More Tube Screamer Diddlin' - Clipping Diode Comparison

[duhvoodooman***]

In response to a request by another pedal modder over at the BYOC forum, below is a link to an audio clip I recorded to demonstrate the different clipping tones afforded by various diode combinations, using my Zonkin' Yellow Screamer as the "test bed". I disconnected the two wires connecting the switchable diode setup to the PCB, and soldered alligator clips to each end of the wires. Then it was a simple matter of just spot-soldering the various diode combos together and attaching the alligator clips to either end. Here's a photo, showing a yellow LED/1N4148 silicon asymmetric diode combo ready for testing:



The audio clip was recorded using my Epi Elitist LP Standard (bridge p'up) through my AD30VT. The amp model used was the Boutique Clean (for minimal coloration), with a bit of reverb and no other effects. Once set up, the amp wasn't touched during the recording of the different clipping combinations. I had the pedal set up at the normal Overdrive gain range and the stock TS 720Hz bass rolloff, the Tone at midpoint and the Drive control dimed. Level was adjusted to keep the amp speaker output at a relatively consistent volume.

The same riff sequence is played through a total of ten times. Here is the order of diode combos used:

1. Clean (no pedal)
2. 1N4148 silicon pair (symmetric; TS-808 stock)
3. 1N4001 silicon pair (symmetric)
4. 1N34A germanium pair (symmetric)
5. 1N4148/1N34A (asymmetric)
6. Red LED/1N34A (asymmetric)
7. Red LED pair (symmetric)
8. Yellow LED pair (symmetric)
9. Yellow LED/1N4148 (asymmetric)
10. 1N4148/2x1N4001 (asymmetric; clipping option included in BYOC Overdrive kit)

Here's the link to the audio clip:

http://www.box.net/public/xa79ot2xuf

IMO, the differences between these various diode combos has a much more significant impact on the sound of the pedal than what kind of opamp is used. But see what you think....

[oldguy]

IMO, the differences between these various diode combos has a much more significant impact on the sound of the pedal than what kind of opamp is used. But see what you think....

Huh?
I have a mental image of a mad scientist running current supplied by lightning strikes through his creation. Laughing diabolically and screaming "It's Alive! Alive, I tell you!"

Sounds good, DVM. It's obvious that you are on a quest, and won't settle for "that's close enough". I applaud you, my friend.

[warren0728]

wow....what a lot of work!

truly i think they all sounded good except maybe #4 - 1N34A germanium pair (symmetric).

ww

[duhvoodooman***]

truly i think they all sounded good except maybe #4 - 1N34A germanium pair (symmetric).

Actually, I like the germaniums quite a bit, but it's almost a completely different sound vs. the silicon diodes and the LED's. Germanium diodes clip very softly, so you get a very smooth & subtle overdrive compared to silicon diodes or LED's. Nice for that just-starting-to-break-up overdriven amp sound, and particularly well suited for blues. The germaniums also have a significantly lower volume output, so you have to crank up the pedal's Level knob or roll up the volume at the amp. I wouldn't want a pedal with only the germanium clipping diodes, but using them as one of 3 switchable diode combos (the other two being silicons and LED's) gives the pedal quite a diverse range of overdrive tones. There are other diode types that can be used for clipping, like Zeners or MOSFETS, but I didn't get that far into it. Even a geek like me has his limits!

BTW, funny story about this experiment. Some of you may be familiar with how crystal radios work, and the fact that they commonly use germanium diodes for the detector. Well, while I was changing between sets of diodes, I put in one of germanium-containing combos and grounded the diode by gripping the metal alligator clip on one end. I was wearing headphones from my amp's line out at the time, and all of a sudden, I'm listening to the radio--one of our strong local AM channels! It was faint, but very clear. Seems that I'd turned my ZYS pedal into a crystal radio receiver by grabbing the clip! As soon as I would release my hold on the alligator clip, it would stop. Grab hold again, and the radio was back. Pretty wild....

[Jimi75]

Hell what a pedal. I liked all sound clips, especially 2. and 5. kicked me. Congratulations DVM.

You know, I was always like so and so satisfied with my TS808, but your pedal convinced me entirely.

[oldguy]

Hey, Voodoo! Maybe you could add an option pkg that includes a tiny set of rabbit ears, a 3in. tweeter, and a miniature frequency dial!

[duhvoodooman***]

Hell what a pedal. I liked all sound clips, especially 2. and 5. kicked me. Congratulations DVM.

You know, I was always like so and so satisfied with my TS808, but your pedal convinced me entirely.

It was fun to try all these combos and see how they differed. Some are very significantly different, while others are (at least to my ears) indistinguisable. The "permanent" clipping diode combos in my ZYS pedal, switchable by a 3-way toggle, are the asymmetric silicon (#10), the yellow LED symmetric (#8), and an asymmetric variation on the germanium diodes (#4) using a single 1N34A diode on one side and two of them on the other. But I've found that the germanium clipping is subtle enough that you really can't hear any difference adding that third diode, so I'll stick to just the symmetric pair for future builds.

Pairing up a germanium with a silicon doesn't seem to make much audible difference either, because the character of the silicon seems to dominate. However, the combo with the red LED and the 1N34A germanium is very unique sounding; it seems to accentuate the bottom end vs. the mid-to-upper emphasis of most of the diode combos. The yellow LED/1N4148 silicon combo shows this same character, but to a somewhat lesser degree. Ah, the endless possibilities....

[marnold***]

I know that LEDs are still diodes no matter what, but I just find it to be a riot that they can be used to create distortion. Then again, it's been said that I'm easily amused.

[duhvoodooman***]

I know that LEDs are still diodes no matter what, but I just find it to be a riot that they can be used to create distortion. Then again, it's been said that I'm easily amused.

Not only that, but when you push the gain way up and provide a strong signal (like a power chord) , they light up! Not much, but definitely visible, especially in a darkened room.

I suppose that if I used an LED/germanium diode combo, I could get radio with a light show!

P.S. I'm easily amused, too. I'm also Lutheran (LCMS)!