Compressor Board for Hollow-body Guitars
Features:
  • Acommodates base, mid and treble pickups
  • Pots and pickup switch are hard-wired
  • Lithium powered for years of operation
  • Circuit has been updated for improved operation

Application Examples

The guitars shown have our circuit board installed. The black guitar has three pickups and uses the full capabilities of the circuit. The bottom guitar has base and treble pickups , so the mid control is not used. The guitars are wired for the drawing in Figure 3. This circuit board is not for beginners and must be installed and hand-wired into your guitar. There are different versions for right or left-hand guitars.

Dual Parallel TDA7293 Board Assembly
Features:
  • Your choice of parallel mono or separate stereo TDA7293-based amplifiers
  • Double-sided board with plated-through holes
  • High-current layout with large traces and large feed-through holes
  • Stereo version has on-board bridge rectifier.
  • Mono version has provision for Boucherot Cell
  • Optional chassis ground jumper
  • Optional Mute function
Mono Schematic
Stereo Schematic

Application Example

The picture on the right shows a pair of our amplifier boards installed in a well-known amplifier chassis from the 1970's. Our boards replace a quad of TO-3 output transistors and a driver board and a power supply board. Power output and reliability are much improved. An aluminum angle was installed as a heat spreader for each board to compensate for unwanted existing holes in the heat sinks. Insulating pads and shoulder washers isolate the TDA7293 tabs from the heat sinks. Makes a good replacement for amps with a single chip and fan: no fan is required and there is more drive to the speaker.

Board size: 3.8 X 2.5 in. with corner holes for #6 hardware.

Bare boards $30 and kits available. E-mail for a quote.

Tube Amp Power Supply Board Assembly

Features:

  • Double-sided board with plated-through holes
  • High-voltage layout with large traces
  • Sturdy snap-mount capacitors
  • Caps rated up to 500 Volts
  • Bias rectifier and bias adjust included
  • Optional ground jumper
Schematic

Circuit Description:

Our Caps and Bias Circuit Board supports a variety of configurations for tube amp powers supplies:
The main rectifier may be Bridge, Full-Wave or Voltage Doubler.
Bridge Rectifier:
Bias is stepped-down from one side of the high voltage winding via the .047uF coupling cap.
Bridge Rectifier with center-tap:
If the high voltage winding has a center-tap, the center-tap may be connected to the junction of C1 / C2 and R1 / R2 may be omitted.
Full-wave rectifier (2 diodes):
Bias is stepped down from one side of the high-voltage winding via a resistive voltage divider.
Bias winding or separate bias transformer:
BIAS AC may be connected directly to the bias winding, or through a resistor if some reduction in voltage is required.

Bias adjust is Fail-Safe: If the pot should fail, bias will go to its maximum voltage.

Application Example

The picture on the right shows our Caps and Bias board installed in a 50W amplifier. The board sits behind the power tube sockets and is nestled between the power transformer and the main PCB or terminal board.

WARNING: Risk of Fatal Electric Shock.

Assemble your kit carefully! These kits are intended for experienced amp builders who know what they want to accomplish. If you are considering this kit, you MUST be knowledgeable of vacuum tube circuitry and of the LETHAL voltages involved and you MUST have at least moderate skill soldering components on printed circuit boards. If you do not have the necessary skills or equipment then get a technician to build it for you or buy the assembled kit.

Bare boards $30 and kits are available. Let us know your requirements. Snap-in caps are 22mm diameter. Values of up to 220UF/400V are available for C1-C4. Board size: 3.8 X 2.5 in. with corner holes for #6 hardware.