Introduction: Passive Guitar Overdrive (Black Ice)

Picture of Passive Guitar Overdrive (Black Ice)

A friend of mine brought to my attention a passive guitar effect, called "Black Ice" which takes the place of the capacitor (or wired with the capacitor) on the tone knob, and when used, gives the guiatr's sound a "crunch" similar to an overdrive. He wanted to know if i could make it, as opposed to buying one for 30 dollars. After a bit of research, I found out is was simpler than I first anticipated, and a whole heck of a lot cheaper. Along with building the effect as it was originally supposed to be done, i threw in my own twist. I found the amount that the version one effect changed the sound was underwhelming, but my version, when wired in as i specify in the instructable, has a profound change to the guitars sound. 

Version one is the original Black Ice circuit. It produces an overdrive-type crunch, though it is not exactly like a true overdrive. It is a little more "hummy" than an overdrive, and the tone is more mellow.
Version two, my version, has a smoother tone than version one, until it is turned up all the way, when it becomes more agressive of a crunch, and plenty of 'wanted unwanted' distortion. It also modulates the higher frequencies into the loswer ones. The tone is also less mellow. I prefer its more noticable and agressive tone as compared to the priginal Black Ice circuit, but it does require a more complex hookup. 

Step 1: Parts

Picture of Parts

For version one, you need two diodes. Thats it. The type of diode does matter however. Schottky diodes are what the original circuit uses, but cat-whisker diodes can be used as well, as long as they have a very low voltage drop. I made a version using Schottkys, but for this instructable i will feature the cat whisker diodes. This version is the original Black Ice circuit.
For version two, you need 4 diodes. This is my version of the circuit. 

Step 2: Circuit

Picture of Circuit

For version one, the two diodes are wired in parallel with opposite polarity. In version two, they are wired as a full wave rectifier circuit.

ATTENTION!
My version was originally intended to be wire as seen in the schematic. But after some experimentation i found a better way to wire it. On step 4 there is a diagram showing how to wire in the effect. Us the diagram on this step to build it, the diagram in step 4 to wire it

Step 3: Finishing Touches

Picture of Finishing Touches

Once soldered together, you can then fix them in your guitar. Or, you can jazz them up a little. These are going to my friend, who will then be installing them. Since his soldering skills are....lacking, I bundled everything up with shrink wrap so the joints dont come apart during soldering. Longer leads were also  added, to make installation easier. With the version two effect, it is polarity sensitive, so make sure you dont mix it up. I added a dot of paint on the postitive output from the circuit. The negative output is directly opposite it, and the inputs from the guitar pickups are the two leads adjacent to the marked one. 

Step 4: Wiring It Up

Picture of Wiring It Up

For the first version, It is wired in place of the capacitor on the tone pot. Polarity is not an issue. If you want to use the cap along with the overdrive, see below:

The tone pot has three contacts. First, wire the signal input for the tone knob into the middle contact. Then, the capacitor is wired to one of the outside contacts and the back of the tone pot, and the overdrive effect to the other contact and the back of the pot. The back of the pot is then grounded as normal. This allows the tone to be anywhere from full capacitor, to half capacitor half overdrive, to full overdrive. This does however mean that the tone/overdrive will always be on to some extent, and cant be turned alost off like it can be when just a single effect is used.

To wire in the version two effect, nothing to the original guitar's wiring needs to be changed. (If you saw this before i made this change, disregard the original information). Follow the diagram. There are two ways to wire it. The basic wiring is the same, but the opposite lead from the marked lead can be left unatatched for a stronger overdrive effect. Do not touch any of the exhisitng wires in the guitar.

Step 5: Jam Session!

Now that the effects are built and installed, its time to play! The tone knob is used as normal, unless you wired both the capacitor and overdrive onto the tone pot. Then, in one direction it controls the overdrive, and in the other, it controls the tone cap. With version two, the tone pot not only controls the amount of crunch, but how rough the crunch is. The higher it is turned up, the rougher the crunch. The diodes also have the effect of modulating the higher frequencies with the lower ones. The nice thing is that this effect is different in  sound than overdrive delivered by an amp, but it can be controlled on the guitar itself, and unlike pedals, goes with you everywhere on stage, seeing as it is built into the guitar. 

There will be a video up soon demonstrating the sound of the effect. 

Congratulations on the completion of your own passive overdrive effect!

Comments

dannyboyPH (author)2016-11-30

Great! Is there a way to place a switch so that I can deactivate it if I won't use it?

MatthiasH7 (author)2016-01-14

Please someone tell me which diodes i have to use. i bought some 1N34A germanium diodes, but they dont work :-(

jimdkc (author)2014-05-15

Here's an analysis of your circuit. First, I labeled the diodes, D1 through D4. Then I redrew the schematic. Vd is the voltage at which any of the diodes will turn on. First thing I noticed, diode D4 is grounded on both ends. That means it is shorted out, and it performs no function. D4 can be removed from the circuit. Next, I looked at D3. On the positive half of the input signal, D3 will turn on at it's forward voltage (+Vd) any voltage over +Vd will be shunted to ground. However that remaining positive voltage will be blocked by diode D1 and will not appear at the output. Therefore, D3 performs no function. D3 can be removed from the circuit. Now looking at diode D1, on the positive half of the input signal, D1 will block the positive voltage, but on the negative half of the input signal D1 will block the signal until it reaches -Vd, and then the D1 will turn on and allow the signal to pass until absolute value of the input voltage drops below Vd, then the diode will turn off again. D1 does perform a function in this circuit. It can stay. Finally, looking at D2, it will attempt to shunt any positive voltage to ground. However D3 has already shunted any positive voltage higher than Vd to ground, and D1 has blocked any remaining positive voltage from reaching the output. Therefore, D2 performs no function. D2 can be removed from the circuit. So, you can see, the whole circuit can be replaced by a single diode.

DanR5 (author)jimdkc2014-12-01

Your analysis is correct.

tkjn (author)DanR52014-12-05

If you remove D3 from the circuit then you can't use it's function as justification for removing D2

JoeBeau (author)tkjn2014-12-05

But D2/D4 is not connected to ground in the corrected schematic. It is functioning as a bridge rectifier.

DanR5 (author)JoeBeau2014-12-10

Both positive and negative peaks of the input sine wave will be clipped with this circuit.

pjuelsgaard (author)DanR52015-10-13

So does that mean that both the + and - go to the output jack?

DanR5 (author)pjuelsgaard2015-10-16

Yes

jimdkc (author)JoeBeau2014-12-05

OK... this is a correct bridge rectifier circuit. Both postive and negative peaks higher than 2 x Vd will be let through as Negative pulses (the way you have this wired...)

jimdkc (author)tkjn2014-12-05

No positive voltage will get past D1 to be shunted to ground by D2... So D2 can be removed regardless of D3...

JoeBeau (author)jimdkc2014-12-05

Ive been thinking about why this is distinctly different than the analysis I had done for this.... That schematic I posted is incorrect. It is a bridge rectifier in function- that ground between D2 and D4 should be the other wire from the pickups- the pickup is wired to the D1/D3 node and D2/D4 node. The D3/D4 node is grounded to the ground from the cable and the D1/D2 node is the output

TehGunky (author)2015-08-22

What I want to do is add both versions of this with an on-off-on switch. But I'm having trouble figuring out how to make that happen.

The 2-diode version is easy enough - "tap" the signal from the volume pot, bleed to ground. The 4-diode version needs to be added back to the signal path, and that's where I'm running into confusion.

Here's where I'm at with it. Any help would be appreciated!

NiallT1 (author)2015-04-25

This doesn't sound like a useful improvement over the traditional circuit.

The Black Ice (and its predecessors) attempt to model amp clipping by bleeding signal peaks to earth.

By putting the diodes into the signal path, you're doing things the other way round -- blocking the signal below the peaks, and only letting the peaks through. You'll get a distorted sound, right enough, but it will be a very different beast from typical guitar overdrive/distortion.

When the diodes bias and debias, you get a very sudden change in signal, which by the time it reaches you speaker is a "high-energy transient". You're asking your drivers to jump suddenly from one position to another, accelerating and braking far beyond their rated levels, this is very bad for your speakers or headphones.

Speaking of things that are bad for your speakers, why did you want a rectifier in the first place? It'll emphasise the second harmonic, but a rectified signal stays one side of 0V, and only uses half the travel of the driver coils. This won't do your speakers any favours either.

Ploopy made it! (author)2015-04-12

I gave it a try!

this works well in a simulator.

Next I just have to install it in a guitar/electric ukulele.

Ploopy (author)2015-04-12

Ploopy (author)2015-03-25

Cool!

austin.schaper.77 (author)2015-02-25

Can someone post the final correct diagram with the best results please? I'd love to put this in my bass

jimdkc (author)2014-12-05

As you noted, the voltage drops of Germanium or Schottky diodes will be lower, letting through more signal.

AndyC5 (author)2014-10-11

Hey, I was thinking about putting both versions of this mod in a single guitar and use a 3-way slide switch to move between off-1 diode version on-2diode version on. But I'm worried that this might not work very well, because I don't know if the difference between the two versions is really that big.

ssampson4 (author)2014-02-11

Hey Joe...(sorry, couldn't resist!) So I think it's working now...thanks! It's not really a huge change in the sound though. Would adding more diodes to the circuit make the effect more noticeable?
Thanks again!!

JoeBeau (author)ssampson42014-02-11

I would try different diodes. Germanium diodes often work the best in terms of noticeable change. They can be found online pretty easily as well as in old radios. They are cat whisker diodes like the glass ones I use in the instructable. Look up 1N34A diode.

ssampson4 (author)2014-02-10

Here's a better one maybe

JoeBeau (author)ssampson42014-02-10

Sorry it took a while for a response. I had class all day.

Everything looks right, assuming that black is signal and red is ground, correct? also, it looks as if you are using a stereo jack. The tip and the large sleeve are the two that should be connected, so just double check that. Also, reheat and remelt the solder joints. It is easy to have a joint where they are physically adhered but not conductive.

ssampson4 (author)2014-02-10

Okay...Sorry, probably my fault....here it is:

ssampson4 (author)2014-02-10

Hey Joe...here's the pic of the way it is currently wired. The black wire coming into the switch is from the volume pot. Does this help?

JoeBeau (author)ssampson42014-02-10

Sorry, but your picture didn't post.

ssampson4 (author)2014-02-07

Hi..I was interested in doing this on my bass guitar. I wanted to use a simple switch rather than a tone pot, as I don't want the blended tones....all or none!! I tried to use 2 schotky diodes, but there was on tone or sound change...do my bass pickups not put out enough voltage to drive this? Any advice or ideas is much appreciated!

JoeBeau (author)ssampson42014-02-07

i would guess you have it wired incorrectly. If the pickups didn't offer enough output you would hardly hear them with the effect on. I am thinking that you wired the effect in the ground instead of signal, as since guitars sometimes have extra ground connections, you might have bypassed it. It is hard to say without seeing it. Some pictures might help

ssampson4 (author)JoeBeau2014-02-08

Thanks for the input!! I'm in the building stages, so right now the electronics are outside the guitar. I'm trying different configurations to figure what sound I like best. I'm trying different values of pots, and different values of capacitors on the the tone pots. I have the diodes operating on a switch. I don't have the guitar at home, so I can't take pic until Monday. But I'm sure I have the hot from the vol pot to the middle pole of switch. Also from middle of switch to output jack. From the side pole of switch I have the two diodes running to ground. They are in reverse directions. Does this sound right?
Thanks again for your input!!!

JoeBeau (author)2013-09-11

With the way the schematic is presented, you either have clipping or the filter cap or half and half when the pot is in the center position (and other mixtures in between). Removing the cap removes the tone adjustment.

With what you are describing, it would seem as if your capacitor is wired in series with the control pot. This would allow the overdrive to clip the signal still when the capacitor is disconnected, but removing the capacitor removes the pot from the circuit. Try uploading a picture of your guitar's wiring. It would make it easier to diagnose

dgēllērēr (author)2013-09-04

hey my friend!
i dont get that thing with 4 diodes running correctly.
when i put it in the guitar like shown in the lower picture WITHOUT the cap a get that clipping sound, but i cant blend it out. with the cap i can blend from clipping to less treble.
but i just want to blend between the clipping and the normal signal. how do i wire that up? i tried different stuff - nothing seemed to work.

could you quickly paint it down for me? ;)

crms1496 (author)2012-08-17

I do not know much about diodes, but began looking them up when I saw this. I saw that an overdrive instructable used 1n4148 silicon diodes. Will this work as well as schottky diodes? Do 1n4148s have low voltage drops?

JoeBeau (author)crms14962012-08-18

The best way to test this is to take a reading of the voltage from a battery (like a 9 volt) and then hook up the diode in series with the battery and meter and take another voltage reading. With the diode pointing one way, the voltage should read near 0. The other way, it should give you a reading but somewhat lower than the reading you got before from the battery alone. If the difference is so small it is hardly (or maybe impossible) to tell the difference, the diode should work. Too much of a voltage drop, and you wont get any signal from the guitar.
That being said, different diodes provide different sound. Diodes with higher voltage drops and/or slower switching will create muddier, heavier distortion.

A quick google search turns up a lot of information. Just be typing in 1n4148 you can find the data sheet (first result) for the diode. It does not give voltage drop information there, but generally silicon diodes do have a voltage drop from .5 volt to 1 volt. Too high for this

bhoffman (author)2011-11-27

what are the specs of the diodes you are using?

JoeBeau (author)bhoffman2011-11-28

Unfortunately they are salvaged and have no markings except for the band. What you want from the diodes however are to be fast switching with a low voltage drop. Germanium diodes work well as well as schottkey diodes.

RazorDude (author)JoeBeau2012-06-13

What about LEDs?

mrmerino (author)RazorDude2012-08-13

Better have some high output pickups; LEDs have mean voltage drops.

smokeandlights (author)2012-04-23

Awesome Instructable! I too wondered about the black Ice effect. Can you post some audio or video of the effect in action? I'd love to hear it.

I thought about installing this effect using a push/pull pot, so I could go clean with it pulled out (just original wiring), or push it in to go crunchy. Would that work?

I'm very glad you made this 'ible!

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