diode in electric guitar/bass?

[fuzzy645]

I have heard rumor about a strange concept (strange to me anyway), namely that Jack Bruce had some kind of diode in his EB-3 bass which is an entirely passive instrument.  To me this makes absolutely no sense whatsoever.  Assuming the rumor is in fact true,  what on earth would a diode do in a passive guitar circuit and how could it remotely have anything to do with tone? 

[Mark Hammer]

here is your answer: http://www.stewmac.com/freeinfo/Electronics/Misc/i-5065.html

[fuzzy645]

here is your answer: http://www.stewmac.com/freeinfo/Electronics/Misc/i-5065.html

Thanks. 

So "Black Ice" is nothing more than a diode?  So do you think you can stick any old diode in a guitar circuit and it will work the same, or is the black ice some special kind of diode with magical properties?

The thing is they show it hooked up to a tone pot in the same way a normal cap would be hooked up and they don't seem to show any polarity, but diodes are polarized.

Thoughts?

[artifus]

diodes.

http://www.beavisaudio.com/bboard/projects/bbp_DiodeMods.pdf

[ashcat_lt]

In order for it to affect a passive instrument it would have to have a low forward voltage - a shottke or a germanium.  If there's only one, it will provide asymmetrical clipping.  It'll clip off either the peaks or the valleys.  The difference is negligible, so it doesn't really matter which way it points.  The pot lets you dail in the effect.

[Earthscum]

If I get to it tonight I'll snap pics of mine. I use a 1N5818 from ground to the tip, switchable. I used a pushbutton, and am considering running a second one the other way. As mine sits, it is Cathode to tip and Anode to ground. Works great on bass, IMHO.

[Mark Hammer]

The diodes have to be selected for a low forward voltage, and the pickups have to have a substantial output, or else the clipping will not happen.

For example, a person could NOT stick in a pair of 1N4001s or a pair of LEDs in a guitar equipped with "vintage correct" single-coils and expect to hear much effect unless they did a Pete Townshend "windmill" strum, and even then it would likely be for only the first 200msec of the strum.

So, it "works" but requires some very favourable circumstances to do so.  Not for everybody.

[fuzzy645]

The diodes have to be selected for a low forward voltage, and the pickups have to have a substantial output, or else the clipping will not happen.

OK, that makes sense.  The EB-3 (I believe) had an ultra high output humbucker.  I can see this making some sense now in a bass, particularly one who plays hard in the vain of Jack Bruce.

So I bet Stewmac (or whoever is the manufacturer) found a diode with low forward voltage and slapped it in some epoxy casing.....LOL!!!!

[artifus]

So I bet Stewmac (or whoever is the manufacturer) found a diode with low forward voltage and slapped it in some epoxy casing.....LOL!!!!

ice cube tray mould?

[Earthscum]

ice cube tray mould?

There was a discussion in the lounge a couple months back about some distortion unit you plug into a Twin Reverb or some Tweed amp to use the reverb driver as a distortion. Anyways, it came up in discussion about the Black Ice Overdrive modules... the thought is that "black Ice" was named after these amp modules... which WERE molded in ice cube trays. I just thought it was interesting.

ETA: Old EB auction...

[Mark Hammer]

These things were first introduced a LONG time ago, possibly over 30 years ago.  I recall seeing ads for them in Guitar Player waaayyyyyyy back.

[Earthscum]

Here's mine. I only clip half the signal, nice overdrive sound. The button is from Mammoth.

[DavenPaget]

Here's mine. I only clip half the signal, nice overdrive sound. The button is from Mammoth.

O_O A LED and a 5818 ? What's the total Vf ? That seems like a lot ! How does your pickup even have enough output ?

[Earthscum]

It's just the schotky diode. No LED. It only clips when the negative voltage exceeds the Vf, which is really low in most situations if whatever I plug into has a high enough impedance, about what you expect to retain tone.

[DavenPaget]

It's just the schotky diode. No LED. It only clips when the negative voltage exceeds the Vf, which is really low in most situations if whatever I plug into has a high enough impedance, about what you expect to retain tone.

Oh i correct myself , that's a pushbutton switch 

[Earthscum]

Oh i correct myself , that's a pushbutton switch 

Ah! I get it... I never noticed how much it looked like an LED in a holder. 

[nascarbean_97]

Old bump, but hey, I'm adding!
I found you can do this with a germanium tranny, you couple two of the legs, those go to ground, and the third goes to the pot prong. Not sure which leg is which, I just experimented and found it out.