Firefly 1 Watt Tube Guitar Amp Build

[illwood]

Based on the response from massacre's guitar string thread, here is my tube amp build thread. This was my first larger scale electronics venture. I have repaired laptop power jacks in the past, wired my own guitar pickups, and modded a pedal or two, but nothing from the ground up. I see a Marshall 1974X clone in my future. . . If I get good at it, maybe a little bit of a side business.

The amp is a 1 Watt Firefly (http://ax84.com/media/ax84_m276.gif) as designed by Doug Hammond.

First off, the background work. . .

I decided that I wanted to build this on a turret board (old-school) and that I wanted it to be in a form factor that would fit on my 80's Marshall Lead 12 Micro Stack. With that in mind, I proceeded to layout my board (on paper first).

http://i9.photobucket.com/albums/a88/illwood/Firefly/BoardLayout1.jpg

Then I transferred that into a CAD layout for the turret board and finally a solid model of the chassis.

http://i9.photobucket.com/albums/a88/illwood/Firefly/BoardLayout2.jpg

http://i9.photobucket.com/albums/a88/illwood/Firefly/chassis-view1.jpg

http://i9.photobucket.com/albums/a88/illwood/Firefly/chassis-view2.jpg

Note that I decided to move the power lamp before construction, I did update my model, but didn't create an image of it.

[illwood]

I printed out the turret board layout full-scale and used it with a center punch to locate the holes.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1412.jpg

Here is the board with the turrets installed. The extra holes by some of the turrets are wire routing holes like some Marshall amps of the past.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1413.jpg

The completed board loaded with components.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1414.jpg

The wires installed.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1415.jpg

[illwood]

Some close-up shots of the turret board.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1416.jpg

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1417.jpg

[illwood]

Front and rear views of the drilled chassis (with the power transformer mounted). The chassis is an off-the-shelf Hammond aluminum enclosure.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1418.jpg

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1419.jpg

The underside showing the power wiring and tube sockets installed.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1421.jpg

I wrapped the grey (115VAC) tap from the 269EX transformer and then taped it to the chassis to keep it from flopping around.

[illwood]

Here is the turret board installed in the chassis.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1422.jpg

This view shows the wired front panel and the tube sockets with the heaters wired.

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1424.jpg

[illwood]

The completed chassis:

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1425.jpg

Controls (from left to right):
Power, Standby, Power Lamp, Boost Switch, Boost Knob, Volume Knob, Input Jack

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1426.jpg

Rear-view controls (left to right):

Impedance (up is 4Ω, down is 8Ω), Speaker Jack 1, Speaker Jack 2, Fuse, Mains Input

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1427.jpg

Gut shot (a little messier than intended, but not bad).

http://i9.photobucket.com/albums/a88/illwood/Firefly/IMG_1432.jpg

[massacre]

That
is
one
of
the
coolest
things
EVAR!

I went to a website looking for a kit, but I guess they don't make them anymore?

Have you played it yet?
How does it sound?
I would love to do something like this.
About how long did it take you?

[illwood]

That
is
one
of
the
coolest
things
EVAR!

I went to a website looking for a kit, but I guess they don't make them anymore?

Have you played it yet?
How does it sound?
I would love to do something like this.
About how long did it take you?
Thanks!

Ah, that must be the "Firefly PCB" that a guy was selling for a while. I saw that, but decided to go the turret board route. I think the design files for that are still available and *technically* you could make your own PCB with a laser printer, copper clad board, clothes iron, ferric chloride, and some patience.

I've played it a bit now. Honestly it is too loud through two 10" speakers to get it to distort naturally and not bother the people in my building. It sounds good, I don't feel like it needs any tone controls. I would layout the board a bit differently because I had some problems with some wires getting too close to each other, causing some squealing when you crank the volume.

It probably took about 20 hours to build. I didn't keep track, but that seems like a reasonable estimate. Things would have gone faster if I had access to a full-size drill press and some Greenlee punches.

I bought all of the parts Mouser Electronics and The Tube Depot. The turret board is a pretty easy way to make the components easy to swap out. If I were to build it again, I would consider a bit larger of an enclosure or etching a PCB for it if I wanted it small.

Fortunately, all of my future plans are for bigger amps that will have more working space inside the chassis.

Lastly, I do intend to build a wooden enclosure for it, but I haven't started that yet.

[massacre]

That is great. So cool. Did you use 6L6 tubes? I see they are Fender, wondered if you had considered any of the Russian brands.
How many are power tubes?

I like the turret board setup, and all of your wiring looks awesome, as well.
Any reason for the 2 10" speakers?
I have always liked 12" speakers for guitars.

[ImpalaSlayer]

cool as ****, i dont know what it does but cool to how its built

[fastblackmerc]

cool as ****, i dont know what it does but cool to how its built

+1!!!!!!!!!!!!!

[Mote]

Does this use a 12ax7 for the power tube? Arfe the 3 tubes preamp, phase inverter, power?

Nice work! Looks plenty clean. Now you have to learn coverings, grill and piping :-)

[illwood]

That is great. So cool. Did you use 6L6 tubes? I see they are Fender, wondered if you had considered any of the Russian brands.
How many are power tubes?

I like the turret board setup, and all of your wiring looks awesome, as well.
Any reason for the 2 10" speakers?
I have always liked 12" speakers for guitars.


Does this use a 12ax7 for the power tube? Are the 3 tubes preamp, phase inverter, power?

Nice work! Looks plenty clean. Now you have to learn coverings, grill and piping :-)
Actually, it preamp tubes for everything. A 12AU7 is used as the power amp tube (though it acts like 2 tubes because it has a separate anode, cathode, and grid like the other two preamp tubes). A 12AX7 is used for the boost circuit and another 12AX7 is the main amplifier. The boost tube is bypassed when it is off. There isn't a phase inverter, so this is a Class A amplifier. For tube brands, the Fender / Groove Tubes labeled ones are the 12AX7s and they are Sovteks (I bought them cheap from a guy who was trying some different tubes in his Fender combo). The 12AU7 is an Electro-Harmonix, so technically, they are all Russian tubes.

As for the speakers, I am also typically a 12" speaker guy, but I picked up an 80's Marshall Lead 12 mini stack that has two speaker cabs with a 10" in each (that I upgraded to Celestion V10-60s). I thought that a 1 Watt tube head would be a nice option for it.

As for the enclosure and covering, I'm not concerned with picking it up. I have built and covered several custom sub boxes that I built a few years ago and I'm a quick learner. ;)

[Motorhead350]

When you finish play on it and record it. I wanna hear that sucker. Might even buy one from you if you decide to sell.

[musclemerc]

Illwood, post up some pics when your done. I grew up working on 2 channel tube amps. LOVE the sound, true audiofile quality. ;)

[soultosoul13]

looks great. id also like to hear it....
is that a mercury OT?

[illwood]

When you finish play on it and record it. I wanna hear that sucker. Might even buy one from you if you decide to sell.


Illwood, post up some pics when your done. I grew up working on 2 channel tube amps. LOVE the sound, true audiofile quality. ;)


looks great. id also like to hear it....
is that a mercury OT?

Looks like I'm going to have to put up a YouTube video of it in action and get cracking on building an enclosure for it.

Dom - I would rather get the bugs out of this one before I consider selling my creations. I don't want to put my name on something that is less than perfect. Thanks for the interest!

Travis - Being a guitar amp, I wouldn't exactly call it audiophile (in sound a least). The tubes are biased for a bit more grit. ;) If you mean build quality, then thank you very much for the compliment. I do think building a Dynakit ST-70 clone may be in my future for home audio.

Matt - I wish those were Mercury transformers. They are just Hammond transformers from Mouser. I think when I build that 1974X clone I will go the Mercury route. They don't come cheap, though.

[massacre]

I always wanted to build a Marshall SLP clone, wonder how hard that would be?

[soultosoul13]

Looks like I'm going to have to put up a YouTube video of it in action and get cracking on building an enclosure for it.

Dom - I would rather get the bugs out of this one before I consider selling my creations. I don't want to put my name on something that is less than perfect. Thanks for the interest!

Travis - Being a guitar amp, I wouldn't exactly call it audiophile (in sound a least). The tubes are biased for a bit more grit. ;) If you mean build quality, then thank you very much for the compliment. I do think building a Dynakit ST-70 clone may be in my future for home audio.

Matt - I wish those were Mercury transformers. They are just Hammond transformers from Mouser. I think when I build that 1974X clone I will go the Mercury route. They don't come cheap, though.

i actually really like those hammond transformers. i think they are every bit as good as mercurys (which i think are overpriced and over hyped). i blew the OT in an ampeg jet and replaced it with a hammond, big improvement.

[illwood]

I always wanted to build a Marshall SLP clone, wonder how hard that would be?
That probably depends on how well you can read a schematic and translate it into a layout. There are a ton of amp schematics at the Dr Tube website and I found this section for the 100W Plexi (http://www.drtube.com/marshall.htm#JTM100) amps.

i actually really like those hammond transformers. i think they are every bit as good as mercurys (which i think are overpriced and over hyped). i blew the OT in an ampeg jet and replaced it with a hammond, big improvement.
No kidding? That's some useful knowledge. I figured that Mercury's were overpriced and I can't speak for the overhyped. Maybe I'll try the "Pepsi challenge" between the two.

[F8LBITEva]

Thats awesome dude! Stuff like that boggles my mind.

[Seneca]

Really really neat!!!! Love tube amps!!! :D