Amp Build: Brown Note 18Watt Lite IIB

[tunghaichuan***]

I like the black, too. Maybe you could go with gold lettering? That would look classy.

Thanks for the suggestion. BNP has aluminum stock that is black that engraves to gold lettering:

http://www.bnplasers.com/AMPBUILDERSMATERIALS.htm

I'm REALLY interested in this build, Tung--I've been kicking around the idea of making an 18W Marshall clone for quite a while and just haven't gotten down to it yet. Maybe this will light a fire under me!

I hope so, I think this will be a cool build. One of the features of this amp is the inputs: one input is a single triode of the 12AX7. The other input is both triodes in parallel which gives slightly more gain and a bit more complexity in the tone due to the differences in the triodes.

I'm curious about how you're planning to go on the transformers, too.

As detailed in an earlier post, I'm using a NOS Custom Coil Unit. It is rated for 70-90mA, 290-0-290. It also has 5V and 6.3V taps. Instead of a 6.3V rectifier, I'm going to use a 5Y3 or 5V4 on the 5V tap. I built another amp with a 6.3V 6CA4 rectifier on the same filament winding as the other tubes which is a bad idea. If the recto ever shorts out, it will take out the tubes the output transformer. Using a 5Y3 is much safer. I should get about 300v plate volts, which I've found sounds very good in a PP EL84 amp. Also I can run the amp in true Class A. The only limiting factor is whether the OT can take it. Class A is inherently hard on transformers, especially ones made for Class AB operation.

The one thing I don't like about the Edcor transformers is the exposed solder tabs. It is inherently dangerous to have exposed B+ outside the chassis.

BTW, we have a killer player who stops in here occasionally by the name of Chuck D'Aloia, and he's a featured artist for Brown Note. Hangs out/plays in their booth at NAMM shows, etc. Great jazz player and a confirmed Tele guy. Check out his intro HERE, and take a look at his website, which is linked there. He lives up in the Saratoga Springs area, about 30 miles north of here.

Cool, I'll check him out. :

One of my grad school professors lives in Saratoga Springs. He was my favorite, and one of the coolest people I've ever met.

tung

[tunghaichuan***]

The next step: making the eyelet board.

Full pictoral tutorial here:

http://www.diycustomamps.com/images/.../eyelet_board/

Main points:

I make templates from 3" wide, 1/16" thick Grade XX Garolite from McMaster-Carr. The Garolite comes in three inch wide by four feet long strips. Since I don't have a miter box or a power saw, I mark the garolite using a Sharpie and a square, rough saw it to length with a hack saw, and then trim off the end with a laminate trimmer with a flush cutting bit and a straight edge. Kind of a PITA, I know.

Next I take the 1:1 artwork I previously generated in CorelDraw, cut it out and tape it to the front of the blank template. I make a template so that I only have to do the aforementioned step once. Once I have a template it is just a matter of taping the template down to a new blank board and marking it. This is a lot less of a hassle than drilling through paper taped to a board.

Using a jig I made, I set a fence on the drill press to get nice consistent, even results. I then drill out all the eyelet holes and the four board mounting holes.

Next I take the template and trace the holes onto a piece of G10 glass epoxy board using a Sharpie. G10 is used as the substrate for high-quality PCBs. This is a better material for eyelet boards than Garolite, but it is very expensive. I bought a 3' by 4' sheet a few years ago and had it cut into three-inch wid lengths. I'm down to the last of it and unfortunately G10 prices have skyrocketed in the last few years

Then using the same method for the template, I drill out all the holes on the drill press using the attached fence and setup template.

The next step is setting the eyelets into the board. I put an eyelet into each hole (leaving them out of the mounting holes, natch) and tape them down with masking tape. This allows me to turn the board over without all the eyelets falling out.

I flare the eyelets using a small hammer and a 5/16" center punch. I then secure the eyelets by flattening down the flare witha 6" long, 1/4" diameter steel rod. Viola, the board is done.

The same method can be used with turrets as well. The only difference is the setting method. I personally don't like turrets, they do look cool, but are a PITA to modify once the components are soldered to them.

Since this is a scratch build, I have to do all the handwork myself. This is another advantage of kits: the eyelet board comes ready to stuff and install. Also, the chassis comes finished. Making eyelet boards and drilling out chassis can get very tedious.

Next up: drilling all the holes in the chassis.

tung

[Bloozcat]

I'm going for the popcorn, be right back.....