This Week on the Breadboard: The FireDrake

Here's the latest update. I'd call this the final version, but I don't want to jinx myself. I added the rest of the clipping options, reapportioned the gains a little, fine-tuned the filters and added the 6dB/12dB switch on the Treble filter. I have only tested the MOSFET, GE+Schottky, Blue LED/1N4003 clippers and wide open (no clippers). I'm confident the other clipping options will work as intended.

I noticed something when playing with the TREBLE filter: it's possible to raise the Q so we get the "Stuck Wah" voicing. I like the tone better as I have it drawn. If you want to fool around with a higher Q, increase C8 to 100nF and increase R11 to 33K.

FireDrake OD v1.04 sch.png
 
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Remember how I was afraid of jinxing myself? Well, it happened. I had drawn Q1 & Q2 backwards on both schematics and C13 was missing. Schematics have been revised and updated. If you saved a copy of v1.03, delete it and replace it with v1.04.
 
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I asked for it so I better get t show that I built one.... ;)
Ladys and Gents, the Flame Thrower aka as Chuck's Fire Drake. It burns and has a bad to the bone breath.
@jjjimi84 ;)

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Chuck D. Bones said:
What is your assessment of the MODE switch positions? Any favorite settings?
Click to expand...
Ask me in three months, there's so much tweak-ability in this between 8 clipping modes and the compression dial and the very effective tone stack...
But first impression and just my personal taste as I'm getting too old for that high gain stuff: the gentler less clipping options with no clippers at all, the Mosfats, both the LEDs option (blue and 4001/red+red) and the 4148 and 4001 are up my alley. As said those there's tons to tweak and I can get stuff that I don't like so much, obviously, just my ears, and stuff that hits the mark.
Great pedal, certainly nothing for peeps with option anxiety.
 
More compression. A non-inverting soft clipper, like the TS for example, has a built-in clean bleed because the input signal is summed with the clipped signal. The clean bleed reduces compression, which may or may not be desirable. An inverting soft clipper has no built-in clean bleed. The COMP knob allows the user to dial-in the desired amount of clean bleed, from zero to a shitload.
 
so by placing varying amounts of resistance in series with the clipping diodes, you are able to discourage the signal from getting clipped and thus to just pass to the output without clipping? that makes sense actually.

why do you think peter went with non-inverting in the original design? is it maybe because the original design didn't have the comp control and this version was just a further iteration of that design?
 
A more accurate way to describe it is the voltage drop across the series resistance (COMP pot) is proportional to the undistorted input voltage and that is summed with the clipped voltage across the diodes. There are a number of ways to implement clean bleed. I did it this way. The effect of the clean bleed is not just to reduce the total distortion, but to increase dynamics.

I won't try to guess why Mr. Rutter designed the circuit they way he did. He's a smart engineer and knows what he's doing. I went inverting because I wanted to be able to dial the clean bleed down to zero in order maximize the range of the COMP knob. Unlike the VFE Dragon, the FireDrake has a 5x gain stage up front. That has the effect of increasing the clean bleed by 5x if I ran with a non-inverting soft-clipping stage. That much clean bleed in combination with the MOSFET clipping runs the risk of saturating the CA3130.
 
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i would imagine that in a non-inverting soft-clipping stage like the tube screamer or the original dragon, while the clean signal is unity gain at the op-amp output regardless of the amount of distortion gain, still, the higher the gain, the higher the apparent volume, and thus the more the post-clipping volume will be turned down, and with it the clean signal. so as a result, in a certain sense, the higher the gain, the lower the amount of clean signal mixed in. so theoretically it would end up working kind of like a cruder version of the klon's dynamic clean blend...

this is just an idea i had though, i haven't had a chance to test it yet
 
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