Developing the DIY "Champ" for first time builders

[RJ Guitars]

We started a discussion over on the "Trainwreck Discussion" pages about putting together a simple Champish build kit for first time builders. One of the thoughts behind the effort was to see if we could identify all the critical parts and obtain them for under $100.

I made up my own layout drawing and plan to loosely follow the the 5F1 schematic and use a simple rectangular chassis (6" x 12"). You can probably see how the trainwreck builds have influenced my layout. One cautionary note - consider the drawing a work in progress that is thus far untested.

I placed the tranny holes for a specific set of transformers I might use but almost anything will fit in those spots. In time I'll put together a layout drawing, BOM, and schematic based on the input from the TAG.

enjoy,

rj

I am going to add an Edit Here and use this as the main page for the latest and greatest in schematics and layouts.

This project has evolved into three amps:

The Eagle 100 - intended to be the $100 DIY Champ

The Eagle Premium - schematically identical to the 100 - upgraded transformers and filter capacitors.

The Eagle Supre - The big brother of the Eagles and more of a customized personal version. http://ampgarage.com/forum/viewtopic.php?t=14349 The associated schematics and layout info will be on that thread.

rj

[selloutrr]

sounds fun!

Tubes and transformers are going to be the deciding factor for cost.
Hammond PT P-T290AX ~ $62
Hammond OT P-T1750C ~ $34

JJ or sovtek Tubes
Rec - ~ $15
Power - ~ $15
Pre ~ $10

Is the $100 goal taking into consideration a group buy or for a one off?

I like your chassis drawing - Have you considered making the dimensions based on a standard production project box. Hammond and bud chassis offer punching in factory for bulk orders.

[xtian]

Trannies at http://www.musicalpowersupplies.com/ run about $70 total including shipping.

I'd love to see you put together a kit for under $100--it would be a magic trick, I think!

[TheGimp]

I've used an Allied 6K49VG which is built by Hammond and only runs $23.21 in single quantity. B+ is 460CT at 50ma which is will give near 325V if SS rectified.

OPT for a low cost solution is limited to single impedance output but the Edcor XSE10-8-4K is a nice 8 ohm output with 4K primary and rated at 10W for only $17.22 in single quantity and is available in other output impedances (4 and 16 ohm).

[Dr-Joned]

I would say to try and source "local" parts. In the US, you could use a hammond box, edcor trannys, and and maybe a Ken Watts $12 eyelet board. If this is just for the learning curve, then quality of components shouldn't be a major concern. (ie Sozo caps, etc.)

[RJ Guitars]

It sounds like you guys are on track with me. I would definitely do a group buy to help bring the prices down as low as we can get them.

I made the layout to use one of my own 6 x 12 inch chassis blanks. I like them not only because I have them but they also fit my existing head and combo cabinets plus they are a heavier gauge than the Hammond. I know that "Gainmaster" here on the forum is making up blank chassis' that I think I are a very decent quality and at a price that would be tough to beat.

On the other hand, using something generic, cheap, and easy to find, especially the already existing kind of stuff is really where we wanted to go with this. I'm going to look up that board, the price is excellent.

Transformers from Edcor always make me smile. Excellent company and product plus they really work with me on supplying what I ask for. Great prices and they are one of the few New Mexico companies I can be proud of... we don't have a lot of industry out here ya know.

$100 for all parts currently commercially available is the goal, although not a mandate.

Tubes - if modern production runs the price up too much, there are some excellent quality and cheap prices available in Russian NOS supplies.

You are exactly right, it's a learning tool and not the ultimate amp build.

thanks for the input.

rj

[M Fowler]

rj I already have your Champ chassis but need a cabinet or make one, I need trannys though.

Complete parts group buy would be good also.

Mark

[TheGimp]

I built a champ like amp with a 6P1P output with selectable feedback, and selectable tone stack that uses a Hammond chassis (H1444-18, $14.35 @ Antique Electronic Supply) if you don't mind the size.

I put it in an oak head like a Trainwreck.

Thread is here:

http://ampgarage.com/forum/viewtopic.php?t=13307

[Normster]

If you really want to keep the price down, maybe consider a solid state rectifier and build with terminal strips instead of a board. That knocks about $20 off the build. With a few tweaks, I'm pretty sure you guys can keep it right at $100. As for a chassis, it "could" be built on a scrap of plywood.

[statorvane]

If you really want to keep the price down, maybe consider a solid state rectifier and build with terminal strips instead of a board. That knocks about $20 off the build.

Yes. The rectifier substitution is an excellent idea. I don't believe the 5Y3s in current production are real-deal 5Y3s anyway - too stiff.

I think a tag board would be far easier for a newbie to wire up compared to terminal strips. There is a cost-benefit trade there.

[FYL]

One of the thoughts behind the effort was to see if we could identify all the critical parts and obtain them for under $100.

You may use a SS recto and lower the parts cost: SE amps run in class A with a nearly constant current draw. A valve here offers very little benefits sound-wise - OK, HF noise can be lower, it was used because silicon wasn't available. And if you want to simulate sag, just add a series resistor in the B+ line...

[David Root]

Suggestion--Use 7-pin NOS tubes, cheep cheep! 6AQ5, 6AV6. 6X4 if you want a tube rectifier, like FYL sez, SS is cheeper and OK too.

Good tone, maybe even a little raunchier than than noval tubes!

[rawnster]

If you really want to keep the price down, maybe consider a solid state rectifier and build with terminal strips instead of a board.

Say it ain't so. Terminal strips are from the devil!

[davesi]

Another board option could be preloaded 12"X2.36" (AES # P-HTUR-60) @$9.95. Turrets are easy on first time builders and plenty of room for everything.

[RJ Guitars]

Another board option could be preloaded 12"X2.36" (AES # P-HTUR-60) @$9.95. Turrets are easy on first time builders and plenty of room for everything.

I have a lot of "stuff" here that I was going through looking for parts to build this Champ amp. I came across one of the Blank perf boards from AES. Same size as the ones mentioned but no turrets. Either way you are under $10 for a board. I gotta say I don't really like this perf board but it is adequate albeit ugly. I don't like these turrets so much either because they are kinda massive. I soldered up the board this afternoon and found I had to turn my iron up a bit to get the solder to flow the way I like it. But for the price, it's a winner. I did compact things a bit from the design above before I soldered in the components so there are two less rows now.

Solid State rectifier - This would eliminate the need for the 5V tap which makes the transformer options better... might be the right answer. I shoulda left those extra two rows and I could put the diodes onto my board - Doh @!$@%. Maybe I can create a PCB board version (now we are really walking on the dark side!)

I love 6AQ5 tubes and I also agree you can't beat the price of the Russian stuff. I don't really like the 7 pin triodes for the preamp since they would add another tube to the mix. Any of these are easy to accommodate.

I've found a few good transformers - I want to go with the 250-0-250 and not run the B+ up too high. This will allow for some of the those 6AQ5's and Russian tubes to work. Is 60mA enough... I know somebody is going to tell me do the math?

Champ output trannies are pretty cheap but also have a 4 Ohm secondary. I'd really like to have 8 ohms so i am still looking at the options there as well.

Thanks for all the good help!

rj