simplest possible push pull 6v6 cathode bias guitar amp?

[Illinest]

I imagine that there must be a schematic out there that fits the idea but i cant find it.

I found 5e3 tweed fender amp but i think they sound a little too raunchy. I don't want to build a tweed.
I found aa1164 fender blackface princeton and it has a sound that i like but it's also got fixed bias and a reverb circuit.

I just want a preamp, a volume control, a phase inverter and an output.

No reverb. No tone stack. Just the dead simplest thing i can find. I like blackface fender sounds a lot. (Especially deluxe) I want some chimey clean tones. I only play at bedroom levels so high watts is not important.

I have 12ax7, 12au7, 5751 and 12bh7 tubes to choose from for my preamp section. I have 6v6 tubes for power section. I have other tubes but i don't think it's necessary to list them here.

I have iron that will serve. I have tubes that will serve. I have chassis, sockets, switches, wires, etc but i need to stop screwing around with schematic changes. Need to get a schematic and start ordering parts. Need to stop changing my mind.

 

[jjman]

All of the push pull BF/SF Fenders have a tone stack IIRC. They all "scoop" the mids somewhat, even if it has a mid control that is set at max. And they all have Bass and Treble controls. Some also have Mid control. LTPI vs Cathodine needs to be decided and it can be either. Any of the fixed bias setups can be run using cathode bias instead. You may want to look at the Brown era. 6g3 Deluxe and 6g2 Princeton. Just erase the trem sections, assuming you don't want trem, ground the junction of the output grid leaks and use cathode bias.

Here's the 6g2 w/o trem and 1 input. Add screen resistors!

 

[Illinest]

All of the push pull BF/SF Fenders have a tone stack IIRC. They all "scoop" the mids somewhat, even if it has a mid control that is set at max. And they all have Bass and Treble controls. Some also have Mid control. LTPI vs Cathodine needs to be decided and it can be either. Any of the fixed bias setups can be run using cathode bias instead. You may want to look at the Brown era. 6g3 Deluxe and 6g2 Princeton. Just erase the trem sections, assuming you don't want trem, ground the junction of the output grid leaks and use cathode bias.

Here's the 6g2 w/o trem and 1 input. Add screen resistors!

YEEEEESSSSSSS!

Is that your own drawing? I have been looking for something like that. It's not exactly what i was describing but it's within spitting distance for sure.
I can work with that. I've even got lots of the parts mounted on a chassis already.
Did you ever build it yourself? Curious about how it sounds.

Wait... is that a 315v b+?!
That's what i've got! I wouldn't even need to worry about bias!

 

[jjman]

It's the 6g2 and some “photoshopping.” Don't assume the voltages will come out that way since the load from the trem tube is missing. You could adjust the power supply dropping resistors to change the preamp voltages. The B+ will depend on the rectifier tube and the power tranny mostly. The (shared) output cathode resistor should probably be 250-500 ohms or so and bypassed with a ~50u cap. You could eliminate the tone control and its 2 caps if you wanted and adjust overall eq by adjusting the values of cathode and/or coupling caps. You could reduce potential gain (distortion) by eliminating the 1st stage cathode cap. Plenty of options

 

[Illinest]

I clicked on just about every fender schematic i could find. I think i probably disregarded that one because it's a tweed(brownface?) for one thing, but also because i wasn't sure how complicated a tremolo circuit removal would be. Not very complicated at all it seems. I figured if I was going to remove a tremolo circuit from any drawing it would make sense to remove it from a blackface. That leads me to the next question which is "what is responsible for the difference between tweed/brownface and blackface?"
I am guessing that the tweed input tube has a lot to do with it? Is that a balancing circuit of some sort?
http://www.spearfoot.net/kl5e3deluxe/deluxe_5e3_schem.gif


I'm trying to balance my enthusiasm for once. I've been overly-excited in the past but I've come to the conclusion that the best thing I can do is to make an ultra simple circuit first so that I have a baseline understanding of the build. Then I can add caps and tweak resistances and see how it goes from there.

 

[Printer2]

"what is responsible for the difference between tweed/brownface and blackface?"

The Tweed (simple tone knob) either rolls off the highs or bypasses the highs around the volume control. The Blackface tone stack has a dip in the response which allows the bass or treble to be boosted or cut. The Tweed has the least amount of attenuation of the signal, actually turned up all the way there is minimal loss. There is not much attenuation from the one stage to the next.

The BF stack has a lot of attenuation, to have boost at the bass or the treble the tone stack has to cut the signal, it is a passive eq, you always end up with less than what you started with. If you do not mind playing cleanly (there still is enough gain with the BF stack to get mild distortion) and like the BF sound it is not all that more difficult to build.

 

[famousmockingbird]

If you want blackface tone then building anything else isn't going to get you where you want. As stated before the tone stack in the blackface is much different then tweed or brownface era's and is probably the only way you will get the sound you are looking for.

Blackface era amps have a scooped mids sound and the tweeds won't get you there. I love and use both because they do things differently.

 

[Illinest]

I found an AA1164 drawing that I liked because it makes use of the other half of the second 12ax7 tube so I wouldn't feel as if I was wasting half of it.
I am aiming for Blackface, so I'm guessing that this is more appropriate than the brown that JJman kindly altered for me.
Truthfully - the amp that I'd most like to own (so far anyways) is this one:
https://www.youtube.com/watch?v=BKeMpPEWIyo
but a Princeton seems like a MUCH more realistic target for a first build.

Changes made:
I deleted trem and reverb portions of the drawing.

I changed the power supply to match the parts that I have available.
The big PT is .075 kva and the little one is .025 kva

Then I realized that I made a big mistake with the OT. My OT was sized for 6L6, not 6v6.
So... uh..... I guess I should use 6L6 tubes instead, but this thing is going to end up being loud.

I think I might have a screen resistor but I'm not sure if I understood that right.

Is there anything that I'm completely out to lunch on here? I'm guessing that there shouldn't be any reason why I can't build this as is?

 

[Malcolm Irving]

It is good to have individual screen-stopper resistors at the tube sockets (similar to grid-stoppers). There is an interesting discussion about them here:

Why should I run screen resistors?

 

[JonSnell Electronic]

Using fixed bias is a good way of getting the sound you want. A smooth bassy Fender sound, run the valves hot and a Marshall sound, run them cold.

 

[mcgruff]

The Divided by 13 CJ11 has a blackface pre mated to a cathodyne PI dual 6V6 power amp almost identical to the 5E3. There's a good ProGuitarShop youtube video which runs through all the noises it makes.

Matchless Spitfire/Lightning might have been another option but they're EL84.

 

[Printer2]

The CJ11 has all the preamp gain stages biased cold where the BF amps and the 5E3 use 1.5k per triode. Gives it its own sound.

 

[Printer2]

Using fixed bias is a good way of getting the sound you want. A smooth bassy Fender sound, run the valves hot and a Marshall sound, run them cold.

Really?

 

[famousmockingbird]

Illinest,
Have you drawn up a schematic yet? Are you still looking to use the 12BHY's?

I just got your PM from like a month ago sorry for the delayed response.

 

[Printer2]

What is the voltage and current ratings of your two transformers? Also what is the primary impedance of your output transformer and do you have multiple taps for different speaker impedances or if only one which? You can run 6L6's at a lower voltage which makes less power and one set will probably last you a heck of a long time if they are just loafing.

 

[caseycampell77]

hey listen dude, i've got 8 pages of layouts and schematics on my gallery page here:

Amplifiers

there are a ton of really simple amps that'll fit your requirements. towards the bottom of the page, there is an area where you can go to all 8 pages...kind of hard to see fyi.