3.75 v or 5v Sound Organ? Help?

[notor]

Hi guys. I'm pretty new at this. I'm trying to get a reeeeally simple light organ going on. Something that will just respond to bass thumps.

Basically I'm just trying to power a bunch of 3.2v LEDs (in parallel)

I bought one of these:

**broken link removed**

but it runs off 9v.

This isn't the first time I've looked for help, someone wrote this back to me on Reddit:

Unfortunately, due to the supply-sensitive bias techniques used in this circuit, it will not like being powered by 5V unless a lot of resistors are changed. This circuit has 4 stages of amplification (4 transistors). Each transistor has resistors around it to provide biasing and feedback to set the gain of each stage. Since those resistors are designed assuming a 9V supply, their values will need to be recalculated for a supply of 5V. Otherwise, the gain of each stage will be messed up, and some of the amplifier stages will simply not work because the transistors are cut off due to low bias voltage, so the input will become clipped and distorted. That said, the circuit's input is a microphone and output is a bunch of LEDs, so perhaps at 5V supply those LEDs will still be doing something interesting, but most likely they will just be off or faintly glimmering, and that would be lame.
I suggest you find a way to get 9V supply, or roll up your sleeves and prepare to do some redesign.​

So. . . . Yeah i have to redesign the circuit but I don't know how. :/

Any advice?

 

[audioguru]

You need to learn about how transistors work for you to re-design the circuit.

 

[colin55]

The circuit will work on 5v. Just use 1 LED and if you want more LEDs, just add them between the collector of the BC557 and 0v rail via a 100R resistor.

 

[mneary]

The circuit might want a few minor changes, even for 9V.

Change:

R10 820k
R12 100k
R5 4k7

Same values are OK for 5V.