Velleman MK 103 LED mod help

Thread Starter


Joined Apr 9, 2012
So, i want to use a Velleman MK 103 sound-to-light circuit to light up LED's in a guitar i am going to make, the thing is that i want to use six blue superflux LED's instead of the red high-intensity ones that are already included with the circuit. i plan to wire the new LED's un in parallel, will this work? or will i need something else to help power the LED's?

Here's a link to the velleman circuit:

Here's a link to the LED's i am going to use:


Joined Nov 30, 2010
Unfortunately, the "Detailed Description" doesn't tell anything about the circuit. Based on that, I can't answer the question.

A schematic is necessary to tell how the LEDs are powered and if anything needs to be modified. I'll have to ask you for that...or maybe another Allaboutcircuits helper has used this kit?

Blue requires higher voltage than red and that might queer the deal.


Joined Dec 20, 2007
The schematic was not posted so somebody must look for it.
The LEDs have no datasheet and nobody knows which manufacturer.

Google found the schematic. It is from Velleman, not from All Electronics.
The four red LEDs are in series and have a current of somewhere from 1.7mA to 38mA. I think you will see the original LEDs dim as the battery voltage runs down.

NOBODY (except some Chinese flashlight makers) connects LEDs in parallel unless they are tested and matched. With LEDs in parallel then the circuit must be re-designed for the much higher current and the little 9V battery will not last long.



Joined Nov 30, 2010
I'm picking up blue LEDs as 3.5 to 4 volts each. You're going to have to run 4 in parallel off T4 to have the battery last more than half an hour. You can try 2 strings of 2 LEDs each but I'm afraid you'll run out of voltage as the 9V battery drops to 8 volts during use.

Of course, each led or led string will need its own resistor to limit the current to a reasonable amount.