Velleman K4700 Speaker Protection Kit

Features & Specifications

Features

• Protects loudspeakers from switch-on transients and DC current.
• Suitable for amplifiers with symmetrical power supply.
• Suitable for amplifiers with asymmetrical power supply.

Specifications

• Switch-delay: ± 6 seconds
• DC protection: +1V/-1V
• Max. input voltage: 200Vpp + DC
• Max. switching current: 10A
• LED indication: WAIT (switch-on delay), ERROR (DC on speaker output)
• Supply voltage: 220VAC
• PCB dimensions: 55 x 125mm (2.2" x 4.9")

Assembly Hints

Proper assembly is crucial for the successful operation of this project. Read all instructions carefully.

Required Tools

• Good quality soldering iron (25-40W) with a small tip.
• Wet sponge or cloth for cleaning the soldering iron tip.
• Thin raisin-core solder (flux or grease not recommended).
• Diagonal cutter for trimming excess wires.
• Needle nose pliers for bending leads and holding components.
• Small blade and Phillips screwdrivers.
• A basic multimeter may be required or handy for some projects.

Assembly Tips

• Ensure your skill level matches the project's complexity.
• Follow instructions carefully, understanding each step before proceeding.
• Perform assembly in the specified order.
• Position parts on the PCB as shown in diagrams.
• Values on the circuit diagram may change; values in the assembly guide are correct.
• Use provided checkboxes [ ] to track progress.
• Refer to included safety and customer service information.

Soldering Hints

1. Mount components against the PCB surface and carefully solder the leads.
2. Ensure solder joints are cone-shaped and shiny.
3. Trim excess leads as close as possible to the solder joint.

Note: Axial components are taped in the correct mounting sequence. Remove them one at a time.

Construction - Component Lists

This section details the components required for assembly. Polarity must be observed for diodes, Zener diodes, electrolytic capacitors, ICs, and LEDs.

Important Final Checks:

• CHECK THE ENTIRE MODULE PROFOUNDLY ONCE AGAIN.
• CHECK IF ALL SOLDERINGS ARE CORRECT AND THAT THERE ARE NO SHORT-CIRCUITS!

Testing

Follow these steps to test the assembled module.

Initial Test

1. Connect a power cord to the MAINS.
2. Check that after approximately 6 seconds, the yellow LED 'WAIT' extinguishes.
3. Simultaneously, listen for the click of the relay switching.

Testing the Left Channel

1. Connect the PA point of the left channel to the -V point (refer to Figure 1.0). The red LED 'ERROR' should light up along with the yellow LED 'WAIT'.
2. Interrupt the connection again (refer to Figure 2.0). The red LED should extinguish, followed by the yellow LED after approximately 6 seconds.

Repeat this testing procedure by connecting the PA point to the +V point.

Testing the Right Channel

1. Connect the PA point of the right channel to the -V point (refer to Figure 3.0). The red LED 'ERROR' should light up along with the yellow LED 'WAIT'.
2. Interrupt the connection again (refer to Figure 4.0). The red LED should extinguish, followed by the yellow LED after approximately 6 seconds.

Repeat this testing procedure by connecting the PA point to the +V point.

The module is now ready for definitive connection to the amplifier.

Connection

Install the protection module in a suitable location, for example, against the back-side of the amplifier housing.

Making Connections

• MAINS: Connect to the NET-connection of the transformer in the amplifier, after the main power switch.
• PA: Connect this point to the speaker output of the amplifier for the left and right signals (see Figure 5.0). For bridge amplifiers (Figure 6.0), two "hot" connections may be needed.
• MASS: Connect to the amplifier's ground (mass).
• LS: Connect the left or right loudspeaker to this point.

Manual Loudspeaker Disconnection

Install a switch between the -V and MAN points. When the switch is closed, speakers are disconnected permanently. Opening the switch reconnects them after approximately 6 seconds.

Remark on Power Supply Types

For amplifiers with asymmetrical power supply (e.g., with output capacitors and resistances R23-R26) rated over 300W/4 Ohm or 150W/8 Ohm, it is not recommended to disconnect speakers at full power for extended periods, as the mentioned resistances could overheat.

If the module is used with a bridge amplifier having an asymmetrical power supply, diodes D7 and D8 should not be mounted. In this case, the DC protection function may not operate correctly, as the module's voltage reference will be opposed to the mass.

Diagram Explanations

Figure 5.0: Stereo Power Amplifier Connection

This diagram illustrates the connection of the K4700 module to a stereo power amplifier. It shows the amplifier's inputs (INPUT LEFT/RIGHT) and outputs (OUTPUT LEFT/RIGHT), a power supply block, and how the P4700 module interfaces with the amplifier's MAINS, PA (speaker output), and LS (speaker input) terminals for both left and right channels.

Figure 6.0: Bridge Power Amplifier Connection

This diagram shows the connection of the K4700 module to a bridge power amplifier. Similar to the stereo setup, it depicts the amplifier's single input and output, power supply, and the P4700 module's connections to MAINS, PA, and LS terminals.

PCB Layout

The PCB layout diagram provides a top-down view of the printed circuit board, indicating the precise placement and orientation of all components, including resistors (R1-R26), capacitors (C1-C13), diodes (D1-D14), transistors (T1-T4), IC socket (IC1), relays (RY1, RY2), LEDs (LD1, LD2), Zener diode (ZD1), and transformer (TRANSFO). Key connection points such as MAINS, +V, -V, MAN, PA, and LS are clearly labeled.

Schematic Diagram

The detailed schematic diagram illustrates the complete circuit design, showing the interconnections between all components. This includes operational amplifiers (A1-A4, identified as IC1), transistors (T1-T4), diodes, resistors, capacitors, LEDs, relays, and the transformer. It maps out signal paths for left and right audio channels (PA-LEFT, PA-RIGHT), power supply connections (+V, -V, GND), and control signals (ERROR, WAIT, MAN, LS).