L.E.D.'s effect on tone?

How do L.E.D lights in a pedal affect tone?

I'm going to make a homemade pedal, with an (as much as possible) analog circuit structure.
It's going to be an overdrive, kind of like a tube screamer, but with a killswitch and true bypass.
I got the idea from The ultimate DS-1 mod( http://www.ultimate-guitar.com/forum/showthread.php?t=747311 ).

But I'm gonna try to make this compact, analog as possible, and run off of a 9V battery.

Anyone know what the best way to wire this would be?

Size: approximately as big as say, an altoids box, but can be bigger.

How do L.E.D lights in a pedal affect tone?


Not at all unless you're using them as clipping diodes.

If you ARE using them in place of Si or Ge diodes in the clipping circuit of a pedal, then yeah, they'll affect tone in that they'll change the amount of distortion and/or the quality of it (bassy vs trebley, etc). That article you linked to pretty-much sums it up although your results will vary depending on the pedal...in other words I wouldn't build an MXR Dist+ with anything other than Ge diodes, while I only like Si diodes in a Tubescreamer circuit. I've experimented with LEDs and didn't like them at all in clipping circuits but your opinion might be different.


Anyone know what the best way to wire this would be?


Wire WHAT? A tubescreamer w/ an LED in the clipping circuit?

Yeah, an LED isn't actually a light, it's a Light Emitting Diode and as such it can be used in place of any diode in a circuit. Obviously it'll have different tonal qualities.

In the DS1 LED's tend to sound warmer and fatter than the stock diodes, but without as much fizz and grit. I think the DS1 uses 4148 diodes stock.

Another popular replacement for them would be the 1n4001. You can try running combo's of LED's, 1n4001's and the stock 4148's in almost infinite combinations, including running pairs in series.

I have heard the different colored LEDs have different effects on tone. I have heard lots of people using yellow LEDs and then a few using red ones in the clipping sections. I think some Landgraff mods involve LEDs.

I have heard the different colored LEDs have different effects on tone. I have heard lots of people using yellow LEDs and then a few using red ones in the clipping sections. I think some Landgraff mods involve LEDs.

This is true and observable, if you have a good ear.

All diodes have a voltage or current at which they switch on:

-Germaniums are notoriously low - this is why you get a ton of compression and typically a great reduction in output.

-Silicons (most common) and rectifier type diodes are generally next up the chain. Some folks swear they can hear a difference. Possibly, but I bet most of them wouldn't pass a double blind test.

-LED's are higher than most other types of diodes. A typical LED will take roughly 2.5 times the power of a silicon/rectifier type to switch on.

The immediate benefit of LED's is typically an immense reduction of compression, and a great increase of gain. By gain I mean clean signal, NOT distortion. Since you've got a greater range to work with before your signal clips, a pedal with LED's will typically clean up much better.

I find LED's to work best for asymmetrical clipping. I like to run a single silicon with a single LED. No goofy series combinations. This combination seems to give me a good balance of everything - enough compression, cleans up well, adequate gain, extra even order harmonics that symmetrical clipping will never be able to produce...

LED clipping has been out for awhile, actually. The Marshall Guv'nor came stock with it.

Many meters let you test diodes so that you can see how much voltage/current it takes to make them switch. Then you can go with whatever type fit within a "threshold" that you like.

The typical LED takes about 1.3 volts before it switches on. Ge takes about .3, rectos about .45, silicons are around .55 volts. Super bright LED's and some colors can take 1.7 volts and above!

You can't determine an LED's switching point just by it's dimensions or luminosity, though. I've found the little red (3 mm) ones to typically be on the high side, at 1.55 volts. Actually, big greens tend to be on the lower side.

You can't determine an LED's switching point just by it's dimensions or luminosity, though. I've found the little red (3 mm) ones to typically be on the high side, at 1.55 volts. Actually, big greens tend to be on the lower side.

It doesn't depend on color either...not every red LED is the same (in size, output, or voltage drop).

There's a DIY booster/OD pedal circuit (simple, something like 8 components) called a Microdrive that uses two LEDs. They also blink when a string is played. :razz:

It's cool that more and more peds with LED clippers are popping up.

If you want a greater range before the signal gets clipped, or if you despise heavy compression when the signal gets clipped, LED's might be right down your alley.

At the very least, it's a cheap and easily reversed change to most pedals that use diodes for clipping.

Another pedal that's been out for a decade now that uses LED's is the Turbo Tubescreamer, or TS9DX. It looks just like a TS-9, but has 4 knobs. The extra knob gives you access to four "modes" - TS9, +, Hot, and Turbo. The Hot Mode uses LED's. The first two use standard clipping diode setups, and the Turbo mode uses no clipping diodes at all. If you want a quick and dirty idea of what different diodes sound like, this pedal is typically pretty easy to track down and audition.

I find LED's to work best for asymmetrical clipping. I like to run a single silicon with a single LED. No goofy series combinations.

But isn't that symmetrical clipping? Asymmetrical requires an odd number of diodes......

The immediate benefit of LED's is typically an immense reduction of compression, and a great increase of gain. By gain I mean clean signal, NOT distortion. Since you've got a greater range to work with before your signal clips, a pedal with LED's will typically clean up much better.

I think that's why a lot of people say LED's sound more "tube-like". I think they sound smoother (as in less buzzy). I have a DS-1 that was virtually unusable until I replaced the clipping diodes with LED's. The LED's "removed the bees from the can", and made the pedal SCARY loud. I've also modded my SD-1 and BD-2 for LED's. Those mods made all of those pedals more usable for me, but as always, YMMV.

But isn't that symmetrical clipping? Asymmetrical requires an odd number of diodes......

No - two different type diodes will create asymmetrical clipping. The cheapest way to do it with a mass produced pedal is to run 2 one way and one the other.

You can run 6 of the same one way, and one the other way, until you run out of room...

Some folks swear that only germaniums (1N34A's) sound good, but they typically have to run 3 or four per side to stave off the early limiting/compression.

I've settled on a 1N148 and 3 mm amber LED - with that pair, I get ~.6V threshold with the silicon, and ~1.5 with the LED. Sometimes I'll run a pair of 1N148's with the LED, and then the mismatch is only .3V. It's very subtle, though.

I've also modded my SD-1 and BD-2 for LED's.

At one point, my SD-1 had a 1N4002/LED pair - I forget what's in there now.

My BD-2 uses a combination of silicon, rectifier, and LED's for both the 2 clipping circuits built into the pedal, plus I added clipping diodes in the place of 2 small signal caps in the dual gain FET stages. These were asymmetrical LED's - a rectangular white and a rectangular amber. I also cut the drive of the pedal overall. I don't think that any pedal sounds like a tube amp, but my
BD-2 sounds pretty complex for a little solid state box.

My personal taste is to use asymmetrical clipping in a soft-clip overdrive circuit, while using 1N4001 in a hard clip. I like the raunchy, in-your-face effect it produces.

Another good thing to do is to put a .001 cap across a diode if using it opposite an LED. This helps smooth out the edges a little. Makes the clipping warmer.

Also, if modding a pedal, remember that 1N400x rectifier series diodes have a thicker lead than the smaller signal diodes. It will be necessary to drill out the existing hole. If the board is single sided, then great care must be taken to not damage the trace. If it is double sided thru-hole, then I suggest not doing it. Use smaller leads clipped from other components to create a post to attach the larger diodes to.

If designing your own layout, a good rule of thumb is to start with a 1N400x footprint. That way, the options are wide open.

C'MON!!! Everyone knows that pretty, sparkly, twinkly lights make ALL musical equipment sound better!

mud

At one point, my SD-1 had a 1N4002/LED pair - I forget what's in there now.

My BD-2 uses a combination of silicon, rectifier, and LED's for both the 2 clipping circuits built into the pedal, plus I added clipping diodes in the place of 2 small signal caps in the dual gain FET stages. These were asymmetrical LED's - a rectangular white and a rectangular amber. I also cut the drive of the pedal overall. I don't think that any pedal sounds like a tube amp, but my
BD-2 sounds pretty complex for a little solid state box.

+1, especially on your last statement. I really disliked my BD-2 stock. I bought it because I thought i had to have one.:roll: After a month or so, I got very disgusted with the "fizziness", and decided to get the Monte Allums mod kit, which is essentially what you describe. What a big difference.

Another good thing to do is to put a .001 cap across a diode if using it opposite an LED. This helps smooth out the edges a little. Makes the clipping warmer.

Also, if modding a pedal, remember that 1N400x rectifier series diodes have a thicker lead than the smaller signal diodes. It will be necessary to drill out the existing hole. If the board is single sided, then great care must be taken to not damage the trace. If it is double sided thru-hole, then I suggest not doing it. Use smaller leads clipped from other components to create a post to attach the larger diodes to.

Actually, if you use the "smoothie cap" that you mention above, you don't have to do anything to the board - simply solder the 1N400X across the cap's leads, and install the cap's leads in the PCB holes. Just keep the diode close to the cap so that you don't have a lot of bare lead hanging out on the board, and make sure you have to diode's polarity going the right way.

If the diodes shunt to ground, you can get away with bigger smoothie cap values - the most popular DS-1 mods call for a cap as big as .047 uF. If the diodes are in the feedback loop, the cap typically must be much smaller or you end up killing too much top end. 470 pF seems to be the upper limit.

The "piggyback" method also works great anywhere you want to add diodes, a smoothy cap, or resistor to modify the drive. You just solder them up in a little ladder with everything running parallel. If space is tight, you can build up in a triangle or rectangle, as viewed on end.

bump

So that's why my yellow Tele sounds different to my sunburst one, different colours. :wink:

So that's why my yellow Tele sounds different to my sunburst one, different colours. :wink:

Haha

OK, I don't know much about wiring effects, but I have a cheap SS practice amp in my living room with distortion. The amp does not have a master volume and I was trying to get more headroom out of it, so I clipped a leg off of each of the LEDs (2) in the distortion circuit.

I'm still getting too much OD from the amp. Is there anything I can wire in place of the LED's to get more headroom?

Is there anything I can wire in place of the LED's to get more headroom?

What you need to do is reduce the gain by reducing some resistor values - it could be as little as one resistor.

You don't even have to yank the PCB out - when you determine which resistor is the culprit, simply "piggyback" it with one of the same value (solder it parallel to the existing one). Resistors in parallel = less resistance.

You need a schematic of the amp in order to know which resistor(s) to deal with. Alternatively, you could trace the circuit board and figure it out, but that's kind of time consuming.

You're basically looking for resistors in the "feedback loop(s)." In the case of the schematic below, they are the 470K resistor that ties together pins 1 and 2, and the 150K resistor that ties together pins 6 and 7. I chose the VLO schematic because it uses the most common op amp in the world - the TL072, which is most likely what's in your amp. If it's a different chip, not to worry - they are all more alike than they are different.

very informative thread, my Nashville pedal has LEDs and someone explained them to me, more headroom
JIm

My personal taste is to use asymmetrical clipping in a soft-clip overdrive circuit, while using 1N4001 in a hard clip. I like the raunchy, in-your-face effect it produces.

Another good thing to do is to put a .001 cap across a diode if using it opposite an LED. This helps smooth out the edges a little. Makes the clipping warmer.

Also, if modding a pedal, remember that 1N400x rectifier series diodes have a thicker lead than the smaller signal diodes. It will be necessary to drill out the existing hole. If the board is single sided, then great care must be taken to not damage the trace. If it is double sided thru-hole, then I suggest not doing it. Use smaller leads clipped from other components to create a post to attach the larger diodes to.

If designing your own layout, a good rule of thumb is to start with a 1N400x footprint. That way, the options are wide open.


1N400?S Have standard 0.9mm dia leads.