Home-made guitar amps

Firefly type amp


Parts waiting to be built. I buy from DigiKey. They are almost local and get me parts in 48 hours typically.


Not everyone has a nice work bench to build amps on. I'm stuck using an edge of my desk.


The cabinet is birch and was originally built for a different size chassis.


I'm totally impressed by the tone of this little 8" Weber speaker (8A100).


Drilling the chassis is the hardest part of the job.


Square holes? Ah, now I know why everyone uses those big ugly round switches.


Powersupply, ground buss and part of the filament heaters are wired in.


Most of the circut is placed on a phenolic board so that it is easier to debug now and tweak later.


This is basically Rev 1 of Doug Hammond's Firefly. I left room on the board for the Cascode Boost circuitry when I get bored.


Almost complete. I chose to use carbon composites for the preamp plate resistors.


Doesn't look like much. Tossed on a JJ 12AX7 preamp tube and a Mullard 12AU7A for the power stage.


Here's the schematic. Profuse apologies for the hand written job. The cathode error in the powerstage has been fixed. Suggestions?

Soundclip

Ah yes, here is the token sound clip. The mic is a Sony F-V610 placed 6" from the Weber speaker. Guitar is a circa 1980 Les Paul Custom. Mic and sound card fail to capture the nice tone of the amp but give a rough idea of it. The artist responsible for the poor playing will remain nameless. (:->)


Comments on the design:

1) Used a higher voltage power supply, then used a tube rectifier to drop the voltages to within range.

2) Pushed the plate voltages higher to get a fatter tone. This resulted in a higher B+2 than B+1.

 

3) Used a 68K rather than a 33K resistor in the input.

4) Can not hear the resonance pot at all.

Thanks again to Doug Hammond for the great initial design, Carl B. for some excellent suggestions and the whole AX84.com group for the wealth of expertise they so freely share.

 

Raffler

 

Other Guitar Amps


This is a High Octane build from the AX84 site.
The cabinet was made by an prominent amp manufacturer who unloaded it.
The amp works but has some noise problems.
I plan on putting a Kay Bass amp into this head cabinet.

A friend built the cabinet with a flame maple from panel.
I finished it using an oak Danish Oil and about twenty coats of water-based polyurethane.
This is the P2 as seen on the AX84 site.
We fixed some minor issues with the amp and now it sounds like a Marshall at tolerable volumes.

This is the Raffler prototype sitting in Carl's H2O cabinet.

View showing the controls.

This is the actual Raffler before it was complete. I slapped on some old knobs to see the settings.

John Ward did an absolutely superb job finishing out the cabinet for this amplifier.

Underside view of the Raffler showing the EL34, 6sj7WGT, and 12AX7 tubes as well as the power transfomer, output transformer and external capacitors.