PT and tube limitations

[eschertron]

I'm just a grouchy old bear in winter

[pdf64]

...can we say with confidence that the champ does not draw more current when grossly overdriven?

Under extreme overdrive, I think it will depend on the mark-space ratio of the signal at the power tube control grid; if the tube is more 'on' than 'off' then plate current will likely rise above the 'max clean output' level, and visa versa.
And what determines the mark-space of the drive signal will tend to be affected by how hard each successive preceding stage is pushed, so it's a signal level and control setting variable, might well vary moment to moment according to the signal envelope and frequency spectrum
So on average, the power tube current when overdriven is probably going to be about the same as the max clean level, which itself is only a little more than at idle.

[Randall]

Do I get over my head much?

[g1]

Randall, you mentioned the 2 versions, have you picked the one you are going to build, and can you post the schematic?
My understanding is there are more differences than just the supply, such as the load and choice of outputs?

[Randall]

Here are the two versions, I'm leaning towards the second one, the H-ZOG, I don't want to use a tube rectifier since neither version ever had one, and also I can't get with no PS filters.

http://www.thetubestore.com/lib/thet...G12H-H-Zog.pdf

[eschertron]

and also I can't get with no PS filters.

The 5C1, an early champ, had 8/8/8u PSU caps. By the late 70s, the champ had 20/20/20u by the schem and 40/20/20 in actuality. For your application, I'd suggest erring on the side of big caps. Keep in mind you've discussed adding another stage of filtering even before the plate, so add another cap of the largest size. And with SS rectification, there's no restriction on cap inrush current.

I'd recommend putting the 6R/10W load resistor on a shorting jack, so you could plug a speaker in, and use your champ as the guitar amplifier that it is. I've had wonderful fun with a champ into a 2x12!

[g1]

and also I can't get with no PS filters.

That's got to be an error in the schematic?

[eschertron]

That's got to be a typo?

the schem linked omits PSU caps from the drawing. Strange, yes?

[g1]

I'd recommend putting the 6R/10W load resistor on a shorting jack, so you could plug a speaker in, and use your champ as the guitar amplifier that it is. I've had wonderful fun with a champ into a 2x12!

I think this is what the second schematic shows?

[The Dude]

That's got to be an error in the schematic?

It's like "daughter" and "honor". The caps are silent.

[eschertron]

I think this is what the second schematic shows?

Ah. Late to the party again. I only looked at the first page.

[eschertron]

I think this is what the second schematic shows?

...and yes, the second schem also shows the 'extra' first stage of filtering. My recommendation for cap values still stands

[Chuck H]

I might make one mod suggestion. Early this year I modified a Champ to take an el34 tube and to improve the overdrive character. I found that a higher value HV rail resistor between the plate and screen allowed for more/better plate clipping without over dissipating the screen at higher input signal levels. For an el34 using a 4k primary I found 3.3k did the trick. Not sure what value would be best for a 6v6 with something like 8k primary? Possibly no additional resistance is necessary because of the higher primary. Just watch for screen grid torture and know that adding resistance can help.

[eschertron]

+1 to screen control. I have a SF-era champ that I added a screen stopper to (absent in the original). I made it 6k, and added a 1.8u cap to ground from the screen. I like the compressed sound I get in high overdrive. of course, YMMV