simple question. GE VS SI diodes?

[darron]

hey. which are better? the GE cause less voltage drop. is there any reason not to use them? are they less reliable? there's not much diffence between the ge and schottky. but that 0.1 volt might just make the difference

any variance in ge from factory wouldn't bother me if the average is still less than a schottky.

ge look cooler too....

any words of wisdom from those more experienced than i?

thanks (:

darron.

[PerroGrande]

It isn't so much a matter of one being better than another (with a few exceptions)... They merely have different characteristics and behaviors that is a result of the different materials involved in the construction.   As a result of these differences, tonal differences emerge when they are placed in a circuit.  Which one is "better", in audio terms, can often be a very subjective answer. 

For example, Ge diodes require typically less voltage to forward-bias the junction.  Thus, if they are used as clippers, they will clip "sooner" than a silicon diode or an LED.  Germanium diodes tend to leak more (the nature of the beast -- same for Germanium transistors), and this too creates issues -- but can also create a sound that one might like.

As long as you understand some basic implications of the different flavors of diodes available (such as the forward-bias voltage), you have some latitude to experiment with the different types to get the sound you like. 

There are a few exceptions to this "rule" -- circuits that are leakage sensitive might not fare well (or work at all) with a leaky Ge diode.  A circuit that depends on fast diode recovery might need a specific diode characteristic.  However, for many audio circuits, you have some latitude to experiment and find what has the sound you want

[Zben3129]

Diodes are like flavors. You may thing you know your favorite flavor till you try another...

Some types:
Si
Ge
5mm LED red
5mm LED green(and so on and so forth)
3mm led red
3mm led green(yada yada)
Silicon transistors
Germanium transistors
Zener

Thats only a partial list. And within all those types, theres hundreds of types. Think of it this way, Silicon diodes are chocolate icecream, germanium vanilla. Say you like vanilla more than chocolate. Now think about how many different types and makers of vanilla there are. Same goes for diodes, while they all taste like vanilla, they all have a little something different. Maybe theres that one type of chocolate that you like more than vanilla, when you are in the mood for chocolate. Maybe theres one kind of vanilla you just don't like.

Kinda like diodes 

[darron]

woh woh... hold on.... of course i understand using diodes as clippers. i meant using them in their most common use, as polarity protection. sorry, i should have specified that i guess. i wouldn't start a thread on something that subjective.

the interesting point that you made is that they become 'leaky' ? so they will allow a bit of reverse current earlier on? i'm not quite sure what you mean on that one...

[Gus]

then there is junction capacitance.  IIRC Craig Anderson had a short article in a late 80s? Guitar player issue in it the use of the junction capacitance vs signal of an LED was written about.

  Varactor diodes

[mac]

I'm not an expert but I guess that if you use the diode in series a Ge has lower voltage drop. Across the rail a tough 1n400x is ideal if the polarity is reversed.

mac

[darron]

hey mac. now you're talking! how do you compare the ge to a schottky though? what are the pros and cons. i was thinking of incorporating both protection, parallel and series, but i read (geofex  think?) that the series diode can burn out and become a jumper, keeping all power from the circuit then on. do you suggest by "tough" that a 1N4007 would never do this though? most places in australia only stock the 1n4007 (1000V, 1A), compared to 1n4001 etc.  but it's only like $0.15 so it doesn't matter.

thanks (:

[kurtlives]

Diodes are like flavors. You may thing you know your favorite flavor till you try another...

Some types:
Si
Ge
5mm LED red
5mm LED green(and so on and so forth)
3mm led red
3mm led green(yada yada)
Silicon transistors
Germanium transistors
Zener

Thats only a partial list. And within all those types, theres hundreds of types. Think of it this way, Silicon diodes are chocolate icecream, germanium vanilla. Say you like vanilla more than chocolate. Now think about how many different types and makers of vanilla there are. Same goes for diodes, while they all taste like vanilla, they all have a little something different. Maybe theres that one type of chocolate that you like more than vanilla, when you are in the mood for chocolate. Maybe theres one kind of vanilla you just don't like.

Kinda like diodes 

So there is actually a difference between the size of the diodes and the colors? Can you explain how different ones sound?

[Zben3129]

"Can you explain how some of them sound?"

Yes. And No.

I can tell you how a few I have used in a few pedals with a few of my guitars on a fewof my amps sounds to my ears. But this may change for your setup and ears.

My personal favs are germaniums. I use 1n34a's sometimes. Most of the time, however, I use these clear ones that I have a stash of. Don't know what they are, just that they are germanium. They sound awesome. To me.

LED's are a little crunchier, more distorted basically

They all sound different. It is hard to explain. The best was I can tell you is to listen to them yourself. Breadboard something like the tube reamer, something easy. Then, swap in multiple diodes/diode combos and see what you like. Dont forget to try things like symmetrical, asymmeyrical, mismatched, combos, strings etc etc

Hope this helps, if you need any specific pointers on a certain kind of diodes, I may also be able to help, but it is just too hard to explain diodes, without listening them you won't fully understand it.

Cheers

Zach

[R.G.]

See GEO, "Advanced Power Switching and Polarity Protection", 1999 http://geofex.com/Article_Folders/mosswitch/mosswitch.htm, paragraphs 3, 4, and 5. Shoot, read the rest of it too.

Also "Cheap - and Good - Polarity Protection", 2004, http://geofex.com/Article_Folders/cheapgoodprot.htm

You can use silicon, schottky, or germanium for series protection. It works, but you lose the voltage with silicon, schottky is expensive, and germanium is unreliable. You can use an active device as in either one of the circuits I show and get series protection and not lose the voltage.

You can use either of the as a reverse shunt diode. If this goes on for long, the diode burns out, then the board gets fried. Shunt is really only good for momentary battery reversals.

[darron]

Thanks R.G. I'd read those pages before, they are clever and get to the precise point (:

Ge being unreliable is the answer I'm looking for. I'm not rich but I often don't look at costs much as it's all a bit of fun to get things working and have good results. So for places where only one diode will work, I'll be sticking to the schottky now.

(:

[R.G.]

Schottky is a good choice if you can get them at reasonable prices. The 1N5819 family is good.

Be aware that Schottky diodes are fairly low voltage. 20-30V is about all you could get in Schottky for a long time, although I think you can get up to 60V these days. Generally 20-30V is OK for polarity protection.

[mac]

Schottky is a good choice if you can get them at reasonable prices. The 1N5819 family is good.

I got some at $0,20 (us$0,06) in my country, forward voltage drop about 150mV, less than a typical Ge.

mac

[brett]

1N5819

Put one in series with the circuit and you're laughing.  Low voltage drop, tiny, incredibly reliable.
Why do people "shunt" electrons when they could easily stop them?

[R.G.]

Because they do not know the electronics or think hard about the issue. Series polarity protection is far preferable if you can stand the diode drop.

But to get there you have to know:
- most pedals are no longer only battery powered (shunt is almost perfect for momentary battery reversals at replacement time)
- some diodes have lower drops these days
- the low drop diodes are getting cheaper.

Still, a series diode can't get as low as a saturated active device. In switching power supplies, long the home of power Schottky diodes, the critical applications use power MOSFETs as synchronous rectifiers, achieving higher speeds, lower losses, and lower voltage drop than Schottky diodes.

[darron]

1N5819 is pretty much what i have on hand here. it's good to get some good feedback on them. i only play with 9-18 volt. i'll try the geofex voltage multiplier soon (:

i'll use 1n4007 diodes to make that though as i WANT the voltage just that little bit lower as it comes close to some component ratings.