Developing the DIY "Champ" for first time builders

[mcrracer]

Musical Power Supplies
OT8SE
5W to 8W SE Guitar Amp Output XFMR
82Hz to 10KHz, 45mADC
7000 Ohm and 5000 Ohm inputs to 3.2/8/16Ohm Outputs.

Circuits: Champ, Bronco, VibroChamp, Valve Jr etc using a single EL84 or 6V6 Power Tube
$18.95
Best deal out there in my opinion

[bigsmitty]

Magnetic components Champ OT have 4 and 8 ohm taps.

[Phil_S]

Can you make it work with these?
http://cgi.ebay.com/Terminal-Board-40Lu ... 3caf1b8358

You'll have to get away from the traditional layout, but these are about as inexpensive as you are going to get. Remember to include the standoffs in your BOM.

If you have enough quantity, you can probably get a price break from either MPS, Edcor, or Magnetic Components.

Edcor will do a custom run for a very modest setup charge, but you will need to have enough quantity to spread out the setup charge to each piece. Edcor responds to email, a little on the slow side. They claim to have a library of designs not published on the website, so getting them to dig out the champ specs shouldn't be too difficult. If I were serious about this, I'd contact Edcor with what I wanted and see if they already have a design on file. If you have to actually give them a design (wire size, turns, inductance, impedance, etc.) then you are moving this to a whole new level of complexitiy, but if they have what you need on file, you just need to get the order to enough pieces to make it worthwhile.

Good thread, great idea!

[RJ Guitars]

Can you make it work with these?
http://cgi.ebay.com/Terminal-Board-40Lu ... 3caf1b8358

You'll have to get away from the traditional layout, but these are about as inexpensive as you are going to get. Remember to include the standoffs in your BOM.

If you have enough quantity, you can probably get a price break from either MPS, Edcor, or Magnetic Components.

Edcor will do a custom run for a very modest setup charge, but you will need to have enough quantity to spread out the setup charge to each piece. Edcor responds to email, a little on the slow side. They claim to have a library of designs not published on the website, so getting them to dig out the champ specs shouldn't be too difficult. If I were serious about this, I'd contact Edcor with what I wanted and see if they already have a design on file. If you have to actually give them a design (wire size, turns, inductance, impedance, etc.) then you are moving this to a whole new level of complexitiy, but if they have what you need on file, you just need to get the order to enough pieces to make it worthwhile.

Good thread, great idea!

Thank you Phil for info and encouraging words. Those turret boards will work and prove the point that there are many inexpensive ways to get this done.

I'll attach an image of the loaded board I made up but keep the cruel comments to a minimum, the photography came out a touch too crisp and you can see things a little too clearly. Looks like I could have taken out one more row. Perf board does give you the option of placing the components in the 5F1 layout, but that isn't a critical need. In this case the turret board and enough turrets to mount everything, add the rectifier circuit, and make a couple mistakes is going to be under $6.

I'm on a first name basis with Edcor. They custom wind the Trainwreck spec trannies I sell plus they are located here in New Mexico where I live. Great company and great folks to work with. I'll probably buy the power tranny from them in a 235-0-235 secondary. Edcor rates their trannies at a loaded value and the B+ can run a little high. In addition to that I'll be using the SS rectifier and the voltages will be a little hot anyway.

There seem to be a bunch of output tranny options for around $20 but I think we can do better! I like the dual primary/secondary options but I do want to avoid any that have exposed B+ terminals. Fixed wires are pretty important to avoid creating something requiring extra steps to make it safe. I'll talk with the vendors tomorrow and see what they can do. I'll probably order a dozen of each tranny as a starting point.

thanks again everybody,

rj

[CaseyJones]

Magnetic components Champ OT have 4 and 8 ohm taps.

The second worst sounding SE transformer I've used in Champ style builds. A Champ is supposed to "chime". An OT with limited bandwidth eliminates that desirable feature.

[mcrracer]

Board looks great to me RJ.

[M Fowler]

I bought a bunch of those boards they are 1/16 and work out well for my projects. I think I paid $6.79 each for them and they are long so one would make two of these champ boards probably.

Lots of room in a Fender champ style chassis compared to tweed chassis so need to cramp things in.

I like Edcor iron very well make iron and I bet you would hear a big different in a blind taste test against many others.

Mark

[ChrisM]

You could even make it smaller by putting the grid stopper right at the socket pin, where it should be.

[NEjoe]

Any thoughts on speakers? 12 inch or 10 or 8?

What sounds good single ended with about 3~6 Watts?

[David Root]

Based on my experience I would say try to find a very sensitive 10", at least 100dB @ 1M . I think it would roar! Failing that an Alnico Weber for period correct tone.

I know that a Princeton sounds better with a 12" rather than a 10", for example, and I have even been told that a tweed Champ thru a 4x12 sounds amazing, but never tried it.

[xtian]

tweed Champ thru a 4x12 sounds amazing, but never tried it.

I was just testing my 5f1 build, wide open, thru a 2x12 Avatar cab. Sounded pretty good. Then the 8" Weber AlNiCo in the blackface Champ cab sounded pretty much like a cardboard pile of poo.

[mike9]

I'm definitely down for a group buy thing. I want all the learning curve I can get. Yeah - I'm a sick mofo -

[M Fowler]

I really don't like the smaller speakers but some 10 inch are good, normally I just buy all 12 inch cabinets, even for my champ octal cage amp.

Come to think of it the only 10 inch speakers I have left are in my Super Reverb.

[selloutrr]

Champs sound great with all sorts of speaker(s) and configurations it's more about voicing the amp with the proper tubes and not over loading the input.

but

keeping it true to a champ the speaker would need to be a 6" or 8" speaker with a 4ohm load.
The champion 600 was a 6" speaker
The 5E1 and 5F1 where 8" speakers

[RJ Guitars]

I'm definitely down for a group buy thing. I want all the learning curve I can get. Yeah - I'm a sick mofo -

I'll start a list for anybody that wants to do this. I can see that the under $100 goal still looks good. I bought a dozen 6 watt 5K/8 Ohm output trannies for about $13 each delivered. We'll see how they look when they get here. I've also identified a premium tranny set for for $60, but that might be something for phase II of the effort.

I have a little cabinet design for a head and also one for small combo that has a 10" speaker in it. I have an excellent cabinet builder who can do the cabinets in hardwood or Birch Ply, with or without tolex for those interested. I can also provide drawing specs for the real DIY guys.

One thing I am looking at right now is how to do the SS rectifier with only one switch. I know I can do it with an On/Off/On but that has you going through the Off position in the transition from Standby to On. I know that has been done in the past, what is the down side? Other amps (Fender Pro Junior) just go ahead and whack the output tubes with the B+ as they wait for the tubes to heat up... seems wrong but it has been effective for thousands of amps.

Any thoughts?

rj