How to Build a Portable Bluetooth Tube Amplifier
Introduction: How to Build a Portable Bluetooth Tube Amplifier
After seeing several builds of bluetooth speaker boxes I wanted to try one myself, but with a twist. It has to use vacuum tubes, but small, not a converted tube radio, a scratch build. And it has to use batteries, otherwise, where is the fun?
Before we start, be aware that we will use Li-Ion batteries, which if not handled correctly can catch fire and explode. 58
We will also work with high voltages, which can be dangerous. To make things safe, we are going to use an existing and safe charging module, which disconnects the load while the battery is being charged. The high voltage will be supplied at small currents, through a small switched-mode-power-supply (SMPS).
In the next steps we will go trough most of the designing and building process. If want to skip the designing part, where we draw and simulate the circuit go you can jump to step 5, where we start with the wooden box.
For this build you will need the following tools:
* handsaw
* hacksaw
* hand drill and set of drill bits, including some drills of larger diameters, or something to punch 22 mm holes
* rotary tool
* screw drivers
* metal files
* sandpaper (180, 400, 600, 1200)
* dust mask and googles
* pencil
* ruler
* compass
* box cutter
* scissor
* pliers
* Soldering Iron
* Multimeter
Supplies
The parts needed for this build listed for each different section:
Wooden box:
* 1000x100x5 mm wooden board
* 200x100x1.5 mm brass sheet
* 1000x5x5 mm wooden stick
* Wood glue
Tube amplifier:
* 2x9 pin tube sockets with set of screws
* 7-way tag strip
* 1x 10 W 100 v line transformer (or any push-pull transformer with a 10k or 20k primary, for example the Hammond 125A)
* Resistors:
+ 1x 1k ohm 1 W
+ 2x 1.5k ohms 1/4 W
+ 2x 3k ohms 1/4 W
+ 2x 68k ohms 1/4 W
+ 3x 100k ohms 1/4 W
+ 2x 150k ohms 1/4 W
+ 2x 220k ohms 1/4 W
+ 2x 1M ohm 1/4 W
* Capacitors:
* 2x 100 nF 50 v
* 3x 100 nF 400 v
* 1x 10u F 16 v
* 1x 10u F 350 v
* 1x 22u F 350 v
* 2x 100u F 50 v
Bluetooth module:
* MH-M18 module
* B0505S 1W isolated DC/DC converter
* 2x 10u F 16 v capacitors
* 1x 100n F 16 v ceramic capacitor
555 SMPS:
* 1x 555 IC
* 1x IRF644Pb mosfet or any other for 250 v or more and Rds_on less than 0.2 ohms.
* 1x BC547 transistor
* 1x 47u H 3A inductor low ESR
* 1x ES2G diode or any other ultra fast diode (UF4004)
* 1x 1k ohm trimmer
* Resistors:
+ 1x 470 ohms 1/4 W
+ 1x 1k ohm 1/4 W
+ 1x 10k ohm 1/4 W
+ 1x 2.2k ohms 1/4 W
+ 1x 56k ohms 1/4 W
+ 1x 240k ohms 1/4 W
* Capacitors:
* 1x 100p F 50 v
* 1x 2.2n F 50 v
* 1x 4.7u F 350 v low ESR
* 1x 330u F 25 v low ESR
Other parts:
* 1x TP4056 charger with separate pads for the load
* 2x 2.5" (65 mm) 88 dB speakers
* 2x oval (70x40 mm) passive bass radiator
* 1x circular (50 mm) passive bass radiator
* 4x 18650 batteries
* 4x DPDT 6 mm push buttons (of good quality)
* 3 mm LEDs: 1x red, 1x blue, 1x white (or desired colour)
* 1x 3 mm LED socket
* 1x 3. 98