Developing the DIY "Champ" for first time builders

[angelodp]

Good looking build, welcome. You do realize that this amp building is pretty addictive! What's next... kidding. Enjoy it. I am getting ready to build the Supre for my grandson, should be fun.

Cheers Ange

[surfsup]

GKT, nice looking build. I look forward to seeing your mods!

Question, is your IEC ground (the green run from the three prong wall jack) just soldered to the chassis under the PT mounting?

[Ian444]

Looks good gtk, only thing I noticed is it looks like you got the active and neutral swapped, active should go to the fuse, easy fix anyway. You've done a great job on that amp. Surfsup I think the answer to your question is yes, click on the image to make it bigger.

[M Fowler]

Greg,

Good job and congrats on getting it going.

Mark

[Andy Le Blanc]

That is a good looking rig. Champs are great mod platforms.

I miss the tube rectifier.... if its destined to be kit, I would add socket punch outs

so another pre tube can be added easily by the end user.
With two tubes in the pre it becomes a hi gain test bed.

nothing like a jcm 800 lead master volume in a champ

I had a champ that I converted to a princeton with an extra pre tube
and used the rectifier socket (ss rect.) for push-pull.

A couple extra holes if your stamping out sheet metal for chassis
could go a long way for the end user and extend the kits life as a learning platform

[Structo]

Nice amp for your first time.

A little constructive critisizm, if I may.

You see how you have those green wires for your grounds off of the black caps and over to the other components there?

It would be cleaner to have a bare buss wire run across all those connections, then take a lone black or green wire to your ground lug.

The ground lugs would be best if they were bolted directly to the chassis with their own screw and lock nut.
Less chance of coming loose.

The hot wire from the IEC connector should go to the fuse first then to the switch.

If you have the preamp cathodes going to the power supply ground it is possibly better to have those go to the input ground, quieter there.

Have your heater wires twisted tightly and run them over head of the sockets then straight down to the pins they are connected to.
You want to keep that AC power away from things to reduce hum.

Good job!

[gktamps]

Hello, and thank you for all of the comments - very much appreciated.
Ange - yes, I can assure you I've been aware of the addiction, and am just the sort of victim that falls prey to it.
Surfsup - Yes, the IEC ground is soldered to a tab which together with the tab for the center taps, is bolted to the chassis, per RJ's design. I deviated in that instead of running a long ground wire from the input jack to that same point, I tied it to the right lower corner of the board an inch away, in an attempt to minimize ground loop effects (don't know if that was warranted or not).
Ian444 - It sounds like I may have read the layout drawing wrong and flipped the IEC socket so that the neutral and hot are reversed. Thanks for catching that!
Mark and Andy - thank you.
Structo - Having seen what you describe in many other amps, including my 18 watt clone, I thought about that as well, but decided to follow the exact layout RJ provided, to use as a baseline. Going with a buss wire appeals to me however, so I will make that change, as well as bolt the grounds direct to the chassis. Thanks for catching the IEC jack wiring.
Thank you all very much,
Greg

[RJ Guitars]

Greg,

Really nice work! I have found that when I share my work here I end up with a better amp each time... great collection of minds and experience to draw from.

The guys talking about the IEC socket wiring are on the ball. That is important to get it done right so you save yourself or somebody else an AC shock. In three wire AC (hot / neutral / ground) you always break the hot wire for fuses and switches.

Great looking amp and sounds like you've got some good tones out of it already. They are surprising loud and decent sounding for so few parts and doesn't require an oversized roady to move it around for you.

Hope you enjoy it and we'll look for the itch to build again to begin soon... some guys are hooked before the first one is finished but most of us can quit any time we want to.

rj

[gktamps]

Thanks, RJ. I have enough good amps to have no unrealistic expectations for the tone of this little thing, and am treating it like an inexpensive learning and testing tool.
I made the changes recommended by everyone - ground buss for the filter caps, grounds on chassis rather than on the board standoffs, swapped the IEC jack.
Now to play with a volume control cap (500pf sound right to start?), then a tone circuit, maybe the tube rectifier (5V4 OK?).
Thanks again, everyone,
Greg

[Zippy]

Now to play...maybe the tube rectifier (5V4 OK?).

I suggest you make it switchable between tube and SS. Then you can tell us whether you can distinguish a difference.

What volumes are you running? The higher you turn the volume control, the less effect of the volume bypass cap.

I was once proposing to RJ that the amp didn't need ANY knobs! That was a big deal for me since I can usually come up with a knob or a switch to answer every need.

[rp]

I was once proposing to RJ that the amp didn't need ANY knobs! That was a big deal for me since I can usually come up with a knob or a switch to answer every need.

Don't joke, I don't think the 5C1 I just built needs a knob, I can't tell much difference btwn rolling back the guitar or the amp's vol. It's not so loud as to scare anyone and it really sounds best wide open, or just a touch rolled back from the guitar, and you never have to get up. Who needs a steenkin' knob on a 5W amp

[Zippy]

Amen - or on any other amp that's the correct size for the application.

A volume knob is kinda like putting brakes on a motorcycle - it only slows you down.

Tone controls are like putting padding in the seat.

A bright switch is like having turn signals.

Someone stop me - this is getting out of control.

[RJ Guitars]

I added a 100pf bright cap across the volume pot. You might try the 500pF and if it doesn't add enough low volume brightness then go for the 100pF.

rj

[guitardude57]

some guys are hooked before the first one is finished but most of us can quit any time we want to.

rj

RJ,

Yeah right.............................

[gktamps]

Zippy - Yes, switchable tube vs. diode is what I'll do.
It's too loud for my small music/work room (and house) when turned up past 1 o'clock, so I've been playing it at around 11-12. My wife thinks it needs a much "bigger" knob than it has (= more effective). I don't even play my 100 or 30 watt amps when she's home - keeps the smiles from turning upside down.
As I mentioned, this is my test/learning tool, not my holy grail amp. With such a simple circuit, small changes seem to make a big difference.
RP - This amp seems pretty sensitive to input volume, so the effect from dialing down the guitar's volume really affects the tone as well.
RJ - I'll try different values with my capacitor substitution box to get some clues, then put in two caps - one on either side of an on-off-on switch.
Also, is there any advantage to altering the negative feedback resistor for this amp, or any cautions about doing so?

Cheers,
Greg