amadden24@yahoo.com wrote:
One other question; I noticed the first time I fired up the pedal, the clipping LEDs lit up (as they should I would imagine), but they no longer light up at all. On any settings of the gain or level knob. So, I replaced them and still get the same issues; middle position on the switch there is no output and in any position the clipping LEDs do not light up.
The LED's are probably working fine....just not in the way you're expecting. In this mode of usage, their function is not to light up but rather to divert (i.e. clip) some portion of the audio signal away from the output path and thereby introduce some signal distortion. The first part of
THIS ARTICLE describes it better than I ever could. The amount of the signal that gets clipped will be that portion that exceeds the forward voltage threshold (FVT) of whatever type of clipper you're using. Because these LEDs have a high FVT (something in the range of 1.5 - 2V), it takes a very strong signal (by electric guitar pickup output standards) for them to clip a portion it. Since the signal is the strongest at the initial attack of the note, that's where the most LED clipping will occur. But in most pedal circuits with LED clippers, that only happens for a short time interval, maybe a tenth of a second or so. But if the signal is strong enough, it will light up the LED as it's clipped, though usually dimly & briefly. Here's your best bet for being able to see it: Dial your Drive control up to the max, plug in a guitar with a strong output (most humbucker guitars will suffice nicely), set the clipping toggle on your GP to the LED setting, and turn off the lights in a room with little or no ambient light. Now strike a chord HARD and see if those LEDs flash on for a moment. I'll bet they do.
Incidentally, this clipping behavior relates to another observation you made. Since different kinds of diodes can have widely different FVT's, they will clip more (low FVT) or less (high FVT) of the signal. This explain why you heard a substantial volume difference between the LED and Si positions of the clipping toggle switch. Silicon diodes typically have an FVT in the 0.5 - 0.6V range, so they clip a much larger portion of the signal than the LED's. More signal clipped = less signal output. It also means a more distorted and compressed output.
What baffles me about your problem is that you are getting NO output with the clipping toggle in the middle/off position (i.e. no signal being passed through either set of clippers), which should give the
strongest output. I can't even understand how that's possible. But maybe Keith/byoc has an idea for that one....
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