paX Protct. unit

The amplifier/loudspeaker protection system.
This comprehensive amplifier/loudspeaker protection system is a perfect match with Jan Didden's amplifier with Error Correction, as well as any other analog power amplifier. Most protection systems detect a combination of current in the amplifier power transistors and their Vce and limit the output if a set level is exceeded. However, these protection systems often start limiting the output well before the protection trip level. This affects the sound quality even before the protection threshold.

This amplifier/speaker protection unit is based on the Safe Operating Area (SOA) parameters of the power transistors and matched with the amplifier output circuitry. It does not prematurely limit the output (and sound quality) but only acts when it is really necessary.

Further this protection unit handles:

• Delayed connection of the loudspeaker to the amplifier when switching on the power.
• Fast disconnecting of the loudspeaker from the amplifier when switching off the power.
• Detection of DC on the amplifier output.

There is no need for a separate powersupply as it uses the power supply of the ampilfier.

You can select the mode of operation: either, if the protection is tripped, the amplifier remains disconnected until repowering the amplifier, or the amplifier is connected again to the loudspeaker automatically when the situation gets back to normal.

We are happy to offer a kit for this unique protection unit containing all the parts (including the parts not so easily obtainable) , PCB, flatcable, connectors and a Construction Guide. Included also is a special-purpose relay that is specifically designed for switching loudspeakers. It has high current tungsten contacts which are bridged by a gold plated contact after closure. The gold contact releases before the tungsten contact. This results in outstanding characteristics in switching high currents while at the same time providing an excellent low signal performance. Not included are the speaker terminals as they are depending on personal preferences.
This kit is for one channel.

There will be a separate MS Exel spreadsheet that calculates component values for adapting the protection system to other amplifiers. The spreadsheet will be available on the Elektor website as well as the Linear Audio website.