Developing the DIY "Champ" for first time builders

[surfsup]

RJ and anyone, on your layout, you have the OT secondaries coming out right at where the mains are. Is this okay to do?

Also, it would be great to get actual dimensions once your layout is finalized so I could begin to alter mine to fit yours.

[Zippy]

I suppose you noticed the KT-88 in my Supre... don't know if that is the right output for the DLM but that's my inclination.

EL34

[RJ Guitars]

RJ and anyone, on your layout, you have the OT secondaries coming out right at where the mains are. Is this okay to do?...

Absolutely OK, but placing that tranny further away is generally a good idea when you have the option. This is how all Trainwreck amps are done and a Rocket amp can be dead quiet. If you look at any of my recent layouts you'll ind that I have been heavily influenced by the trainwreck amps.

I actually don't prefer to do it this way but the small chassis and my desire to make this future flexible kinda pushed me that direction. If you are gonna do this, there are a couple good practices to use.
1 - Keep the mains wiring and transformer wiring away from each other to the best extent you can.
2 - Anytime those wires are in proximity to each other and or cross each other, try to have them pass at 90 degrees to each other.

For your build you could move that transformer way over. My layout will allow you to add reverb, and move to a push-pull output... but in this case I'll prototype one before I declare it a good idea.

I'll send you or post up those chassis dimensions.

rj

[Zippy]

I modeled up the PT/OT...

What do you mean???

FWIW, I'm looking at the 230-0-230/15W et.

[RJ Guitars]

I suppose you noticed the KT-88 in my Supre... don't know if that is the right output for the DLM but that's my inclination.

EL34

I've actually heard that there are two DLM's, and I know one of them does claim the EL34...

I might be confusing my stories here too because I know that one of Ken Fischers amp testing buddies is always telling me about his love for the tone of KT-88's...

So many amps to build and so little time?

[jrc]

Hello everybody, I'm brand new to TAG. I just saw this thread and would love to try the basic build. Message sent to RJ, hope you have an extra kit.

[surfsup]

surfsup wrote:
I modeled up the PT/OT...

What do you mean???

I mean that I modeled 'em up just goofin' around - I hope to fully model RJ's kit at some point once he has it finalized just for fun. I figure the solids will help me see components in 3D space better for future designs. Check it:

pic deleted...

[M Fowler]

I am trying the Mojotone American Vintage AV10C 10'’ Speaker 8
OHM 25W in my Premium Eagle combo cab kit.

I liked mojo tones Vintage 30 style speakers so this one should sound good as well.

Mark

[surfsup]

I'm thinking 300/300 is the way to go for the supre to use the big bottles 6L6/EL34 etc. Something like:

PT Choices:
Hammond 272DX 300-0-300 144mA, 5V @3A, 6.3V @4A ($64)
Edcor XPWR008-120 300-0-300 200mA, 5V @3A, 6.3V @4A ($61) (preferred)
Edcor XPWR009-120 275-0-275 at 175mA, 5V @3A, 6.3A @4A ($51)

OT choices:
Hammond 125ESE 15Watt 80mA (has 4-8-16ohm leads) ($67)
Edcor GXSE15-8-5k 15Watt (8ohm lead only) ($38) (I like the Hammond but its $30 more)

So really if you're going with Edcor because you have a dealer account, the OT you picked seems to be fine to me (keep in mind I'm totally new to amp building). The PT I would not do the XPWR156-120/125 in favor of the XPWR008-120 which has a little more output for $5 bucks more. If you wanted less V, the second I listed is cheaper at $51 and has more output than the XPWR156 but I'm not sure why it is less than the other one. Any comments?

[M Fowler]

The higher the mA more windings and copper wire isn't cheap.

The 320-0-320 at 120mA was suggested a while back.

I made this SwampThing SE amp a few years ago using cheap PT/OT the whole amp could not have cost me $100. But I would rather get some good quality iron like rj is doing and built a great Champ.

Mark

[surfsup]

I don't see this on the Edcor website. If I click 640V first it should come up with all the 320-0-320 PTs there are only two listed.

I did find this at $53:
XPWR047-120V, 60Hz. line to 660V (330-0-330) at 120mA center tapped, 6.3V (3.15-3.15) at 2.5A center tapped and 5V at 3A.

[Zippy]

I'm thinking 300/300 is the way to go for the supre to use the big bottles 6L6/EL34...

Any reason why???

...keep in mind I'm totally new to amp building...

Any comments?

I'd recommend building and learning a bit before you start "designing"...

[surfsup]

Zippy, here is a detailed response (sorry if its long - but you wanted my thought process);

History of my amp-building experience (quite new as I mentioned):
4 months total experience. In that time:

-I built four guitar effects pedals - three were my design, a wah and two fuzz (one still doesn't work haha) so three successful builds, one still in-process

-I built one amp successfully "connecting the dots" - ax84 HO that I've modded a few times

-I rewired, tested and rewired that amp upteen times (sounds good now!)

-I mathematically calculated the entire ax84 HO amp design with the help of the P1x doc and Blencowe and Megantz

-I built a spreadsheet to automatically "build" an amp with two 12ax7 preamps and a single ended PT EL84, with minimal input (bias points, frequency values, etc) generating R and C values based on the HO design (just to physically enter in the math so I would remember it better).

-I mathematically calculated a second schematic design that I think I did correctly

-I've perused numerous other schematics to try and figure out what the passive components are doing

-I created two schematics from looking at only a layout (one was a champ clone - the Ceriatone Ultra Champ)

-I nearly read Merlin's Preamp and PS design books completely, rereading many areas

-I read Rob Megantz's Design and Construction of tube gtr amplifiers

-I read what seems to be +1000 posts at TAG, AX84, BYOC, DIYStomps, etc. (and forgotten 90% of it!)

Because I feel like I have to explain why I posted in a public forum:

-RJ emailed me for my opinion the other day on what I was thinkingI would want (I'm sure just out of curiosity, not actually wanting my advice for his Supre) and I figured I would post it for all to see and get comments back.

-Others posted they were interested in the Supre-Eagle but no concensus yet on a PT/OT choice. I figured I would start the conversation going.

- My "any comments?" comment was clearly an invite to get helpful comments. Since you are all more knowledgeable than me, I didn't bother with my math because I assumed you guys all know this already. But in the spirit of helping others and "taking one for the newb team"...feel free to slice and dice my reasoning, I figure I'll learn something:

Reasons why I think 300-0-300 with +100mA:
I realize it is important to first select a transformer V range that will get me in the range of where I want to be to get a certain sound. I am not totally familiar with 100 amp sounds so I rely on other's designs/schemos to see where they are at with V values at preamp plates, B+, etc. So here's the reasoning:

-My HO has a Hammond 269DX PT and with the EL34 "option" this tranny is too light. I'm a little disappointed with that discovery. Could use more current supply. I don't want to be limited and would rather just pay the $5 or $10 more now and have a bigger tranny to mod, or repurpose at a future day.

-Fender uses the 300-0-300 for their 5F1 - similar circuit to what I wanna do - many have stated there's nothing wrong with copying a successful builder

-mains voltage in the USA has gone up in the last 30 years (mine is 125VAC). So for a 5E3, that is 330-0-330, something 115/125 = 0.92 = 330 * 0.92 = ~300V

-Flexibility in dropping resistors (is this a valid point?)

-Want a clean amp, and believe a larger plate voltage will kick the load line out more to the right to allow for more headroom in picking a bias point on the graph.

-Going higher than 600-650 gets too close to 5y3 valve rectifier tube max plate V = 350
http://tdsl.duncanamps.com/show.php?des=5Y3

- The tube recto I was interested in doing drops some voltage so the transformer needs to supply more. Here is my math, hopefully I have this correct because I spent a TON of time trying to figure out how to mathematically integrate a tube recto into the design:

300 * 1.3 = 390VDC (using 1.3 instead of 1.4 because the internal inductance in the transformer, itself, per Megantz which is appx. 10%)
Tube mA draw:
EL34 + 12ax7 + 12ax7
EL34 = 25W/375V = 67mA
(forgot the screen which would draw about 10mA as well but this only affects sag another 3V-ish)
12ax7 = 3mA * 2 tubes = 6mA
mA draw = ~70+10+7 = 87mA we'll call this 90mA
@90mA 5Y3 sag = 48V - http://www.triodeel.com/5y3_p2.gif
390 - 48 = 345V
Merlin says take into account the addl. V drop from Rlim for 5Y3 - the new 5Y3s as I understand it pretty much negate this and this can probably be ignored, but for education's sake (because I got some used 5Y3s being sent to me now and I don't know the brands, how old they are, etc):
5Y3 has two plates, per http://www.tubezone.net/pdf/5y3.pdf at a supply of 700 and 1000Vrms, there is 50 and 140R resistance. I'll just take the 50R value as the value for 600V (hopefully I am looking at the right values on the PDF for Rlim). The transformer probably supplies enough but to get the sag, I would want to put a resister in front of each plate, anyway. So at 80mA, a 10R will be a Vdrop = (10R+50R@600v)*0.08*2 (for two plates) = 10V

So now the HT is at approximately 335V, which might even be a tad low, see below (so 320-0-320 might be the way to go)

Looking at schematics that I have for comparisons:
320V HT - Fender Champ (I'm a little over this but the Champ has only one 12ax7 and 6V6)
380V HT - Champ with verb (not sure who's schemo)
355V HT - champ with verb with "tweed" B+ (not sure who's schemo)
320-0-320 - ceriatone Ultra Champ with tremolo
320-0-320 - Fender AA764
315-0-315 - Fender VibroChamp
400V HT - Fender Super Champ (more complex circuit)

[xtian]

History of my amp-building experience

I recognize a knowledge sponge when I see one! Soak it up, man.

[surfsup]

Just wanted to give some evidence that although I'm asking for some handouts here and there, I am putting in some effort...btw, did I get that tube recto math right?