I take 3 K4007 kits to use on 3 amplifiers.
I built the first and placed in an old mosfet 150W final amplifier and 250 W RMS 3 way speakers.
When I raise the volume about 1/3 of maximum, the music stops because it goes in protection mode.
I tryed also with 2 other pairs of speakers but it’ s the same.
It seems to be too sensible to the current that runs in.
Obviously whitout the protection circuit, amplifier and speakers work correctly but when i turn up the amplifier i feel the classic “bump”.
How can I do to set a different sensitivity of the circuit to raise the level of the overload ?
I plain to use the other two circuits on two final amplifiers in bridged mode to obtain two 250W RMS mosfet final amplifiers and i need them to work.
Sorry for my english,
hope you can understand the problem and give me an answer.
Thank you.

Sorry, K4007 is not a correct reference.
Please check the board/manual.

Where, onthe reference manual should i see ?
The only thing that i can see on the box and in the reference manual is K4700, it’ s a two way speaker protection kit.
You can see it also in the website and in the end of the page you can find the link:
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Velleman Projects Service Forum
Warranty for kits
This stereo speaker protection prevents switch-on clicks and DC components on the output of the amplifier connected.
•switch-delay: ± 6 seconds
•DC protection: +1V/-1V
•max. input voltage: 200Vpp + DC
•max. switching current: 10A
•LED indication for: WAIT (switch-on delay) and ERROR (DC on speaker output)
•supply voltage: 220VAC
•PCB dimensions: 55 x 125mm / 2.2 x 4.9"
Packaging information
Type of packaging: Box (Carton)
Bar code (EAN-13): 5410329047009
velleman.eu/distributor/prod … w/?id=9233

Ah, it’s a K4700.
In order to decrease the sensitivity, you can use two diodes in series instead of one for D5 and D6.

Should the diodes be the same as d5 and d6 ?


Thank you i will tray as soon as possible.