World's smallest stack? [Tubey practice amp project content]

[christw]

Looking for a small working tube chassis to convert into a mini amp yielded me this:







(Better pics here: eBay sale page)

What is it? An old Executone intercom that uses the speakers as microphones that still works according to the seller. I'm taking no chances and I've got it on the Variac, just stepped to 30VAC.

As for the dangers inherent in working with tube amplifiers, I am quite aware of them. I've had plenty of run ins with electricity, usually 120VAC doing maintenance work on people's apartments. I don't mean that to sound like I've seen the worst or I'm cocky about it-I haven't and I'm not. I take a lot of caution, especially when dealing with high voltages.

I chose a simple amp for my first real "all me" tube amp project. I expected to be in for a cap job and various amounts of troubleshooting with whatever I bought. It'll give me something to do for the next month while I heal up and start physical therapy. Hopefully it gives me a little trouble.

Current mod/build ideas:

• Find the kinks and work them out

• 1/4" input - the speaker/mic wiring was a breeze to figure out!

• New speakers. I don't want to kill the original speakers between bass and guitar overdrive. They trade mic and speaker duty but never work at once. I need to make sure the total nominal impedance matches that of a single stock speaker (Re: ~6 ohms) if I want to run a stack.

• Homebrew cabs and head case if I have time and enjoy doing this too much. A tiny stack with, two 1x4, 5, or 6" cabs. Or maybe a 4x3 with a 1x6 to "add low end", right?

• Jess Oliver tribute: take the chassis and make a baby flip top (in looks at least)

Thoughts?

PS- I know it's only going to put out 2 watts or so. Cool by me. I don't need loud. I need a project and it's here!

[christw]

80VAC and it's functional and feeds back into itself if I turn up the volume. No hum, no buzz. It's silent! It has a kind of telephoney tubey OD to it when you overdrive it with your voice. Up to 90VAC now and looking forward to full power.

[jimmy rocket]

I like the mini flip-top idea. I've got an old chassis sitting around right now that I was thinking about doing a similar thing with.

looking forward to seeing where this goes!

[dhsierra1]

what a cool little project Any idea what the wattage is?

I know someone was posting recently about reviving a little 40s vintage RCA amp for guitar so something must be in the air for these things

[christw]

Winter boredom and some messed up ligaments in my shoulder demanded that I do something fun but not physical and I was on eBay looking for a sub $50 working chassis. This thing was a whole lot more!

Oh, it's alive and kicking. I'd estimate 1-2 watt output. It has a 23 watt draw, a Valve Jr clocks in at 35w. This runs a 12AU6, 5085(??), and 35W4

The tone is bright. It makes my nasal sick voice sound bright and full of life. It did the same for my acoustic guitar. By the time it hits OD, I had it feeding back. It's wired always on with the extension speaker as the mic as I got it. It has a little buzz but with respect to its total output the buzz is not nearly enough to warrant a cap job. This thing is going to be so much fun!

Mini fliptop is sooo tempting! I've got my eyes on a Weber Signature AlNiCo 6 unless someone can recommend me a better choice of 6" driver (preferably highly efficient) that'll play well with overdriving this amp.

[fuzzy beard]

Sweet !

[christw]

Guys, would you forgive me if I used 1/8" jacks and cables if I made it a mini stack or fliptop? I just want to make the proportions a bit more right.

[christw]

Next consideration. I think I'm moving in the fliptop direction. More detailed plans to follow as I disassemble and create a schematic since it's still working well. Better catalogue it before it's not! I bet plenty of stuff is out of spec but I want a schematic of it drawn up from stock(?) before I start prodding, if I need to. Hoping everything hasn't drifted too far out of spec.

I'm thinking 1x6 flip top. I want to keep it as small as I can. I'd love to have it ported for fun's sake. I was thinking of this guy but I'd need someone to model it for me once I have a more thought out design. Or someone to point me in the direction to do it myself which is much preferred! I want to learn from this project! I need knowledge. Need power. [Says the guy trying to build a 2 watt flip top!]

Oh, and I got a couple of saws and a router for my birthday and Christmas. My parents listen even when you think they're not. So that means that a build is inevitable. Seriously though, my parents are incredible people. I'm very thankful for all of the things they have done and do to support me. They weren't perfect but they love their kids.

Oh yeah, build... Hmmm. Let's get some ideas on paper.

[LowEndMan2112]

Looking forward to how this works out! I think it's just you trying to get over the fact that you're having to move all your delicious Ampeg gear though

[christw]

Nah, I'm over it. ('Twas easy to rationalize my friend! ) I'm moving on to fEarfuls when I get to a point that I can afford it. I've got my B15 sticking with me and my upgraded Marshall 410 loaded with '69 SVT 10's. It sounds just like half of the real thing and only cost me $50 to make. The Ampegs have infiltrated and are staying. It's just hard to tell.

Truth be told, later in life I do plan to pick up the very same Ampegs when I have safe space to store them in where I can crank them loud but it'll be a while. I'm comfortable with that. By the time I'm nostalgic about them, I'll be able to afford them!

[VanillaThundah]

mini fliptop is a great idea...post some pics for us to see when you are done!

[LowEndMan2112]

Originally Posted by christw

Nah, I'm over it. ('Twas easy to rationalize my friend! ) I'm moving on to fEarfuls when I get to a point that I can afford it.

fEarful, the bane of all TBers seeking to rid of gas

Sounds like you've got it all figured out, that B15 is definitely the hardest to come by out of the bunch! One day I will get my hands on a vintage B15.. but like you, it'll be at a time where I've got the space to warrant a big collection of gear.

[John D]

Perhaps pay tribute to this.

[christw]

Originally Posted by John D

Perhaps pay tribute to this.

I saw that the other day and didn't even think of it! So many ideas!

[fuzzy beard]

Originally Posted by John D

Perhaps pay tribute to this.

What is this?

[christw]

An early Everett Hull bass amp IIRC

[fuzzy beard]

Could i get a link so i dont hijack your thread?

[christw]

I don't remember. Try PM'ing John D?

[bassingeorge]

Subbed!

[christw]

This one is pretty much designated to be mini fliptop unless I get a better idea.

I'm scouring eBay again to find a 10-40w amp with a small footprint to make into a 2x6" stack.