Low-Voltage Chunk from Diode Distortion!
Did you know you can add a simple circuit to your guitar or bass that produces onboard distortion — without using a battery?
The idea is pretty simple — you attach a pair of diodes to the guitar’s output via a pot or switch. With the diodes connected to ground, you get a fairly nice distortion sound. With the connection to ground broken, you get your regular tones. It’s the same method used to create distortion in a several ’70s distortion pedals, notable the MXR Distortion+ and the DOD 250.
You can purchase the necessary components in a sleek black housing under the name Black Ice for $27.50, or you can do a DIY version for about $2 in parts. I’ll explain how after this brief video demo:
My reactions: It’s a pretty cool effect, though the volume drop when engaging the distortion might be an issue. If would be great, however, in any context where you need a crunch sound at restrained levels, like when playing in a stage pit band. It’s not a terribly refined tone, but definitely a usable one.
Before recording this demo, I tried a Black Ice in a vintage-voiced Strat. It definitely created a distortion effect, but it’s much more gratifying here with the higher output P-90s and humbuckers.
This dual-pickup guitar is wired for two volumes and one tone. The fourth pot adds the Black Ice distortion — that ominous black cube.
I rewired the demo guitar — which you may recognize from this post about makeovers for cheapo axes — for two volume knobs and a single tone, freeing up the fourth pot for the Black Ice circuit. But I don’t think I’d repeat this method.
The blended settings just don’t do much for me — the pot acts more as a clean/dirty blend than a distortion control per se, and the mixed settings strike me as a thin trickle of distortion suspended over a clean sound. Furthermore, the recommended A250K pot seems like a poor choice, since all the usable sounds are clumped together at one end of the pot’s range. In the future, I’ll experiment with other pot values — or more likely, just attach the diodes to a SPST switch and consider it an all-or-nothing effect. This wiring will work great for the latter approach:
Use the low-voltage Schottky diodes specified in the article. Be sure they're oriented in opposite directions — the cathode (banded end) of one diode connects to ground, as does the anode (non-banded end) of the other.
I like the Black Ice package — it’s a snap to install, and I even bought a second one to try in my P-Bass. But you can definitely get a similar effect using a pair of low-voltage Schottky diodes like these or these. I have no idea which exact diodes the Black Ice uses, but the two types I mentioned will get you very close. (FYI, I tried a dozen or so diode types, and none sounded nearly as good as the two I linked to.)
Conclusions: Interesting, inexpensive, and possibly useful. Worth a try! 
You know, just the other day I was wondering if something like this would work. Clearly your blog has made a tinkerer out of me…
Wow that seems like a pretty cool idea!!! What should I change to make a floor pedal version of it? Do you know any on line store that I can get the items for cheap in Europe? Definitely waiting for more projects like this in the future. Thank you!!!
Lots of my European friend order from Germany’s Bonzai Music (http://www.banzaimusic.com/). But these aren’t specialized guitar parts — you can get everything you need from any electronics supplier.
Hmm — a pedal version? Well, it would be the simplest pedal in the world, with no battery (unless you insist on adding an LED). But I’m not sure you’d LIKE it — the volume drop is a genuine issue, and if you’re going to go all the way and build a distortion stompbox, why not make a diode-based distortion with proper volume and gain controls, like DIY Club Project #1? :)
I really want to make the #1 project but It needs more effort and time that I don’t really have right now.
The volume drop isn’t an issue for me as I’m not switching between clean and distortion often. So how can I make the pedal version? Could you please make a nice scheme as you made above? Thanks!!
Must agree…that’s a pretty cool one. It’s a shame the blending isn’t any better. Be sure to update us it you find a different pot value works better. Thanks for more great ideas!
Very cool! I’ve seen the Black Ice & wondered about putting it in, but I like your super low-cost solution… I might do this to the Batman Logo guitar!
I can’t think of a more fitting home for it! :)
Have you tried Ge diodes such as 1n34a? Might be a alternative to the Schottkys.
It may give you too much of a voltage drop. The diodes Joe is using have a turn on voltage of .75 and 1.0 turn-on volts whereas Ge types run around 0.2 volt drop it may vreate a very low level output. Standard silicon diodes typically turn on at about 0.6 volts. You might also want to try 2 or 3 or even 4 or more Ge diodes in series rather than a single diode to get a higher turn on voltage, you could also do a mismatch which should give you an asymmetric clipping 2 diodes in one direction vs 3 in the other. This might also work with LED is you could find one that fired with low enough voltage. This would probably be very cool with active high output pickups.
Hi Matt –
Usually Schottky diodes turn on at around 0.2V, and have a relatively low resistance once on. Ge diodes turn on around 0.3V, and the on-resistance is quite a bit higher. Standard Si diodes turn on about 0.7V. LEDs are all different beasts, and the turn-on voltage depends on the semiconductor material and the wavelength; the lowest turn-on voltage is about 1.6V and can go up to about 4V for some Violet/UV LEDs.
Anyway, with Ge diodes (as compared to Schottky), they would start clipping at around the same voltage or just a little higher (making them just a little louder). Also, they would have a higher on-resistance, making for more of soft-clipped sound. Just a thought.
-Jeff
Thanks guys — that is a TON of stuff I didn’t know. I’m definitely going to check out a Ge version once I dig myself out from this mountain of crap soon. :)
Yep I misread the specs and I mistook the maximum forward voltage drop for the firing voltage on the links provided in the original post. I’ve never used Shottky diodes much in audio, my only experience with them was in chemistry instrumentation. Ge diodes I have used all seemed to fire around .2 volts or a little more when I used them as clippers but that was when they were after an IC or in the feedback loop for the IC circuit. I always liked the Ge diodes best in those circuits. The Ge diodes I use are all from my stash that I purchased in the early to mid 70′s from small electronic suppliers that were going out of business. So my Ge diodes are definitely the old school glass types many of which are fairly leaky. In any case it always amazed me that the best sounding guitar circuits sort of break the rules of electronic engineering.
Back in the 1970s there were a couple of devices called Blue and Black Ice Cubes that plugged in the rear jacks in place of the reverb tank on Fender and other amps. It created a parallel distorted signal varied by the reverb control. They were basically diodes with a couple of resistors and capacitors that were also encased in plastic resin. Nils Lofgren used to use one on a Twin Reverb quite a bit back then to achieve his lead tone (according to his brother Tom who was in our dinner club).
I usually figure that any circuit or device encased in plastic or epoxy is an embarrassingly simple design that the makers worry everyone will build themselves [Dumble amps ?] :-).
I was curious about having this turned on and running through the buffer(to make up for the volume drop) then into either the distortion or the rangemaster.
Is this a good idea, or would it get all muddy sounding?
Well, the buffer wouldn’t change anything, but the booster/buffer from DIY club would.
But honestly, I think it’s probably best to take this effect as it is, volume drop and all. If you want loud distortion, well, see my reply to DohminSemper above.
I’ve actually built a few pedals using the Black Ice. The first one is based on the one that includes a switch to turn it on FULL. I used a 250push/pull pot & use a capasitor for humbuckers. It seeems louder then the single coil type.
Cool! I don’t suppose I could persuade you to sketch out and post a little schematic? :)
Stewart MacDonald Parts
1-Mega Pot for volume
1-250 push/pull
1-BlackIce
1-.20mf capacitor
Radioshack Parts
1-SPST Toggle Switch(279-0834
2-1/4 Mono Audio Jacks
Fry’s Electronics Parts
Push on-Push Off Standard Pushbutton (Parts No. 38-448)
Home Depo Part
1-Round PVC style used for electric wiring (Trim & modified for it’s out shell/Digitalcamo Duct Tape for outer appearance)
I basically used the same StewMac diagram, I added a 1 Meg Volume & kill switch.
Use a 3 way switch and you can toggle between 2 different diode combinations…
Ok – I know this is kind of counter to the original premise….but COULD we stick a battery in there?
Totally! No problem putting a battery in there. But pragmatically speaking, it’ll sort of be like putting a battery in a cantaloupe.
Hey
This is great, btw
If I put a signal booster on when the distorted sound was there? Would that mess with the distortion, or just make it louder?
Yeah, that would totally work. It’ll change the sound, in the sense that more level will be hitting your amp, and the tone will be more distorted than it would otherwise be. But it’ll retain the basic color.
HAHAHAHA :)
I have an original Black Ice – it’s a little black thing (with a serial number on it) with two rca male connections aligned to fit precisely into the reverb circuit of a Fender Princeton Reverb. It’s a little strange but its an ultra rarity that no one will own up to – but i suspect it was made by EHX. Actually I had three i gave two away to fender loving friends. it came in a box a bought in the 80′s along with 4 versions of Treble boost/Screaming Bird – i kept an original of that one too… very basic effects but they do the job pretty well. I’m amazed how some of the EHX effects have remained in my pedal chain – none which are newer than 1983.
You could also try changing out just ONE of the diodes, e.g. use a Schottky on one side and the Ge diode on the other. That way your distortion will be asymmetrical, giving more even harmonics. I won’t go so far as to say “tube” tone.
Now I did try putting a battery in a canteloupe, and WOW!
what about just using 1 diode or LED? and how would you describe the difference in sound between a led and a silicone diode? will just 1 led mean less signal loss?
Sorry, that just won’t work at all — you need to two diodes oriented in opposite direction to produce the effect. Also, while using different diodes is a cool way to customize the sound of a 9v-powered distortion pedal, only certain types of diodes work in this PASSIVE circuit. LEDs won’t work at all. There may be some other options that work here (maybe some of the electronics aces who read this site can help me here), but as far as I know, the effect you hear in my demo is pretty much the only option.
Can anyone expand on that?
Ok, you could use only 1 diode – but it would clip only half of the waveform. You would probably end up with a strong octave effect.
The choice of diode dramatically impact the amount of clipping available. The clipping happens when the diode goes from being “off” to “on”. While off, the diode lets the signal go through unaffected. However, once the input voltage reaches the diode’s threshold voltage, it turns on, and doesn’t allow the signal to get any bigger.
With active effects, you can boost the signal to allow diodes with higher threshold voltages to work. However, when using passive pickups, you need to have diodes with relatively low threshold voltages – otherwise they will never clip and never have any overdrive.
If you look at the comments above, I quoted some specifications on other diodes.
Always experiment!
Also, there is a new version of the “Black Ice” available from StweMac. It can be found here: http://www.stewmac.com/shop/Electronics,_pickups/Components:_Black_Ice_overdrive/Black_Ice.html?actn=100101&xst=3&xsr=17287 This new version has four available configurations. Check it out!
-Jeff
Today I added some clips over at my forum post about rectification http://tonefiend.com/tonefiend-forum/?mingleforumaction=viewtopic&t=85.0. A single diode will only result in half wave rectification and does not create an octave effect. It creates a strong second harmonic but it just sounds really distorted.
That seems like a great idea. But how the two diodes add distortion? Could you please explain how this works?
Also to make a pedal box that’s permanently turned on, what will I need? A metallic box, 2 mono jacks, cable and the diodes only?
Hi Nick — actually, I’d recommend taking a look at my first DIY stompbox project, even if you don’t want to actually build it, because it explains all the hardware and wiring necessary to build amy first DIY stompbox effect into an enclosure. The dual-diode distortion will totally work in stompbox form, and it’s a super-easy build. :)
Well, what I don’t understand is where is the “ground”. Do I have to solder a cable from one side of the peftboard to the other and call it “ground”? Is the negative side of a battery the groudn? Could you explain this please?
Here’s my suggestion for someone putting in a diode clipper on their guitar: Use an SPDT center-off switch and get two different distortion sounds.
1) Put two identical diodes back to back from ground to one terminal. This creates a “thin” distortion sound.
2) Put two diodes with different forward voltages (e.g. a silicon and a Schottky) back to back from ground to the other terminal. This creates a “thick” distortion sound. The output level will be lower still than the “thin” sound so you’ll need to compensate for that somehow.
You could run the guitar into a compressor or volume pedal to take care of the output level differences.
This arrangement will give you three sounds:
1) No distortion (center off)
2) Thin distortion
3) Thick distortion
I should stick to the forum, where I can edit my stupid remarks!
If you start with two low voltage diodes like Schottkys, and then unbalance it by replacing one with a silicon or germanium diode, the result will be louder. Whichever combination has the lower sum of forward voltages is the quietest.
LOL — hey Larry, I’m sorry I haven’t figured out how to add a revision feature to comments. But trust me, man — no one thinks you’re stupid. Your suggestions abou passive diode distortion are brilliant, I don’t think anyone anywhere has spelled it out that well, and I can’t tell you how much I appreciate you sharing your expertise here. :)
Hey, Joe.
Just wanted to drop a line to thank you for posting those diode “model numbers”. I added both to a tiny box I made so now I have an outboard pedal that I can select between the two types.
The silicon diodes actually have no perceivable (that I can tell) volume drop compared to the germanium ones.
Cheers for this post…it was very helpful.
Be well.
E.
Awesome! I’m delighted it worked out for you.