Firefly 1.5W Tube Amp Build

[just strum]

did you get a 20w soldering iron to replace that branding iron you have now?

[luvmyshiner]

Not yet, but it's on the list. Along with the Irwin Unibit stepped drill bits that Tung recommended. But I'm planning on picking those up locally.

[just strum]

Not yet, but it's on the list. Along with the Irwin Unibit stepped drill bits that Tung recommended. But I'm planning on picking those up locally.

boy, I would use this opportunity to put a list of "Tools I need for this project" that is a little longer than that. Don't you need a radial arm saw, table jointer, router, Craftsman 250 pc socket set, Fender Strat and Marshall amp? I don't see you finishing this project without these essentials.

[luvmyshiner]

boy, I would use this opportunity to put a list of "Tools I need for this project" that is a little longer than that. Don't you need a radial arm saw, table jointer, router, Craftsman 250 pc socket set, Fender Strat and Marshall amp? I don't see you finishing this project without these essentials.

Hmmm, good point Strummy. HEY, isnt' Father's day, or . . . um Easter or . . . something coming up??? I gotta get Baby Girl posting over here so she can get present ideas.

[duhvoodooman***]

Now tell me, how cool is this!

Certainly a familiar sight at my house, Shiner! :

[Kazz]

Get those damn parts off the pool table Shiner....you are committing sacrilege lmao.

Love the asteroids game...I am looking for a pacman or mrs pacman game or asteroids game for our basement game room....and a full sized air hockey table to go along with the pool table we already have down there.

[ted s]

Looking good Shiner ! looking forward to reading/seeing the progress !

[tot_Ou_tard]

I Now tell me, how cool is this!

Answer: d@mned cool indeed! :

[Rocket]

Get those damn parts off the pool table Shiner....you are committing sacrilege lmao.

That's the Sunday-company fancy eatin' table... just drop yer chicken bones in the holes.

[duhvoodooman***]

Just a brief resurrection of this old thread just to underscore again what a cool little amp--and DIY project--the Firefly is....

I just finished a small modification to the amp, adding a rotary switch to the rear of the chassis that lets me easily change the rating of the power tube cathode resistor to one of four discrete values. I've acquired four different pin-compatible tube types that can be used for the power tube in the Firefly, and this allows me to dial in the right bias on each to get them up in the range of 85 - 100% of their rated dissipation values, where they sound their best. The four tube types are the 12AU7 (the "stock" Firefly power tube), 12AT7, 6BH7 and ECC99, and their dissipation ratings vary from 2.5 to 5.0W. The four cathode resistors wired to the switch vary between 220 and 510 ohm, a pretty wide range. Sunday night, I wired up the switch, and last night I ran all four tube types in the amp and checked the actual dissipation values vs. what I'd expected to see (they were all very close).

Naturally, I didn't just conduct my testing with a DMM--I also played a few licks with my LP Std. through each type to see how they sounded. In a word, GREAT! Though it will do a cleaner tone, this little bugger's forte is crunch--that vintage Marshall stack kind of tone from a tiny little package. I dial the Boost stage gain up around 80% and then use the main Preamp control to set the overall volume. The thing just nails that early Zeppelin-AC/DC-Who tone. Lawdy mama--have mercy!!

So I just wanted to encourage you do-it-yourselfers with a bit of prior electronics experience to give this amp project a shot. While I wouldn't recommend it for a rank beginner, you don't need a lot of experience to tackle this one, especially if you use John Calhoun's super PCB and outstanding build documentation. It won't break the bank, either--you can get all the parts you'll need for under $200. So far, the only Fretter I've seen who seems to be serious about building one of these little monsters is Luvmyshiner--and don't be too surprised if he changes his ID to "Luvmyfirefly" after he does!

As always, let me interject the required safety warning here: Working inside a tube amplifier exposes you to potentially LETHAL levels of DC voltage, so follow all recommended safety practices and BE CAREFUL. If you don't know what these are, you're better off not attempting such a project.

But if you understand how to work safely with high voltages and you love that Marshall crunch, by all means give this one a try. I promise you--you won't be disappointed!

[luvmyshiner]

Well, here's what I got done today. All the soldering is done. Tomorrow I get to start cutting out the box. I've really learned a lot. The first dozen or so solders were pretty rough. But then I got the hang of things. I'll keep y'all updated.

[ET335]

Looks like you have done a nice job putting that amp together Shiner.
Looks Great to me!:

[warren0728]

looking great shiner!

ww

[Tone2TheBone]

Wow Shiner that deserves a beer or two! Great job!

[Kazz]

Ah come on now Shine.....you can't be excellent at everything you do....your wood working skills most around here would take out a hit contract for.

Soldering is a developed skill and one that the term if you don't use it, you'll lose it is very true....I have tried a few small soldering projects in the last few weeks and lets just say it was not like riding a bike....it took some trial and error.....tinning wires is one thing, but not producing a cold solder joint is another.....it's not for the weak of stomach LOL.


Turn that board over and let's see your joints. Knowing you for the last 2 years or so, I will be they are far above average :-)

I will be following this with great anticipation, as when Shiner does something he goes all the way, and I love that about him.

I am really digging the idea of a diy Marshall tone, just wish I had an extra 200 to spend.....but then again if I did...I would probably have an Epiphone Valve Jr that has been heavily modded from a local member sitting next to me already :-)


I do have a project in the works tho.....I got a Vox Wah from another forum member that I plan on modding a little after I record some baseline stuff with it.

Probably looking to add a Fasel inductor and something to clean it up a bit in the hotzone. The one thing I can say...if you think your electric lead tone is missing something and you are not quite sure what it is, get a Vox Wah....click in on and nail the pedal down......it is pure hair metal a great lead boost.

I now return you to your regularly scheduled programming :-)

[marnold***]

Aren't you just the cutest little amp? Yes, you are! Yes, you are!

[duhvoodooman***]

Lookin' aces so far there, Shiner! :

BTW, where'd you get the tubes and what kind?

[Mark]

Excellent work man!!

[just strum]

Aren't you just the cutest little amp? Yes, you are! Yes, you are!

Hmmm, the latest batch of brew must be ready.