Sound Reactive LED on Fuzz

[daveed235]

Hello all,

I've got a Shin Ei Companion fuzz that I have breadboarded, and I was experimenting with clipping diodes from output to ground. When I use LEDs for clipping, they light up a little bit when the signal is being clipped, and it looks really cool, but it is very dim. What would be a simple way to make the LED brighter while still reacting to the guitar signal, using a BJT or JFET perhaps? I think it would make a really neat indicator instead of the conventional light.

I don't think I've seen or heard of this before, but I'm also pretty new to making pedals and I have a lot to learn!

Thanks,

Dave

[bluebunny]

Welcome to DIYSB, Dave.

When LEDs are used for clipping, they're not really intended to give you any kind of light show.    If they light up at all, it's a bonus.  If you really want some kind of flickering "this is being clipped" display, then you might want to consider a completely separate bit of circuitry (that you can bolt on) to complement what you've already got.  Have a search for "sound to light".

[digi2t]

Opamp amplifier?

[diffeq]

There are numerous ways to do it - with BJT, with comparator or with LM386, with opamp and even logic inverter if the signal is beefy enough to move within 3V-6V thresholds of the Schmitt trigger:



Personally, I'd go with LM386. It's cheap and easy.

[daveed235]

Thanks guys! I'm going to try doing something like this. I hope this will look pretty cool, and I will keep you guys posted. I don't have any opamps on hand so I will try it out with just BJTs.

[antonis]

Depending on your specific LED forward voltage drop, you may need a Collector resistor for Q2, 'cause a heavily saturated BJT on 5V could burn out the LED..
(with a rough estimation, Q2 Collector current shoud be over 40mA to 100mA for hfe of 100-250..)
Unless you have a guaranteed low current gain Q2 (max less than 50) it's not wise to feed LEDs without current limiting resistor..
(e.g. for 5V Collector voltage drop & 2V LED Fvd, Collector resistor should be calculated by 3V/Ic, where Ic should be LED working current..)

The above should only work for asymmetrical clipping (one way to GND diodes) - for a pair of antiparallel diodes you should need a push-pull like circuit..

[EBK]

Welcome to the forum!

Unfortunately, in the LED arrangement that you illustrated, you'll likely find that the LEDs compete rather than cooperate with each other.  Whichever LED has the lowest forward voltage will most fully conduct, and the others will either be dimmer or not light up at all (you might get lucky and have a couple LEDs with nearly identical forward voltage measurements, but you can't generally rely on that being true).  To light multiple LEDs simultaneously, either place them in series or give them each a series resistor.

[antonis]

I can also hear a "Huston, we've 5k8-ish input impedance problem" call from an unbuffered signal source..

[GibsonGM]

I can also hear a "Huston, we've 5k8-ish input impedance problem" call from an unbuffered signal source..

And a 1201 and 1202 alarm, if you're unlucky!!   (inside joke!)