3.5 watt 6K6 “Champ”

JohnnyCrash

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Another junk drawer build…

I’ve got an extra capacitor doghouse from a BF/SF style Bassman chassis (I actually have two) and figured I’d try to build a full tube amp into it as a tiny chassis.

I’ve also got a few 8 ohm Jensen MOD 10s.

And I’ve got an old 6K6 tube.

I think I can just shoehorn an Antek 200 v toroidal power transformer (hanging slightly off of the “chassis”), a Hammond 1750AX output transformer, an octal, and a noval tube socket onto the doghouse chassis.

Just ordered the PT and OT. Let’s see how a 3.5 watt 1x10” combo using a doghouse chassis turns out :D
 

JohnnyCrash

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Started digging through the junk drawer while the PT and OT are shipping.

Looks like linear dime sized pots all around :D

50k Mid pot. I’m thinking of throwing a 6.8k on its tail.

This will likely be 95% point to point with a 3 lug tag strip or two. Ain’t much room, everything’s right next to everything else.

For the voltage I should be near 280. I’m thinking of starting with a 1k cathode for the 6K6 (bypassed with a 25uF or maybe even 50uF cap) and a 470 grid leak from the pre to the 6K6.

I’ll be aiming for a little shy of max plate dissipation, which is 8.5 watts. It seems single enders sound best like that (like Champs sounding good with a plate diss around 12-14 watts!).

I’m open to all the suggestions I can get. I’m not used to working with 6K6s.


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NTC

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Deleted. Post was not adding any value....
 
Last edited:

Thumper

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Another junk drawer build…

I’ve got an extra capacitor doghouse from a BF/SF style Bassman chassis (I actually have two) and figured I’d try to build a full tube amp into it as a tiny chassis.

I’ve also got a few 8 ohm Jensen MOD 10s.

And I’ve got an old 6K6 tube.

I think I can just shoehorn an Antek 200 v toroidal power transformer (hanging slightly off of the “chassis”), a Hammond 1750AX output transformer, an octal, and a noval tube socket onto the doghouse chassis.

Just ordered the PT and OT. Let’s see how a 3.5 watt 1x10” combo using a doghouse chassis turns out :D
I mark the side of a cardboard box with a sharpie (the size of the inside face of the enclosure) and mount stuff to that. It gives you a 3D model of the room available. And poking holes in cardboard goes really fast.

Sometime there‘s enough room for the components, but when you start to visualize the connects there’s just not enough room to physically get an iron in there With stuff right next to it.

I discovered this on a mini 5E3 project and ended up remounting my components into little larger but more realistic enclosure. Stability can also be an issue when they are packed that tight.

Hope that helps, Steve
 

JohnnyCrash

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I mark the side of a cardboard box with a sharpie (the size of the inside face of the enclosure) and mount stuff to that. It gives you a 3D model of the room available. And poking holes in cardboard goes really fast.

Sometime there‘s enough room for the components, but when you start to visualize the connects there’s just not enough room to physically get an iron in there With stuff right next to it.

I discovered this on a mini 5E3 project and ended up remounting my components into little larger but more realistic enclosure. Stability can also be an issue when they are packed that tight.

Hope that helps, Steve



Yeah, I tend to jump into things without fully thinking them through :D

I was tempted to replace the power tube’s grid leak resistor with a pot as a “master volume,” but space is definitely at a premium with the “chassis” I’ve decided on!

Hopefully it all fits. Otherwise, a small aluminum Hammond will probably be ordered.
 

Huddy

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Yeah, I tend to jump into things without fully thinking them through :D

I was tempted to replace the power tube’s grid leak resistor with a pot as a “master volume,” but space is definitely at a premium with the “chassis” I’ve decided on!

Hopefully it all fits. Otherwise, a small aluminum Hammond will probably be ordered.
image.jpg


It’s gonna be a snug fit for sure.
 

JohnnyCrash

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More junk drawer foraging…

So far:

Fuse holder; an old octal socket; a 6v LED lamp (from either an AX84 Hi Octane or an 18 watt/1974x project ten years ago?); Cliff style input and output jacks; 125v/5a DPDT switch (probably rated enough for a power switch?); a 47uF/450v filter cap (B+ 1); a Sylvania 6K6 (I think leftover from a standalone reverb unit I built in the 2000s?); and a noval tube socket shield (I had two noval sockets somewhere… I need to clean and organize my workbench!).

Almost everything. More foraging tomorrow.

Pots are all dime sized linear. 1 meg Volume, 250k for both Bass and Treble, and a 50k for the mid pot.

To maximize space, I’m considering a tweed style hang down setup with the tube sockets on the bottom, tubes hanging down.

So with the picture below, the pots/input would be at the top, tube sockets at the bottom. I’ll need to double check the octal diameter, though.


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Huddy

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Ahhhh... okay... was wondering where you were going to place the OT but if you got the donut off the side 1- 1.25" that just might work. Really looking forward to stealing an idea or two on how to cram in parts ;-)
 

JohnnyCrash

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Probably my only meager contribution to TDPRI is that I so freely share my many self-inflicted mistakes that people learn from them what not to do :D

Sometimes, actual sensible people get new ideas just by trying to help me solve something I’ve blindly stumbled myself into :D
 

thorminus

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I was going to suggest the Hammond P-T290WEX which is their replacement for the Fender 6G15 reverb power transformer. It's smaller than the toroid with a more manageable form factor. I used one in a champ-esque build last year with a 12AX7 and a pair of 6aq5 in self-split push pull. Works very nicely. However, I just looked at the price and they are going for over $58 right now (forgot what I paid, probably low $40's so not nearly as cost-effective as the Antek toroid. I've used Antek stuff before and it's pretty decent. Probably cheaper in the long run to get a slightly bigger chassis and stick with the toroid if you have space problems.
 

King Fan

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Probably my only meager contribution to TDPRI is that I so freely share my many self-inflicted mistakes that people learn from them what not to do :D

Sometimes, actual sensible people get new ideas just by trying to help me solve something I’ve blindly stumbled myself into :D

LOL, good one. Don't sell yourself short. First of all, you do some great builds -- pathfinder creative stuff. And then there's the entertainment value -- can he pull this off? How's he gonna do it? Keep it up.
 

JohnnyCrash

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LOL, good one. Don't sell yourself short. First of all, you do some great builds -- pathfinder creative stuff. And then there's the entertainment value -- can he pull this off? How's he gonna do it? Keep it up.


And I thought getting myself in over my head was only comically entertaining to me! :D
 

JohnnyCrash

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Alright, the OT came in (as did two backup 6K6 tubes, not pictured). As tiny as I was hoping it’d be. I was sorta gambling, I ordered it to fit the tube and voltage, didn’t really check its size/dimensions specs.

I really shouldn’t do things by the seat of my GAS :D

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JohnnyCrash

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Had to toss the octal socket, its mounting ring was damaged and I didn’t notice it. I’ve still got some brown micalex octal sockets somewhere…

Also found a noval socket.

Just gotta find two filter caps of acceptable capacitance. I’m 80% certain I have them, just not sure which box of junk they’re in.

I know exactly where my resistors and coupling caps are, and the stock isn’t low. Should have everything I need.

Once I finish detective-Columbo’ing around this rat’s nest to forage the remaining bits, I’ll start brainstorming parts and chassis placement.



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