5F1 build using EIA wiring color code!

[XYZGnomon]

I can't seem to find it, but a few months ago I commented on an old thread about wiring colors, asking about standards, and I decided to start a new build using the EIA Chassis Wiring Color Code someone posted. After searching this site (add "site:el34world.com" to any Google search), it turns out this question gets asked a lot!

So I built a 5F1 Champ using the color code. I made some editorial decisions that only inexperienced amateurs like me would, such as covering the passive component leads with fake spaghetti tubing made from gutted push-back wiring insulation. I probably shouldn't have done that. It looks silly! I also shellac'ed the cabinet.

I got a non-chromed chassis from Tube Audio Supply and drilled out a new location for the fuse. It's very well made, although its holes did not line up with the G10 board from Antique Electronic Supply, so I drilled new mounting holes in both.

For some reason, the Mersen caps' lettering flaked off. Mersen is the new name for F&T, but it's confusing because Mojotone seems to be the only vendor who has Mersen-branded F&T caps.





It worked right out of the gate, without much drama. Studying up and gathering the components has taught me a lot about how tube amps work, and the color coding actually helped quite a lot. I still have a lot to learn, but I feel like this was a natural next step after building the StewMac kit back in 2021.

I have some ideas about how to improve the board layout, which I know the host of this website is a subject matter expert on. For example, it seems like everything on the right side of the board could be done differently to save space, and I'm not really a fan of the routing for some of the cables that pass under the board.

The next step for me is probably to machine my own design G10 board, since i used to be a machinist and I have my own CNC router, and then maybe one day I'll take on the 6G16 Vibroverb I dream about.

[AmberB]

That looks like a nice clean build!
I use a color code system for my amp builds, I don't know if it's similar to EIA, I sort of came up with it myself.  I use red for the B+ line, black for the grounds, and green for the heaters.  Sometimes I use orange for the power tube screen grid power, if I have the orange wire available, otherwise I use red.  The signal wires tend to be whatever I have on hand, white, yellow, gray, purple, whatever, as long as it's not red, orange, black, or green.
As for space, I can see how there's extra space that could potentially be used more efficiently on the board, but you don't need to do that on a build like this.  A more complex amp would probably benefit from more efficient use of the space.

[XYZGnomon]

I found the post I was talking about, BTW: https://el34world.com/Forum/index.php?topic=12815

[PRR]

Spaghetti is good. Spaghetti is mostly not needed on short stiff runs or parts.

[XYZGnomon]

Happily I can report that it sounds actually pretty great too, BTW.

The adventure I went on a few years ago with the StewMac Champ kit - lowering the volume - seems to still apply here. It sounds great when it's socially inappropriately loud. I don't think I want to drill any more holes in this thing, but then it dawned on me... do I really need the regular volume pot? Can't I just convert that into a master volume?

My current level of understanding:

1) The first volume pot is in the guitar. It attenuates unamplified signal.

2) The second volume pot is on the amp control panel. It attenuates preamplified signal.

3) The third (if it exists) volume pot is master volume. It attenuates gain stage signal.

Do I have that right? The guy in the link above wasn't successful, so I am willing to accept that I don't actually know what's what.

Do I actually need the volume control between the preamp stage and the gain stage? If I eliminate it and substitute a master volume instead, what would be the result?

I refuse to believe that I am the first to ever think of this, and I doubt I have read about someone else doing it, so I assume this is a bad idea. There must be a reason the volume pot is where it is, and isn't where it isn't.

[sluckey]

The soldered ground connection on the side of the chassis looks like it needed a lot more heat for a solid connection. Big iron or big gun.

[PRR]

> There must be a reason the volume pot is where it is

The multiple pots let you the musician change WHERE the distortion happens, and at what level. And relative to finger-effort or room-racket. And some choice of the residual hiss/hum if you (ever) stop playing.

While I am inclined to K.I.S.S., if you aren't sure, you should throw the few bucks for several pots and play a LOT. All different levels. First for 'noise', then with e-guitar you want an extended study of distortion flavor (loud).

[sluckey]

Leo was not building distortion amps. He was building clean sounding amps when played at a reasonable loudness. The champ is the cheapest amp Leo ever sold. The volume pot does exactly what it was designed to do.