, is all about the assembly of the last Allen Amplification Class Act head kit (at least in its current form.)

The Class Act is a small, class A amplifier that has 1 output tube (of course), 2 preamp tubes, and one rectifier tube. The output tube can be a KT88 (10W), EL34 (7W), 6L6 (7W), 6K6 (4W), or 6K6 (3W). It's designed as a plexi style preamp, so I chose the EL34. The controls consist of Volume, Master Volume, Bass, Mid, Treble, On/Off, and Play/Standby. There are high and low input jacks, and high and low impedance outputs. A fairly basic amp that gets rave reviews from everyone who owns one.

I've actually done quite a bit of work on the amp already - I'm a bit behind getting the progress posted here. I started the kit the same way as the Old Flame kit, by completely inventorying everything and going over the assembly instructions. If you're not familiar with Allen kits, they come complete with everything you need to end up with a functioning amplifier. You have to do all the work, except for the cabinet, which comes prefinished. Well, I had to put the logo on mine, but that was it. One of the best aspects of the kit is the assembly instructions and the color diagrams.

Somehow, I lost the picture showing the kit as it comes out of the box, but it looks very much like this pic (http://www.cmwebsite.com/images/OldFlame/OldFlameParts1_sm.jpg) of the Old Flame kit. There's just a lot less stuff. All of the parts are high quality. Switchcraft jacks, Sprague caps, JJ/Tesla and Electro Harmonix tubes, upgraded transformers, etc. No skimping here.

After making sure I had everything, I began putting all the stuff into the chassis. I should note that I'm not following the order of the instructions. Since I just finished the other kit, I'm familiar with the process. I am checking the instructions, though, to make sure I do everything right.

So here's the first progress photo, showing all of the switches, tube sockets, and jacks installed, along with some dressing of the output transformer wires.

http://www.cmwebsite.com/images/ClassAct/ClassActAssembly1_sm.jpg

I've decided to be fanatical about routing and dressing the wires and installing the components in this amp. It takes a lot more time, but I want it to look really neat when I finish. Also, proper dressing reduces noise, so there's a practical aspect to it, too.

You can see the beginnings of this fanaticism in this pic, where I've installed the power transformer and put in the circuit board for reference.

http://www.cmwebsite.com/images/ClassAct/ClassActAssembly2_sm.jpg

More wiring and more dressing are shown here, along with the installation of the terminal strip and a couple of the components on it.

http://www.cmwebsite.com/images/ClassAct/ClassActAssembly3_sm.jpg
(High-res pic here (http://www.cmwebsite.com/images/ClassAct/ClassActAssembly3.jpg).)

Next I'll install the wiring that looks like it will be easier without the circuit board installed. But I'm waiting on some tweaky audiophile wire. I'm going to use Wonder Wire (stupid name,) a 19ga silver clad, solid core copper wire that comes with a Teflon casing. The dielectric is rated at 9000VDC, and doesn't melt when you solder, making it neater. Being solid core, it's easy to bend to exactly how you want it. I'll have to be very careful because I won't be able to rely on colors.

I'll post progress more often now that I've finally started this thread, which means the posts won't be so long.

[TheArchitect]

So your the guy!!! I emailed him about this amp and he told me all he had left was a combo and that would be it for a while. You got the last one!!! Congrats and keep us posted on progress!

[-CM-]

Ok, I got the tweaky wire from Michael Percy Audio (http://www.percyaudio.com/) and accomplished quite a bit yesterday. First, I had to twist a bunch of it together for the heater leads. With a major stroke of luck, I managed to end up with just enough twisted wire to do the job.

I've learned that it's important to properly dress the heater wires so that they are twisted together, and are as far away from other wires as possible. When they do meet other wires, they need to cross at right angles. And they need to run along the chassis to reduce noise. So I painstakingly routed the wires as you see in the photo. One of the nice things about this wire is that the Teflon insulation is very thin, and takes up little room (but still has very high electrical and heat ratings.) This allowed me to route the wires right in the chassis corners without interfering with the mounting screws. (Note for those who have built Class Act kits previously: I'm mounting the circuit board up on 1/2" standoffs, so it won't rest on the chassis where I ran the wires.) I went above the output wires for the run between V2 and the output tube.

I also wired the resistors on the pots and the input jacks, in addition to a couple of the ground wires for the pots. For these, I ran them from the pots back against the chassis and down to the common ground bolt. Each wire will get its own lug.

Now it's time to start the circuit board assembly.

http://www.cmwebsite.com/images/ClassAct/ClassActAssembly4_sm.jpg
High-res version here (http://www.cmwebsite.com/images/ClassAct/ClassActAssembly4.jpg).

Edit: Note that I made a mistake that has been corrected. The capacitor connected to the terminal strip should not have been oriented over the big 15W ceramic resistor becuase it will get too hot. I moved it to the other side of the terminal strip.

Thanks for the email from to someone who's monitoring my progress and knows what he's talking about.

[-CM-]

This update actually includes 2 evening's work. I've completed putting the components on the circuit board and am now ready to wire it into the chassis.

It really doesn't look like much, but this board was more work than the one for the Old Flame, even though that one had many more components. The reason for that is that the Class Act board is much smaller, and there are many more shared eyelets. In cases where 3 or more component leads go into a hole, it simply takes longer to do. Plus I was trying to make everything really neat and tidy. I was mostly successful, but there's only so much one can do when you have to bend things around to get them to fit.

http://www.cmwebsite.com/images/ClassAct/ClassActAssembly5_sm.jpg

High-res version here (http://www.cmwebsite.com/images/ClassAct/ClassActAssembly5.jpg).

Note that not all of the leads are attached to the board. I want to route them as neatly as possible, so I left some so that I could determine how long the wires actually need to be. I attached the ones that would have been too difficult or impossible to do with the board installed in the chassis.

One of my ideas, which is probably not unique, but nonetheless helpful, is the scheme I came up with for organizing the components to make assembly easier. I find it to be a pain to hunt for the appropriate value resistor from a pile during assembly. For the last kit, I separated all the components into the compartments of a plastic organizer. This worked to some degree, but I still had to hunt around a bit for the component I wanted. This time, I used this method:
http://www.cmwebsite.com/images/ClassAct/ClassActcomp.jpg

When I inventoried the kit, I ordered the components by type and value, cleaned the leads, created a label for them, and stuck them in a piece of corrugated cardboard. I tacked the cardboard "Component Palette"* to the wall near my workplace. During assembly, it was a simple matter of looking at the chart and grabbing the desired component. No hunting around, which is rather tedious. It worked well for me, and I'll do this from now on.

So it's into the home stretch for this project, although the remaining wiring will take some time because I want the wires to go just so.

Stay tuned.

*I just made that up, and hereby copyright, trademark, or whatever-mark it. Feel free to use the idea, though.

[-CM-]

Insomnia can be a good thing for making progress on an amp kit. I was able to finish all the wiring except for the power cord by today, and I spent the morning checking the amp out completely (for the second time.) I did well this time as I didn't make any mistakes.

Here's the amp completely wired:
http://www.cmwebsite.com/images/ClassAct/ClassActAssembly6_sm.jpg
High-res version here (http://www.cmwebsite.com/images/ClassAct/ClassActAssembly6.jpg).

I'm fairly pleased with the way it turned out, and once again have renewed appreciation for the amp builders who can make the guts of an amp look like art.

Here's the amp with the tubes in it:
http://www.cmwebsite.com/images/ClassAct/ClassActAssembly7_sm.jpg

One more helpful hint I have is my method of getting those cord clamps into the chassis. If you've ever put these in, you know what I'm talking about. If not, just accept that it's one major pain to do it. The picture says it all:
http://www.cmwebsite.com/images/cordclamp.jpg

After I got the amp completely wired, I went through the pre-power on final checks listed in the instructions, put some tubes in, connected a cab, and turned it on. It hummed to life without and major bad noises or smells - so far so good. I plugged in a guitar and turned the volume controls up a smidge. Nothing. Turned up a little more. Still nothing. Tried other input jack and output jack. Still nothing. Turned amp off and reseated tubes. Still nothing. Damn, it doesn't work! I was about to start swapping tubes when I remembered to turn up the guitar volume. <sheepish grin> That helped a lot.

Let me say that I REALLY like this amp. It has a wide range of clean to crunchy sound, depending on the volume control (Master and Volume) settings, and which input (hi or lo) is used. The controls have a nice range to them, too. Even with the 12AX7 preamp tubes, you can turn the knobs a good bit without blasting yourself to bits. It's fairly minimalist, too, having only a few controls. And it's not too loud all the time. It will get loud, but nothing like the bigger amps I have, which is a good thing for me. I'm very glad I bought and built this kit.

Here's the final pic, shown with my PRS SAS:
http://www.cmwebsite.com/images/classact_sas.jpg

[Scott Peterson]

Beautiful work. My deepest respect and admiration. That looks incredible inside; your guts on this one is my new wallpaper for the computer.

Congrats!

[-CM-]

Thanks for the compliments. I wish the final wiring pic had turned out better. I didn't look at the pictures until after I installed it in the cab. I didn't realize the glare was so bad. Maybe I'll pull it out and take another one.

I'd be remiss if I didn't mention the quality of the kits and instructions provided by Dave Allen of Allen Amps (http://www.allenamps.com/index.php), though. Along with the kits come excellent support, too. I think it'd be hard to go wrong with any of his kits. (I'm not affiliated with Allen Amps, just a fan.)

[-CM-]

I'm bumping this thread so it doesn't disappear.

[Serious_Poo]

Thanks for taking the time to writing such a nice thread and taking such great photos. One day I'd love to build my own amp, and the work you've done on this little tone monster is pretty inspiring to me.

:dude: